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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thrombosis and thrombolysis 5 (1998), S. 9-14 
    ISSN: 1573-742X
    Keywords: fibrinogen ; platelets ; fibrinolysis ; tissue-type plasminogen activator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Oxidant stress leads to covalent oxidative modification of several plasma proteins, chief among which is fibrinogen. Aspirin can nonenzymatically acetylate fibrinogen's lysine residues, the functional groups most susceptible to oxidative modification. Because oxidation of fibrinogen may occur in the atheromatous environment, we studied the effects of oxidative modification on fibrinogen function and the consequences of acetylation by aspirin on fibrinogen's susceptibility to oxidation and functional properties. We exposed fibrinogen to Fe3+ ascorbate for 1 hour and showed that the carbonyl/protein molar ratio increased from 0.71 ± 0.18 to 2.86 ± 0.50 mol carbonyl/mol protein (P 〈 0.02) with an accompanying reduction in the α-helical content of the protein from 34% to 29%. Exposure of fibrinogen to aspirin led to acetylation of lysine residues and inhibition of oxidation. Oxidized fibrinogen was more readily able to form fibrin, and acetylation prevented this enhancement of clot formation. Oxidized fibrinogen also supported platelet aggregation better than did native, unoxidized fibrinogen, and acetylation of fibrinogen prior to oxidation prevented the enhanced platelet aggregation. Oxidized fibrinogen was less effective in stimulating plasminogen activation by tissue-type plasminogen activator (t-PA), with a catalytic efficiency that was reduced by 88% compared with native, unoxidized fibrinogen; acetylated fibrinogen, by contrast, enhanced plasminogen activation by t-PA with a catalytic efficiency that was increased by 18% compared with native, unoxidized fibrinogen (P 〈 0.05) and was increased by 51% compared with oxidized fibrinogen(P 〈 0.05). Acetylation prevented the reduction in catalytic efficiency induced by oxidation. These data show that oxidized fibrinogen manifests prothrombotic effects that can be prevented by acetylation and suggest that inhibition of fibrinogen oxidation may be an additional antithrombotic benefit of aspirin therapy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 5 (1989), S. 156-165 
    ISSN: 0887-3585
    Keywords: retrovirus integrase ; circular dichroism ; homologous proteins ; secondary structural predictions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The retrovirus integrase (IN) protein is essentialfor integration of viral DNA into host DNA. The secondary structure of thepurified IN protein from avian myeloblastosis virus was investigated by bothcircular dichroism (CD) spectroscopy and five empirical prediction methods. The secondary structures determined from the resolving of CD spectra through a least-squares curve fitting procedure were compared with those predicted from four statistical methods, e.g., the Chou-Fasman, arnier-Osguthorpe-Robson, Nishikawa-Ooi, and a JOINT scheme which combined all three of these methods, plus a pure a priori one, the Ptitsyn-Finkelstein method. Among all of the methods used, the Nishikawa-Ooiprediction gave the closest match in the composition of secondary structureto the CD result, although the other methods each correctly predictedoneor more secondary structural group. Most of the α-helix and β-sheet states predicted by the Ptitsyn-Finkelstein methodwere in accord with the Nishikawa-Ooi method. Secondary structural predictions by the Nishikawa-Ooi method were extended further toinclude IN proteins from four phylogenetic distinct retroviruses. The structuralrelationships between the four most conserved amino acid blocks of these IN proteins were compared using sequence homology and secondary structure predictions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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