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  • Articles  (36)
  • Kinetics
  • American Association for the Advancement of Science (AAAS)  (36)
  • Blackwell Publishing Ltd
  • 1995-1999  (26)
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  • Articles  (36)
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  • 1
    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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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
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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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  • 8
    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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  • 9
    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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  • 10
    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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