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  • Amino Acid Sequence  (3)
  • Cell & Developmental Biology
  • Organic Chemistry
  • 1990-1994  (5)
  • 1935-1939
  • 1994  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Unusual nuclear structure of the spermatozoon in a marsupial, Sminthopsis crassicaudata (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 78-86 
    Details
    ISSN: 1040-452X
    Keywords: Marsupial ; Sperm head ; Chromatin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The organization of sperm chromatin in the dasyurid marsupial, Sminthopsis crassicaudata, was investigated using various morphological techniques. Transmission electron microscopy indicates two quite distinct chromatin regions became evident late in spermiogenesis with an outer globular region containing blocks of very electron-dense chromatin. Fluorescent light microscopical studies after staining with DNA dyes and 7-amino actinomycin D of testicular, caput, and cauda epididymal spermatozoa showed that this region fluoresced less brightly than the rest of the nucleus, indicating the presence of fewer DNA binding sites. Freeze fracture showed that the chromatin in most of the nucleus had randomly arranged particles of various sizes, but that of the outer region was composed entirely of small particles. This outer region was more resistant to low concentrations of the ionic detergent, SDS, whereas both guanidine hydrochloride and urea together with sodium chloride generally dispersed all the chromatin except that in the outer globular region and in a localized area of the nucleus beneath the acrosome. This study has thus revealed that the outer globular chromatin of these spermatozoa responds differently to ionic detergents and protein denaturing agents and has a different chromatin organization than most of the rest of the nucleus. The significance of these differences remains, however, to be determined. © 1994 Wiley-Liss, Inc.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370111
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  • 2
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    Sensing starvation: a homoserine lactone--dependent signaling pathway in Escherichia coli (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-07-22
    Description: When nutrients become limiting, many bacteria differentiate and become resistant to environmental stresses. For Escherichia coli, this process is mediated by the sigma s subunit of RNA polymerase. Expression of sigma s was induced by homoserine lactone, a metabolite synthesized from intermediates in threonine biosynthesis. Homoserine lactone-dependent synthesis of sigma s was prevented by overexpression of a newly identified protein, RspA. The function of homoserine lactone derivatives in many cell density-dependent phenomena and the similarity of RspA to a Streptomyces ambofaciens protein suggest that synthesis of homoserine lactone may be a general signal of starvation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huisman, G W -- Kolter, R -- New York, N.Y. -- Science. 1994 Jul 22;265(5171):537-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7545940" target="_blank"〉PubMed〈/a〉
    Keywords: 4-Butyrolactone/*analogs & derivatives/metabolism/pharmacology ; Amino Acid Sequence ; Bacterial Proteins/*biosynthesis/chemistry/genetics/metabolism ; Catalase/metabolism ; Escherichia coli/genetics/*metabolism ; Gene Expression Regulation, Bacterial ; Models, Biological ; Molecular Sequence Data ; Operon ; Phenotype ; Sigma Factor/*biosynthesis/genetics ; *Signal Transduction ; Transcription, Genetic ; Vibrio/genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Crystal structure of a catalytic antibody with a serine protease active site (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-08-19
    Description: The three-dimensional structure of an unusually active hydrolytic antibody with a phosphonate transition state analog (hapten) bound to the active site has been solved to 2.5 A resolution. The antibody (17E8) catalyzes the hydrolysis of norleucine and methionine phenyl esters and is selective for amino acid esters that have the natural alpha-carbon L configuration. A plot of the pH-dependence of the antibody-catalyzed reaction is bell-shaped with an activity maximum at pH 9.5; experiments on mechanism lend support to the formation of a covalent acyl-antibody intermediate. The structural and kinetic data are complementary and support a hydrolytic mechanism for the antibody that is remarkably similar to that of the serine proteases. The antibody active site contains a Ser-His dyad structure proximal to the phosphorous atom of the bound hapten that resembles two of the three components of the Ser-His-Asp catalytic triad of serine proteases. The antibody active site also contains a Lys residue to stabilize oxyanion formation, and a hydrophobic binding pocket for specific substrate recognition of norleucine and methionine side chains. The structure identifies active site residues that mediate catalysis and suggests specific mutations that may improve the catalytic efficiency of the antibody. This high resolution structure of a catalytic antibody-hapten complex shows that antibodies can converge on active site structures that have arisen through natural enzyme evolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, G W -- Guo, J -- Huang, W -- Fletterick, R J -- Scanlan, T S -- DK39304/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1994 Aug 19;265(5175):1059-64.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8066444" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Antibodies, Catalytic/*chemistry/immunology/metabolism ; Binding Sites ; Computer Graphics ; Crystallization ; Crystallography, X-Ray ; Haptens/metabolism ; Hydrogen Bonding ; Hydrogen-Ion Concentration ; Hydrolysis ; Models, Molecular ; Molecular Sequence Data ; Protein Conformation ; Serine Endopeptidases/*chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    An all D-amino acid opioid peptide with central analgesic activity from a combinatorial library (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-12-23
    Description: A synthetic combinatorial library containing 52,128,400 D-amino acid hexapeptides was used to identify a ligand for the mu opioid receptor. The peptide, Ac-rfwink-NH2, bears no resemblance to any known opioid peptide. Simulations using molecular dynamics, however, showed that three amino acid moieties have the same spatial orientation as the corresponding pharmacophoric groups of the opioid peptide PLO17. Ac-rfwink-NH2 was shown to be a potent agonist at the mu receptor and induced long-lasting analgesia in mice. Analgesia produced by intraperitoneally administered Ac-rfwink-NH2 was blocked by intracerebroventricular administration of naloxone, demonstrating that this peptide may cross the blood-brain barrier.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dooley, C T -- Chung, N N -- Wilkes, B C -- Schiller, P W -- Bidlack, J M -- Pasternak, G W -- Houghten, R A -- DA-000138/DA/NIDA NIH HHS/ -- DA-02615/DA/NIDA NIH HHS/ -- DA-03742/DA/NIDA NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1994 Dec 23;266(5193):2019-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Torrey Pines Institute for Molecular Studies, San Diego, CA 92121.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7801131" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Analgesics/chemistry/metabolism/*pharmacology ; Animals ; Brain/metabolism ; Dose-Response Relationship, Drug ; Endorphins/pharmacology ; Enkephalin, Ala(2)-MePhe(4)-Gly(5)- ; Enkephalin, D-Penicillamine (2,5)- ; Enkephalins/metabolism ; Guinea Pigs ; Injections, Intraventricular ; Male ; Mice ; Models, Molecular ; Molecular Sequence Data ; Naloxone/administration & dosage/pharmacology ; Opioid Peptides/chemistry/metabolism/*pharmacology ; Pain Measurement ; Protein Conformation ; Rats ; Receptors, Opioid, mu/agonists/metabolism ; Stereoisomerism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 7. Neuartig verknüpfte Pyrazolyl- und Isoxazolyl-tetrazole aus Enaminoketon-Vorstufen (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 79-82 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 7. New Types of Pyrazolyl- and Isoxazolyl-tetrazoles from Enamino Ketone Precursors
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360118
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