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  • Articles  (256)
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  • American Association for the Advancement of Science (AAAS)  (256)
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  • 1
    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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  • 2
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    American Association for the Advancement of Science (AAAS)
    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
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  • 3
    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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  • 4
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    American Association for the Advancement of Science (AAAS)
    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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  • 5
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    American Association for the Advancement of Science (AAAS)
    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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  • 6
    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
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  • 7
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    American Association for the Advancement of Science (AAAS)
    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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  • 8
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    American Association for the Advancement of Science (AAAS)
    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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  • 9
    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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  • 10
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    American Association for the Advancement of Science (AAAS)
    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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  • 11
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    American Association for the Advancement of Science (AAAS)
    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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  • 12
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    American Association for the Advancement of Science (AAAS)
    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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  • 13
    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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  • 14
    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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  • 15
    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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  • 16
    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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  • 17
    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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  • 18
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    American Association for the Advancement of Science (AAAS)
    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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  • 19
    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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  • 20
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    American Association for the Advancement of Science (AAAS)
    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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  • 21
    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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  • 22
    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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  • 23
    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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  • 24
    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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  • 25
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    American Association for the Advancement of Science (AAAS)
    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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  • 26
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    American Association for the Advancement of Science (AAAS)
    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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  • 27
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    American Association for the Advancement of Science (AAAS)
    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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  • 28
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    American Association for the Advancement of Science (AAAS)
    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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  • 29
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    American Association for the Advancement of Science (AAAS)
    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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  • 30
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    American Association for the Advancement of Science (AAAS)
    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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  • 31
    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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  • 32
    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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  • 33
    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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  • 34
    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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  • 35
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    American Association for the Advancement of Science (AAAS)
    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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  • 36
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    American Association for the Advancement of Science (AAAS)
    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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  • 37
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    American Association for the Advancement of Science (AAAS)
    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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  • 38
    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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  • 39
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    American Association for the Advancement of Science (AAAS)
    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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  • 40
    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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  • 41
    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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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 42
    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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  • 43
    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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  • 44
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    American Association for the Advancement of Science (AAAS)
    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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  • 45
    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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  • 46
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    American Association for the Advancement of Science (AAAS)
    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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  • 47
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    American Association for the Advancement of Science (AAAS)
    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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  • 48
    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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  • 49
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    American Association for the Advancement of Science (AAAS)
    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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  • 50
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    American Association for the Advancement of Science (AAAS)
    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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  • 51
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    American Association for the Advancement of Science (AAAS)
    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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  • 52
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    American Association for the Advancement of Science (AAAS)
    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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  • 53
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    American Association for the Advancement of Science (AAAS)
    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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  • 54
    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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  • 55
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    American Association for the Advancement of Science (AAAS)
    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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  • 56
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    American Association for the Advancement of Science (AAAS)
    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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  • 57
    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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  • 58
    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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  • 59
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    American Association for the Advancement of Science (AAAS)
    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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  • 60
    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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  • 61
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    American Association for the Advancement of Science (AAAS)
    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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  • 62
    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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  • 63
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    American Association for the Advancement of Science (AAAS)
    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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  • 64
    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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  • 65
    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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  • 66
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    American Association for the Advancement of Science (AAAS)
    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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  • 67
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    American Association for the Advancement of Science (AAAS)
    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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  • 68
    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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  • 69
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    American Association for the Advancement of Science (AAAS)
    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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  • 70
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    American Association for the Advancement of Science (AAAS)
    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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  • 71
    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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  • 72
    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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  • 73
    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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  • 74
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    American Association for the Advancement of Science (AAAS)
    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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  • 75
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-09-08
    Description: The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen. An unusual family of enzymes, the superoxide dismutases, protect against the deleterious actions of this radical by catalyzing its dismutation to hydrogen peroxide plus oxygen.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fridovich, I -- New York, N.Y. -- Science. 1978 Sep 8;201(4359):875-80.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/210504" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Binding Sites ; Catalase/metabolism ; Free Radicals ; Inflammation/metabolism ; Kinetics ; Metals ; Oxidation-Reduction ; Oxygen/*metabolism ; Paraquat/pharmacology ; Peroxidases/metabolism ; Superoxide Dismutase/*metabolism ; Superoxides/*metabolism/toxicity
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  • 76
    Publication Date: 1978-07-07
    Description: The density but not the affinity of beta-adrenergic receptors declined significantly with age in rat pineal gland, corpus striatum, and cerebellum, as determined by the binding of tritiated dihydroalprenolol. Exposing rats to light for 12 hours increased the binding of this radioligand in 3-month-old but not in 24-month-old rats. The reduced responsiveness to catecholamines seen in aging may be due to a decrease in the number of beta-adrenergic receptors which, in turn, may be caused by an impaired capacity of receptors in aged animals to adapt to changes in adrenergic neuronal input.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Greenberg, L H -- Weiss, B -- New York, N.Y. -- Science. 1978 Jul 7;201(4350):61-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/208145" target="_blank"〉PubMed〈/a〉
    Keywords: *Aging ; Alprenolol/analogs & derivatives/metabolism ; Animals ; Brain/*metabolism ; Cerebellum/metabolism ; Circadian Rhythm ; Corpus Striatum/metabolism ; Kinetics ; Light ; Male ; Neuroglia/metabolism ; Pineal Gland/*metabolism ; Rats ; Receptors, Adrenergic/*metabolism ; Receptors, Adrenergic, beta/*metabolism
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  • 77
    Publication Date: 1978-11-17
    Description: When adenosine deaminase activity is inhibited, low concentrations of adenosine are toxic to human lymphoblast mutants that are unable to convert adenosine to intracellular nucleotides. In order to identify the mediator of this cytotoxicity, we searched for a cytoplasmic protein capable of binding adenosine with high affinity. Such a protein was identified in extracts of human lymphoblasts and placenta as the enzyme S-adenosylhomocysteine hydrolase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hershfield, M S -- Krodich, N M -- New York, N.Y. -- Science. 1978 Nov 17;202(4369):757-60.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/715439" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine/*metabolism ; Adenosine Deaminase/*deficiency ; Carrier Proteins/*metabolism ; Female ; Humans ; Hydrolases/*metabolism ; Kinetics ; Lymphocytes/metabolism ; Nucleoside Deaminases/*deficiency ; Placenta/metabolism ; Pregnancy ; S-Adenosylhomocysteine/metabolism
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  • 78
    Publication Date: 1978-10-13
    Description: Volunteer subjects with previous histories of cocaine use were administered cocaine hydrochloride intravenously or intranasally. There was a positive relationship between peak plasma concentration, physiological and subjective responses, and dose administered. The rate of cocaine disappearance after intravenous administration paralleled the drop in physiological and subjective drug effects. After intranasal administration, blood levels remained elevated for a considerably longer period.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Javaid, J I -- Fischman, M W -- Schuster, C R -- Dekirmenjian, H -- Davis, J M -- New York, N.Y. -- Science. 1978 Oct 13;202(4364):227-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/694530" target="_blank"〉PubMed〈/a〉
    Keywords: Administration, Intranasal ; Cocaine/administration & dosage/*blood/*pharmacology ; Dose-Response Relationship, Drug ; Euphoria/*drug effects ; Heart Rate/drug effects ; Humans ; Injections, Intravenous ; Kinetics ; Metabolic Clearance Rate
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  • 79
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-01-27
    Description: A stopped-flow circular dichroism instrument, with a total accessible wavelength range of 200 to 750 nanometers, has been constructed and provides a spectroscopic method for kinetic investigations of a wide array of fast reactions in which optical activity changes in absorbing regions are involved. An important biochemical application depends on the far-ultraviolet capability, which allows observation of the rapid alterations in backbone conformation associated with folding and unfolding reactions of proteins. Results obtained by following two such reactions at 222 nanometers represent direct monitoring by circular dichroism of rapid secondary structure changes in proteins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Luchins, J -- Beychok, S -- New York, N.Y. -- Science. 1978 Jan 27;199(4327):425-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/619462" target="_blank"〉PubMed〈/a〉
    Keywords: *Circular Dichroism ; Hemoglobins ; Kinetics ; Methemoglobin ; *Protein Conformation ; Protein Denaturation ; Spectrophotometry, Ultraviolet/methods ; *Spectrum Analysis
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  • 80
    Publication Date: 1978-09-01
    Description: Hepatic pigment clearance in rats can be followed continuously with photometric detectors designed for high-pressure liquid chromatography. This method showed that light has a fast effect on bilirubin metabolism in homozygous Gunn rats, even at low doses and intensities. This is consistent with geometric isomerization of bilirubin IXalpha as a primary step in phototherapy.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McDonagh, A F -- Ramonas, L M -- New York, N.Y. -- Science. 1978 Sep 1;201(4358):829-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/581101" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bile/metabolism ; Bilirubin/blood/*metabolism/radiation effects ; *Disease Models, Animal ; Humans ; Infant, Newborn ; Jaundice, Neonatal/*therapy ; Kinetics ; Liver/metabolism ; *Phototherapy ; Rats
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  • 81
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-03-10
    Description: Incubation of ribonuclease with 0.1M mercaptoethanol at pH 8.5 can increase the enzyme's hydrolytic activity toward cytidine 2',3'-monophosphate (cyclic CMP) under standard assay conditions. Cation-exchange chromatography of the ribonuclease-thiol reaction mixture revealed seven fractions. The fraction with the highest activity had an approximate tenfold decrease in the apparent Michaelis constant for cyclic CMP with respect to native ribonuclease. The enhanced activity is a metastable property since this fraction reverts back to the control activity and chromatographic behavior of native ribonuclease on standing in solution at room temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Watkins, J B -- Benz, F W -- New York, N.Y. -- Science. 1978 Mar 10;199(4333):1084-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/564548" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cattle ; Disulfides/pharmacology ; Enzyme Activation/drug effects ; Glutathione/pharmacology ; Kinetics ; Mercaptoethanol/*pharmacology ; Oxidation-Reduction ; Pancreas/enzymology ; Protein Conformation ; Ribonucleases/*metabolism ; Structure-Activity Relationship
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  • 82
    Publication Date: 1979-09-14
    Description: Binding sites for tritum-labeled gamma-aminobutyric acid (GABA) in cerebellar cortex of Huntington's chorea patients have an increased affinity but unaltered maximum capacity as compared to binding sites in tissue from control patients. A similar binding pattern is produced in control membranes by treatment with Triton X-100, phospholipase C, or glycerophosphoethanolamine. Thus, it is likely that phospholipids or their metabolites regulate the accessibility of the GABA binding site and that this regulation is abnormal in Huntington's chorea.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lloyd, K G -- Davidson, L -- New York, N.Y. -- Science. 1979 Sep 14;205(4411):1147-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/224459" target="_blank"〉PubMed〈/a〉
    Keywords: Cerebellar Cortex/*metabolism ; Humans ; Huntington Disease/*metabolism ; Kinetics ; Membrane Lipids ; Phosphatidylethanolamines/physiology ; Polyethylene Glycols/pharmacology ; Receptors, Neurotransmitter/drug effects/*metabolism ; gamma-Aminobutyric Acid/*metabolism
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  • 83
    Publication Date: 1979-05-25
    Description: Single islet cells in monolayer cultures of neonatal rat pancreas were microinjected with fluorescein and scanned topographically by microfluorometry. Fluorescein spread from an injected islet cell directly into neighboring islet cells, and, in the presence of 16.7 millimolar glucose, significantly more islet cells communicated with the injected cell than in glucose-free medium. Islet cells were also microinjected with glycolytic substrates and activators that produced transient changes in cellular levels of reduced pyridine nucleotides-nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate [NAD(P)H]. Changes in NAD(P)H fluorescence were observed in islet cells incubated first for 18 hours in very low glucose concentrations and then in a glucose-free medium and injected with glycolytic substrates and activators; however, little change of fluorescence occurred in adjacent islet cells. In contrast, after adding 16.7 millimolar glucose to the medium, injection of glycolytic substrates and activators produced transient changes in NAD(P)H fluorescence in the injected cell and in neighboring cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kohen, E -- Kohen, C -- Thorell, B -- Mintz, D H -- Rabinovitch, A -- New York, N.Y. -- Science. 1979 May 25;204(4395):862-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/35828" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Cell Communication/drug effects ; Fluoresceins ; Glucose/pharmacology ; Glycolysis ; Islets of Langerhans/cytology/*physiology ; Kinetics ; NAD/metabolism ; NADP/metabolism ; Rats ; Spectrometry, Fluorescence
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  • 84
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-11-30
    Description: The tertiary structures of all liganded hemoglobins in the R state differ in detail. Steric hindrance arising from nonbonded ligand-globin interactions affects the binding of ligands such as CO and cyanide which preferentially form linear axial complexes to heme; these ligands bind in a strained off-axis configuration. Ligands such as O2 and NO, which preferentially form bent complexes, encounter less steric hindrance and can bind in their (preferred) unstrained configuration. Linear complexes distort the ligand pockets in the R state (and by inference, in the T state) more than bent complexes. These structural differences between linear and bent complexes are reflected in the kinetic behavior of hemoglobin. Structural interpretation of this kinetic behavior indicates that the relative contributions of nonbonded ligand-globin interactions and nonbonded heme interactions to transition state free energies differ for linear and bent ligands. The relative contributions of these interactions to the free energy of cooperativity may also differ for linear and bent ligands. Thus the detailed molecular mechanism by which the affinity of heme is regulated differs for different ligands.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moffat, K -- Deatherage, J F -- Seybert, D W -- New York, N.Y. -- Science. 1979 Nov 30;206(4422):1035-42.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/493990" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Animals ; Heme/*metabolism ; Hemoglobins/metabolism ; Horses ; Kinetics ; Ligands ; Oxygen/*metabolism ; Oxyhemoglobins/*metabolism ; Protein Conformation ; Stereoisomerism ; Structure-Activity Relationship
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  • 85
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-01-05
    Description: An adenylate cyclase activated as much as 25-fold by low concentrations of octopamine has been identified in the firefly lantern. The relative potency of octopamine and various other amines in stimulating this enzyme, and effects of antagonists in blocking octopamine activation, correlate well with the known effects of these agents in affecting light production. In addition to suggesting a role for adenosine 3',5'-monophosphate (or pyrophosphate) in the neural control of firefly flashing, identification of this potent enzyme should facilitate the characterization of phenylethylamine receptors in excitable tissue.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nathanson, J A -- New York, N.Y. -- Science. 1979 Jan 5;203(4375):65-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/214856" target="_blank"〉PubMed〈/a〉
    Keywords: Adenylyl Cyclases/*metabolism ; Animals ; Beetles/*physiology ; Catecholamines/pharmacology ; Cyclic AMP/*biosynthesis ; Dose-Response Relationship, Drug ; Enzyme Activation/drug effects ; Kinetics ; Octopamine/*pharmacology ; Phentolamine/pharmacology ; Propranolol/pharmacology ; Receptors, Cell Surface/*drug effects ; Receptors, Neurotransmitter/*drug effects ; Structure-Activity Relationship
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  • 86
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-08-10
    Description: A competitive inhibitor of colchicine binding to tubulin has been found in rat brain. Most of the inhibitor is associated with microsomes but some inhibitor, with an apparent molecular weight of approximately 250,000, is found in the cytosol. Both the microsomal and cytosol inhibitors are heat- and trypsin-sensitive, indicating that a protein moiety is required for activity. The microsomes bind tubulin directly; the microsomal and cytosol fractions both inhibit microtubule assembly in vitro. The inhibitor may function in the living cell to bind and sequester non-polymerized tubulin. Regulation of tubulin attachment to microsomes could then control the concentration of cytosolic tubulin available for microtubule assembly.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sherline, P -- Schiavone, K -- Brocato, S -- New York, N.Y. -- Science. 1979 Aug 10;205(4406):593-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/451622" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Brain/*metabolism ; Colchicine/*metabolism ; Cytosol/physiology ; Glycoproteins/*metabolism ; Kinetics ; Microsomes/metabolism ; Microtubules/ultrastructure ; Nerve Tissue Proteins/*physiology ; Protein Binding/drug effects ; Rats ; Tubulin/*metabolism
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  • 87
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-08-17
    Description: Platelet lysates obtained from blood of humans, dogs, and rats catalyzed the transamination of 4-aminobutyrate with 2-oxoglutarate as cosubstrate. Human platelet 4-aminobutyrate:2-oxoglutarate aminotransferase (36.5 +/- 3.2 picomoles per minute per milligram of platelet protein) resembled the brain enzyme in kinetic properties and in response to cofactors and inhibitors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉White, H L -- New York, N.Y. -- Science. 1979 Aug 17;205(4407):696-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/462176" target="_blank"〉PubMed〈/a〉
    Keywords: 4-Aminobutyrate Transaminase/*blood ; Animals ; Blood Platelets/*enzymology ; Brain/enzymology ; Dogs ; Enzyme Activation/drug effects ; Humans ; Kinetics ; Pyridoxal Phosphate/pharmacology ; Rats ; Substrate Specificity ; Transaminases/*blood ; gamma-Aminobutyric Acid/blood
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  • 88
    Publication Date: 1980-03-28
    Description: When microbial strains compete for the same limiting nutrient in continuous culture, resource-based competition theory predicts that only one strain will survive and all others will die out. The surviving strain expected from theory will be the one with the smallest subsistence or "break-even" concentration of the limiting resource, a concentration defined by the J parameter. This prediction has been confirmed in the case of auxotrophic bacterial strains competing for limiting tryptophan. Because the value of J can be measured on the strains grown alone, the theory can predict the qualitative outcomes of mixed-growth competition in advance of actual competition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hansen, S R -- Hubbell, S P -- New York, N.Y. -- Science. 1980 Mar 28;207(4438):1491-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6767274" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteria/*growth & development ; Culture Media ; Drug Resistance, Microbial ; Escherichia coli/growth & development ; Kinetics ; Models, Theoretical ; Nalidixic Acid/pharmacology ; Nutritional Physiological Phenomena ; Pseudomonas aeruginosa/growth & development ; Tryptophan/metabolism
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  • 89
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1980-02-15
    Description: Autoradiographic and biochemical analyses of the hearts of female rhesus monkeys and baboons indicate that atrial and ventricular myocardial cells contain androgen receptors. Although the specific effects of nuclear uptake and retention of androgen on the function of heart muscle cells are not known, the presence of this receptor suggests that sex steroid hormones may affect myocardial function directly and may explain some of the peculiar differences in heart disease between men and women.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGill, H C Jr -- Anselmo, V C -- Buchanan, J M -- Sheridan, P J -- New York, N.Y. -- Science. 1980 Feb 15;207(4432):775-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6766222" target="_blank"〉PubMed〈/a〉
    Keywords: Androgens/*metabolism ; Animals ; Coronary Disease/*etiology ; Dihydrotestosterone/metabolism ; Estradiol/metabolism ; Female ; Haplorhini ; Kinetics ; Macaca mulatta ; Myocardium/*metabolism ; Papio ; Receptors, Androgen/*metabolism ; Receptors, Steroid/*metabolism ; Sex Factors
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  • 90
    Publication Date: 1980-07-25
    Description: Accurate measurements of intracellular calcium activities in salivary gland epithelial cells of the insect Phormia regina were obtained with microelectrodes in which N,N'-di(11-ethoxycarbonyl)undecyl-N,N'-4,5-tetramethyl-3,6-dioxaoctane diacid diamide wsa incorporated in a liquid membrane system. When calibrated in solutions approximating the ionic concentration of the cell interior, these microelectrodes gave rapid stable responses that were linear functions of the logarithm of calcium activities and were not affected by potassium, sodium and magnesium. Continuous monitoring of calcium activities during serotonin-induced saliva release provided direct evidence of hormonal influence on transmembrane calcium movement and spontaneous regulation of intracellular calcium by stimulated cells.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Doherty, J -- Youmans, S J -- Armstrong, W M -- Stark, R J -- New York, N.Y. -- Science. 1980 Jul 25;209(4455):510-3.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7394518" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Transport/drug effects ; Calcium/*metabolism ; Diptera/*metabolism ; Epithelium/metabolism ; Kinetics ; Magnesium/pharmacology ; Microelectrodes ; Salivary Glands/drug effects/*metabolism ; Serotonin/pharmacology
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  • 91
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1980-11-21
    Description: The rate at which glucose enters nerve terminals in muscle was estimated indirectly by measuring changes in miniature end-plate potential frequency D-Glucose entered nerve terminals in muscles with a fast twitch more rapidly than it entered those with a slow twitch. This suggests that nerve terminals in fast- and slow-twitch muscles differ in their rate of metabolism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pickett, J B -- New York, N.Y. -- Science. 1980 Nov 21;210(4472):927-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7434009" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Transport ; Diaphragm/innervation ; Glucose/*metabolism ; Kinetics ; Membrane Potentials ; Nerve Endings/*metabolism ; Neuromuscular Junction/*metabolism ; Osmolar Concentration ; Rats
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  • 92
    Publication Date: 1980-08-22
    Description: The binding of [6-alanine]gonadotropin-releasing hormone to pituitary plasma membranes increased threefold between metestrus and early proestrus in female rats. Receptor numbers fell rapidly on the afternoon of proestrus coincident with the preovulatory gonadotropin surge. The numbers of receptors for gonadotropin-releasing hormone were positively correlated with concentrations of estradiol in serum; this pattern may be a necessary component of increased pituitary sensitivty to gonadotropin-releasing hormone observed during proestrus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Savoy-Moore, R T -- Schwartz, N B -- Duncan, J A -- Marshall, J C -- New York, N.Y. -- Science. 1980 Aug 22;209(4459):942-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6250218" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Membrane/metabolism ; Estradiol/blood ; *Estrus ; Feedback ; Female ; Follicle Stimulating Hormone/blood ; Gonadotropin-Releasing Hormone/analogs & derivatives/*metabolism ; Kinetics ; Luteinizing Hormone/blood ; Pituitary Gland, Anterior/*metabolism ; Pregnancy ; Progesterone/blood ; Rats ; Receptors, Cell Surface/*metabolism
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 93
    Publication Date: 1981-07-31
    Description: Benzodiazepines inhibit Ca2+-calmodulin-stimulated membrane protein phosphorylation. The effects of the benzodiazepines on protein phosphorylation are stereospecific and produced by membrane-bound benzodiazepine. The potency of benzodiazepine kinase inhibition is correlated with the ability of the benzodiazepines to inhibit electric shock-induced convulsions. These findings provide evidence that some of the anticonvulsant and neuronal stabilizing effects of benzodiazepines may be modulated by the Ca2+-calmodulin protein kinase system and indicate that this calmodulin-kinase system represents an identifiable benzodiazepine receptor in brain that is distinquishable by several criteria from the previously described high affinity benzodiazepine receptor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉DeLorenzo, R J -- Burdette, S -- Holderness, J -- NS 1352/NS/NINDS NIH HHS/ -- NSI-EA-1-K04-NS245/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1981 Jul 31;213(4507):546-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6264605" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Benzodiazepines/metabolism ; Brain/*enzymology ; Calcium/*pharmacology ; Calcium-Binding Proteins/*pharmacology ; Calmodulin/*pharmacology ; Cell Membrane/enzymology ; Chlordiazepoxide/*pharmacology ; Diazepam/*pharmacology ; Enzyme Activation ; Kinetics ; Molecular Weight ; Phosphorylation ; Protein Kinases/*metabolism ; Rats ; Receptors, Drug/metabolism ; Receptors, GABA-A
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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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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-08-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Evans, C H -- Tew, W P -- New York, N.Y. -- Science. 1981 Aug 7;213(4508):653-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7256262" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Cations ; *Erbium ; Kinetics ; *Magnetics
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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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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-06-12
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gonzalez, M F -- Deutsch, J A -- New York, N.Y. -- Science. 1981 Jun 12;212(4500):1283-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7233218" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Feeding Behavior ; Kinetics ; Male ; Rats ; *Satiation ; *Satiety Response ; Stomach/*physiology ; *Vagotomy
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  • 96
    Publication Date: 1981-12-04
    Description: The persistence of synthetic herbicides such as 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and its release in massive amounts as a herbicide (Agent Orange) have created toxicological problems in many countries. In nature, 2,4,5-T is slowly degraded by cooxidation and is not utilized as a sole source of carbon and energy. The technique of plasmid-assisted molecular breeding has led to the development of bacterial strains capable of totally degrading 2,4,5-T by using it as their sole source of carbon at high concentrations (greater than 1 mg/ml). Spectrophotometry and gas chromatography reveal various intermediates during growth of the culture with 2,4,5-T.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kellogg, S T -- Chatterjee, D K -- Chakrabarty, A M -- New York, N.Y. -- Science. 1981 Dec 4;214(4525):1133-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7302584" target="_blank"〉PubMed〈/a〉
    Keywords: 2,4,5-Trichlorophenoxyacetic Acid/*metabolism ; Bacteria/*genetics/metabolism ; Biotransformation ; Cell Division ; Kinetics ; Nucleic Acid Hybridization ; *Plasmids
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  • 97
    Publication Date: 1981-06-05
    Description: Two divalent cation ionophores, A23187 and Ionomycin, which are selective for calcium, stimulated the resorption of fetal rat long bones in organ culture at 0.1 to 1 micromolar but not at higher concentrations. Both agents inhibited DNA synthesis at concentrations that stimulated resorption. These results might explain the differences in ionophore effects on bone previously reported, and they imply that cell replication is not required for osteoclast formation in fetal rat long bone cultures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lorenzo, J A -- Raisz, L G -- AM 07290/AM/NIADDK NIH HHS/ -- AM 18063/AM/NIADDK NIH HHS/ -- New York, N.Y. -- Science. 1981 Jun 5;212(4499):1157-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6785885" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Anti-Bacterial Agents/*pharmacology ; Bone Resorption/*drug effects ; Bone and Bones/drug effects/*metabolism ; Calcimycin/*pharmacology ; Calcium/metabolism ; Calcium Radioisotopes ; Cells, Cultured ; DNA/*biosynthesis ; DNA Replication/*drug effects ; Ethers/pharmacology ; Fetus ; Ionomycin ; Ionophores/pharmacology ; Kinetics ; Mice ; Parathyroid Hormone/pharmacology
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  • 98
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-07-31
    Description: A loss in the number of functional, sodium ion-dependent, high-affinity choline transport sites was observed in the cortex and hippocampus of mice given an intracerebroventricular injection of 65 nanomoles of AF64A (ethylcholine mustard aziridinium ion) 3 days earlier. Such an effect was not observed in the striatum. This effect of AF64A represents a long-term neurochemical deficit at cholinergic nerve terminals in some brain regions which can lead to a persistent deficiency in central cholinergic transmission. The AF64A-treated animal may thus be a model for certain psychiatric or neurological disorders that appear to involve central cholinergic hypofunction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mantione, C R -- Fisher, A -- Hanin, I -- MH 26320/MH/NIMH NIH HHS/ -- MH/AG 34893/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 1981 Jul 31;213(4507):579-80.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6894649" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Aziridines/*pharmacology ; Azirines/*pharmacology ; Biological Transport/drug effects ; Brain/drug effects/*metabolism ; Cerebral Cortex/metabolism ; Choline/*analogs & derivatives/*metabolism/pharmacology ; Corpus Striatum/metabolism ; Hippocampus/metabolism ; Kinetics ; Mice ; Sodium/pharmacology ; Synaptosomes/drug effects/*metabolism
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  • 99
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-07-31
    Description: During normal development of the hamster eye, there is a substantial loss of cells from the retinal ganglion cell layer in the first two postnatal weeks. If one eye is lost at birth, this cell death is reduced in the remaining eye. This may account for the increased ipsilateral projection from this eye to the thalamus and midbrain observed in these animals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sengelaub, D R -- Finlay, B L -- New York, N.Y. -- Science. 1981 Jul 31;213(4507):573-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7244655" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Animals, Newborn ; Cell Survival ; Cricetinae ; Kinetics ; Neurons/*physiology ; Rats ; Retina/cytology/*physiology
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  • 100
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-07-17
    Description: Bee venom and phospholipase A2 extracted from bee venom enhanced guanylate cyclase (E.C. 4.6.1.2) activity two- to threefold in rat liver, lung, heart, kidney, ileum, and cerebellum. Dose-response relationships revealed that bee venom at concentrations as low as 1 microgram per milliliter and phospholipase A2 at 1 microunit per milliliter caused a maximal enhancement of guanylate cyclase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vesely, D L -- New York, N.Y. -- Science. 1981 Jul 17;213(4505):359-60.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6113689" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bee Venoms/*pharmacology ; Dose-Response Relationship, Drug ; Enzyme Activation ; Guanylate Cyclase/*metabolism ; Kinetics ; Organ Specificity ; Phospholipases/*pharmacology ; Phospholipases A/*pharmacology ; Phospholipases A2 ; Rats
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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