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  • Kinetics
  • American Association for the Advancement of Science (AAAS)  (22)
  • American Association for the Advancement of Science
  • American Association of Petroleum Geologists (AAPG)
  • American Physical Society
  • Elsevier
  • 1990-1994  (22)
  • 1994  (22)
Collection
Publisher
  • American Association for the Advancement of Science (AAAS)  (22)
  • American Association for the Advancement of Science
  • American Association of Petroleum Geologists (AAPG)
  • American Physical Society
  • Elsevier
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  • 1990-1994  (22)
Year
  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-06-24
    Description: The basic notions of transition state theory have been exploited in the past to generate highly selective catalysts from the vast library of antibody molecules in the immune system. These same ideas were used to isolate an RNA molecule, from a large library of RNAs, that catalyzes the isomerization of a bridged biphenyl. The RNA-catalyzed reaction displays Michaelis-Menten kinetics with a catalytic rate constant (kcat) of 2.8 x 10(-5) per minute and a Michaelis constant (Km) of 542 microM; the reaction is competitively inhibited by the planar transition state analog with an inhibition constant (Ki) value of approximately 7 microM. This approach may provide a general strategy for expanding the scope of RNA catalysis beyond those reactions in which the substrates are nucleic acids or nucleic acid derivatives.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Prudent, J R -- Uno, T -- Schultz, P G -- GM08352A/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jun 24;264(5167):1924-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8009223" target="_blank"〉PubMed〈/a〉
    Keywords: Base Sequence ; Biphenyl Compounds/chemistry/metabolism ; Catalysis ; Kinetics ; Molecular Sequence Data ; Nucleic Acid Conformation ; Nucleic Acid Denaturation ; Polymerase Chain Reaction ; RNA, Catalytic/chemistry/*metabolism ; Stereoisomerism ; Temperature
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  • 2
    Publication Date: 1994-08-19
    Description: A small molecule called PD 153035 inhibited the epidermal growth factor (EGF) receptor tyrosine kinase with a 5-pM inhibition constant. The inhibitor was specific for the EGF receptor tyrosine kinase and inhibited other purified tyrosine kinases only at micromolar or higher concentrations. PD 153035 rapidly suppressed autophosphorylation of the EGF receptor at low nanomolar concentrations in fibroblasts or in human epidermoid carcinoma cells and selectively blocked EGF-mediated cellular processes including mitogenesis, early gene expression, and oncogenic transformation. PD 153035 demonstrates an increase in potency over that of other tyrosine kinase inhibitors of four to five orders of magnitude for inhibition of isolated EGF receptor tyrosine kinase and three to four orders of magnitude for inhibition of cellular phosphorylation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fry, D W -- Kraker, A J -- McMichael, A -- Ambroso, L A -- Nelson, J M -- Leopold, W R -- Connors, R W -- Bridges, A J -- New York, N.Y. -- Science. 1994 Aug 19;265(5175):1093-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, MI 48105.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8066447" target="_blank"〉PubMed〈/a〉
    Keywords: 3T3 Cells ; Animals ; Cell Transformation, Neoplastic/drug effects ; Epidermal Growth Factor/pharmacology ; Fibroblast Growth Factor 2/pharmacology ; Gene Expression/drug effects ; Humans ; Kinetics ; Mice ; Mitosis/drug effects ; Phosphorylation/drug effects ; Platelet-Derived Growth Factor/pharmacology ; Protein-Tyrosine Kinases/antagonists & inhibitors ; Quinazolines/*antagonists & inhibitors ; Receptor, Epidermal Growth Factor/*antagonists & inhibitors ; Tumor Cells, Cultured ; Tyrosine/metabolism
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  • 3
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-09-23
    Description: The functional consequences of single proton transfers occurring in the pore of a cyclic nucleotide-gated channel were observed with patch recording techniques. These results led to three conclusions about the chemical nature of ion binding sites in the conduction pathway: The channel contains two identical titratable sites, even though there are more than two (probably four) identical subunits; the sites are formed by glutamate residues that have a pKa (where K(a) is the acid constant) of 7.6; and protonation of one site does not perturb the pKa of the other. These properties point to an unusual arrangement of carboxyl side-chain residues in the pore of a cation channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Root, M J -- MacKinnon, R -- 5 T32 GM083113/GM/NIGMS NIH HHS/ -- GM47400/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 23;265(5180):1852-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Harvard Medical School, Boston, MA 02115.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7522344" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Binding Sites ; Calcium Channels/metabolism ; Catfishes ; Electric Conductivity ; Hydrogen-Ion Concentration ; Ion Channel Gating ; Ion Channels/chemistry/genetics/*metabolism ; Kinetics ; Molecular Sequence Data ; Mutation ; *Protons ; Sodium/metabolism ; Xenopus
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  • 4
    Publication Date: 1994-09-16
    Description: A reverse protocol for measurements of molecular binding and reactivity by excited-state quenching has been developed in which the quencher, held at a fixed concentration, is titrated by a photoexcitable probe molecule whose decay is monitored. The binding stoichiometries, affinities, and reactivities of the electron-transfer complexes between cytochrome c (Cc) and cytochrome c peroxidase (CcP) were determined over a wide range of ionic strengths (4.5 to 118 millimolar) by the study of photoinduced electron-transfer quenching of the triplet excited state of zinc-substituted Cc (ZnCc) by Fe3+CcP. The 2:1 stoichiometry seen for the binding of Cc to CcP at low ionic strength persists at the physiologically relevant ionic strengths and likely has functional significance. Analysis of the stoichiometric binding and rate constants confirms that one surface domain of CcP binds Cc with a high affinity but with poor electron-transfer quenching of triplet-state ZnCc, whereas a second binds weakly but with a high rate of electron-transfer quenching.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, J S -- Hoffman, B M -- HL13531/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 16;265(5179):1693-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Northwestern University, Evanston, IL 60208-3113.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8085152" target="_blank"〉PubMed〈/a〉
    Keywords: Cytochrome c Group/chemistry/*metabolism ; Cytochrome-c Peroxidase/chemistry/*metabolism ; Electron Transport ; Ferric Compounds ; Kinetics ; Osmolar Concentration ; Oxidation-Reduction ; Zinc
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  • 5
    Publication Date: 1994-01-28
    Description: As changes in synaptic strength are thought to be critical for learning and memory, it would be useful to monitor the activity of individual identified synapses on mammalian central neurons. Calcium imaging of cortical neurons grown in primary culture was used to visualize the activation of individual postsynaptic elements by miniature excitatory synaptic currents elicited by spontaneous quantal release. This approach revealed that the probability of spontaneous activity differed among synapses on the same dendrite. Furthermore, synapses that undergo changes in activity induced by glutamate or phorbol ester treatment were identified.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Murphy, T H -- Baraban, J M -- Wier, W G -- Blatter, L A -- New York, N.Y. -- Science. 1994 Jan 28;263(5146):529-32.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7904774" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/*metabolism ; Cells, Cultured ; Cerebral Cortex ; Dendrites/*metabolism ; Glutamates/pharmacology ; Glutamic Acid ; Kinetics ; Microelectrodes ; Neuronal Plasticity ; Neurons/*physiology ; Phorbol Esters/pharmacology ; Rats ; Receptors, N-Methyl-D-Aspartate/physiology ; Synapses/*physiology ; *Synaptic Transmission ; Tetrodotoxin/pharmacology
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  • 6
    Publication Date: 1994-12-09
    Description: AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor channels mediate the fast component of excitatory postsynaptic currents in the central nervous system. Site-selective nuclear RNA editing controls the calcium permeability of these channels, and RNA editing at a second site is shown here to affect the kinetic aspects of these channels in rat brain. In three of the four AMPA receptor subunits (GluR-B, -C, and -D), intronic elements determine a codon switch (AGA, arginine, to GGA, glycine) in the primary transcripts in a position termed the R/G site, which immediately precedes the alternatively spliced modules "flip" and "flop." The extent of editing at this site progresses with brain development in a manner specific for subunit and splice form, and edited channels possess faster recovery rates from desensitization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lomeli, H -- Mosbacher, J -- Melcher, T -- Hoger, T -- Geiger, J R -- Kuner, T -- Monyer, H -- Higuchi, M -- Bach, A -- Seeburg, P H -- New York, N.Y. -- Science. 1994 Dec 9;266(5191):1709-13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Molecular Neuroendocrinology, University of Heidelberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7992055" target="_blank"〉PubMed〈/a〉
    Keywords: Alternative Splicing ; Amino Acid Sequence ; Animals ; Base Sequence ; Brain/embryology/*metabolism ; Cell Nucleus/metabolism ; Exons ; Glutamic Acid/pharmacology ; Glycine/genetics ; Introns ; Kinetics ; Membrane Potentials ; Molecular Sequence Data ; Oocytes ; PC12 Cells ; Patch-Clamp Techniques ; *RNA Editing ; Rats ; Rats, Wistar ; Receptors, AMPA/*genetics/*metabolism ; Recombinant Proteins/metabolism ; Xenopus
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  • 7
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-02-18
    Description: Molecular chaperones of the Hsp70 type transiently sequester unfolded segments of proteins and promote their correct folding. Target peptides were labeled with an environmentally sensitive fluorophore so that their binding to the molecular chaperone DnaK of Escherichia coli could be followed in real time. The two-step process was characterized by relaxation times of 27 seconds and 200 seconds with 2 microM DnaK and 0.1 microM ligand at 25 degrees C. In the presence of adenosine triphosphate, the formation of the complex was greatly accelerated and appeared to be a single-exponential process with a relaxation time of 0.4 second. The binding-release cycle of DnaK thus occurs in the time range of polypeptide chain elongation and folding and is too fast to be stoichiometrically coupled to the adenosine triphosphatase activity of the chaperone (turnover number, 0.13 per minute at 30 degrees C).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmid, D -- Baici, A -- Gehring, H -- Christen, P -- New York, N.Y. -- Science. 1994 Feb 18;263(5149):971-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biochemisches Institut, Universitat Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8310296" target="_blank"〉PubMed〈/a〉
    Keywords: 2-Naphthylamine/analogs & derivatives ; Adenosine Triphosphatases/metabolism ; Adenosine Triphosphate/analogs & derivatives/pharmacology ; Amino Acid Sequence ; Aspartate Aminotransferases/metabolism ; Bacterial Proteins/*metabolism ; Binding Sites ; Enzyme Precursors/metabolism ; *Escherichia coli Proteins ; Fluorescent Dyes ; *HSP70 Heat-Shock Proteins ; Heat-Shock Proteins/*metabolism ; Kinetics ; Molecular Sequence Data ; Peptide Fragments/*metabolism
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  • 8
    Publication Date: 1994-08-05
    Description: The high-mobility group protein 14 (HMG-14) is a non-histone chromosomal protein that is preferentially associated with transcriptionally active chromatin. To assess the effect of HMG-14 on transcription by RNA polymerase II, in vivo-assembled chromatin with elevated amounts of HMG-14 was obtained. Here it is shown that HMG-14 enhanced transcription on chromatin templates but not on DNA templates. This protein stimulated the rate of elongation by RNA polymerase II but not the level of initiation of transcription. These findings suggest that the association of HMG-14 with nucleosomes is part of the cellular process involved in the generation of transcriptionally active chromatin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ding, H F -- Rimsky, S -- Batson, S C -- Bustin, M -- Hansen, U -- GM-36667/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 5;265(5173):796-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Molecular Genetics, Dana-Farber Cancer Institute, Boston, MA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8047885" target="_blank"〉PubMed〈/a〉
    Keywords: Chromatin/metabolism ; HeLa Cells ; High Mobility Group Proteins/*physiology ; Humans ; Kinetics ; RNA Polymerase II/*metabolism ; Simian virus 40/genetics ; Templates, Genetic ; Transcription, Genetic/*physiology
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  • 9
    Publication Date: 1994-08-05
    Description: Activation of 2-5A-dependent ribonuclease by 5'-phosphorylated, 2',5'-linked oligoadenylates, known as 2-5A, is one pathway of interferon action. Unaided uptake into HeLa cells of 2-5A linked to an antisense oligonucleotide resulted in the selective ablation of messenger RNA for the double-stranded RNA (dsRNA)-dependent protein kinase PKR. Similarly, purified, recombinant human 2-5A-dependent ribonuclease was induced to selectively cleave PKR messenger RNA. Cells depleted of PKR activity were unresponsive to activation of nuclear factor-kappa B (NF-kappa B) by the dsRNA poly(I):poly(C), which provides direct evidence that PKR is a transducer for the dsRNA signaling of NF-kappa B.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maran, A -- Maitra, R K -- Kumar, A -- Dong, B -- Xiao, W -- Li, G -- Williams, B R -- Torrence, P F -- Silverman, R H -- AI 28253/AI/NIAID NIH HHS/ -- AI 34039-02/AI/NIAID NIH HHS/ -- CA 44059/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 5;265(5173):789-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cancer Biology, Cleveland Clinic Foundation, OH 44195.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7914032" target="_blank"〉PubMed〈/a〉
    Keywords: Adenine Nucleotides/chemical synthesis/*pharmacology ; Base Sequence ; Endoribonucleases/metabolism ; Enzyme Activation ; HeLa Cells ; Humans ; Kinetics ; Molecular Sequence Data ; NF-kappa B/*antagonists & inhibitors ; Oligonucleotides, Antisense/chemical synthesis/*pharmacology ; Oligoribonucleotides/chemical synthesis/*pharmacology ; Protein-Serine-Threonine Kinases/*genetics ; RNA, Messenger/drug effects ; Signal Transduction/*drug effects ; eIF-2 Kinase
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  • 10
    Publication Date: 1994-07-29
    Description: The Escherichia coli chaperonins GroEL and GroES facilitate protein folding in an adenosine triphosphate (ATP)-dependent manner. After a single cycle of ATP hydrolysis by the adenosine triphosphatase (ATPase) activity of GroEL, the bi-toroidal GroEL formed a stable asymmetric ternary complex with GroES and nucleotide (bulletlike structures). With each subsequent turnover, ATP was hydrolyzed by one ring of GroEL in a quantized manner, completely releasing the adenosine diphosphate and GroES that were tightly bound to the other ring as a result of the previous turnover. The catalytic cycle involved formation of a symmetric complex (football-like structures) as an intermediate that accumulated before the rate-determining hydrolytic step. After one to two cycles, most of the substrate protein dissociated still in a nonnative state, which is consistent with intermolecular transfer of the substrate protein between toroids of high and low affinity. A unifying model for chaperonin-facilitated protein folding based on successive rounds of binding and release, and partitioning between committed and kinetically trapped intermediates, is proposed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Todd, M J -- Viitanen, P V -- Lorimer, G H -- New York, N.Y. -- Science. 1994 Jul 29;265(5172):659-66.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉E. I. DuPont de Nemours and Company, Central Research and Development Department, Wilmington, DE 19880.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7913555" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/*metabolism ; Bacterial Proteins/*metabolism ; Binding Sites ; Chaperonin 10 ; Chaperonin 60 ; Heat-Shock Proteins/*metabolism ; Kinetics ; Models, Chemical ; *Protein Folding ; Ribulose-Bisphosphate Carboxylase/metabolism
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  • 11
    Publication Date: 1994-09-02
    Description: A beta 1-40, a major component of Alzheimer's disease cerebral amyloid, is present in the cerebrospinal fluid and remains relatively soluble at high concentrations (less than or equal to 3.7 mM). Thus, physiological factors which induce A beta amyloid formation could provide clues to the pathogenesis of the disease. It has been shown that human A beta specifically and saturably binds zinc. Here, concentrations of zinc above 300 nM rapidly destabilized human A beta 1-40 solutions, inducing tinctorial amyloid formation. However, rat A beta 1-40 binds zinc less avidly and is immune to these effects, perhaps explaining the scarcity with which these animals form cerebral A beta amyloid. These data suggest a role for cerebral zinc metabolism in the neuropathogenesis of Alzheimer's disease.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bush, A I -- Pettingell, W H -- Multhaup, G -- d Paradis, M -- Vonsattel, J P -- Gusella, J F -- Beyreuther, K -- Masters, C L -- Tanzi, R E -- R01 AG11899-01/AG/NIA NIH HHS/ -- R01 NS30428-03/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 2;265(5177):1464-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Genetics and Aging, Massachusetts General Hospital, Boston.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8073293" target="_blank"〉PubMed〈/a〉
    Keywords: Alzheimer Disease/etiology/*metabolism ; Amyloid beta-Peptides/chemistry/*metabolism ; Animals ; Brain/metabolism ; Edetic Acid/pharmacology ; Humans ; Kinetics ; Mice ; Peptide Fragments/chemistry/*metabolism ; Rats ; Solubility ; Zinc/*metabolism/pharmacology
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  • 12
    Publication Date: 1994-07-08
    Description: Monoclonal antibodies, induced with a phosphonate diester hapten, catalyzed the coupling of p-nitrophenyl esters of N-acetyl valine, leucine, and phenylalanine with tryptophan amide to form the corresponding dipeptides. All possible stereoisomeric combinations of the ester and amide substrates were coupled at comparable rates. The antibodies did not catalyze the hydrolysis of the dipeptide product nor hydrolysis or racemization of the activated esters. The yields of the dipeptides ranged from 44 to 94 percent. The antibodies were capable of multiple turnovers at rates that exceeded the rate of spontaneous ester hydrolysis. This achievement suggests routes toward creating a small number of antibody catalysts for polypeptide syntheses.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hirschmann, R -- Smith, A B 3rd -- Taylor, C M -- Benkovic, P A -- Taylor, S D -- Yager, K M -- Sprengeler, P A -- Benkovic, S J -- GM-45611/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jul 8;265(5169):234-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Pennsylvania, Philadelphia 19104.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8023141" target="_blank"〉PubMed〈/a〉
    Keywords: Antibodies, Catalytic/*metabolism ; Antibodies, Monoclonal/*metabolism ; Binding Sites, Antibody ; Dipeptides/*biosynthesis ; Esters ; Haptens ; Kinetics ; Leucine/analogs & derivatives/metabolism ; Molecular Conformation ; Phenylalanine/analogs & derivatives/metabolism ; Stereoisomerism ; Tryptophan/analogs & derivatives/metabolism ; Valine/analogs & derivatives/metabolism
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  • 13
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-03-11
    Description: The repair of cyclobutane pyrimidine dimers (CPDs), DNA lesions induced by ultraviolet light, was studied at nucleotide resolution. Human fibroblasts were irradiated with ultraviolet light and allowed to repair. The DNA was enzymatically cleaved at the CPDs, and the induced breaks along the promoter and exon 1 of the PGK1 gene were mapped by ligation-mediated polymerase chain reaction. Repair rates within the nontranscribed strand varied as much as 15-fold, depending on nucleotide position. Preferential repair of the transcribed strand began just downstream of the transcription start site but was most pronounced beginning at nucleotide +140 in exon 1. The promoter contained two slowly repaired regions that coincided with two transcription factor binding sites.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gao, S -- Drouin, R -- Holmquist, G P -- CA54773/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1994 Mar 11;263(5152):1438-40.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Beckman Research Institute of the City of Hope, Department of Biology, Duarte, CA 91010.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8128226" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Cells, Cultured ; *DNA Repair ; Exons ; *Genes ; HeLa Cells ; Humans ; Kinetics ; Phosphoglycerate Kinase/*genetics ; Promoter Regions, Genetic ; Pyrimidine Dimers/*metabolism ; Skin/metabolism/*radiation effects ; Transcription Factors/metabolism ; Transcription, Genetic ; Ultraviolet Rays
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  • 14
    Publication Date: 1994-08-12
    Description: The critical discriminatory event in the activation of T lymphocytes bearing alpha beta T cell receptors (TCRs) is their interaction with a molecular complex consisting of a peptide bound to a major histocompatibility complex (MHC)-encoded class I or class II molecule on the surface of an antigen-presenting cell. The kinetics of binding were measured of a purified TCR to molecular complexes of a purified soluble analog of the murine MHC class I molecule H-2Ld (sH-2Ld) and a synthetic octamer peptide p2CL in a direct, real-time assay based on surface plasmon resonance. The kinetic dissociation rate of the MHC-peptide complex from the TCR was rapid (2.6 x 10(-2) second-1, corresponding to a half-time for dissociation of approximately 27 seconds), and the kinetic association rate was 2.1 x 10(5) M-1 second-1. The equilibrium constant for dissociation was approximately 10(-7) M. These values indicate that TCRs must interact with a multivalent array of MHC-peptide complexes to trigger T cell signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Corr, M -- Slanetz, A E -- Boyd, L F -- Jelonek, M T -- Khilko, S -- al-Ramadi, B K -- Kim, Y S -- Maher, S E -- Bothwell, A L -- Margulies, D H -- New York, N.Y. -- Science. 1994 Aug 12;265(5174):946-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular Biology Section, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8052850" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Biosensing Techniques ; H-2 Antigens/*metabolism ; Histocompatibility Antigen H-2D ; Kinetics ; *Major Histocompatibility Complex ; Mice ; Molecular Sequence Data ; Oligopeptides/*metabolism ; Receptors, Antigen, T-Cell, alpha-beta/*metabolism ; Solubility
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  • 15
    Publication Date: 1994-02-04
    Description: Age-specific mortality rates in isogenic populations of the nematode Caenorhabditis elegans increase exponentially throughout life. In genetically heterogeneous populations, age-specific mortality increases exponentially until about 17 days and then remains constant until the last death occurs at about 60 days. This period of constant age-specific mortality results from genetic heterogeneity. Subpopulations differ in mean life-span, but they all exhibit near exponential, albeit different, rates of increase in age-specific mortality. Thus, much of the observed heterogeneity in mortality rates later in life could result from genetic heterogeneity and not from an inherent effect of aging.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Brooks, A -- Lithgow, G J -- Johnson, T E -- K04-AG00369/AG/NIA NIH HHS/ -- R01-AG08332/AG/NIA NIH HHS/ -- R01-AG10248/AG/NIA NIH HHS/ -- New York, N.Y. -- Science. 1994 Feb 4;263(5147):668-71.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Behavioral Genetics, University of Colorado, Boulder 80309.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8303273" target="_blank"〉PubMed〈/a〉
    Keywords: Aging ; Animals ; Caenorhabditis elegans/genetics/*physiology ; *Genetic Variation ; Kinetics ; Longevity/genetics ; Mortality
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  • 16
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-06-24
    Description: Formation of a short (less than 2.5 angstroms), very strong, low-barrier hydrogen bond in the transition state, or in an enzyme-intermediate complex, can be an important contribution to enzymic catalysis. Formation of such a bond can supply 10 to 20 kilocalories per mole and thus facilitate difficult reactions such as enolization of carboxylate groups. Because low-barrier hydrogen bonds form only when the pKa's (negative logarithm of the acid constant) of the oxygens or nitrogens sharing the hydrogen are similar, a weak hydrogen bond in the enzyme-substrate complex in which the pKa's do not match can become a strong, low-barrier one if the pKa's become matched in the transition state or enzyme-intermediate complex. Several examples of enzymatic reactions that appear to use this principle are presented.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cleland, W W -- Kreevoy, M M -- GM 18938/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Jun 24;264(5167):1887-90.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Enzyme Research, University of Wisconsin, Madison 53705.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8009219" target="_blank"〉PubMed〈/a〉
    Keywords: Aconitate Hydratase/chemistry/metabolism ; Binding Sites ; Carboxypeptidases/chemistry/metabolism ; *Catalysis ; Citrate (si)-Synthase/chemistry/metabolism ; Enzymes/*metabolism ; *Hydrogen Bonding ; Isomerases/chemistry/metabolism ; Kinetics ; Orotidine-5'-Phosphate Decarboxylase/chemistry/metabolism ; Racemases and Epimerases/chemistry/metabolism ; Thermolysin/chemistry/metabolism
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 17
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-05-27
    Description: Two major goals for the design of new catalysts are the facilitation of chemical transformations and control of product outcome. An antibody has been induced that efficiently catalyzes a cationic cyclization in which an acyclic olefinic sulfonate ester substrate is converted almost exclusively (98 percent) to a cyclic alcohol. The key to the catalysis of the reaction and the restriction of the product complexity is the use of antibody binding energy to rigidly enforce a concerted mechanism in accord with the design of the hapten. Thus, the ability to direct binding energy allows the experimenter to dictate a reaction mechanism which is an otherwise difficult task in chemistry. New catalysts for cationic cyclization may be of general use in the formation of carbon-carbon and carbon-heteroatom bonds leading to multi-ring molecules including steroids and heterocyclic compounds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, T -- Janda, K D -- Ashley, J A -- Lerner, R A -- GM-43858/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 May 27;264(5163):1289-93.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Scripps Research Institute, Department of Molecular Biology, La Jolla, CA 92037.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8191282" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibodies, Catalytic/*chemistry ; Antibodies, Monoclonal/chemistry ; Catalysis ; Cations/*chemistry ; Chromatography, Gas ; Cyclization ; Haptens ; Kinetics ; Mice ; Organosilicon Compounds/*chemistry ; Sulfanilic Acids/*chemistry
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  • 18
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-03-04
    Description: Any RNA, when in a complex with another oligoribonucleotide known as an external guide sequence (EGS), can become a substrate for ribonuclease P. Simulation of evolution in vitro was used to select EGSs that bind tightly to a target substrate messenger RNA and that increase the efficiency of cleavage of the target by human ribonuclease P to a level equal to that achieved with natural substrates. The most efficient EGSs form transfer RNA precursor-like structures with the target RNA, in which the analog of the anticodon stem has been disrupted, an indication that selection for the optimal substrate for ribonuclease P yields an RNA structure different from that of present-day transfer RNA precursors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yuan, Y -- Altman, S -- AI31876/AI/NIAID NIH HHS/ -- GM19422/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Mar 4;263(5151):1269-73.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Yale University, New Haven, CT 06520.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8122108" target="_blank"〉PubMed〈/a〉
    Keywords: Anticodon/chemistry/metabolism ; Base Sequence ; Chloramphenicol O-Acetyltransferase/genetics ; Endoribonucleases/*metabolism ; Humans ; Kinetics ; Magnesium/pharmacology ; Molecular Sequence Data ; Nucleic Acid Conformation ; Oligoribonucleotides/chemistry/*metabolism ; RNA Precursors/chemistry/metabolism ; RNA, Catalytic/*metabolism ; RNA, Guide/chemistry/*metabolism ; RNA, Messenger/chemistry/*metabolism ; RNA, Transfer/chemistry/metabolism ; Ribonuclease P ; Thermodynamics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 19
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-08-12
    Description: The folding pathways of large, highly structured RNA molecules are largely unexplored. Insight into both the kinetics of folding and the presence of intermediates was provided in a study of the Mg(2+)-induced folding of the Tetrahymena ribozyme by hybridization of complementary oligodeoxynucleotide probes. This RNA folds via a complex mechanism involving both Mg(2+)-dependent and Mg(2+)-independent steps. A hierarchical model for the folding pathway is proposed in which formation of one helical domain (P4-P6) precedes that of a second helical domain (P3-P7). The overall rate-limiting step is formation of P3-P7, and takes place with an observed rate constant of 0.72 +/- 0.14 minute-1. The folding mechanism of large RNAs appears similar to that of many multidomain proteins in that formation of independently stable substructures precedes their association into the final conformation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zarrinkar, P P -- Williamson, J R -- New York, N.Y. -- Science. 1994 Aug 12;265(5174):918-24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8052848" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Introns ; Kinetics ; Magnesium/metabolism/pharmacology ; Models, Chemical ; Molecular Sequence Data ; *Nucleic Acid Conformation ; Nucleic Acid Hybridization ; Oligonucleotide Probes ; RNA, Catalytic/*chemistry/metabolism ; RNA, Protozoan/*chemistry ; Ribonuclease H/metabolism ; Temperature ; Tetrahymena/*genetics
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 20
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-04-08
    Description: Editing reactions are essential for the high fidelity of information transfer in processes such as replication, RNA splicing, and protein synthesis. The accuracy of interpretation of the genetic code is enhanced by the editing reactions of aminoacyl transfer RNA (tRNA) synthetases, whereby amino acids are prevented from being attached to the wrong tRNAs. Amino acid discrimination is achieved through sieves that may overlap with or coincide with the amino acid binding site. With the class I Escherichia coli isoleucine tRNA synthetase, which activates isoleucine and occasionally misactivates valine, as an example, a rationally chosen mutant enzyme was constructed that lacks entirely its normal strong ability to distinguish valine from isoleucine by the initial amino acid recognition sieve. The misactivated valine, however, is still eliminated by hydrolytic editing reactions. These data suggest that there is a distinct sieve for editing that is functionally independent of the amino acid binding site.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmidt, E -- Schimmel, P -- GM 15539/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Apr 8;264(5156):265-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8146659" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Binding Sites ; Escherichia coli/enzymology ; Isoleucine/*metabolism ; Isoleucine-tRNA Ligase/chemistry/genetics/*metabolism ; Kinetics ; Mutation ; Protein Structure, Secondary ; *RNA Editing ; RNA, Transfer, Ile/metabolism ; Valine/*metabolism
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  • 21
    Publication Date: 1994-02-25
    Description: Intracellular vesicles destined to fuse with the plasma membrane and secrete their contents must have a mechanism for specifically interacting with the appropriate target membrane. Such a mechanism is now suggested by the demonstration of specific interaction between vesicular proteins and plasma membrane proteins. The vesicle-associated membrane proteins (VAMPs) 1 and 2 specifically bind the acceptor membrane proteins syntaxin 1A and 4 but not syntaxin 2 or 3. The binding site is within amino acids 194 to 267 of syntaxin 1A, and the approximate equilibrium dissociation constants is 4.7 x 10(-6) molar. These data suggest a physical basis for the specificity of intracellular vesicular transport.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Calakos, N -- Bennett, M K -- Peterson, K E -- Scheller, R H -- New York, N.Y. -- Science. 1994 Feb 25;263(5150):1146-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Stanford University Medical Center, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8108733" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antigens, Surface/*metabolism ; Binding Sites ; Cell Line ; Cell Membrane/metabolism ; Cytoplasm/metabolism ; Haplorhini ; Kinetics ; Membrane Proteins/*metabolism ; Molecular Sequence Data ; Nerve Tissue Proteins/*metabolism ; R-SNARE Proteins ; Recombinant Fusion Proteins/metabolism ; Synaptic Vesicles/*metabolism ; Syntaxin 1
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 22
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1994-02-18
    Description: A change in radical pair recombination rates is one of the few mechanisms by which a magnetic field can interact with a biological system. The kinetic parameter Vmax/Km (where Km is the Michaelis constant) for the coenzyme B12-dependent enzyme ethanolamine ammonia lyase was decreased 25 percent by a static magnetic field near 0.1 tesla (1000 gauss) with unlabeled ethanolamine and decreased 60 percent near 0.15 tesla with perdeuterated ethanolamine. This effect is likely caused by a magnetic field-induced change in intersystem crossing rates between the singlet and triplet spin states in the [cob(II)alamin:5'-deoxyadenosyl radical] spin-correlated radical pair.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Harkins, T T -- Grissom, C B -- ES05728/ES/NIEHS NIH HHS/ -- New York, N.Y. -- Science. 1994 Feb 18;263(5149):958-60.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Utah, Salt Lake City 84112.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8310292" target="_blank"〉PubMed〈/a〉
    Keywords: Deuterium ; Ethanolamine ; Ethanolamine Ammonia-Lyase/*metabolism ; Ethanolamines/metabolism ; Kinetics ; *Magnetics ; Photolysis ; Vitamin B 12/pharmacology
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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