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  • Kinetics
  • American Association for the Advancement of Science (AAAS)  (313)
  • American Association for the Advancement of Science
  • American Association of Petroleum Geologists (AAPG)
  • American Physical Society
  • Elsevier
  • 1995-1999  (74)
  • 1990-1994  (239)
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Keywords
Publisher
  • American Association for the Advancement of Science (AAAS)  (313)
  • American Association for the Advancement of Science
  • American Association of Petroleum Geologists (AAPG)
  • American Physical Society
  • Elsevier
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Years
Year
  • 1
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    A processive single-headed motor: kinesin superfamily protein KIF1A (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-02-19
    Description: A single kinesin molecule can move "processively" along a microtubule for more than 1 micrometer before detaching from it. The prevailing explanation for this processive movement is the "walking model," which envisions that each of two motor domains (heads) of the kinesin molecule binds coordinately to the microtubule. This implies that each kinesin molecule must have two heads to "walk" and that a single-headed kinesin could not move processively. Here, a motor-domain construct of KIF1A, a single-headed kinesin superfamily protein, was shown to move processively along the microtubule for more than 1 micrometer. The movement along the microtubules was stochastic and fitted a biased Brownian-movement model.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Okada, Y -- Hirokawa, N -- New York, N.Y. -- Science. 1999 Feb 19;283(5405):1152-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Hongo, Tokyo 113-0033, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10024239" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Amino Acid Sequence ; Animals ; Catalytic Domain ; Diffusion ; Drosophila ; Kinesin/chemistry/*metabolism ; Kinetics ; Microscopy, Fluorescence ; Microtubules/*metabolism ; Models, Chemical ; Molecular Motor Proteins/chemistry/*metabolism ; Molecular Sequence Data ; Nerve Tissue Proteins/chemistry/*metabolism ; Recombinant Fusion Proteins ; Stochastic Processes ; Thermodynamics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    A molecular mechanism for electrical tuning of cochlear hair cells (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-01-08
    Description: Cochlear frequency selectivity in lower vertebrates arises in part from electrical tuning intrinsic to the sensory hair cells. The resonant frequency is determined largely by the gating kinetics of calcium-activated potassium (BK) channels encoded by the slo gene. Alternative splicing of slo from chick cochlea generated kinetically distinct BK channels. Combination with accessory beta subunits slowed the gating kinetics of alpha splice variants but preserved relative differences between them. In situ hybridization showed that the beta subunit is preferentially expressed by low-frequency (apical) hair cells in the avian cochlea. Interaction of beta with alpha splice variants could provide the kinetic range needed for electrical tuning of cochlear hair cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ramanathan, K -- Michael, T H -- Jiang, G J -- Hiel, H -- Fuchs, P A -- DC00276/DC/NIDCD NIH HHS/ -- New York, N.Y. -- Science. 1999 Jan 8;283(5399):215-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Hearing Sciences, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9880252" target="_blank"〉PubMed〈/a〉
    Keywords: Alternative Splicing ; Animals ; Calcium/metabolism ; Cell Line ; Electrophysiology ; Gene Expression ; Hair Cells, Auditory/*physiology ; Humans ; In Situ Hybridization ; *Ion Channel Gating ; Kinetics ; Large-Conductance Calcium-Activated Potassium Channel beta Subunits ; Large-Conductance Calcium-Activated Potassium Channels ; Membrane Potentials ; Patch-Clamp Techniques ; Potassium Channels/genetics/*physiology ; *Potassium Channels, Calcium-Activated ; Quail ; RNA, Messenger/genetics/metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Transfection
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  • 3
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    Increased cortical oxidative metabolism due to sensory stimulation: implications for functional brain imaging (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-11-24
    Description: Modern functional brain mapping relies on interactions of neuronal electrical activity with the cortical microcirculation. The existence of a highly localized, stimulus-evoked initial deoxygenation has remained a controversy. Here, the activity-dependent oxygen tension changes in the microcirculation were measured directly, using oxygen-dependent phosphorescence quenching of an exogenous indicator. The first event after sensory stimulation was an increase in oxygen consumption, followed by an increase in blood flow. Because oxygen consumption and neuronal activity are colocalized but the delayed blood flow is not, functional magnetic resonance imaging focused on this initial phase will yield much higher spatial resolution, ultimately enabling the noninvasive visualization of fundamental processing modules in the human brain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vanzetta, I -- Grinvald, A -- New York, N.Y. -- Science. 1999 Nov 19;286(5444):1555-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Center for Research of Higher Brain Functions, Weizmann Institute of Science, Rehovot 76100, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10567261" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Volume ; Brain Mapping ; Cats ; Cerebrovascular Circulation ; Hemoglobins/analysis ; Humans ; Kinetics ; Luminescence ; Magnetic Resonance Imaging ; Microcirculation ; Neuroglia/metabolism ; Neurons/metabolism ; Oxygen/*blood ; *Oxygen Consumption ; Oxyhemoglobins/analysis ; Photic Stimulation ; Spectrum Analysis ; Visual Cortex/blood supply/*metabolism
    Print ISSN: 0036-8075
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  • 4
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    Electron transfer between bases in double helical DNA (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-01-15
    Description: Fluorescent analogs of adenine that selectively oxidize guanine were used to investigate photoinduced electron transfer through the DNA pi-stack as a function of reactant stacking and energetics. Small variations in these factors led to profound changes in the kinetics and distance dependences of DNA-mediated electron-transfer reactions. Values of beta, a parameter reflecting the dependence of electron transfer on distance, ranged from 0.1 to 1.0 per angstrom. Strong stacking interactions result in the fastest electron-transfer kinetics. Electrons are thus transported preferentially through an intrastrand rather than interstrand pathway. Reactant energetics also modulate the distance dependence of DNA-mediated charge transport. These studies may resolve the range of disparate results previously reported, and paradigms must now be developed to describe these properties of the DNA pi-stack, which can range from insulator- to "wire"-like.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kelley, S O -- Barton, J K -- GM49216/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Jan 15;283(5400):375-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Beckman Institute, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9888851" target="_blank"〉PubMed〈/a〉
    Keywords: 2-Aminopurine/chemistry ; Adenine/analogs & derivatives/chemistry ; Base Pairing ; DNA/*chemistry ; *Electrons ; Guanine/chemistry ; Hydrogen Bonding ; Kinetics ; Light ; Nucleic Acid Conformation ; Oxidation-Reduction ; Spectrometry, Fluorescence ; Thermodynamics
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  • 5
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    Evidence for autoregulation of cystathionine gamma-synthase mRNA stability in Arabidopsis (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-11-13
    Description: Control of messenger RNA (mRNA) stability serves as an important mechanism for regulating gene expression. Analysis of Arabidopsis mutants that overaccumulate soluble methionine (Met) revealed that the gene for cystathionine gamma-synthase (CGS), the key enzyme in Met biosynthesis, is regulated at the level of mRNA stability. Transfection experiments with wild-type and mutant forms of the CGS gene suggest that an amino acid sequence encoded by the first exon of CGS acts in cis to destabilize its own mRNA in a process that is activated by Met or one of its metabolites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chiba, Y -- Ishikawa, M -- Kijima, F -- Tyson, R H -- Kim, J -- Yamamoto, A -- Nambara, E -- Leustek, T -- Wallsgrove, R M -- Naito, S -- New York, N.Y. -- Science. 1999 Nov 12;286(5443):1371-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10558994" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Arabidopsis/*enzymology/genetics ; Carbon-Oxygen Lyases/chemistry/*genetics/metabolism ; Exons ; Gene Expression Regulation, Enzymologic ; *Gene Expression Regulation, Plant ; Genes, Plant ; Genes, Reporter ; Kinetics ; Methionine/metabolism ; Molecular Sequence Data ; Mutation ; RNA, Messenger/genetics/*metabolism ; Sequence Alignment ; Transcription, Genetic ; Transfection
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  • 6
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    Emergent properties of networks of biological signaling pathways (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-01-15
    Description: Many distinct signaling pathways allow the cell to receive, process, and respond to information. Often, components of different pathways interact, resulting in signaling networks. Biochemical signaling networks were constructed with experimentally obtained constants and analyzed by computational methods to understand their role in complex biological processes. These networks exhibit emergent properties such as integration of signals across multiple time scales, generation of distinct outputs depending on input strength and duration, and self-sustaining feedback loops. Feedback can result in bistable behavior with discrete steady-state activities, well-defined input thresholds for transition between states and prolonged signal output, and signal modulation in response to transient stimuli. These properties of signaling networks raise the possibility that information for "learned behavior" of biological systems may be stored within intracellular biochemical reactions that comprise signaling pathways.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bhalla, U S -- Iyengar, R -- GM-54508/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1999 Jan 15;283(5400):381-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pharmacology, Mount Sinai School of Medicine, New York, NY 10029, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9888852" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcineurin/metabolism ; Calcium/metabolism ; Calcium-Calmodulin-Dependent Protein Kinase Type 2 ; Calcium-Calmodulin-Dependent Protein Kinases/metabolism ; *Cell Cycle Proteins ; Computer Simulation ; Cyclic AMP/metabolism ; Dual Specificity Phosphatase 1 ; Enzyme Activation ; Epidermal Growth Factor/pharmacology ; Feedback ; Immediate-Early Proteins/metabolism ; Isoenzymes/metabolism ; Kinetics ; Long-Term Potentiation ; Memory ; *Models, Biological ; Neurons/metabolism ; Phospholipase C gamma ; *Phosphoprotein Phosphatases ; Phosphorylation ; Protein Kinase C/metabolism ; Protein Phosphatase 1 ; Protein Tyrosine Phosphatases/metabolism ; Receptor, Epidermal Growth Factor/metabolism ; Receptors, N-Methyl-D-Aspartate/metabolism ; Second Messenger Systems ; *Signal Transduction ; Synapses/metabolism ; Type C Phospholipases/metabolism
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  • 7
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    Wing rotation and the aerodynamic basis of insect flight (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-06-18
    Description: The enhanced aerodynamic performance of insects results from an interaction of three distinct yet interactive mechanisms: delayed stall, rotational circulation, and wake capture. Delayed stall functions during the translational portions of the stroke, when the wings sweep through the air with a large angle of attack. In contrast, rotational circulation and wake capture generate aerodynamic forces during stroke reversals, when the wings rapidly rotate and change direction. In addition to contributing to the lift required to keep an insect aloft, these two rotational mechanisms provide a potent means by which the animal can modulate the direction and magnitude of flight forces during steering maneuvers. A comprehensive theory incorporating both translational and rotational mechanisms may explain the diverse patterns of wing motion displayed by different species of insects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dickinson, M H -- Lehmann, F O -- Sane, S P -- New York, N.Y. -- Science. 1999 Jun 18;284(5422):1954-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. flymannd@socrates.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10373107" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biomechanical Phenomena ; Drosophila melanogaster/*physiology ; Flight, Animal/*physiology ; Kinetics ; Models, Biological ; Movement ; Robotics ; Rotation ; Wings, Animal/*physiology
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  • 8
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    Energy transduction on the nanosecond time scale: early structural events in a xanthopsin photocycle (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-16
    Description: Photoactive yellow protein (PYP) is a member of the xanthopsin family of eubacterial blue-light photoreceptors. On absorption of light, PYP enters a photocycle that ultimately transduces the energy contained in a light signal into an altered biological response. Nanosecond time-resolved x-ray crystallography was used to determine the structure of the short-lived, red-shifted, intermediate state denoted [pR], which develops within 1 nanosecond after photoelectronic excitation of the chromophore of PYP by absorption of light. The resulting structural model demonstrates that the [pR] state possesses the cis conformation of the 4-hydroxyl cinnamic thioester chromophore, and that the process of trans to cis isomerization is accompanied by the specific formation of new hydrogen bonds that replace those broken upon excitation of the chromophore. Regions of flexibility that compose the chromophore-binding pocket serve to lower the activation energy barrier between the dark state, denoted pG, and [pR], and help initiate entrance into the photocycle. Direct structural evidence is provided for the initial processes of transduction of light energy, which ultimately translate into a physiological signal.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perman, B -- Srajer, V -- Ren, Z -- Teng, T -- Pradervand, C -- Ursby, T -- Bourgeois, D -- Schotte, F -- Wulff, M -- Kort, R -- Hellingwerf, K -- Moffat, K -- New York, N.Y. -- Science. 1998 Mar 20;279(5358):1946-50.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9506946" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Proteins/*chemistry/metabolism ; Chromatiaceae/chemistry ; Crystallography, X-Ray ; Energy Metabolism ; Fourier Analysis ; Hydrogen Bonding ; Isomerism ; Kinetics ; *Light ; Models, Molecular ; *Photoreceptors, Microbial ; *Protein Conformation ; Signal Transduction
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  • 9
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    The era of pathway quantification (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-05-23
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Koshland, D E Jr -- New York, N.Y. -- Science. 1998 May 8;280(5365):852-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA. dek@uclink4.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9599157" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium-Calmodulin-Dependent Protein Kinases/metabolism ; *Cell Cycle ; Cells/metabolism ; Kinetics ; Ligands ; Oocytes/cytology/enzymology/*metabolism ; Xenopus
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  • 10
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    Deuteronomy?: a puzzle of deuterium and oxygen on Mars (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-06-27
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yung, Y L -- Kass, D M -- New York, N.Y. -- Science. 1998 Jun 5;280(5369):1545-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125, USA. yly@mercu1.gps.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9644019" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Deuterium/*analysis ; *Extraterrestrial Environment ; Hydrogen/*analysis ; Kinetics ; *Mars ; Oxygen/analysis ; Oxygen Isotopes ; Temperature ; Thermodynamics ; *Water
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  • 11
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    How temperature changes reset a circadian oscillator (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-08-07
    Description: Circadian rhythms control many physiological activities. The environmental entrainment of rhythms involves the immediate responses of clock components. Levels of the clock protein FRQ were measured in Neurospora at various temperatures; at higher temperatures, the amount of FRQ oscillated around higher levels. Absolute FRQ amounts thus identified different times at different temperatures, so temperature shifts corresponded to shifts in clock time without immediate synthesis or turnover of components. Moderate temperature changes could dominate light-to-dark shifts in the influence of circadian timing. Temperature regulation of clock components could explain temperature resetting of rhythms and how single transitions can initiate rhythmicity from characteristic circadian phases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Y -- Merrow, M -- Loros, J J -- Dunlap, J C -- GM34985/GM/NIGMS NIH HHS/ -- MH01186/MH/NIMH NIH HHS/ -- MH44651/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 1998 Aug 7;281(5378):825-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9694654" target="_blank"〉PubMed〈/a〉
    Keywords: Biological Clocks/*physiology ; Blotting, Northern ; *Circadian Rhythm ; Darkness ; Fungal Proteins/biosynthesis/genetics/*metabolism ; Immunoblotting ; Kinetics ; Light ; Neurospora/genetics/metabolism/*physiology ; RNA, Fungal/genetics/metabolism ; RNA, Messenger/genetics/metabolism ; Temperature
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  • 12
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    Single-molecule enzymatic dynamics (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-04
    Description: Enzymatic turnovers of single cholesterol oxidase molecules were observed in real time by monitoring the emission from the enzyme's fluorescent active site, flavin adenine dinucleotide (FAD). Statistical analyses of single-molecule trajectories revealed a significant and slow fluctuation in the rate of cholesterol oxidation by FAD. The static disorder and dynamic disorder of reaction rates, which are essentially indistinguishable in ensemble-averaged experiments, were determined separately by the real-time single-molecule approach. A molecular memory phenomenon, in which an enzymatic turnover was not independent of its previous turnovers because of a slow fluctuation of protein conformation, was evidenced by spontaneous spectral fluctuation of FAD.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lu, H P -- Xun, L -- Xie, X S -- New York, N.Y. -- Science. 1998 Dec 4;282(5395):1877-82.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Pacific Northwest National Laboratory, William R. Wiley Environmental Molecular Sciences Laboratory, Richland, WA 99352, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9836635" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Brevibacterium/enzymology ; Cholesterol/*metabolism ; Cholesterol Oxidase/*metabolism ; Flavin-Adenine Dinucleotide/*metabolism ; Kinetics ; Microscopy, Fluorescence ; Oxidation-Reduction ; Probability ; Spectrometry, Fluorescence ; Stochastic Processes
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  • 13
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    KCNQ2 and KCNQ3 potassium channel subunits: molecular correlates of the M-channel (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-04
    Description: The M-current regulates the subthreshold electrical excitability of many neurons, determining their firing properties and responsiveness to synaptic input. To date, however, the genes that encode subunits of this important channel have not been identified. The biophysical properties, sensitivity to pharmacological blockade, and expression pattern of the KCNQ2 and KCNQ3 potassium channels were determined. It is concluded that both these subunits contribute to the native M-current.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, H S -- Pan, Z -- Shi, W -- Brown, B S -- Wymore, R S -- Cohen, I S -- Dixon, J E -- McKinnon, D -- New York, N.Y. -- Science. 1998 Dec 4;282(5395):1890-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular Cardiology, Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9836639" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Animals ; Anthracenes/pharmacology ; Brain/metabolism ; Ganglia, Sympathetic/metabolism ; Gene Expression ; Humans ; Indoles/pharmacology ; KCNQ2 Potassium Channel ; KCNQ3 Potassium Channel ; Kinetics ; Neurons/drug effects/physiology ; Oocytes ; Patch-Clamp Techniques ; Potassium/*metabolism ; Potassium Channels/chemistry/drug effects/genetics/*metabolism ; Potassium Channels, Voltage-Gated ; Pyridines/pharmacology ; Rats ; Sympathetic Nervous System/drug effects/physiology ; Tetraethylammonium/pharmacology ; Xenopus
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  • 14
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    A marine natural product inhibitor of kinesin motors (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-05-02
    Description: Members of the kinesin superfamily of motor proteins are essential for mitotic and meiotic spindle organization, chromosome segregation, organelle and vesicle transport, and many other processes that require microtubule-based transport. A compound, adociasulfate-2, was isolated from a marine sponge, Haliclona (also known as Adocia) species, that inhibited kinesin activity by targeting its motor domain and mimicking the activity of the microtubule. Thus, the kinesin-microtubule interaction site could be a useful target for small molecule modulators, and adociasulfate-2 should serve as an archetype for specific inhibitors of kinesin functions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sakowicz, R -- Berdelis, M S -- Ray, K -- Blackburn, C L -- Hopmann, C -- Faulkner, D J -- Goldstein, L S -- New York, N.Y. -- Science. 1998 Apr 10;280(5361):292-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pharmacology, Division of Cellular and Molecular Medicine, Howard Hughes Medical Institute, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0683, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9535660" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Diphosphate/metabolism ; Adenosine Triphosphatases/antagonists & inhibitors ; Adenosine Triphosphate/metabolism ; Animals ; Binding Sites ; Cell Division/drug effects ; Drosophila/embryology ; Enzyme Inhibitors/chemistry/*isolation & purification/*pharmacology ; HeLa Cells ; Humans ; Kinesin/*antagonists & inhibitors/metabolism ; Kinetics ; Microtubules/*metabolism ; Mitosis/drug effects ; Porifera/*chemistry ; Sulfuric Acid Esters/chemistry/*isolation & purification/*pharmacology
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  • 15
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    Characterization of an ammonium transport protein from the peribacteroid membrane of soybean nodules (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-08-26
    Description: Nitrogen-fixing bacteroids in legume root nodules are surrounded by the plant-derived peribacteroid membrane, which controls nutrient transfer between the symbionts. A nodule complementary DNA (GmSAT1) encoding an ammonium transporter has been isolated from soybean. GmSAT1 is preferentially transcribed in nodules and immunoblotting indicates that GmSAT1 is located on the peribacteroid membrane. [14C]methylammonium uptake and patch-clamp analysis of yeast expressing GmSAT1 demonstrated that it shares properties with a soybean peribacteroid membrane NH4〈SUP ARRANGE="STAGGER"〉+ channel described elsewhere. GmSAT1 is likely to be involved in the transfer of fixed nitrogen from the bacteroid to the host.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kaiser, B N -- Finnegan, P M -- Tyerman, S D -- Whitehead, L F -- Bergersen, F J -- Day, D A -- Udvardi, M K -- New York, N.Y. -- Science. 1998 Aug 21;281(5380):1202-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Biochemistry and Molecular Biology, The Australian National University, Canberra ACT 0200, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9712587" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Base Sequence ; Biological Transport ; Carrier Proteins/chemistry/*genetics/*metabolism/*secretion ; *Cation Transport Proteins ; Cell Membrane/metabolism ; DNA, Complementary ; Ion Channels/metabolism ; Kinetics ; Methylamines/metabolism ; Molecular Sequence Data ; Organelles/metabolism ; Patch-Clamp Techniques ; Plant Roots/genetics/metabolism/microbiology ; Potassium/metabolism ; Quaternary Ammonium Compounds/*metabolism ; Saccharomyces cerevisiae/genetics/metabolism ; *Soybean Proteins ; Soybeans/chemistry/*genetics/metabolism/microbiology ; Spheroplasts/metabolism ; Symbiosis ; Transformation, Genetic
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  • 16
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    Interaction of human Arp2/3 complex and the Listeria monocytogenes ActA protein in actin filament nucleation (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-07-04
    Description: Actin filament assembly at the cell surface of the pathogenic bacterium Listeria monocytogenes requires the bacterial ActA surface protein and the host cell Arp2/3 complex. Purified Arp2/3 complex accelerated the nucleation of actin polymerization in vitro, but pure ActA had no effect. However, when combined, the Arp2/3 complex and ActA synergistically stimulated the nucleation of actin filaments. This mechanism of activating the host Arp2/3 complex at the L. monocytogenes surface may be similar to the strategy used by cells to control Arp2/3 complex activity and hence the spatial and temporal distribution of actin polymerization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Welch, M D -- Rosenblatt, J -- Skoble, J -- Portnoy, D A -- Mitchison, T J -- AI26919/AI/NIAID NIH HHS/ -- GM48027/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Jul 3;281(5373):105-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9651243" target="_blank"〉PubMed〈/a〉
    Keywords: Actin-Related Protein 2 ; Actin-Related Protein 3 ; Actins/chemistry/*metabolism/ultrastructure ; Bacterial Proteins/chemistry/*metabolism ; Biopolymers ; Cell Membrane/metabolism ; Cytochalasin D/pharmacology ; *Cytoskeletal Proteins ; Humans ; Kinetics ; Listeria monocytogenes/*metabolism ; Membrane Proteins/chemistry/*metabolism ; Microscopy, Electron
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  • 17
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    Visualization of single RNA transcripts in situ (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-09
    Description: Fluorescence in situ hybridization (FISH) and digital imaging microscopy were modified to allow detection of single RNA molecules. Oligodeoxynucleotide probes were synthesized with five fluorochromes per molecule, and the light emitted by a single probe was calibrated. Points of light in exhaustively deconvolved images of hybridized cells gave fluorescent intensities and distances between probes consistent with single messenger RNA molecules. Analysis of beta-actin transcription sites after serum induction revealed synchronous and cyclical transcription from single genes. The rates of transcription initiation and termination and messenger RNA processing could be determined by positioning probes along the transcription unit. This approach extends the power of FISH to yield quantitative molecular information on a single cell.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Femino, A M -- Fay, F S -- Fogarty, K -- Singer, R H -- GM 54887/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Apr 24;280(5363):585-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Anatomy and Structural Biology and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9554849" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/genetics ; Animals ; Cell Line ; Fluorescein-5-isothiocyanate ; *In Situ Hybridization, Fluorescence ; Kinetics ; Oligonucleotide Probes ; RNA Processing, Post-Transcriptional ; RNA, Messenger/*analysis/*genetics/metabolism ; Rats ; *Transcription, Genetic
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  • 18
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    Hepatitis C viral dynamics in vivo and the antiviral efficacy of interferon-alpha therapy (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-10-02
    Description: To better understand the dynamics of hepatitis C virus and the antiviral effect of interferon-alpha-2b (IFN), viral decline in 23 patients during therapy was analyzed with a mathematical model. The analysis indicates that the major initial effect of IFN is to block virion production or release, with blocking efficacies of 81, 95, and 96% for daily doses of 5, 10, and 15 million international units, respectively. The estimated virion half-life (t1/2) was, on average, 2.7 hours, with pretreatment production and clearance of 10(12) virions per day. The estimated infected cell death rate exhibited large interpatient variation (corresponding t1/2 = 1.7 to 70 days), was inversely correlated with baseline viral load, and was positively correlated with alanine aminotransferase levels. Fast death rates were predictive of virus being undetectable by polymerase chain reaction at 3 months. These findings show that infection with hepatitis C virus is highly dynamic and that early monitoring of viral load can help guide therapy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Neumann, A U -- Lam, N P -- Dahari, H -- Gretch, D R -- Wiley, T E -- Layden, T J -- Perelson, A S -- A1/DK41320-2/DK/NIDDK NIH HHS/ -- A139049-2/PHS HHS/ -- RR06555/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1998 Oct 2;282(5386):103-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9756471" target="_blank"〉PubMed〈/a〉
    Keywords: Alanine Transaminase/blood ; Antiviral Agents/administration & dosage/*therapeutic use ; Cell Death ; Dose-Response Relationship, Drug ; Half-Life ; Hepacivirus/*physiology ; Hepatitis C/immunology/*therapy/*virology ; Humans ; Interferon-alpha/administration & dosage/*therapeutic use ; Kinetics ; Models, Biological ; RNA, Viral/blood ; Recombinant Proteins ; Regression Analysis ; Viral Load ; Viremia/virology ; Virion/physiology ; Virus Replication
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  • 19
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    The biochemical basis of an all-or-none cell fate switch in Xenopus oocytes (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-23
    Description: Xenopus oocytes convert a continuously variable stimulus, the concentration of the maturation-inducing hormone progesterone, into an all-or-none biological response-oocyte maturation. Here evidence is presented that the all-or-none character of the response is generated by the mitogen-activated protein kinase (MAPK) cascade. Analysis of individual oocytes showed that the response of MAPK to progesterone or Mos was equivalent to that of a cooperative enzyme with a Hill coefficient of at least 35, more than 10 times the Hill coefficient for the binding of oxygen to hemoglobin. The response can be accounted for by the intrinsic ultrasensitivity of the oocyte's MAPK cascade and a positive feedback loop in which the cascade is embedded. These findings provide a biochemical rationale for the all-or-none character of this cell fate switch.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ferrell, J E Jr -- Machleder, E M -- CA09302/CA/NCI NIH HHS/ -- GM56383/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 May 8;280(5365):895-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Pharmacology, Stanford University School of Medicine, Stanford, CA 94305-5332, USA. ferrell@cmgm.stanford.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9572732" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carrier Proteins/pharmacology ; Cell Cycle ; Cycloheximide/pharmacology ; Enzyme Activation ; Feedback ; Kinetics ; Maltose-Binding Proteins ; Mitogen-Activated Protein Kinase 1/*metabolism ; Oocytes/*cytology/drug effects/enzymology/*metabolism ; Phosphorylation ; Progesterone/*pharmacology ; Protein Synthesis Inhibitors/pharmacology ; Proto-Oncogene Proteins c-mos/*pharmacology ; Recombinant Fusion Proteins/pharmacology
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  • 20
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    Rapid turnover of T lymphocytes in SIV-infected rhesus macaques (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-03-21
    Description: Studies of lymphocyte turnover in animal models have implications for understanding the mechanism of cell killing and the extent of lymphocyte regeneration in human immunodeficiency virus infection. Quantitative analyses of the sequential changes in bromodeoxyuridine labeling of CD4 and CD8 T lymphocytes not only revealed the normal proliferation and death rates of these cell populations in uninfected macaques, but also showed a substantial increase in these rates associated with simian immunodeficiency virus (SIV) infection. Faster labeling and delabeling in memory and naive T lymphocyte subpopulations as well as in NK (natural killer) and B cells were also observed in infected macaques, suggesting a state of generalized activation induced by SIV.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mohri, H -- Bonhoeffer, S -- Monard, S -- Perelson, A S -- Ho, D D -- AI40387/AI/NIAID NIH HHS/ -- AI41534/AI/NIAID NIH HHS/ -- AI45128/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1998 Feb 20;279(5354):1223-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Aaron Diamond AIDS Research Center, The Rockefeller University, 455 First Avenue, New York, NY 10016, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9469816" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bromodeoxyuridine/metabolism ; CD4 Lymphocyte Count ; CD4-Positive T-Lymphocytes/*immunology/pathology ; CD8-Positive T-Lymphocytes/*immunology/pathology ; Cell Death ; Cell Division ; Humans ; Kinetics ; Lymphocyte Activation ; Lymphocyte Count ; Macaca mulatta ; Mathematics ; Models, Biological ; Regression Analysis ; Simian Acquired Immunodeficiency Syndrome/*immunology/virology ; Simian Immunodeficiency Virus/physiology ; T-Lymphocyte Subsets/*immunology/pathology ; Viral Load
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  • 21
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    Peptides by activation of amino acids with CO on (Ni,Fe)S surfaces: implications for the origin of life (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-07-31
    Description: In experiments modeling volcanic or hydrothermal settings amino acids were converted into their peptides by use of coprecipitated (Ni,Fe)S and CO in conjunction with H2S (or CH3SH) as a catalyst and condensation agent at 100 degreesC and pH 7 to 10 under anaerobic, aqueous conditions. These results demonstrate that amino acids can be activated under geochemically relevant conditions. They support a thermophilic origin of life and an early appearance of peptides in the evolution of a primordial metabolism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huber, C -- Wachtershauser, G -- New York, N.Y. -- Science. 1998 Jul 31;281(5377):670-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department for Organic Chemistry and Biochemistry, Technische Universitat Munchen, Lichtenbergstrasse 4, D-85747 Garching, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9685253" target="_blank"〉PubMed〈/a〉
    Keywords: Acetic Acid/chemical synthesis ; Amino Acids/chemistry ; Aminoacylation ; Anaerobiosis ; Carbon Monoxide/*chemistry ; Catalysis ; Dipeptides/chemical synthesis ; Ferrous Compounds/*chemistry ; Hot Temperature ; Hydrogen Sulfide/chemistry ; Hydrogen-Ion Concentration ; Kinetics ; Nickel/*chemistry ; *Origin of Life ; *Peptide Biosynthesis ; Sulfhydryl Compounds/chemistry ; Thermodynamics
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  • 22
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    A trivalent system from vancomycin.D-ala-D-Ala with higher affinity than avidin.biotin (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-05-23
    Description: Tris(vancomycin carboxamide) binds a trivalent ligand derived from D-Ala-D-Ala with very high affinity: dissociation constant (Kd) approximately 4 x 10(-17) +/- 1 x 10(-17) M. High-affinity trivalent binding and monovalent binding are fundamentally different. In trivalent (and more generally, polyvalent) binding, dissociation occurs in stages, and its rate can be accelerated by monovalent ligand at sufficiently high concentrations. In monovalent binding, dissociation is determined solely by the rate constant for dissociation and cannot be accelerated by added monomer. Calorimetric measurements for the trivalent system indicate an approximately additive gain in enthalpy relative to the corresponding monomers. This system is one of the most stable organic receptor-ligand pairs involving small molecules that is known. It illustrates the practicality of designing very high-affinity systems based on polyvalency.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rao, J -- Lahiri, J -- Isaacs, L -- Weis, R M -- Whitesides, G M -- GM 30367/GM/NIGMS NIH HHS/ -- GM 51559/GM/NIGMS NIH HHS/ -- GM 53210/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 May 1;280(5364):708-11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9563940" target="_blank"〉PubMed〈/a〉
    Keywords: Alanine/*analogs & derivatives/chemistry/metabolism ; Avidin/metabolism ; Biotin/metabolism ; Calorimetry ; Chromatography, High Pressure Liquid ; Dipeptides/chemistry/*metabolism ; Kinetics ; Ligands ; Thermodynamics ; Vancomycin/*analogs & derivatives/chemistry/*metabolism
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  • 23
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    Immune versus natural selection: antibody aldolases with enzymic rates but broader scope (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-02-12
    Description: Structural and mechanistic studies show that when the selection criteria of the immune system are changed, catalytic antibodies that have the efficiency of natural enzymes evolve, but the catalytic antibodies are much more accepting of a wide range of substrates. The catalytic antibodies were prepared by reactive immunization, a process whereby the selection criteria of the immune system are changed from simple binding to chemical reactivity. This process yielded aldolase catalytic antibodies that approximated the rate acceleration of the natural enzyme used in glycolysis. Unlike the natural enzyme, however, the antibody aldolases catalyzed a variety of aldol reactions and decarboxylations. The crystal structure of one of these antibodies identified the reactive lysine residue that was selected in the immunization process. This lysine is deeply buried in a hydrophobic pocket at the base of the binding site, thereby accounting for its perturbed pKa.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barbas, C F 3rd -- Heine, A -- Zhong, G -- Hoffmann, T -- Gramatikova, S -- Bjornestedt, R -- List, B -- Anderson, J -- Stura, E A -- Wilson, I A -- Lerner, R A -- CA27489/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1997 Dec 19;278(5346):2085-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉The Skaggs Institute for Chemical Biology and the Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9405338" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Catalytic/chemistry/immunology/*metabolism ; Binding Sites ; Catalysis ; Crystallography, X-Ray ; Decarboxylation ; *Evolution, Molecular ; Fructose-Bisphosphate Aldolase/chemistry/immunology/*metabolism ; Glycolysis ; Hydrogen-Ion Concentration ; Immunization ; Immunoglobulin Fab Fragments/chemistry/immunology/*metabolism ; Kinetics ; Lysine/chemistry/metabolism ; Mice ; Models, Molecular ; Protein Conformation ; Pyridoxal/metabolism ; Selection, Genetic ; Substrate Specificity
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  • 24
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    A sequencing method based on real-time pyrophosphate (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-08-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ronaghi, M -- Uhlen, M -- Nyren, P -- New York, N.Y. -- Science. 1998 Jul 17;281(5375):363, 365.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biotechnology, The Royal Institute of Technology, SE-10044 Stockholm, Sweden.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9705713" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Apyrase/metabolism ; Automation ; DNA/biosynthesis ; DNA Primers ; DNA-Directed DNA Polymerase/metabolism ; Deoxyribonucleotides/metabolism ; Diphosphates/*metabolism ; Kinetics ; Light ; Luciferases/metabolism ; Polymerase Chain Reaction ; Sequence Analysis, DNA/*methods ; Sulfate Adenylyltransferase/metabolism ; Templates, Genetic
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  • 25
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    Regulation of neurotransmitter release kinetics by NSF (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-03-21
    Description: NSF (N-ethylmaleimide-sensitive factor) is an adenosine triphosphatase (ATPase) that contributes to a protein complex essential for membrane fusion. The synaptic function of this protein was investigated by injecting, into the giant presynaptic terminal of squid, peptides that inhibit the ATPase activity of NSF stimulated by the soluble NSF attachment protein (SNAP). These peptides reduced the amount and slowed the kinetics of neurotransmitter release as a result of actions that required vesicle turnover and occurred at a step subsequent to vesicle docking. These results define NSF as an essential participant in synaptic vesicle exocytosis that regulates the kinetics of neurotransmitter release and, thereby, the integrative properties of synapses.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schweizer, F E -- Dresbach, T -- DeBello, W M -- O'Connor, V -- Augustine, G J -- Betz, H -- New York, N.Y. -- Science. 1998 Feb 20;279(5354):1203-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9469810" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/antagonists & inhibitors/metabolism ; Amino Acid Sequence ; Animals ; Calcium/metabolism ; Carrier Proteins/chemistry/*metabolism/pharmacology ; Decapodiformes ; Excitatory Postsynaptic Potentials ; Exocytosis ; Glutamic Acid/metabolism ; Kinetics ; Membrane Fusion ; Membrane Proteins/pharmacology ; Molecular Sequence Data ; N-Ethylmaleimide-Sensitive Proteins ; Neurotransmitter Agents/*metabolism ; Patch-Clamp Techniques ; Peptide Fragments/pharmacology ; Presynaptic Terminals/*metabolism ; Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins ; Synaptic Transmission ; Synaptic Vesicles/*metabolism/physiology ; *Vesicular Transport Proteins
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  • 26
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    RNA folding at millisecond intervals by synchrotron hydroxyl radical footprinting (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-16
    Description: Radiolysis of water with a synchrotron x-ray beam permits the hydroxyl radical-accessible surface of an RNA to be mapped with nucleotide resolution in 10 milliseconds. Application of this method to folding of the Tetrahymena ribozyme revealed that the most stable domain of the tertiary structure, P4-P6, formed cooperatively within 3 seconds. Exterior helices became protected from hydroxyl radicals in 10 seconds, whereas the catalytic center required minutes to be completely folded. The results show that rapid collapse to a partially disordered state is followed by a slow search for the active structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sclavi, B -- Sullivan, M -- Chance, M R -- Brenowitz, M -- Woodson, S A -- GM39929/GM/NIGMS NIH HHS/ -- GM51506/GM/NIGMS NIH HHS/ -- GM52348/GM/NIGMS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1998 Mar 20;279(5358):1940-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology and Biophysics, Center for Synchrotron Biosciences, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9506944" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Hydroxyl Radical ; Kinetics ; Magnesium ; Models, Molecular ; *Nucleic Acid Conformation ; RNA, Catalytic/*chemistry ; Solvents ; Synchrotrons ; Tetrahymena/chemistry ; X-Rays
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    Kinetic intermediates trapped by native interactions in RNA folding (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-16
    Description: In the magnesium ion-dependent folding of the Tetrahymena ribozyme, a kinetic intermediate accumulates in which the P4-P6 domain is formed, but the P3-P7 domain is not. The kinetic barriers to P3-P7 formation were investigated with the use of in vitro selection to identify mutant RNA molecules in which the folding rate of the P3-P7 domain was increased. The critical mutations disrupt native tertiary interactions within the P4-P6 domain and increase the rate of P3-P7 formation by destabilizing a kinetically trapped intermediate. Hence, kinetic traps stabilized by native interactions, and not simply by mispaired nonnative structures, can present a substantial barrier to RNA folding.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Treiber, D K -- Rook, M S -- Zarrinkar, P P -- Williamson, J R -- New York, N.Y. -- Science. 1998 Mar 20;279(5358):1943-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, MB33, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9506945" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding Sites ; Kinetics ; Magnesium/metabolism ; Models, Molecular ; Mutation ; *Nucleic Acid Conformation ; RNA, Catalytic/*chemistry/genetics/metabolism ; Tetrahymena/chemistry
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  • 28
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    Chemical dynamics in proteins: the photoisomerization of retinal in bacteriorhodopsin (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-04-16
    Description: Chemical dynamics in proteins are discussed, with bacteriorhodopsin serving as a model system. Ultrafast time-resolved methods used to probe the chemical dynamics of retinal photoisomerization in bacteriorhodopsin are discussed, along with future prospects for ultrafast time-resolved crystallography. The photoisomerization of retinal in bacteriorhodopsin is far more selective and efficient than in solution, the origins of which are discussed in the context of a three-state model for the photoisomerization reaction coordinate. The chemical dynamics are complex, with the excited-state relaxation exhibiting a multiexponential decay with well-defined rate constants. Possible origins for the two major components are also discussed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gai, F -- Hasson, K C -- McDonald, J C -- Anfinrud, P A -- DK45306/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1998 Mar 20;279(5358):1886-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9506931" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteriorhodopsins/*chemistry/metabolism ; Halobacterium salinarum/chemistry/metabolism ; Isomerism ; Kinetics ; *Light ; Models, Chemical ; Protein Conformation ; Retinaldehyde/*chemistry/metabolism ; Spectrum Analysis ; Thermodynamics
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  • 29
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    A euryarchaeal lysyl-tRNA synthetase: resemblance to class I synthetases (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-11-14
    Description: The sequencing of euryarchaeal genomes has suggested that the essential protein lysyl-transfer RNA (tRNA) synthetase (LysRS) is absent from such organisms. However, a single 62-kilodalton protein with canonical LysRS activity was purified from Methanococcus maripaludis, and the gene that encodes this protein was cloned. The predicted amino acid sequence of M. maripaludis LysRS is similar to open reading frames of unassigned function in both Methanobacterium thermoautotrophicum and Methanococcus jannaschii but is unrelated to canonical LysRS proteins reported in eubacteria, eukaryotes, and the crenarchaeote Sulfolobus solfataricus. The presence of amino acid motifs characteristic of the Rossmann dinucleotide-binding domain identifies M. maripaludis LysRS as a class I aminoacyl-tRNA synthetase, in contrast to the known examples of this enzyme, which are class II synthetases. These data question the concept that the classification of aminoacyl-tRNA synthetases does not vary throughout living systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ibba, M -- Morgan, S -- Curnow, A W -- Pridmore, D R -- Vothknecht, U C -- Gardner, W -- Lin, W -- Woese, C R -- Soll, D -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1119-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biophysics and Biochemistry, Yale University, Post Office Box 208114, 266 Whitney Avenue, New Haven, CT 06520-8114, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353192" target="_blank"〉PubMed〈/a〉
    Keywords: Acylation ; Amino Acid Sequence ; Animals ; Bacteria/enzymology ; Cloning, Molecular ; Electrophoresis, Polyacrylamide Gel ; Euryarchaeota/enzymology/genetics ; Evolution, Molecular ; Genes, Archaeal ; Humans ; Kinetics ; Lysine-tRNA Ligase/*chemistry/*classification/genetics/metabolism ; Methanococcus/*enzymology/genetics ; Molecular Sequence Data ; Phylogeny ; RNA, Transfer, Amino Acyl/biosynthesis ; Sequence Alignment ; Sulfolobus/enzymology
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    Orbital steering in the catalytic power of enzymes: small structural changes with large catalytic consequences (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-07-11
    Description: Small structural perturbations in the enzyme isocitrate dehydrogenase (IDH) were made in order to evaluate the contribution of precise substrate alignment to the catalytic power of an enzyme. The reaction trajectory of IDH was modified (i) after the adenine moiety of nicotinamide adenine dinucleotide phosphate was changed to hypoxanthine (the 6-amino was changed to 6-hydroxyl), and (ii) by replacing Mg2+, which has six coordinating ligands, with Ca2+, which has eight coordinating ligands. Both changes make large (10(-3) to 10(-5)) changes in the reaction velocity but only small changes in the orientation of the substrates (both distance and angle) as revealed by cryocrystallographic trapping of active IDH complexes. The results provide evidence that orbital overlap produced by optimal orientation of reacting orbitals plays a major quantitative role in the catalytic power of enzymes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mesecar, A D -- Stoddard, B L -- Koshland, D E Jr -- GM49857/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jul 11;277(5323):202-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular and Cell Biology, Stanley Hall, University of California, Berkeley, CA 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9211842" target="_blank"〉PubMed〈/a〉
    Keywords: Cadmium/metabolism ; Calcium/metabolism ; Catalysis ; Chemistry, Physical ; Crystallography, X-Ray ; Hydrogen Bonding ; Isocitrate Dehydrogenase/*chemistry/*metabolism ; Kinetics ; Ligands ; Magnesium/metabolism ; Models, Molecular ; Mutagenesis, Site-Directed ; NAD/analogs & derivatives/metabolism ; NADP/metabolism ; Physicochemical Phenomena ; *Protein Conformation
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    How thiamine diphosphate is activated in enzymes (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-01-03
    Description: The controversial question of how thiamine diphosphate, the biologically active form of vitamin B1, is activated in different enzymes has been addressed. Activation of the coenzyme was studied by measuring thermodynamics and kinetics of deprotonation at the carbon in the 2-position (C2) of thiamine diphosphate in the enzymes pyruvate decarboxylase and transketolase by use of nuclear magnetic resonance spectroscopy, proton/deuterium exchange, coenzyme analogs, and site-specific mutant enzymes. Interaction of a glutamate with the nitrogen in the 1'-position in the pyrimidine ring activated the 4'-amino group to act as an efficient proton acceptor for the C2 proton. The protein component accelerated the deprotonation of the C2 atom by several orders of magnitude, beyond the rate of the overall enzyme reaction. Therefore, the earlier proposed concerted mechanism or stabilization of a C2 carbanion can be excluded.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kern, D -- Kern, G -- Neef, H -- Tittmann, K -- Killenberg-Jabs, M -- Wikner, C -- Schneider, G -- Hubner, G -- New York, N.Y. -- Science. 1997 Jan 3;275(5296):67-70.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Biochemie, Martin-Luther Universitat Halle-Wittenberg, Kurt-Mothes-Strasse 3, D-06120 Halle, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8974393" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Binding Sites ; Catalysis ; Deuterium/metabolism ; Enzyme Activation ; Glutamic Acid/metabolism ; Hydrogen-Ion Concentration ; Kinetics ; Magnetic Resonance Spectroscopy ; Mutagenesis, Site-Directed ; Protons ; Pyruvate Decarboxylase/chemistry/*metabolism ; Pyruvates/metabolism ; Thermodynamics ; Thiamine Pyrophosphate/chemistry/*metabolism ; Transketolase/chemistry/*metabolism
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    Microtubule treadmilling in vivo (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-01-10
    Description: In vivo, cytoplasmic microtubules are nucleated and anchored by their minus ends at the centrosome and are believed to turn over by a mechanism termed dynamic instability: depolymerization and repolymerization at their plus ends. In cytoplasmic fragments of fish melanophores, microtubules were shown to detach from their nucleation site and depolymerize from their minus ends. Free microtubules moved toward the periphery by treadmilling-growth at one end and shortening from the opposite end. Frequent release from nucleation sites may be a general property of centrosomes and permit a minus-end mechanism of microtubule turnover and treadmilling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rodionov, V I -- Borisy, G G -- GM25062/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jan 10;275(5297):215-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706, USA. ggborisy@facstaf.wisc.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8985015" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Membrane/metabolism ; Cells, Cultured ; Centrosome/metabolism ; Cytoplasm/metabolism/ultrastructure ; Fishes ; Kinetics ; Melanophores/ultrastructure ; Microtubules/metabolism/*physiology/ultrastructure ; Movement ; Pigments, Biological/metabolism ; Polymers
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    Inhibition of brain Gz GAP and other RGS proteins by palmitoylation of G protein alpha subunits (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-11-14
    Description: Palmitoylation of the alpha subunit of the guanine nucleotide-binding protein Gz inhibited by more than 90 percent its response to the guanosine triphosphatase (GTPase)-accelerating activity of Gz GAP, a Gz-selective member of the regulators of G-protein signaling (RGS) protein family of GTPase-activating proteins (GAPs). Palmitoylation both decreased the affinity of Gz GAP for the GTP-bound form of Galphaz by at least 90 percent and decreased the maximum rate of GTP hydrolysis. Inhibition was reversed by removal of the palmitoyl group by dithiothreitol. Palmitoylation of Galphaz also inhibited its response to the GAP activity of Galpha-interacting protein (GAIP), another RGS protein, and palmitoylation of Galphai1 inhibited its response to RGS4. The extent of inhibition of Gz GAP, GAIP, RGS4, and RGS10 correlated roughly with their intrinsic GAP activities for the Galpha target used in the assay. Reversible palmitoylation is thus a major determinant of Gz deactivation after its stimulation by receptors, and may be a general mechanism for prolonging or potentiating G-protein signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tu, Y -- Wang, J -- Ross, E M -- GM30355/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Nov 7;278(5340):1132-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9041, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9353196" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Dithiothreitol/pharmacology ; *GTP-Binding Protein alpha Subunits ; GTP-Binding Proteins/*metabolism ; GTPase-Activating Proteins ; Guanosine 5'-O-(3-Thiotriphosphate)/metabolism ; Guanosine Triphosphate/metabolism ; *Heterotrimeric GTP-Binding Proteins ; Hydrolysis ; Kinetics ; Palmitic Acid/*metabolism ; Palmitoyl Coenzyme A/metabolism ; Phosphoproteins/antagonists & inhibitors/metabolism ; Proteins/*antagonists & inhibitors/metabolism ; *RGS Proteins ; Signal Transduction
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    A metalloradical mechanism for the generation of oxygen from water in photosynthesis (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-09-26
    Description: In plants and algae, photosystem II uses light energy to oxidize water to oxygen at a metalloradical site that comprises a tetranuclear manganese cluster and a tyrosyl radical. A model is proposed whereby the tyrosyl radical functions by abstracting hydrogen atoms from substrate water bound as terminal ligands to two of the four manganese ions. Molecular oxygen is produced in the final step in which hydrogen atom transfer and oxygen-oxygen bond formation occur together in a concerted reaction. This mechanism establishes clear analogies between photosynthetic water oxidation and amino acid radical function in other enzymatic reactions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hoganson, C W -- Babcock, G T -- GM-37300/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Sep 26;277(5334):1953-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Michigan State University, East Lansing, MI 48824-1322, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9302282" target="_blank"〉PubMed〈/a〉
    Keywords: Electrons ; Eukaryota/metabolism ; Hydrogen/metabolism ; Kinetics ; Ligands ; Manganese/*metabolism ; Models, Chemical ; Oxidation-Reduction ; Oxygen/*metabolism ; *Photosynthesis ; Photosynthetic Reaction Center Complex Proteins/*metabolism ; Photosystem II Protein Complex ; Plants/metabolism ; Tyrosine/*metabolism ; Water/*metabolism
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    Calcium waves in retinal glial cells (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-02-07
    Description: Calcium signals were recorded from glial cells in acutely isolated rat retina to determine whether Ca2+ waves occur in glial cells of intact central nervous system tissue. Chemical (adenosine triphosphate), electrical, and mechanical stimulation of astrocytes initiated increases in the intracellular concentration of Ca2+ that propagated at approximately 23 micrometers per second through astrocytes and Muller cells as intercellular waves. The Ca2+ waves persisted in the absence of extracellular Ca2+ but were largely abolished by thapsigargin and intracellular heparin, indicating that Ca2+ was released from intracellular stores. The waves did not evoke changes in cell membrane potential but traveled synchronously in astrocytes and Muller cells, suggesting a functional linkage between these two types of glial cells. Such glial Ca2+ waves may constitute an extraneuronal signaling pathway in the central nervous system.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2410141/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2410141/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Newman, E A -- Zahs, K R -- EY04077/EY/NEI NIH HHS/ -- EY10383/EY/NEI NIH HHS/ -- R01 EY004077/EY/NEI NIH HHS/ -- R01 EY004077-19/EY/NEI NIH HHS/ -- New York, N.Y. -- Science. 1997 Feb 7;275(5301):844-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology, University of Minnesota, 435 Delaware Street, SE, Minneapolis, MN 55455, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9012354" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/pharmacology ; Animals ; Astrocytes/*metabolism ; Calcium/*metabolism ; Calcium Channels/metabolism ; Electric Stimulation ; Heparin/pharmacology ; In Vitro Techniques ; Inositol 1,4,5-Trisphosphate Receptors ; Kinetics ; Membrane Potentials ; Neuroglia/*metabolism ; Physical Stimulation ; Rats ; Receptors, Cytoplasmic and Nuclear/metabolism ; Retina/*cytology/metabolism ; Signal Transduction ; Stimulation, Chemical ; Thapsigargin/pharmacology
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    Postsynaptic glutamate transport at the climbing fiber-Purkinje cell synapse (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-09-05
    Description: The role of postsynaptic, neuronal glutamate transporters in terminating signals at central excitatory synapses is not known. Stimulation of a climbing fiber input to cerebellar Purkinje cells was shown to generate an anionic current mediated by glutamate transporters. The kinetics of transporter currents were resolved by pulses of glutamate to outside-out membrane patches from Purkinje cells. Comparison of synaptic transporter currents to transporter currents expressed in Xenopus oocytes suggests that postsynaptic uptake at the climbing fiber synapse removes at least 22 percent of released glutamate. These neuronal transporter currents arise from synchronous activation of transporters that greatly outnumber activated AMPA receptors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Otis, T S -- Kavanaugh, M P -- Jahr, C E -- NS21419/NS/NINDS NIH HHS/ -- NS33270/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1997 Sep 5;277(5331):1515-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Vollum Institute, L-474, Oregon Health Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, OR 97201, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9278516" target="_blank"〉PubMed〈/a〉
    Keywords: *Amino Acid Transport System X-AG ; Animals ; Aspartic Acid/analogs & derivatives/pharmacology ; Biological Transport ; Carrier Proteins/*metabolism ; Dicarboxylic Acids/pharmacology ; Glutamate Plasma Membrane Transport Proteins ; Glutamic Acid/*metabolism ; In Vitro Techniques ; Kinetics ; Nerve Fibers/*metabolism ; Oocytes ; Patch-Clamp Techniques ; Purkinje Cells/*metabolism ; Pyrrolidines/pharmacology ; Rats ; Receptors, AMPA/metabolism ; Receptors, Glutamate/*metabolism ; *Symporters ; Synapses/*metabolism ; *Synaptic Transmission ; Xenopus
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    A proficient enzyme revisited: the predicted mechanism for orotidine monophosphate decarboxylase (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-05-09
    Description: A mechanism is proposed to explain the activity of orotidine 5'-monophosphate decarboxylase (ODCase). This enzyme is the one of the most proficient known, with a catalytic proficiency (kcat/Km)/knon = 10(23) M-1. Quantum mechanical calculations predict a mechanism involving a stabilized carbene intermediate, which represents a previously unrecognized mode of enzymatic activity for ODCase. The proposed mechanism involves proton transfer from a weak acid (pKa = 7, where Ka is the acid constant) concerted with decarboxylation, in a nonpolar enzyme environment. Such a mechanism makes possible different approaches to the design of ODCase inhibitors. Furthermore, the prediction that general acid catalysis may only be effective in low dielectric media is of general significance for understanding the activity of many enzymes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lee, J K -- Houk, K N -- New York, N.Y. -- Science. 1997 May 9;276(5314):942-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9139656" target="_blank"〉PubMed〈/a〉
    Keywords: Barbiturates/pharmacology ; Binding Sites ; Catalysis ; Decarboxylation ; Enzyme Inhibitors/pharmacology ; Hydrogen-Ion Concentration ; Kinetics ; Orotidine-5'-Phosphate Decarboxylase/antagonists & inhibitors/*metabolism ; Protons ; Thermodynamics ; Uridine Monophosphate/*analogs & derivatives/metabolism
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    Kinetics of response in lymphoid tissues to antiretroviral therapy of HIV-1 infection (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-05-09
    Description: In lymphoid tissue, where human immunodeficiency virus-type 1 (HIV-1) is produced and stored, three-drug treatment with viral protease and reverse transcriptase inhibitors markedly reduced viral burden. This was shown by in situ hybridization and computerized quantitative analysis of serial tonsil biopsies from previously untreated adults. The frequency of productive mononuclear cells (MNCs) initially diminished with a half-life of about 1 day. Surprisingly, the amount of HIV-1 RNA in virus trapped on follicular dendritic cells (FDCs) decreased almost as quickly. After 24 weeks, MNCs with very few copies of HIV-1 RNA per cell were still detectable, as was proviral DNA; however, the amount of FDC-associated virus decreased by 〉/=3.4 log units. Thus, 6 months of potent therapy controlled active replication and cleared 〉99.9 percent of virus from the secondary lymphoid tissue reservoir.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cavert, W -- Notermans, D W -- Staskus, K -- Wietgrefe, S W -- Zupancic, M -- Gebhard, K -- Henry, K -- Zhang, Z Q -- Mills, R -- McDade, H -- Schuwirth, C M -- Goudsmit, J -- Danner, S A -- Haase, A T -- AI 25017/AI/NIAID NIH HHS/ -- AI 28246/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1997 May 9;276(5314):960-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9139661" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Anti-HIV Agents/*therapeutic use ; CD4-Positive T-Lymphocytes/virology ; DNA, Viral/analysis ; Dendritic Cells/cytology/*virology ; Drug Therapy, Combination ; HIV Infections/*drug therapy/virology ; HIV Protease Inhibitors/therapeutic use ; HIV-1/*drug effects/isolation & purification/physiology ; Humans ; Image Processing, Computer-Assisted ; In Situ Hybridization ; Kinetics ; Lamivudine/therapeutic use ; Leukocytes, Mononuclear/cytology/*virology ; Macrophages/virology ; Palatine Tonsil/*virology ; Proviruses/genetics ; RNA, Viral/analysis ; Reverse Transcriptase Inhibitors/therapeutic use ; Ritonavir/therapeutic use ; Viral Load ; Virus Replication/drug effects ; Zidovudine/therapeutic use
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    Asymmetric catalysis with water: efficient kinetic resolution of terminal epoxides by means of catalytic hydrolysis (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-08-15
    Description: Epoxides are versatile building blocks for organic synthesis. However, terminal epoxides are arguably the most important subclass of these compounds, and no general and practical method exists for their production in enantiomerically pure form. Terminal epoxides are available very inexpensively as racemic mixtures, and kinetic resolution is an attractive strategy for the production of optically active epoxides, given an economical and operationally simple method. Readily accessible synthetic catalysts (chiral cobalt-based salen complexes) have been used for the efficient asymmetric hydrolysis of terminal epoxides. This process uses water as the only reagent, no added solvent, and low loadings of a recyclable catalyst (〈0.5 mole percent), and it affords highly valuable terminal epoxides and 1, 2-diols in high yield with high enantiomeric enrichment.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tokunaga, M -- Larrow, J F -- Kakiuchi, F -- Jacobsen, E N -- GM-43214/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Aug 15;277(5328):936-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9252321" target="_blank"〉PubMed〈/a〉
    Keywords: *Catalysis ; Epoxy Compounds/*chemistry/isolation & purification ; Hydrolysis ; Kinetics ; Stereoisomerism ; Water/*chemistry
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  • 40
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    Stereoselective bimolecular phenoxy radical coupling by an auxiliary (dirigent) protein without an active center (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-01-17
    Description: The regio- and stereospecificity of bimolecular phenoxy radical coupling reactions, of especial importance in lignin and lignan biosynthesis, are clearly controlled in some manner in vivo; yet in vitro coupling by oxidases, such as laccases, only produce racemic products. In other words, laccases, peroxidases, and comparable oxidases are unable to control regio- or stereospecificity by themselves and thus some other agent must exist. A 78-kilodalton protein has been isolated that, in the presence of an oxidase or one electron oxidant, effects stereoselective bimolecular phenoxy radical coupling in vitro. Itself lacking a catalytically active (oxidative) center, its mechanism of action is presumed to involve capture of E-coniferyl alcohol-derived free-radical intermediates, with consequent stereoselective coupling to give (+)-pinoresinol.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Davin, L B -- Wang, H B -- Crowell, A L -- Bedgar, D L -- Martin, D M -- Sarkanen, S -- Lewis, N G -- New York, N.Y. -- Science. 1997 Jan 17;275(5298):362-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8994027" target="_blank"〉PubMed〈/a〉
    Keywords: Dimerization ; Flavin Mononucleotide/metabolism ; Flavin-Adenine Dinucleotide/metabolism ; Free Radicals ; Furans/chemistry/*metabolism ; Kinetics ; Laccase ; Lignans/*biosynthesis/chemistry ; Molecular Conformation ; Oxidation-Reduction ; Oxidoreductases/chemistry/*metabolism ; Phenols/chemistry/*metabolism ; Plant Proteins/*metabolism ; Stereoisomerism
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  • 41
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    Kinetic measurement of the step size of DNA unwinding by Escherichia coli UvrD helicase (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-01-17
    Description: The kinetic mechanism by which the DNA repair helicase UvrD of Escherichia coli unwinds duplex DNA was examined with the use of a series of oligodeoxynucleotides with duplex regions ranging from 10 to 40 base pairs. Single-turnover unwinding experiments showed distinct lag phases that increased with duplex length because partially unwound DNA intermediate states are highly populated during unwinding. Analysis of these kinetics indicates that UvrD unwinds duplex DNA in discrete steps, with an average "step size" of 4 to 5 base pairs (approximately one-half turn of the DNA helix). This suggests an unwinding mechanism in which alternating subunits of the dimeric helicase interact directly with duplex DNA.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ali, J A -- Lohman, T M -- GM45948/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jan 17;275(5298):377-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8994032" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/*metabolism ; Adenosine Triphosphate/metabolism ; Base Composition ; DNA/chemistry/*metabolism ; DNA Helicases/*metabolism ; DNA, Single-Stranded/metabolism ; Escherichia coli/*enzymology ; Escherichia coli Proteins ; Kinetics ; *Nucleic Acid Conformation ; Oligodeoxyribonucleotides/chemistry/*metabolism
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 42
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    Elementary calcium-release units induced by inositol trisphosphate (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-06-13
    Description: The extent to which inositol 1,4,5-trisphosphate (InsP3)-induced calcium signals are localized is a critical parameter for understanding the mechanism of effector activation. The spatial characteristics of InsP3-mediated calcium signals were determined by targeting a dextran-based calcium indicator to intracellular membranes through the in situ addition of a geranylgeranyl lipid group. Elementary calcium-release events observed with this indicator typically lasted less than 33 milliseconds, had diameters less than 2 micrometers, and were uncoupled from each other by the calcium buffer EGTA. Cellwide calcium transients are likely to result from synchronized triggering of such local release events, suggesting that calcium-dependent effector proteins could be selectively activated by localization near sites of local calcium release.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Horne, J H -- Meyer, T -- GM-51457/GM/NIGMS NIH HHS/ -- P01-HL-47053/HL/NHLBI NIH HHS/ -- R01-GM-48113/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1997 Jun 13;276(5319):1690-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9180077" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/*metabolism ; Calcium Channels/metabolism ; Cytosol/metabolism ; Egtazic Acid/pharmacology ; Electroporation ; Fluorescent Dyes ; Inositol 1,4,5-Trisphosphate/*pharmacology ; Intracellular Membranes/*metabolism ; Kinetics ; Microscopy, Confocal ; Microscopy, Fluorescence ; Organic Chemicals ; Peptides/metabolism ; Rats ; Signal Transduction ; Tumor Cells, Cultured
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    Thermodynamics and kinetics of a Brownian motor (1997)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1997-05-09
    Description: Nonequilibrium fluctuations, whether generated externally or by a chemical reaction far from equilibrium, can bias the Brownian motion of a particle in an anisotropic medium without thermal gradients, a net force such as gravity, or a macroscopic electric field. Fluctuation-driven transport is one mechanism by which chemical energy can directly drive the motion of particles and macromolecules and may find application in a wide variety of fields, including particle separation and the design of molecular motors and pumps.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Astumian, R D -- R29ES06620/ES/NIEHS NIH HHS/ -- New York, N.Y. -- Science. 1997 May 9;276(5314):917-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Surgery, University of Chicago, MC6035, Chicago, IL 60637, USA. dastumia@surgery.bsd.uchicago.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9139648" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Anisotropy ; Chemistry, Physical ; Diffusion ; Ion Pumps/*metabolism ; Kinetics ; Mathematics ; *Motion ; Particle Size ; Physicochemical Phenomena ; Sodium-Potassium-Exchanging ATPase/metabolism ; Stochastic Processes ; *Thermodynamics
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  • 44
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    Amide cleavage by a ribozyme: correction (1996)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1996-04-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Joyce, G F -- Dai, X -- De Mesmaeker, A -- New York, N.Y. -- Science. 1996 Apr 5;272(5258):18-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8600526" target="_blank"〉PubMed〈/a〉
    Keywords: Amides/*metabolism ; Kinetics ; RNA, Catalytic/*metabolism ; Ribonucleosides/metabolism
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  • 45
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    Catalytic role of 2'-hydroxyl groups within a group II intron active site (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-03-08
    Description: Domain 5 is an essential active-site component of group II intron ribozymes. The role of backbone substituents in D5 function was explored through synthesis of a series of derivatives containing deoxynucleotides at each position along the D5 strand. Kinetic screens revealed that eight 2'-hydroxyl groups were likely to be critical for activity of D5. Through two separate methods, including competitive inhibition and direct kinetic analysis, effects on binding and chemistry were distinguished. Depending on their function, important 2'-hydroxyl groups lie on opposite faces of the molecule, defining distinct loci for molecular recognition and catalysis by D5.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Abramovitz, D L -- Friedman, R A -- Pyle, A M -- GM41371/GM/NIGMS NIH HHS/ -- GM50313/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1996 Mar 8;271(5254):1410-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8596912" target="_blank"〉PubMed〈/a〉
    Keywords: Base Composition ; Base Sequence ; Binding Sites ; Catalysis ; Exons ; Hydrogen Bonding ; Hydroxyl Radical/chemistry ; *Introns ; Kinetics ; Models, Molecular ; Molecular Sequence Data ; Nucleic Acid Conformation ; Oligoribonucleotides/chemistry/metabolism ; RNA/metabolism ; RNA, Catalytic/chemistry/*metabolism
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  • 46
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    Protein folding monitored at individual residues during a two-dimensional NMR experiment (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-11-15
    Description: An approach is described to monitor directly at the level of individual residues the formation of structure during protein folding. A two-dimensional heteronuclear nuclear magnetic resonance (NMR) spectrum was recorded after the rapid initiation of the refolding of a protein labeled with nitrogen-15. The intensities and line shapes of the cross peaks in the spectrum reflected the kinetic time course of the folding events that occurred during the spectral accumulation. The method was used to demonstrate the cooperative nature of the acquisition of the native main chain fold of apo bovine alpha-lactalbumin. The general approach, however, should be applicable to the investigation of a wide range of chemical reactions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Balbach, J -- Forge, V -- Lau, W S -- van Nuland, N A -- Brew, K -- Dobson, C M -- New York, N.Y. -- Science. 1996 Nov 15;274(5290):1161-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Oxford Centre for Molecular Sciences, New Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8895458" target="_blank"〉PubMed〈/a〉
    Keywords: Circular Dichroism ; Fourier Analysis ; Hydrogen-Ion Concentration ; Kinetics ; Lactalbumin/*chemistry ; *Magnetic Resonance Spectroscopy ; Nitrogen Isotopes ; *Protein Folding ; Protein Structure, Secondary ; Protein Structure, Tertiary ; Spectrometry, Fluorescence
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  • 47
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    Enhanced dissociation of HLA-DR-bound peptides in the presence of HLA-DM (1996)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1996-10-25
    Description: Human leukocyte antigen (HLA)-DM is a critical participant in antigen presentation that catalyzes the release of class II-associated invariant chain-derived peptides (CLIP) from newly synthesized class II histocompatibility molecules, freeing the peptide-binding site for acquisition of antigenic peptides. The mechanism for the selective release of CLIP but not other peptides is unknown. DM was found to enhance the rate of peptide dissociation to an extent directly proportional to the intrinsic rate of peptide dissociation from HLA-DR, regardless of peptide sequence. Thus, CLIP is rapidly released in the presence of DM, because its intrinsic rate of dissociation is relatively high. In antigen presentation, DM has the potential to markedly enhance the rate of peptide exchange, favoring the presentation of peptides with slower intrinsic rates of dissociation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weber, D A -- Evavold, B D -- Jensen, P E -- AI30554/AI/NIAID NIH HHS/ -- AI33614/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1996 Oct 25;274(5287):618-20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8849454" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antigen Presentation ; Antigens, Differentiation, B-Lymphocyte/*metabolism ; Binding Sites ; HLA-D Antigens/*metabolism ; HLA-DR Antigens/immunology/*metabolism ; Histocompatibility Antigens Class II/*metabolism ; Humans ; Kinetics ; Molecular Sequence Data ; Peptides/immunology/*metabolism ; Recombinant Fusion Proteins/metabolism
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  • 48
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    Assembly of a ribonucleoprotein catalyst by tertiary structure capture (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-01-19
    Description: CBP2 is an RNA tertiary structure binding protein required for efficient splicing of a yeast mitochondrial group I intron. CBP2 must wait for folding of the two RNA domains that make up the catalytic core before it can bind. In a subsequent step, association of the 5' domain of the RNA is stabilized by additional interactions with the protein. Thus, CBP2 functions primarily to capture otherwise transient RNA tertiary structures. This simple one-RNA, one-protein system has revealed how the kinetic pathway of RNA folding can direct the assembly of a specific ribonucleoprotein complex. There are parallels to steps in the formation of a much more complex ribonucleoprotein, the 30S ribosomal subunit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weeks, K M -- Cech, T R -- New York, N.Y. -- Science. 1996 Jan 19;271(5247):345-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Colorado, Boulder 80309-0215, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8553068" target="_blank"〉PubMed〈/a〉
    Keywords: Catalysis ; Cytochrome b Group/genetics ; Fungal Proteins/*metabolism ; *Introns ; Kinetics ; Magnesium/pharmacology ; *Nucleic Acid Conformation ; RNA Splicing ; RNA, Catalytic/chemistry/*metabolism ; RNA, Fungal/chemistry/*metabolism ; Ribonucleoproteins/*metabolism ; *Saccharomyces cerevisiae Proteins
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  • 49
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    Catalysis of amide proton exchange by the molecular chaperones GroEL and SecB (1996)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1996-02-02
    Description: Hydrogen-deuterium exchange of 39 amide protons of Bacillus amyloliquefaciens ribonuclease (barnase) was analyzed by two-dimensional nuclear magnetic resonance in the presence of micromolar concentrations of the molecular chaperones GroEL and SecB. Both chaperones bound to native barnase under physiological conditions and catalyzed exchange of deeply buried amide protons with solvent. Such exchange required complete unfolding of barnase, which occurred in the complex with the chaperones. Subsequent collapse of unfolded barnase to the exchange-protected folding intermediate was markedly slowed in the presence of GroEL or SecB. Thus, both chaperones have the potential to correct misfolding in proteins by annealing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zahn, R -- Perrett, S -- Stenberg, G -- Fersht, A R -- New York, N.Y. -- Science. 1996 Feb 2;271(5249):642-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Cambridge, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8571125" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Diphosphate/pharmacology ; Amides ; Bacterial Proteins/*metabolism ; Catalysis ; Chaperonin 60/*metabolism ; Hydrogen-Ion Concentration ; Kinetics ; Magnetic Resonance Spectroscopy ; Molecular Chaperones/*metabolism ; Protein Conformation ; *Protein Folding ; Protein Structure, Secondary ; *Protons ; Ribonucleases/*chemistry/metabolism ; Temperature
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  • 50
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    In vitro development of primitive and definitive erythrocytes from different precursors (1996)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1996-05-03
    Description: During mouse embryogenesis the production of "primitive" erythrocytes (EryP) precedes the production of "definitive" erythrocytes (EryD) in parallel with the transition of the hematopoietic site from the yolk sac to the fetal liver. On a macrophage colony-stimulating factor-deficient stromal cell line OP9, mouse embryonic stem cells were shown to give rise to EryP and EryD sequentially with a time course similar to that seen in murine ontogeny. Studies of the different growth factor requirements and limiting dilution analysis of precursor frequencies indicate that most EryP and EryD probably developed from different precursors by way of distinct differentiation pathways.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nakano, T -- Kodama, H -- Honjo, T -- New York, N.Y. -- Science. 1996 May 3;272(5262):722-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medical Chemistry, Faculty of Medicine, Kyoto University, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8614833" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Differentiation ; Cell Division ; Cell Line ; Cell Lineage ; Cell Separation ; Cells, Cultured ; Coculture Techniques ; Erythroid Precursor Cells/*cytology ; *Erythropoiesis ; Erythropoietin/pharmacology ; Kinetics ; Mice ; Signal Transduction ; Stem Cell Factor/physiology
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    Thiyl radicals in ribonucleotide reductases (1996)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1996-01-26
    Description: The ribonucleoside triphosphate reductase (RTPR) from Lactobacillus leichmannii catalyzes adenosylcobalamin (AdoCbl)-dependent nucleotide reduction, as well as exchange of the 5' hydrogens of AdoCbl with solvent. A protein-based thiyl radical is proposed as an intermediate in both of these processes. In the presence of RTPR containing specifically deuterated cysteine residues, the electron paramagnetic resonance (EPR) spectrum of an intermediate in the exchange reaction and the reduction reaction, trapped by rapid freeze quench techniques, exhibits narrowed hyperfine features relative to the corresponding unlabeled RTPR. The spectrum was interpreted to represent a thiyl radical coupled to cob(II)alamin. Another proposed intermediate, 5'-deoxyadenosine, was detected by rapid acid quench techniques. Similarities in mechanism between RTPR and the Escherichia coli ribonucleotide reductase suggest that both enzymes require a thiyl radical for catalysis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Licht, S -- Gerfen, G J -- Stubbe, J -- GM 29595/GM/NIGMS NIH HHS/ -- RR00317/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1996 Jan 26;271(5248):477-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8560260" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Amino Acid Sequence ; Catalysis ; Cobamides/metabolism ; Deoxyadenosines/metabolism ; Electron Spin Resonance Spectroscopy ; *Free Radicals ; Kinetics ; Lactobacillus/enzymology ; Ligands ; Models, Chemical ; Molecular Sequence Data ; Oxidation-Reduction ; Ribonucleotide Reductases/chemistry/*metabolism ; Solvents ; Sulfhydryl Compounds/*metabolism ; Vitamin B 12/analogs & derivatives/metabolism
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    HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-03-15
    Description: A new mathematical model was used to analyze a detailed set of human immunodeficiency virus-type 1 (HIV-1) viral load data collected from five infected individuals after the administration of a potent inhibitor of HIV-1 protease. Productively infected cells were estimated to have, on average, a life-span of 2.2 days (half-life t 1/2 = 1.6 days), and plasma virions were estimated to have a mean life-span of 0.3 days (t 1/2 = 0.24 days). The estimated average total HIV-1 production was 10.3 x 10(9) virions per day, which is substantially greater than previous minimum estimates. The results also suggest that the minimum duration of the HIV-1 life cycle in vivo is 1.2 days on average, and that the average HIV-1 generation time--defined as the time from release of a virion until it infects another cell and causes the release of a new generation of viral particles--is 2.6 days. These findings on viral dynamics provide not only a kinetic picture of HIV-1 pathogenesis, but also theoretical principles to guide the development of treatment strategies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perelson, A S -- Neumann, A U -- Markowitz, M -- Leonard, J M -- Ho, D D -- AI27742/AI/NIAID NIH HHS/ -- N01 AI45218/AI/NIAID NIH HHS/ -- RR06555/RR/NCRR NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1996 Mar 15;271(5255):1582-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Theoretical Division, Los Alamos National Laboratory, NM 87545, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8599114" target="_blank"〉PubMed〈/a〉
    Keywords: Antiviral Agents/administration & dosage/therapeutic use ; CD4 Lymphocyte Count ; CD4-Positive T-Lymphocytes/*cytology/*virology ; Cell Survival ; HIV Infections/drug therapy/*virology ; HIV Protease Inhibitors/administration & dosage/therapeutic use ; HIV-1/drug effects/*physiology ; Half-Life ; Humans ; Kinetics ; Models, Biological ; RNA, Viral/blood ; Regression Analysis ; Ritonavir ; Thiazoles/administration & dosage/therapeutic use ; Valine/administration & dosage/analogs & derivatives/therapeutic use ; Viremia ; Virion/drug effects/*physiology ; Virus Replication
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    Direct measurement of coupling between dendritic spines and shafts (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-05-03
    Description: Characterization of the diffusional and electrotonic coupling of spines to the dendritic shaft is crucial to understanding neuronal integration and synaptic plasticity. Two-photon photobleaching and photorelease of fluorescein dextran were used to generate concentration gradients between spines and shafts in rat CA1 pyramidal neurons. Diffusional reequilibration was monitored with two-photon fluorescence imaging. The time course of reequilibration was exponential, with time constants in the range of 20 to 100 milliseconds, demonstrating chemical compartmentalization on such time scales. These values imply that electrical spine neck resistances are unlikely to exceed 150 megohms and more likely range from 4 to 50 megohms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Svoboda, K -- Tank, D W -- Denk, W -- New York, N.Y. -- Science. 1996 May 3;272(5262):716-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biological Computation Research Department, Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8614831" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Dendrites/metabolism/*physiology/ultrastructure ; Dextrans/metabolism ; Diffusion ; Electric Conductivity ; Electric Impedance ; Fluoresceins/metabolism ; Fluorescence ; In Vitro Techniques ; Kinetics ; Microscopy/methods ; Models, Neurological ; Neuronal Plasticity ; Pyramidal Cells/metabolism/*physiology/ultrastructure ; Rats
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    Cracking the neuronal code (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-11-03
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ferster, D -- Spruston, N -- New York, N.Y. -- Science. 1995 Nov 3;270(5237):756-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7481761" target="_blank"〉PubMed〈/a〉
    Keywords: Action Potentials ; Animals ; Auditory Cortex/cytology/physiology ; Brain/cytology/*physiology ; Electric Conductivity ; Hippocampus/cytology/physiology ; Kinetics ; *Models, Neurological ; Nerve Net/*physiology ; Neurons/*physiology ; Neurons, Afferent/physiology ; *Synaptic Transmission ; Visual Cortex/cytology/physiology
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    Inhibitor-enhanced electron transfer: copper cytochrome c as a redox-inert probe of ternary complexes (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-07-14
    Description: Copper-substituted cytochrome c (CuCc) has been used as a structurally faithful, redoxinert inhibitor to probe the mechanism of electron transfer (ET) between Cc molecules and cytochrome c peroxidase (CcP). This inhibitor enhances photoinduced ET quenching of the triplet excited state of a zinc-substituted protein (ZnCcP or ZnCc) by its iron(III) partner (Fe3+Cc or Fe3+CcP). These results show that CcP and Cc form a ternary complex in which one Cc molecule binds tightly at a surface domain of CcP having low ET reactivity, whereas the second Cc molecule binds weakly to the 1:1 complex at a second domain with markedly greater (approximately 10(3)) reactivity. These results also rule out the possibility that Cc bound at the second domain cooperatively enhances ET to Cc at the first domain. The multiphasic kinetics observed for the photoproduced ET intermediate do not reflect electron self-exchange between two Cc molecules within the ternary complex.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, J S -- Nocek, J M -- DeVan, M L -- Hoffman, B M -- HL13531/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1995 Jul 14;269(5221):204-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7618081" target="_blank"〉PubMed〈/a〉
    Keywords: Cytochrome c Group/chemistry/*metabolism ; Cytochrome-c Peroxidase/chemistry/*metabolism ; *Cytochromes c ; *Electron Transport ; Ferric Compounds/metabolism ; Ferrous Compounds/metabolism ; Hydrogen-Ion Concentration ; Kinetics ; Light ; Models, Chemical ; Oxidation-Reduction ; Zinc/metabolism
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    Measurement of lactose repressor-mediated loop formation and breakdown in single DNA molecules (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-01-20
    Description: In gene regulatory systems in which proteins bind to multiple sites on a DNA molecule, the characterization of chemical mechanisms and single-step reaction rates is difficult because many chemical species may exist simultaneously in a molecular ensemble. This problem was circumvented by detecting DNA looping by the lactose repressor protein of Escherichia coli in single DNA molecules. The looping was detected by monitoring the nanometer-scale Brownian motion of microscopic particles linked to the ends of individual DNA molecules. This allowed the determination of the rates of formation and breakdown of a protein-mediated DNA loop in vitro. The measurements reveal that mechanical strain stored in the loop does not substantially accelerate loop breakdown, and the measurements also show that subunit dissociation of tetrameric repressor is not the predominant loop breakdown pathway.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Finzi, L -- Gelles, J -- New York, N.Y. -- Science. 1995 Jan 20;267(5196):378-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Graduate Department of Biochemistry, Brandeis University, Waltham, MA 02254.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7824935" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Biotin ; DNA/chemistry/*metabolism ; Digoxigenin ; Isopropyl Thiogalactoside/pharmacology ; Kinetics ; Molecular Sequence Data ; *Nucleic Acid Conformation ; Repressor Proteins/*metabolism ; Thermodynamics
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    T cell receptor-MHC class I peptide interactions: affinity, kinetics, and specificity (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-04-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fisher, R J -- Fivash, M -- New York, N.Y. -- Science. 1995 Apr 7;268(5207):115-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7701331" target="_blank"〉PubMed〈/a〉
    Keywords: Histocompatibility Antigens Class I/*immunology ; Kinetics ; *Models, Immunological ; Protein Binding/immunology ; Receptors, Antigen, T-Cell/*immunology
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    Understanding C-H bond oxidations: H. and H- transfer in the oxidation of toluene by permanganate (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-09-29
    Description: The oxidation of toluene by permanganate has been studied as a model for the oxidation of C-H bonds by metal reagents, metalloenzymes, and metal oxide surfaces. In water, the reaction proceeds by hydride (H-) transfer from toluene to a permanganate oxygen, whereas in toluene solution, permanganate abstracts a hydrogen atom (H.). The ability of permanganate to abstract a hydrogen atom is rationalized on the basis of the strong O-H bond formed on H. addition to permanganate. This approach allows understanding and prediction of the rates of hydrogen atom transfer from substrates to metal active sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gardner, K A -- Mayer, J M -- New York, N.Y. -- Science. 1995 Sep 29;269(5232):1849-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Washington, Seattle 98195-1700, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7569922" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon/*chemistry ; Hydrogen/*chemistry ; Kinetics ; Oxidation-Reduction ; Potassium Permanganate/*chemistry ; Solvents ; Spectrophotometry, Ultraviolet ; Thermodynamics ; Toluene/*chemistry
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    A regulatory role for ARF6 in receptor-mediated endocytosis (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-02-24
    Description: Adenosine diphosphate-ribosylation factor 6 (ARF6), ARF6 mutants, and ARF1 were transiently expressed in Chinese hamster ovary cells, and the effects on receptor-mediated endocytosis were assessed. Overexpressed ARF6 localized to the cell periphery and led to a redistribution of transferrin receptors to the cell surface and a decrease in the rate of uptake of transferrin. Similar results were obtained when a mutant defective in guanosine triphosphate hydrolysis was expressed. Expression of a dominant negative mutant, ARF6(T27N), resulted in an intracellular distribution of transferrin receptors and an inhibition of transferrin recycling to the cell surface. In contrast, overexpression of ARF1 had little or no effect on these parameters of endocytosis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉D'Souza-Schorey, C -- Li, G -- Colombo, M I -- Stahl, P D -- New York, N.Y. -- Science. 1995 Feb 24;267(5201):1175-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7855600" target="_blank"〉PubMed〈/a〉
    Keywords: ADP-Ribosylation Factor 1 ; ADP-Ribosylation Factors ; Amino Acid Sequence ; Animals ; Base Sequence ; CHO Cells ; Cell Membrane/metabolism ; Cricetinae ; *Endocytosis ; GTP-Binding Proteins/analysis/genetics/*physiology ; Golgi Apparatus/metabolism/ultrastructure ; Kinetics ; Molecular Sequence Data ; Mutation ; Receptors, Transferrin/metabolism ; Transferrin/metabolism
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    Reactive immunization (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-12-15
    Description: For almost 200 years inert antigens have been used for initiating the process of immunization. A procedure is now described in which the antigen used is so highly reactive that a chemical reaction occurs in the antibody combining site during immunization. An organophosphorus diester hapten was used to illustrate this concept coined "reactive immunization." The organophosphonate recruited chemical potential from the immune response that resembled the way these compounds recruit the catalytic power of the serine hydrolases. During this recruitment, a large proportion of the isolated antibodies catalyzed the formation and cleavage of phosphonylated intermediates and subsequent ester hydrolysis. Reactive immunization can augment traditional immunization and enhance the scope of catalytic antibody chemistry. Among the compounds anticipated to be effective are those that contain appropriate reactive functionalities or those that are latently reactive, as in the mechanism-based inhibitors of enzymes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wirsching, P -- Ashley, J A -- Lo, C H -- Janda, K D -- Lerner, R A -- DA08590/DA/NIDA NIH HHS/ -- GM48351/GM/NIGMS NIH HHS/ -- P01 CA27489-16/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1995 Dec 15;270(5243):1775-82.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Scripps Research Institute, Department of Molecular Biology, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8525366" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Catalytic/*chemistry/immunology ; Antibodies, Monoclonal/chemistry/immunology ; Antigen-Antibody Reactions ; Antigens/*chemistry/immunology ; Binding Sites ; Catalysis ; Cattle ; Esters/chemistry/immunology ; Haptens/chemistry/immunology ; Immunization/*methods ; Kinetics ; Mice ; Organophosphonates/chemistry/*immunology ; Thermodynamics ; Tumor Cells, Cultured
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    Patterns of human growth (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-04-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heinrichs, C -- Munson, P J -- Counts, D R -- Cutler, G B Jr -- Baron, J -- New York, N.Y. -- Science. 1995 Apr 21;268(5209):442-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7716552" target="_blank"〉PubMed〈/a〉
    Keywords: Body Height ; Body Weight ; Cephalometry ; Female ; *Growth ; Humans ; Infant ; Kinetics ; Male ; Regression Analysis
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    Rapid adaptation of cardiac ryanodine receptors: modulation by Mg2+ and phosphorylation (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-03-31
    Description: Channel adaptation is a fundamental feature of sarcoplasmic reticulum calcium release channels (called ryanodine receptors, RyRs). It permits successive increases in the intracellular concentration of calcium (Ca2+) to repeatedly but transiently activate channels. Adaptation of RyRs in the absence of magnesium (Mg2+) and adenosine triphosphate is an extremely slow process (taking seconds). Photorelease of Ca2+ from nitrophenyl-EGTA, a photolabile Ca2+ chelator, demonstrated that RyR adaptation is rapid (milliseconds) in canine heart muscle when physiological Mg2+ concentrations are present. Phosphorylation of the RyR by protein kinase A increased the responsiveness of the channel to Ca2+ and accelerated the kinetics of adaptation. These properties of the RyR from heart may also be relevant to other cells in which multiple agonist-dependent triggering events regulate cellular functions.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242209/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242209/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Valdivia, H H -- Kaplan, J H -- Ellis-Davies, G C -- Lederer, W J -- HL25675/HL/NHLBI NIH HHS/ -- HL30315/HL/NHLBI NIH HHS/ -- HL36974/HL/NHLBI NIH HHS/ -- R01 GM053395/GM/NIGMS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1995 Mar 31;267(5206):1997-2000.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology, University of Maryland Medical School, Baltimore 21201, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7701323" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptation, Physiological ; Adenosine Triphosphate/metabolism/pharmacology ; Animals ; Calcium/*metabolism ; Calcium Channels/drug effects/*metabolism ; Cyclic AMP-Dependent Protein Kinases/metabolism ; Dogs ; Kinetics ; Lipid Bilayers ; Magnesium/*pharmacology ; Muscle Proteins/drug effects/*metabolism ; Myocardium/*metabolism ; Phosphorylation ; Ryanodine Receptor Calcium Release Channel
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    Hemoglobin allostery: resonance Raman spectroscopy of kinetic intermediates (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-09-29
    Description: The end states, R and T, of the allosteric transition in hemoglobin (Hb) are structurally well characterized, but there is little information on intermediate structures along the allosteric pathway. These intermediates were examined by means of time-resolved resonance Raman spectroscopy in the nanosecond-to-microsecond interval after HbCO photolysis. Complementary spectra of the heme group and of the tyrosine and tryptophan residues were recorded during laser excitation at 436 and 230 nanometers. These spectra reveal a sequence of interleaved tertiary and quaternary motions during the photocycle, motions involving the proximal and distal helices, and the alpha 1 beta 2 subunit interface. This sequence leads to a modified form of the T state, in which the alpha 1 beta 2 interface is deformed as a result of two carbon monoxide molecules binding to the same dimer within the tetramer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jayaraman, V -- Rodgers, K R -- Mukerji, I -- Spiro, T G -- GM 25158/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Sep 29;269(5232):1843-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Princeton University, NJ 08544, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7569921" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Carboxyhemoglobin/*chemistry ; Hemoglobins/*chemistry ; Histidine/chemistry ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Iron/chemistry ; Kinetics ; Ligands ; Photolysis ; Protein Conformation ; Protein Structure, Secondary ; Protein Structure, Tertiary ; *Spectrum Analysis, Raman
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    Cleavage of an amide bond by a ribozyme (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-01-13
    Description: A variant form of a group I ribozyme, optimized by in vitro evolution for its ability to catalyze magnesium-dependent phosphoester transfer reactions involving DNA substrates, also catalyzes the cleavage of an unactivated alkyl amide when that linkage is presented in the context of an oligodeoxynucleotide analog. Substrates containing an amide bond that joins either two DNA oligos, or a DNA oligo and a short peptide, are cleaved in a magnesium-dependent fashion to generate the expected products. The first-order rate constant, kcat, is 0.1 x 10(-5) min-1 to 1 x 10(-5) min-1 for the DNA-flanked substrates, which corresponds to a rate acceleration of more than 10(3) as compared with the uncatalyzed reaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dai, X -- De Mesmaeker, A -- Joyce, G F -- New York, N.Y. -- Science. 1995 Jan 13;267(5195):237-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Scripps Research Institute, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7809628" target="_blank"〉PubMed〈/a〉
    Keywords: Amides/*metabolism ; Animals ; Base Composition ; Base Sequence ; Kinetics ; Magnesium/metabolism ; Molecular Sequence Data ; Oligodeoxyribonucleotides/*metabolism ; Oligopeptides/metabolism ; RNA, Catalytic/*metabolism ; Tetrahymena/enzymology
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Direct evaluation of electronic coupling mediated by hydrogen bonds: implications for biological electron transfer (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-09-08
    Description: Three supramolecular bischromophoric systems featuring zinc(II) and iron(III) porphyrins have been synthesized to evaluate the relative magnitudes of electronic coupling provided by hydrogen, sigma, and pi bonds. Laser flash excitation generates the highly reducing singlet excited state of the (porphinato)zinc chromophore that can subsequently be electron transfer quenched by the (porphinato)iron(III) chloride moiety. Measurement of the photoinduced electron transfer rate constants enables a direct comparison of how well these three types of chemical interactions facilitate electron tunneling. In contrast to generally accepted theory, electronic coupling modulated by a hydrogen-bond interface is greater than that provided by an analogous interface composed entirely of carbon-carbon sigma bonds. These results bear considerably on the analysis of through-protein electron transfer rate data as well as on the power of theory to predict the path traversed by the tunneling electron in a biological matrix; moreover, they underscore the cardinal role played by hydrogen bonds in biological electron transfer processes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉de Rege, P J -- Williams, S A -- Therien, M J -- New York, N.Y. -- Science. 1995 Sep 8;269(5229):1409-13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Pennsylvania, Philadelphia 19104-6323, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7660123" target="_blank"〉PubMed〈/a〉
    Keywords: *Electron Transport ; Ferric Compounds/chemistry/*metabolism ; *Hydrogen Bonding ; Kinetics ; Metalloporphyrins/chemistry/*metabolism ; Oxidation-Reduction ; Porphyrins/metabolism ; Thermodynamics ; Zinc/chemistry/*metabolism
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    Protein reaction kinetics in a room-temperature glass (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-08-18
    Description: Protein reaction kinetics in aqueous solution at room temperature are often simplified by the thermal averaging of conformational substates. These substates exhibit widely varying reaction rates that are usually exposed by trapping in a glass at low temperature. Here, it is shown that the solvent viscosity, rather than the low temperature, is primarily responsible for the trapping. This was demonstrated by placement of myoglobin in a glass at room temperature and subsequent observation of inhomogeneous reaction kinetics. The high solvent viscosity slowed the rate of crossing the energy barriers that separated the substates and also suppressed any change in the average protein conformation after ligand dissociation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hagen, S J -- Hofrichter, J -- Eaton, W A -- New York, N.Y. -- Science. 1995 Aug 18;269(5226):959-62.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Chemical Physics, National Institutes of Health, Bethesda, MD 20892-0520, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7638618" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon Monoxide/*chemistry/metabolism ; Glass ; Kinetics ; Ligands ; Myoglobin/*chemistry/metabolism ; Photolysis ; Protein Conformation ; Spectrum Analysis ; Temperature ; Trehalose ; Viscosity
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    Asymmetrical interaction of GroEL and GroES in the ATPase cycle of assisted protein folding (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-08-11
    Description: The chaperonins GroEL and GroES of Escherichia coli facilitate protein folding in an adenosine triphosphate (ATP)-dependent reaction cycle. The kinetic parameters for the formation and dissociation of GroEL-GroES complexes were analyzed by surface plasmon resonance. Association of GroES and subsequent ATP hydrolysis in the interacting GroEL toroid resulted in the formation of a stable GroEL:ADP:GroES complex. The complex dissociated as a result of ATP hydrolysis in the opposite GroEL toroid, without formation of a symmetrical GroEL:(GroES)2 intermediate. Dissociation was accelerated by the addition of unfolded polypeptide. Thus, the functional chaperonin unit is an asymmetrical GroEL:GroES complex, and substrate protein plays an active role in modulating the chaperonin reaction cycle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hayer-Hartl, M K -- Martin, J -- Hartl, F U -- GM 50908/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Aug 11;269(5225):836-41.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7638601" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Diphosphate/metabolism ; Adenosine Triphosphatases/*metabolism ; Adenosine Triphosphate/metabolism ; Chaperonin 10/chemistry/*metabolism ; Chaperonin 60/chemistry/*metabolism ; Endopeptidase K ; Hydrogen-Ion Concentration ; Hydrolysis ; Kinetics ; Magnesium/pharmacology ; *Protein Folding ; Serine Endopeptidases/metabolism
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    Mechanism of inhibition of HIV-1 reverse transcriptase by nonnucleoside inhibitors (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-02-17
    Description: The mechanism of inhibition of HIV-1 reverse transcriptase by three nonnucleoside inhibitors is described. Nevirapine, O-TIBO, and CI-TIBO each bind to a hydrophobic pocket in the enzyme-DNA complex close to the active site catalytic residues. Pre-steady-state kinetic analysis was used to establish the mechanism of inhibition by these noncompetitive inhibitors. Analysis of the pre-steady-state burst of DNA polymerization indicated that inhibitors blocked the chemical reaction, but did not interfere with nucleotide binding or the nucleotide-induced conformational change. Rather, in the presence of saturating concentrations of the inhibitors, the nucleoside triphosphate bound tightly (Kd, 100 nM), but nonproductively. The data suggest that an inhibitor combining the functionalities of a nonnucleoside inhibitor and a nucleotide analog could bind very tightly and specifically to reverse transcriptase and could be effective in the treatment of AIDS.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Spence, R A -- Kati, W M -- Anderson, K S -- Johnson, K A -- GM44613/GM/NIGMS NIH HHS/ -- GM49551/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Feb 17;267(5200):988-93.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park 16802.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7532321" target="_blank"〉PubMed〈/a〉
    Keywords: Antiviral Agents/metabolism/*pharmacology ; Benzodiazepines/metabolism/*pharmacology ; Binding Sites ; DNA/metabolism ; Deoxyadenine Nucleotides/metabolism ; HIV Reverse Transcriptase ; HIV-1/drug effects/*enzymology ; Imidazoles/metabolism/*pharmacology ; Kinetics ; Magnesium/metabolism/pharmacology ; Nevirapine ; Protein Conformation ; Pyridines/metabolism/*pharmacology ; RNA-Directed DNA Polymerase/chemistry/metabolism ; *Reverse Transcriptase Inhibitors
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    A proficient enzyme (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-01-06
    Description: Orotic acid is decarboxylated with a half-time (t1/2) of 78 million years in neutral aqueous solution at room temperature, as indicated by reactions in quartz tubes at elevated temperatures. Spontaneous hydrolysis of phosphodiester bonds, such as those present in the backbone of DNA, proceeds even more slowly at high temperatures, but the heat of activation is less positive, so that dimethyl phosphate is hydrolyzed with a t1/2 of 130,000 years in neutral solution at room temperature. These values extend the known range of spontaneous rate constants for reactions that are also susceptible to catalysis by enzymes to more than 14 orders of magnitude. Values of the second-order rate constant kcat/Km for the corresponding enzyme reactions are confined to a range of only 600-fold, in contrast. Orotidine 5'-phosphate decarboxylase, an extremely proficient enzyme, enhances the rate of reaction by a factor of 10(17) and is estimated to bind the altered substrate in the transition state with a dissociation constant of less than 5 x 10(-24) M.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Radzicka, A -- Wolfenden, R -- GM-18325/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Jan 6;267(5194):90-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7809611" target="_blank"〉PubMed〈/a〉
    Keywords: Catalysis ; Decarboxylation ; Hydrogen-Ion Concentration ; Hydrolysis ; Kinetics ; Micrococcal Nuclease/*metabolism ; Organophosphorus Compounds/chemistry ; Orotic Acid/analogs & derivatives/chemistry ; Orotidine-5'-Phosphate Decarboxylase/*metabolism ; Temperature ; Thermodynamics
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    HIV population dynamics in vivo: implications for genetic variation, pathogenesis, and therapy (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-01-27
    Description: Several recent reports indicate that the long, clinically latent phase that characterizes human immunodeficiency virus (HIV) infection of humans is not a period of viral inactivity, but an active process in which cells are being infected and dying at a high rate and in large numbers. These results lead to a simple steady-state model in which infection, cell death, and cell replacement are in balance, and imply that the unique feature of HIV is the extraordinarily large number of replication cycles that occur during infection of a single individual. This turnover drives both the pathogenic process and (even more than mutation rate) the development of genetic variation. This variation includes the inevitable and, in principle, predictable accumulation of mutations such as those conferring resistance to antiviral drugs whose presence before therapy must be considered in the design of therapeutic strategies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Coffin, J M -- R35 CA 44385/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1995 Jan 27;267(5197):483-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7824947" target="_blank"〉PubMed〈/a〉
    Keywords: Acquired Immunodeficiency Syndrome/drug therapy/immunology/*virology ; Antiviral Agents/pharmacology/therapeutic use ; CD4 Lymphocyte Count ; CD4-Positive T-Lymphocytes/immunology/*virology ; Cell Death ; DNA, Viral/blood ; Drug Resistance, Microbial ; Genetic Variation ; HIV/drug effects/genetics/*physiology ; HIV Infections/drug therapy/immunology/*virology ; Humans ; Kinetics ; Mutation ; Proviruses/genetics/physiology ; RNA, Viral/blood ; Viremia/virology ; Virus Replication
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    Photovoltage of rods and cones in the macaque retina (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-05-19
    Description: The kinetics, gain, and reliability of light responses of rod and cone photoreceptors are important determinants of overall visual sensitivity. In voltage recordings from photoreceptors in an intact primate retina, rods were found to be functionally isolated from each other, unlike the tightly coupled rods of cold-blooded vertebrates. Cones were observed to receive excitatory input from rods, which indicates that the cone pathway also processes rod signals. This input might be expected to degrade the spatial resolution of mesopic vision.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schneeweis, D M -- Schnapf, J L -- F32-EY06399/EY/NEI NIH HHS/ -- R01-EY07642/EY/NEI NIH HHS/ -- New York, N.Y. -- Science. 1995 May 19;268(5213):1053-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Ophthalmology, University of California, San Francisco 94143-0730, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7754386" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; In Vitro Techniques ; Kinetics ; *Light ; Macaca fascicularis ; Membrane Potentials/radiation effects ; Photic Stimulation/methods ; Retinal Cone Photoreceptor Cells/*physiology/radiation effects ; Retinal Rod Photoreceptor Cells/*physiology/radiation effects
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    Molecular identification of an IgE-dependent histamine-releasing factor (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-08-04
    Description: An immunoglobulin E (IgE)-dependent histamine-releasing factor (HRF) produced by lymphocytes of atopic children and present in biological fluids of allergic patients has been identified and purified. Amino-terminal sequencing revealed extensive homology to a mouse protein, p21, and its human homolog, p23. Both recombinant proteins caused histamine release from the human basophils of a subpopulation of donors, and this release was dependent on IgE. Polyclonal antibodies recognized and removed the biological activity of recombinant and native HRF. HRF identifies a heterogeneity of IgE and is believed to play a prominent role in chronic allergic disease processes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉MacDonald, S M -- Rafnar, T -- Langdon, J -- Lichtenstein, L M -- AI 07290/AI/NIAID NIH HHS/ -- AI 32651/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 1995 Aug 4;269(5224):688-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Medicine, Johns Hopkins University School of Medicine, Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7542803" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antibodies/immunology ; Base Sequence ; Basophils/immunology ; *Biomarkers, Tumor ; Cell Line ; Cloning, Molecular ; *Histamine Release ; Humans ; Immunoglobulin E/*immunology ; Kinetics ; Lymphokines/*chemistry/immunology/isolation & purification/pharmacology ; Macrophages/metabolism ; Mice ; Molecular Sequence Data ; Recombinant Fusion Proteins/pharmacology ; Sequence Homology, Amino Acid
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    Role of the ubiquitin-proteasome pathway in regulating abundance of the cyclin-dependent kinase inhibitor p27 (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-08-04
    Description: The p27 mammalian cell cycle protein is an inhibitor of cyclin-dependent kinases. Both in vivo and in vitro, p27 was found to be degraded by the ubiquitin-proteasome pathway. The human ubiquitin-conjugating enzymes Ubc2 and Ubc3 were specifically involved in the ubiquitination of p27. Compared with proliferating cells, quiescent cells exhibited a smaller amount of p27 ubiquitinating activity, which accounted for the marked increase of p27 half-life measured in these cells. Thus, the abundance of p27 in cells is regulated by degradation. The specific proteolysis of p27 may represent a mechanism for regulating the activity of cyclin-dependent kinases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pagano, M -- Tam, S W -- Theodoras, A M -- Beer-Romero, P -- Del Sal, G -- Chau, V -- Yew, P R -- Draetta, G F -- Rolfe, M -- New York, N.Y. -- Science. 1995 Aug 4;269(5224):682-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Mitotix Inc., Cambridge, MA 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7624798" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Anaphase-Promoting Complex-Cyclosome ; Animals ; *Cell Cycle Proteins ; Cell Line ; Cyclin-Dependent Kinase Inhibitor p27 ; Cyclin-Dependent Kinases/*antagonists & inhibitors ; Cysteine Endopeptidases/*metabolism ; Electroporation ; Enzyme Inhibitors/metabolism ; Humans ; Kinetics ; Leupeptins/pharmacology ; Ligases/metabolism ; Mice ; Microtubule-Associated Proteins/*metabolism ; Multienzyme Complexes/*metabolism ; Proteasome Endopeptidase Complex ; Rabbits ; Recombinant Proteins/metabolism ; Succinates/pharmacology ; Tumor Cells, Cultured ; *Tumor Suppressor Proteins ; Ubiquitin-Conjugating Enzymes ; *Ubiquitin-Protein Ligase Complexes ; Ubiquitin-Protein Ligases ; Ubiquitins/*metabolism
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    Mutagenesis and Laue structures of enzyme intermediates: isocitrate dehydrogenase (1995)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1995-06-02
    Description: Site-directed mutagenesis and Laue diffraction data to 2.5 A resolution were used to solve the structures of two sequential intermediates formed during the catalytic actions of isocitrate dehydrogenase. Both intermediates are distinct from the enzyme-substrate and enzyme-product complexes. Mutation of key catalytic residues changed the rate determining steps so that protein and substrate intermediates within the overall reaction pathway could be visualized.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bolduc, J M -- Dyer, D H -- Scott, W G -- Singer, P -- Sweet, R M -- Koshland, D E Jr -- Stoddard, B L -- GM49857/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1995 Jun 2;268(5215):1312-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Fred Hutchinson Cancer Research Center, Program in Structural Biology, Seattle, WA 98104, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7761851" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Catalysis ; Computer Graphics ; *Crystallography, X-Ray ; Isocitrate Dehydrogenase/*chemistry/genetics/metabolism ; Isocitrates/metabolism ; Kinetics ; *Mutagenesis, Site-Directed ; NADP/metabolism ; Protein Conformation
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    Expanding the scope of RNA catalysis (1994)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1994-06-24
    Description: The basic notions of transition state theory have been exploited in the past to generate highly selective catalysts from the vast library of antibody molecules in the immune system. These same ideas were used to isolate an RNA molecule, from a large library of RNAs, that catalyzes the isomerization of a bridged biphenyl. The RNA-catalyzed reaction displays Michaelis-Menten kinetics with a catalytic rate constant (kcat) of 2.8 x 10(-5) per minute and a Michaelis constant (Km) of 542 microM; the reaction is competitively inhibited by the planar transition state analog with an inhibition constant (Ki) value of approximately 7 microM. This approach may provide a general strategy for expanding the scope of RNA catalysis beyond those reactions in which the substrates are nucleic acids or nucleic acid derivatives.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Prudent, J R -- Uno, T -- Schultz, P G -- GM08352A/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jun 24;264(5167):1924-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8009223" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Biphenyl Compounds/chemistry/metabolism ; Catalysis ; Kinetics ; Molecular Sequence Data ; Nucleic Acid Conformation ; Nucleic Acid Denaturation ; Polymerase Chain Reaction ; RNA, Catalytic/chemistry/*metabolism ; Stereoisomerism ; Temperature
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    A specific inhibitor of the epidermal growth factor receptor tyrosine kinase (1994)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1994-08-19
    Description: A small molecule called PD 153035 inhibited the epidermal growth factor (EGF) receptor tyrosine kinase with a 5-pM inhibition constant. The inhibitor was specific for the EGF receptor tyrosine kinase and inhibited other purified tyrosine kinases only at micromolar or higher concentrations. PD 153035 rapidly suppressed autophosphorylation of the EGF receptor at low nanomolar concentrations in fibroblasts or in human epidermoid carcinoma cells and selectively blocked EGF-mediated cellular processes including mitogenesis, early gene expression, and oncogenic transformation. PD 153035 demonstrates an increase in potency over that of other tyrosine kinase inhibitors of four to five orders of magnitude for inhibition of isolated EGF receptor tyrosine kinase and three to four orders of magnitude for inhibition of cellular phosphorylation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fry, D W -- Kraker, A J -- McMichael, A -- Ambroso, L A -- Nelson, J M -- Leopold, W R -- Connors, R W -- Bridges, A J -- New York, N.Y. -- Science. 1994 Aug 19;265(5175):1093-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, MI 48105.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8066447" target="_blank"〉PubMed〈/a〉
    Keywords: 3T3 Cells ; Animals ; Cell Transformation, Neoplastic/drug effects ; Epidermal Growth Factor/pharmacology ; Fibroblast Growth Factor 2/pharmacology ; Gene Expression/drug effects ; Humans ; Kinetics ; Mice ; Mitosis/drug effects ; Phosphorylation/drug effects ; Platelet-Derived Growth Factor/pharmacology ; Protein-Tyrosine Kinases/antagonists & inhibitors ; Quinazolines/*antagonists & inhibitors ; Receptor, Epidermal Growth Factor/*antagonists & inhibitors ; Tumor Cells, Cultured ; Tyrosine/metabolism
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    Two identical noninteracting sites in an ion channel revealed by proton transfer (1994)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1994-09-23
    Description: The functional consequences of single proton transfers occurring in the pore of a cyclic nucleotide-gated channel were observed with patch recording techniques. These results led to three conclusions about the chemical nature of ion binding sites in the conduction pathway: The channel contains two identical titratable sites, even though there are more than two (probably four) identical subunits; the sites are formed by glutamate residues that have a pKa (where K(a) is the acid constant) of 7.6; and protonation of one site does not perturb the pKa of the other. These properties point to an unusual arrangement of carboxyl side-chain residues in the pore of a cation channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Root, M J -- MacKinnon, R -- 5 T32 GM083113/GM/NIGMS NIH HHS/ -- GM47400/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 23;265(5180):1852-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Harvard Medical School, Boston, MA 02115.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7522344" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Binding Sites ; Calcium Channels/metabolism ; Catfishes ; Electric Conductivity ; Hydrogen-Ion Concentration ; Ion Channel Gating ; Ion Channels/chemistry/genetics/*metabolism ; Kinetics ; Molecular Sequence Data ; Mutation ; *Protons ; Sodium/metabolism ; Xenopus
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    Stern-volmer in reverse: 2:1 stoichiometry of the cytochrome c-cytochrome c peroxidase electron-transfer complex (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-09-16
    Description: A reverse protocol for measurements of molecular binding and reactivity by excited-state quenching has been developed in which the quencher, held at a fixed concentration, is titrated by a photoexcitable probe molecule whose decay is monitored. The binding stoichiometries, affinities, and reactivities of the electron-transfer complexes between cytochrome c (Cc) and cytochrome c peroxidase (CcP) were determined over a wide range of ionic strengths (4.5 to 118 millimolar) by the study of photoinduced electron-transfer quenching of the triplet excited state of zinc-substituted Cc (ZnCc) by Fe3+CcP. The 2:1 stoichiometry seen for the binding of Cc to CcP at low ionic strength persists at the physiologically relevant ionic strengths and likely has functional significance. Analysis of the stoichiometric binding and rate constants confirms that one surface domain of CcP binds Cc with a high affinity but with poor electron-transfer quenching of triplet-state ZnCc, whereas a second binds weakly but with a high rate of electron-transfer quenching.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, J S -- Hoffman, B M -- HL13531/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 16;265(5179):1693-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Northwestern University, Evanston, IL 60208-3113.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8085152" target="_blank"〉PubMed〈/a〉
    Keywords: Cytochrome c Group/chemistry/*metabolism ; Cytochrome-c Peroxidase/chemistry/*metabolism ; Electron Transport ; Ferric Compounds ; Kinetics ; Osmolar Concentration ; Oxidation-Reduction ; Zinc
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    Visualization of quantal synaptic transmission by dendritic calcium imaging (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-01-28
    Description: As changes in synaptic strength are thought to be critical for learning and memory, it would be useful to monitor the activity of individual identified synapses on mammalian central neurons. Calcium imaging of cortical neurons grown in primary culture was used to visualize the activation of individual postsynaptic elements by miniature excitatory synaptic currents elicited by spontaneous quantal release. This approach revealed that the probability of spontaneous activity differed among synapses on the same dendrite. Furthermore, synapses that undergo changes in activity induced by glutamate or phorbol ester treatment were identified.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, T H -- Baraban, J M -- Wier, W G -- Blatter, L A -- New York, N.Y. -- Science. 1994 Jan 28;263(5146):529-32.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7904774" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/*metabolism ; Cells, Cultured ; Cerebral Cortex ; Dendrites/*metabolism ; Glutamates/pharmacology ; Glutamic Acid ; Kinetics ; Microelectrodes ; Neuronal Plasticity ; Neurons/*physiology ; Phorbol Esters/pharmacology ; Rats ; Receptors, N-Methyl-D-Aspartate/physiology ; Synapses/*physiology ; *Synaptic Transmission ; Tetrodotoxin/pharmacology
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  • 80
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    Control of kinetic properties of AMPA receptor channels by nuclear RNA editing (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-12-09
    Description: AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor channels mediate the fast component of excitatory postsynaptic currents in the central nervous system. Site-selective nuclear RNA editing controls the calcium permeability of these channels, and RNA editing at a second site is shown here to affect the kinetic aspects of these channels in rat brain. In three of the four AMPA receptor subunits (GluR-B, -C, and -D), intronic elements determine a codon switch (AGA, arginine, to GGA, glycine) in the primary transcripts in a position termed the R/G site, which immediately precedes the alternatively spliced modules "flip" and "flop." The extent of editing at this site progresses with brain development in a manner specific for subunit and splice form, and edited channels possess faster recovery rates from desensitization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lomeli, H -- Mosbacher, J -- Melcher, T -- Hoger, T -- Geiger, J R -- Kuner, T -- Monyer, H -- Higuchi, M -- Bach, A -- Seeburg, P H -- New York, N.Y. -- Science. 1994 Dec 9;266(5191):1709-13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Neuroendocrinology, University of Heidelberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7992055" target="_blank"〉PubMed〈/a〉
    Keywords: Alternative Splicing ; Amino Acid Sequence ; Animals ; Base Sequence ; Brain/embryology/*metabolism ; Cell Nucleus/metabolism ; Exons ; Glutamic Acid/pharmacology ; Glycine/genetics ; Introns ; Kinetics ; Membrane Potentials ; Molecular Sequence Data ; Oocytes ; PC12 Cells ; Patch-Clamp Techniques ; *RNA Editing ; Rats ; Rats, Wistar ; Receptors, AMPA/*genetics/*metabolism ; Recombinant Proteins/metabolism ; Xenopus
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  • 81
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    Kinetics of molecular chaperone action (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-02-18
    Description: Molecular chaperones of the Hsp70 type transiently sequester unfolded segments of proteins and promote their correct folding. Target peptides were labeled with an environmentally sensitive fluorophore so that their binding to the molecular chaperone DnaK of Escherichia coli could be followed in real time. The two-step process was characterized by relaxation times of 27 seconds and 200 seconds with 2 microM DnaK and 0.1 microM ligand at 25 degrees C. In the presence of adenosine triphosphate, the formation of the complex was greatly accelerated and appeared to be a single-exponential process with a relaxation time of 0.4 second. The binding-release cycle of DnaK thus occurs in the time range of polypeptide chain elongation and folding and is too fast to be stoichiometrically coupled to the adenosine triphosphatase activity of the chaperone (turnover number, 0.13 per minute at 30 degrees C).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmid, D -- Baici, A -- Gehring, H -- Christen, P -- New York, N.Y. -- Science. 1994 Feb 18;263(5149):971-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biochemisches Institut, Universitat Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8310296" target="_blank"〉PubMed〈/a〉
    Keywords: 2-Naphthylamine/analogs & derivatives ; Adenosine Triphosphatases/metabolism ; Adenosine Triphosphate/analogs & derivatives/pharmacology ; Amino Acid Sequence ; Aspartate Aminotransferases/metabolism ; Bacterial Proteins/*metabolism ; Binding Sites ; Enzyme Precursors/metabolism ; *Escherichia coli Proteins ; Fluorescent Dyes ; *HSP70 Heat-Shock Proteins ; Heat-Shock Proteins/*metabolism ; Kinetics ; Molecular Sequence Data ; Peptide Fragments/*metabolism
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  • 82
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    Stimulation of RNA polymerase II elongation by chromosomal protein HMG-14 (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-08-05
    Description: The high-mobility group protein 14 (HMG-14) is a non-histone chromosomal protein that is preferentially associated with transcriptionally active chromatin. To assess the effect of HMG-14 on transcription by RNA polymerase II, in vivo-assembled chromatin with elevated amounts of HMG-14 was obtained. Here it is shown that HMG-14 enhanced transcription on chromatin templates but not on DNA templates. This protein stimulated the rate of elongation by RNA polymerase II but not the level of initiation of transcription. These findings suggest that the association of HMG-14 with nucleosomes is part of the cellular process involved in the generation of transcriptionally active chromatin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ding, H F -- Rimsky, S -- Batson, S C -- Bustin, M -- Hansen, U -- GM-36667/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 5;265(5173):796-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Molecular Genetics, Dana-Farber Cancer Institute, Boston, MA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8047885" target="_blank"〉PubMed〈/a〉
    Keywords: Chromatin/metabolism ; HeLa Cells ; High Mobility Group Proteins/*physiology ; Humans ; Kinetics ; RNA Polymerase II/*metabolism ; Simian virus 40/genetics ; Templates, Genetic ; Transcription, Genetic/*physiology
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  • 83
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    Blockage of NF-kappa B signaling by selective ablation of an mRNA target by 2-5A antisense chimeras (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-08-05
    Description: Activation of 2-5A-dependent ribonuclease by 5'-phosphorylated, 2',5'-linked oligoadenylates, known as 2-5A, is one pathway of interferon action. Unaided uptake into HeLa cells of 2-5A linked to an antisense oligonucleotide resulted in the selective ablation of messenger RNA for the double-stranded RNA (dsRNA)-dependent protein kinase PKR. Similarly, purified, recombinant human 2-5A-dependent ribonuclease was induced to selectively cleave PKR messenger RNA. Cells depleted of PKR activity were unresponsive to activation of nuclear factor-kappa B (NF-kappa B) by the dsRNA poly(I):poly(C), which provides direct evidence that PKR is a transducer for the dsRNA signaling of NF-kappa B.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maran, A -- Maitra, R K -- Kumar, A -- Dong, B -- Xiao, W -- Li, G -- Williams, B R -- Torrence, P F -- Silverman, R H -- AI 28253/AI/NIAID NIH HHS/ -- AI 34039-02/AI/NIAID NIH HHS/ -- CA 44059/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 5;265(5173):789-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cancer Biology, Cleveland Clinic Foundation, OH 44195.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7914032" target="_blank"〉PubMed〈/a〉
    Keywords: Adenine Nucleotides/chemical synthesis/*pharmacology ; Base Sequence ; Endoribonucleases/metabolism ; Enzyme Activation ; HeLa Cells ; Humans ; Kinetics ; Molecular Sequence Data ; NF-kappa B/*antagonists & inhibitors ; Oligonucleotides, Antisense/chemical synthesis/*pharmacology ; Oligoribonucleotides/chemical synthesis/*pharmacology ; Protein-Serine-Threonine Kinases/*genetics ; RNA, Messenger/drug effects ; Signal Transduction/*drug effects ; eIF-2 Kinase
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  • 84
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    Dynamics of the chaperonin ATPase cycle: implications for facilitated protein folding (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-07-29
    Description: The Escherichia coli chaperonins GroEL and GroES facilitate protein folding in an adenosine triphosphate (ATP)-dependent manner. After a single cycle of ATP hydrolysis by the adenosine triphosphatase (ATPase) activity of GroEL, the bi-toroidal GroEL formed a stable asymmetric ternary complex with GroES and nucleotide (bulletlike structures). With each subsequent turnover, ATP was hydrolyzed by one ring of GroEL in a quantized manner, completely releasing the adenosine diphosphate and GroES that were tightly bound to the other ring as a result of the previous turnover. The catalytic cycle involved formation of a symmetric complex (football-like structures) as an intermediate that accumulated before the rate-determining hydrolytic step. After one to two cycles, most of the substrate protein dissociated still in a nonnative state, which is consistent with intermolecular transfer of the substrate protein between toroids of high and low affinity. A unifying model for chaperonin-facilitated protein folding based on successive rounds of binding and release, and partitioning between committed and kinetically trapped intermediates, is proposed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Todd, M J -- Viitanen, P V -- Lorimer, G H -- New York, N.Y. -- Science. 1994 Jul 29;265(5172):659-66.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉E. I. DuPont de Nemours and Company, Central Research and Development Department, Wilmington, DE 19880.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7913555" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/*metabolism ; Bacterial Proteins/*metabolism ; Binding Sites ; Chaperonin 10 ; Chaperonin 60 ; Heat-Shock Proteins/*metabolism ; Kinetics ; Models, Chemical ; *Protein Folding ; Ribulose-Bisphosphate Carboxylase/metabolism
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  • 85
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    Rapid induction of Alzheimer A beta amyloid formation by zinc (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-09-02
    Description: A beta 1-40, a major component of Alzheimer's disease cerebral amyloid, is present in the cerebrospinal fluid and remains relatively soluble at high concentrations (less than or equal to 3.7 mM). Thus, physiological factors which induce A beta amyloid formation could provide clues to the pathogenesis of the disease. It has been shown that human A beta specifically and saturably binds zinc. Here, concentrations of zinc above 300 nM rapidly destabilized human A beta 1-40 solutions, inducing tinctorial amyloid formation. However, rat A beta 1-40 binds zinc less avidly and is immune to these effects, perhaps explaining the scarcity with which these animals form cerebral A beta amyloid. These data suggest a role for cerebral zinc metabolism in the neuropathogenesis of Alzheimer's disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bush, A I -- Pettingell, W H -- Multhaup, G -- d Paradis, M -- Vonsattel, J P -- Gusella, J F -- Beyreuther, K -- Masters, C L -- Tanzi, R E -- R01 AG11899-01/AG/NIA NIH HHS/ -- R01 NS30428-03/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 2;265(5177):1464-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Genetics and Aging, Massachusetts General Hospital, Boston.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8073293" target="_blank"〉PubMed〈/a〉
    Keywords: Alzheimer Disease/etiology/*metabolism ; Amyloid beta-Peptides/chemistry/*metabolism ; Animals ; Brain/metabolism ; Edetic Acid/pharmacology ; Humans ; Kinetics ; Mice ; Peptide Fragments/chemistry/*metabolism ; Rats ; Solubility ; Zinc/*metabolism/pharmacology
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  • 86
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    Peptide synthesis catalyzed by an antibody containing a binding site for variable amino acids (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-07-08
    Description: Monoclonal antibodies, induced with a phosphonate diester hapten, catalyzed the coupling of p-nitrophenyl esters of N-acetyl valine, leucine, and phenylalanine with tryptophan amide to form the corresponding dipeptides. All possible stereoisomeric combinations of the ester and amide substrates were coupled at comparable rates. The antibodies did not catalyze the hydrolysis of the dipeptide product nor hydrolysis or racemization of the activated esters. The yields of the dipeptides ranged from 44 to 94 percent. The antibodies were capable of multiple turnovers at rates that exceeded the rate of spontaneous ester hydrolysis. This achievement suggests routes toward creating a small number of antibody catalysts for polypeptide syntheses.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hirschmann, R -- Smith, A B 3rd -- Taylor, C M -- Benkovic, P A -- Taylor, S D -- Yager, K M -- Sprengeler, P A -- Benkovic, S J -- GM-45611/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jul 8;265(5169):234-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Pennsylvania, Philadelphia 19104.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8023141" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Catalytic/*metabolism ; Antibodies, Monoclonal/*metabolism ; Binding Sites, Antibody ; Dipeptides/*biosynthesis ; Esters ; Haptens ; Kinetics ; Leucine/analogs & derivatives/metabolism ; Molecular Conformation ; Phenylalanine/analogs & derivatives/metabolism ; Stereoisomerism ; Tryptophan/analogs & derivatives/metabolism ; Valine/analogs & derivatives/metabolism
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  • 87
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    DNA repair rates mapped along the human PGK1 gene at nucleotide resolution (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-03-11
    Description: The repair of cyclobutane pyrimidine dimers (CPDs), DNA lesions induced by ultraviolet light, was studied at nucleotide resolution. Human fibroblasts were irradiated with ultraviolet light and allowed to repair. The DNA was enzymatically cleaved at the CPDs, and the induced breaks along the promoter and exon 1 of the PGK1 gene were mapped by ligation-mediated polymerase chain reaction. Repair rates within the nontranscribed strand varied as much as 15-fold, depending on nucleotide position. Preferential repair of the transcribed strand began just downstream of the transcription start site but was most pronounced beginning at nucleotide +140 in exon 1. The promoter contained two slowly repaired regions that coincided with two transcription factor binding sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gao, S -- Drouin, R -- Holmquist, G P -- CA54773/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Mar 11;263(5152):1438-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Beckman Research Institute of the City of Hope, Department of Biology, Duarte, CA 91010.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8128226" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Cells, Cultured ; *DNA Repair ; Exons ; *Genes ; HeLa Cells ; Humans ; Kinetics ; Phosphoglycerate Kinase/*genetics ; Promoter Regions, Genetic ; Pyrimidine Dimers/*metabolism ; Skin/metabolism/*radiation effects ; Transcription Factors/metabolism ; Transcription, Genetic ; Ultraviolet Rays
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  • 88
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    T cell receptor-MHC class I peptide interactions: affinity, kinetics, and specificity (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-08-12
    Description: The critical discriminatory event in the activation of T lymphocytes bearing alpha beta T cell receptors (TCRs) is their interaction with a molecular complex consisting of a peptide bound to a major histocompatibility complex (MHC)-encoded class I or class II molecule on the surface of an antigen-presenting cell. The kinetics of binding were measured of a purified TCR to molecular complexes of a purified soluble analog of the murine MHC class I molecule H-2Ld (sH-2Ld) and a synthetic octamer peptide p2CL in a direct, real-time assay based on surface plasmon resonance. The kinetic dissociation rate of the MHC-peptide complex from the TCR was rapid (2.6 x 10(-2) second-1, corresponding to a half-time for dissociation of approximately 27 seconds), and the kinetic association rate was 2.1 x 10(5) M-1 second-1. The equilibrium constant for dissociation was approximately 10(-7) M. These values indicate that TCRs must interact with a multivalent array of MHC-peptide complexes to trigger T cell signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Corr, M -- Slanetz, A E -- Boyd, L F -- Jelonek, M T -- Khilko, S -- al-Ramadi, B K -- Kim, Y S -- Maher, S E -- Bothwell, A L -- Margulies, D H -- New York, N.Y. -- Science. 1994 Aug 12;265(5174):946-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular Biology Section, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8052850" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Biosensing Techniques ; H-2 Antigens/*metabolism ; Histocompatibility Antigen H-2D ; Kinetics ; *Major Histocompatibility Complex ; Mice ; Molecular Sequence Data ; Oligopeptides/*metabolism ; Receptors, Antigen, T-Cell, alpha-beta/*metabolism ; Solubility
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  • 89
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    Mortality rates in a genetically heterogeneous population of Caenorhabditis elegans (1994)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1994-02-04
    Description: Age-specific mortality rates in isogenic populations of the nematode Caenorhabditis elegans increase exponentially throughout life. In genetically heterogeneous populations, age-specific mortality increases exponentially until about 17 days and then remains constant until the last death occurs at about 60 days. This period of constant age-specific mortality results from genetic heterogeneity. Subpopulations differ in mean life-span, but they all exhibit near exponential, albeit different, rates of increase in age-specific mortality. Thus, much of the observed heterogeneity in mortality rates later in life could result from genetic heterogeneity and not from an inherent effect of aging.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brooks, A -- Lithgow, G J -- Johnson, T E -- K04-AG00369/AG/NIA NIH HHS/ -- R01-AG08332/AG/NIA NIH HHS/ -- R01-AG10248/AG/NIA NIH HHS/ -- New York, N.Y. -- Science. 1994 Feb 4;263(5147):668-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Behavioral Genetics, University of Colorado, Boulder 80309.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8303273" target="_blank"〉PubMed〈/a〉
    Keywords: Aging ; Animals ; Caenorhabditis elegans/genetics/*physiology ; *Genetic Variation ; Kinetics ; Longevity/genetics ; Mortality
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  • 90
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    Low-barrier hydrogen bonds and enzymic catalysis (1994)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1994-06-24
    Description: Formation of a short (less than 2.5 angstroms), very strong, low-barrier hydrogen bond in the transition state, or in an enzyme-intermediate complex, can be an important contribution to enzymic catalysis. Formation of such a bond can supply 10 to 20 kilocalories per mole and thus facilitate difficult reactions such as enolization of carboxylate groups. Because low-barrier hydrogen bonds form only when the pKa's (negative logarithm of the acid constant) of the oxygens or nitrogens sharing the hydrogen are similar, a weak hydrogen bond in the enzyme-substrate complex in which the pKa's do not match can become a strong, low-barrier one if the pKa's become matched in the transition state or enzyme-intermediate complex. Several examples of enzymatic reactions that appear to use this principle are presented.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cleland, W W -- Kreevoy, M M -- GM 18938/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jun 24;264(5167):1887-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Enzyme Research, University of Wisconsin, Madison 53705.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8009219" target="_blank"〉PubMed〈/a〉
    Keywords: Aconitate Hydratase/chemistry/metabolism ; Binding Sites ; Carboxypeptidases/chemistry/metabolism ; *Catalysis ; Citrate (si)-Synthase/chemistry/metabolism ; Enzymes/*metabolism ; *Hydrogen Bonding ; Isomerases/chemistry/metabolism ; Kinetics ; Orotidine-5'-Phosphate Decarboxylase/chemistry/metabolism ; Racemases and Epimerases/chemistry/metabolism ; Thermolysin/chemistry/metabolism
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  • 91
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    Antibody catalyzed cationic cyclization (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-05-27
    Description: Two major goals for the design of new catalysts are the facilitation of chemical transformations and control of product outcome. An antibody has been induced that efficiently catalyzes a cationic cyclization in which an acyclic olefinic sulfonate ester substrate is converted almost exclusively (98 percent) to a cyclic alcohol. The key to the catalysis of the reaction and the restriction of the product complexity is the use of antibody binding energy to rigidly enforce a concerted mechanism in accord with the design of the hapten. Thus, the ability to direct binding energy allows the experimenter to dictate a reaction mechanism which is an otherwise difficult task in chemistry. New catalysts for cationic cyclization may be of general use in the formation of carbon-carbon and carbon-heteroatom bonds leading to multi-ring molecules including steroids and heterocyclic compounds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, T -- Janda, K D -- Ashley, J A -- Lerner, R A -- GM-43858/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 May 27;264(5163):1289-93.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Scripps Research Institute, Department of Molecular Biology, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8191282" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Catalytic/*chemistry ; Antibodies, Monoclonal/chemistry ; Catalysis ; Cations/*chemistry ; Chromatography, Gas ; Cyclization ; Haptens ; Kinetics ; Mice ; Organosilicon Compounds/*chemistry ; Sulfanilic Acids/*chemistry
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  • 92
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    Selection of guide sequences that direct efficient cleavage of mRNA by human ribonuclease P (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-03-04
    Description: Any RNA, when in a complex with another oligoribonucleotide known as an external guide sequence (EGS), can become a substrate for ribonuclease P. Simulation of evolution in vitro was used to select EGSs that bind tightly to a target substrate messenger RNA and that increase the efficiency of cleavage of the target by human ribonuclease P to a level equal to that achieved with natural substrates. The most efficient EGSs form transfer RNA precursor-like structures with the target RNA, in which the analog of the anticodon stem has been disrupted, an indication that selection for the optimal substrate for ribonuclease P yields an RNA structure different from that of present-day transfer RNA precursors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yuan, Y -- Altman, S -- AI31876/AI/NIAID NIH HHS/ -- GM19422/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Mar 4;263(5151):1269-73.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Yale University, New Haven, CT 06520.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8122108" target="_blank"〉PubMed〈/a〉
    Keywords: Anticodon/chemistry/metabolism ; Base Sequence ; Chloramphenicol O-Acetyltransferase/genetics ; Endoribonucleases/*metabolism ; Humans ; Kinetics ; Magnesium/pharmacology ; Molecular Sequence Data ; Nucleic Acid Conformation ; Oligoribonucleotides/chemistry/*metabolism ; RNA Precursors/chemistry/metabolism ; RNA, Catalytic/*metabolism ; RNA, Guide/chemistry/*metabolism ; RNA, Messenger/chemistry/*metabolism ; RNA, Transfer/chemistry/metabolism ; Ribonuclease P ; Thermodynamics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 93
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    Kinetic intermediates in RNA folding (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-08-12
    Description: The folding pathways of large, highly structured RNA molecules are largely unexplored. Insight into both the kinetics of folding and the presence of intermediates was provided in a study of the Mg(2+)-induced folding of the Tetrahymena ribozyme by hybridization of complementary oligodeoxynucleotide probes. This RNA folds via a complex mechanism involving both Mg(2+)-dependent and Mg(2+)-independent steps. A hierarchical model for the folding pathway is proposed in which formation of one helical domain (P4-P6) precedes that of a second helical domain (P3-P7). The overall rate-limiting step is formation of P3-P7, and takes place with an observed rate constant of 0.72 +/- 0.14 minute-1. The folding mechanism of large RNAs appears similar to that of many multidomain proteins in that formation of independently stable substructures precedes their association into the final conformation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zarrinkar, P P -- Williamson, J R -- New York, N.Y. -- Science. 1994 Aug 12;265(5174):918-24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8052848" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Introns ; Kinetics ; Magnesium/metabolism/pharmacology ; Models, Chemical ; Molecular Sequence Data ; *Nucleic Acid Conformation ; Nucleic Acid Hybridization ; Oligonucleotide Probes ; RNA, Catalytic/*chemistry/metabolism ; RNA, Protozoan/*chemistry ; Ribonuclease H/metabolism ; Temperature ; Tetrahymena/*genetics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 94
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    Mutational isolation of a sieve for editing in a transfer RNA synthetase (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-04-08
    Description: Editing reactions are essential for the high fidelity of information transfer in processes such as replication, RNA splicing, and protein synthesis. The accuracy of interpretation of the genetic code is enhanced by the editing reactions of aminoacyl transfer RNA (tRNA) synthetases, whereby amino acids are prevented from being attached to the wrong tRNAs. Amino acid discrimination is achieved through sieves that may overlap with or coincide with the amino acid binding site. With the class I Escherichia coli isoleucine tRNA synthetase, which activates isoleucine and occasionally misactivates valine, as an example, a rationally chosen mutant enzyme was constructed that lacks entirely its normal strong ability to distinguish valine from isoleucine by the initial amino acid recognition sieve. The misactivated valine, however, is still eliminated by hydrolytic editing reactions. These data suggest that there is a distinct sieve for editing that is functionally independent of the amino acid binding site.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmidt, E -- Schimmel, P -- GM 15539/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Apr 8;264(5156):265-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8146659" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Binding Sites ; Escherichia coli/enzymology ; Isoleucine/*metabolism ; Isoleucine-tRNA Ligase/chemistry/genetics/*metabolism ; Kinetics ; Mutation ; Protein Structure, Secondary ; *RNA Editing ; RNA, Transfer, Ile/metabolism ; Valine/*metabolism
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 95
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    Protein-protein interactions contributing to the specificity of intracellular vesicular trafficking (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-02-25
    Description: Intracellular vesicles destined to fuse with the plasma membrane and secrete their contents must have a mechanism for specifically interacting with the appropriate target membrane. Such a mechanism is now suggested by the demonstration of specific interaction between vesicular proteins and plasma membrane proteins. The vesicle-associated membrane proteins (VAMPs) 1 and 2 specifically bind the acceptor membrane proteins syntaxin 1A and 4 but not syntaxin 2 or 3. The binding site is within amino acids 194 to 267 of syntaxin 1A, and the approximate equilibrium dissociation constants is 4.7 x 10(-6) molar. These data suggest a physical basis for the specificity of intracellular vesicular transport.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Calakos, N -- Bennett, M K -- Peterson, K E -- Scheller, R H -- New York, N.Y. -- Science. 1994 Feb 25;263(5150):1146-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Stanford University Medical Center, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8108733" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antigens, Surface/*metabolism ; Binding Sites ; Cell Line ; Cell Membrane/metabolism ; Cytoplasm/metabolism ; Haplorhini ; Kinetics ; Membrane Proteins/*metabolism ; Molecular Sequence Data ; Nerve Tissue Proteins/*metabolism ; R-SNARE Proteins ; Recombinant Fusion Proteins/metabolism ; Synaptic Vesicles/*metabolism ; Syntaxin 1
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 96
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    Magnetic field effects on B12 ethanolamine ammonia lyase: evidence for a radical mechanism (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-02-18
    Description: A change in radical pair recombination rates is one of the few mechanisms by which a magnetic field can interact with a biological system. The kinetic parameter Vmax/Km (where Km is the Michaelis constant) for the coenzyme B12-dependent enzyme ethanolamine ammonia lyase was decreased 25 percent by a static magnetic field near 0.1 tesla (1000 gauss) with unlabeled ethanolamine and decreased 60 percent near 0.15 tesla with perdeuterated ethanolamine. This effect is likely caused by a magnetic field-induced change in intersystem crossing rates between the singlet and triplet spin states in the [cob(II)alamin:5'-deoxyadenosyl radical] spin-correlated radical pair.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harkins, T T -- Grissom, C B -- ES05728/ES/NIEHS NIH HHS/ -- New York, N.Y. -- Science. 1994 Feb 18;263(5149):958-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Utah, Salt Lake City 84112.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8310292" target="_blank"〉PubMed〈/a〉
    Keywords: Deuterium ; Ethanolamine ; Ethanolamine Ammonia-Lyase/*metabolism ; Ethanolamines/metabolism ; Kinetics ; *Magnetics ; Photolysis ; Vitamin B 12/pharmacology
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  • 97
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    Role of intracellular calcium in NI-35-evoked collapse of neuronal growth cones (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-01-01
    Description: A myelin-associated protein from the central nervous system, the neurite growth inhibitor NI-35, inhibits regeneration of lesioned neuronal fiber tracts in vivo and growth of neurites in vitro. Growth cones of cultured rat dorsal root ganglion neurons arrested their growth and collapsed when exposed to liposomes containing NI-35. Before morphological changes, the concentration of free intracellular calcium ([Ca2+]i) showed a rapid and large increase in growth cones exposed to liposomes containing NI-35. Neither an increase in [Ca2+]i nor collapse of growth cones was detected in the presence of antibodies to NI-35. Dantrolene, an inhibitor of calcium release from caffeine-sensitive intracellular calcium stores, protected growth cones from collapse evoked by NI-35. Depletion of these caffeine-sensitive intracellular calcium stores prevented the increase in [Ca2+]i evoked by NI-35. The NI-35-evoked cascade of intracellular messengers that mediates collapse of growth cones includes the crucial step of calcium release from intracellular stores.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bandtlow, C E -- Schmidt, M F -- Hassinger, T D -- Schwab, M E -- Kater, S B -- NS24683/NS/NINDS NIH HHS/ -- NS28323/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1993 Jan 1;259(5091):80-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Brain Research Institute, University of Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8418499" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Caffeine/pharmacology ; Calcium/*metabolism ; Cells, Cultured ; Drug Carriers ; Fura-2 ; Ganglia, Spinal/*physiology ; Growth Inhibitors/*pharmacology ; Kinetics ; Liposomes ; Nerve Fibers/drug effects/*physiology/ultrastructure ; Neurons/drug effects/*physiology/ultrastructure ; Rats
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  • 98
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    Rate and mechanism of nonhomologous recombination during a single cycle of retroviral replication (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-01-08
    Description: Oncogenes discovered in retroviruses such as Rous sarcoma virus were generated by transduction of cellular proto-oncogenes into the viral genome. Several different kinds of junctions between the viral and proto-oncogene sequences have been found in different viruses. A system of retrovirus vectors and a protocol that mimicked this transduction during a single cycle of retrovirus replication was developed. The transduction involved the formation of a chimeric viral-cellular RNA, strand switching of the reverse transcription growing point from an infectious retrovirus to the chimeric RNA, and often a subsequent deletion during the rest of viral DNA synthesis. A short region of sequence identity was frequently used for the strand switching. The rate of this process was about 0.1 to 1 percent of the rate of homologous retroviral recombination.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, J -- Temin, H M -- CA-07175/CA/NCI NIH HHS/ -- CA-22443/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1993 Jan 8;259(5092):234-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉McArdle Laboratory for Cancer Research, University of Wisconsin-Madison 53706.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8421784" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; *Cinnamates ; *DNA Replication ; DNA, Viral/chemistry/genetics ; Drug Resistance/genetics ; Genes, Viral ; Genetic Vectors ; Hygromycin B/analogs & derivatives ; Kinetics ; Mice ; Molecular Sequence Data ; Moloney murine leukemia virus/genetics ; Neomycin ; Plasmids ; *Proto-Oncogenes ; RNA, Viral/analysis/genetics ; *Recombination, Genetic ; Repetitive Sequences, Nucleic Acid ; Retroviridae/*genetics/physiology ; Transfection ; *Virus Replication
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  • 99
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    Expression cloning and signaling properties of the rat glucagon receptor (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-03-12
    Description: Glucagon and the glucagon receptor are a primary source of control over blood glucose concentrations and are especially important to studies of diabetes in which the loss of control over blood glucose concentrations clinically defines the disease. A complementary DNA clone for the glucagon receptor was isolated by an expression cloning strategy, and the receptor protein was expressed in several kidney cell lines. The cloned receptor bound glucagon and caused an increase in the intracellular concentration of adenosine 3', 5'-monophosphate (cAMP). The cloned glucagon receptor also transduced a signal that led to an increased concentration of intracellular calcium. The glucagon receptor is similar to the calcitonin and parathyroid hormone receptors. It can transduce signals leading to the accumulation of two different second messengers, cAMP and calcium.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jelinek, L J -- Lok, S -- Rosenberg, G B -- Smith, R A -- Grant, F J -- Biggs, S -- Bensch, P A -- Kuijper, J L -- Sheppard, P O -- Sprecher, C A -- New York, N.Y. -- Science. 1993 Mar 12;259(5101):1614-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉ZymoGenetics Inc., Seattle, WA 98105.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8384375" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Calcium/pharmacology ; Cell Line ; Cloning, Molecular ; Cricetinae ; Cyclic AMP/metabolism ; Glucagon/metabolism/*pharmacology ; Kidney ; Kinetics ; Liver/*metabolism ; Molecular Sequence Data ; Rats ; Receptors, Gastrointestinal Hormone/genetics/metabolism/*physiology ; Receptors, Glucagon ; *Signal Transduction ; Transfection
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  • 100
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    Formation of a molten globule intermediate early in the kinetic folding pathway of apomyoglobin (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-11-05
    Description: Hydrogen exchange pulse labeling and stopped-flow circular dichroism were used to establish that the structure of the earliest detectable intermediate formed during refolding of apomyoglobin corresponds closely to that of a previously characterized equilibrium molten globule. This compact, cooperatively folded intermediate was formed in less than 5 milliseconds and contained stable, hydrogen-bonded secondary structure localized in the A, G, and H helices and part of the B helix. The remainder of the B helix folded on a much slower time scale, followed by the C and E helices and the CD loop. The data indicate that a molten globule intermediate was formed on the kinetic folding pathway.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jennings, P A -- Wright, P E -- DK-34909/DK/NIDDK NIH HHS/ -- GM14541/GM/NIGMS NIH HHS/ -- RR04953/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1993 Nov 5;262(5135):892-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology, Scripps Research Institute, La Jolla, California 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8235610" target="_blank"〉PubMed〈/a〉
    Keywords: Apoproteins/*chemistry ; Circular Dichroism ; Hydrogen/chemistry ; Hydrogen Bonding ; Kinetics ; Magnetic Resonance Spectroscopy ; Models, Molecular ; Myoglobin/*chemistry ; *Protein Conformation ; *Protein Folding ; Protein Structure, Secondary
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