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  • Polymer and Materials Science  (11)
  • Amino Acid Sequence  (3)
  • Cell & Developmental Biology
  • Organic Chemistry
  • 1990-1994  (16)
  • 1935-1939
  • 1994  (16)
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  • 1990-1994  (16)
  • 1935-1939
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  • 1
    ISSN: 0887-6266
    Schlagwort(e): miscibility of polycarbonate blends ; domain size of acrylic and polycarbonate blends ; imaging analysis ; intramolecular interactions in copolymer ; 1H T1p (proton NMR relaxation time) ; Differential Scanning Calorimetry ; Transmission Electron Microscopy ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The miscibility of polycarbonate (PC) with poly(methyl methacrylate-co-cyclohexyl methacrylate) (PMCHM) and with poly(methyl methacrylate) (PMMA) was studied by nuclear magnetic resonance (NMR) 1H spin-lattice relaxation time in the rotating frame (1H T1p), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). A blend of PC/PMCHM (50/50 wt/wt) with the acrylic component PMCHM, a copolymer of PMMA and poly(cyclohexyl methacrylate) (80/20 wt/wt), shows only one T1p value, which indicates high miscibility in this blend. A blend of PC/PMMA (50/50 wt/wt) shows two 1H T1p values, which are similar to those of the homopolymers PC and PMMA. These results indicate high immiscibility. The “domain size” calculated from NMR results of the miscible blend PC/PMCHM is approximately 40 Å. The results of DSC and TEM are similar to the NMR results. However, TEM results show the presence of 3% PC domains in the PC/PMCHM blend, which are not seen by NMR or DSC. Those PC domains are approximately 500 Å. A strong intramolecular repulsion in the copolymer PMCHM and specific intermolecular interactions between PC and PMMA may explain the miscibility in the PC/PMCHM system. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 78-86 
    ISSN: 1040-452X
    Schlagwort(e): Marsupial ; Sperm head ; Chromatin ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: 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.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1913-1916 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Physisorption of nitrogen at one specific pressure is used to determine the specific surface area of a flocculated polystyrene latex by applying BET theory. Assuming that a flocculated sample of Polymer latex is composed of distinct spherical latex particles (i.e., there is no coagulation of particles), the volume-surface-average diameter can be calculated. The resulting diameters are compared to sizes obtained using a disc centrifuge sedimentometer, which fractionizes the particles by sedimentation. The diameters from both techniques were in good agreement, showing that physisorption of nitrogen, which is a simple technique, can be used to determine sizes of flocculated latex particles. This agreement also shows that the flocculation of the polystyrene latex produced separate nonporous spherical particles. When flocculation of a latex is done above its glass transition temperature, coagulation will occur. While other particle sizing techniques can produce particle size distributions, the physisorption of nitrogen only gives the volume-surface-average diameter. However, one advantage of the physisorption of nitrogen is that it covers a broad range of particle sizes compared to most other techniques. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 419-427 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This article describes studies on oxidative-photodegradation of cured Epolite epoxy resin using techniques of IR spectroscopy with attenuated total reflectance optics and scanning electron microscopy. The results show that the oxidative-photodegradation of this epoxy system is characterized by the formation and subsequent decomposition of carbonyl groups and by epoxy ring opening. The carbonyl bonds are apparently formed in the initial stage of photodegradation and then decomposed upon further aging. Changes in the surface morphology of the samples during degradation suggest that there is significant scissioning of the cross-linked polymer structure. This phenomenon was reproduced using three different UV lamps that differed in spectral properties. Our studies provide clues to the mechanism of epoxy polymer degradation by solar light. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1175-1186 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The composition of the protein layer adsorbed to a polymer has been thought to be important for the adhesion of platelets. The state of activation of adherent platelets is an additional factor that may be a predictor of biocompatibility. Activation refers to the degree of change from discoid shape to any of several spread shapes. The conformation and orientation of adsorbed adhesive proteins, which interact with receptors on the membrane of platelets, such as fibrinogen, fibronectin, and von Willebrand factor, may also be important for platelet adhesion and activation. This work deals with the behaviour of fibrinogen adsorbed to PMMA alone, where the experimental variable was incubation time with the substrate, and with adsorbed fibrinogen mixed with albumin, where the experimental variable was the molar percent of fibrinogen in the adsorption solution. Shorter protein incubation times and increased albumin levels in the initial fibrinogen adsorption solution enhanced the percentages of activated platelet morphologies and increased adsorbed fibrinogen redistribution by the platelet. Lower concentrations of albumin in the initial adsorption solution enhanced platelet adhesion numbers; fibrinogen incubation time had no effect. Together, these factors can contribute to the biocompatibility of a biomaterial through their effect on platelet adhesion and activation. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 1994-07-22
    Beschreibung: 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〉
    Schlagwort(e): 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
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 1994-08-19
    Beschreibung: 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〉
    Schlagwort(e): 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
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 1994-12-23
    Beschreibung: 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〉
    Schlagwort(e): 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
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 25 (1994), S. 369-372 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Im vorliegender I. Teil dieses Beitrages werden die theoretischen Grundlagen des Umwandlungsverhaltens und der Kohlenstofflöslichkeit im Austenit von Gußeisen an Hand dafür relevanter Zustandsdiagramme behandelt. Härtbarkeitsuntersuchungen an unlegierten und niedridglegierten Gußeisenwerkstoffen mittels des JOMINY-Tests werden im Teil II des Beitrages vorgestellt und im III. Teil Möglichkeiten zur Charakterisierung des Umwandlungsverhaltens aufgezeigt und diskutiert.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 25 (1994), S. 410-414 
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Nachdem im I. Teil dieses Beitrages die theoretischen Grundlagen des Umwandlungsverhaltens und der Kohlenstofflöslichkeit im Austenit des Gußeisens erörtert wurden, wird im II. Teil die Härtbarkeit von unlegierten und niedriglegierten Gußisenwerkstoffen untersucht. Die Härtbarkeit wird durch die Härtbarkeitskriterien a35 und a45 aus dem JOMINY-Test charakterisiert.Im noch folgenden III. Teil dieser Arbeit werden Möglichkeiten zur Beschreibung des Umwandlungverhaltens von Gußeisen durch kontinuierliche Stirnabschreckproben-Diagramme (KSA) aufgezeigt und diskutiert.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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