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  • FLURBIPROFEN  (1)
  • electron paramagnetic resonance  (1)
  • 1
    ISSN: 1573-5079
    Schlagwort(e): electron paramagnetic resonance ; managanese cluster ; oxygen evolution ; oxygen evolving complex ; Photosystem II ; proton transfer ; tyrosine radical ; water oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Recent magnetic-resonance work on YŻ suggests that this species exhibits considerable motional flexibility in its functional site and that its phenol oxygen is not involved in a well-ordered hydrogen-bond interaction (Tang et al., submitted; Tommos et al., in press). Both of these observations are inconsistent with a simple electron-transfer function for this radical in photosynthetic water oxidation. By considering the roles of catalytically active amino acid radicals in other enzymes and recent data on the water-oxidation process in Photosystem II, we rationalize these observations by suggesting that YŻ functions to abstract hydrogen atoms from aquo- and hydroxy-bound managanese ions in the (Mn)4 cluster on each S-state transition. The hydrogen-atom abstraction process may occur either by sequential or concerted kinetic pathways. Within this model, the (Mn)4/YZ center forms a single catalytic center that comprises the Oxygen Evolving Complex in Photosystem II.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-2568
    Schlagwort(e): ULCEROGENICITY ; SMALL INTESTINE ; FLURBIPROFEN ; ENANTIOMERS ; MECHANISM ; NEUTROPHILS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We previously observed a marked increase ingastrointestinal toxicity of rac -flurbiprofen comparedto the therapeutically equivalent dose of the Senantiomer. This paper quantitates these observations and examines the mechanism by which thisparadoxical toxicity occurs. We have evaluated the ulcerscores, mucosal neutrophil infiltration, byimmunostaining of CD11/18 antigen, and mucosalneutrophil activity by myeloperoxidase measurement at two doselevels of (R)-, (S)-, and rac-flurbiprofen, administeredover 30 days. Dose-response for intestinal ulcerproduction was observed for rac- and (S)-flurbiprofen; animals given (R)flurbiprofen exhibited noulcers. Yet rac-flurbiprofen proved to be twice asulcerogenic as (S)-flurbiprofen. The mechanism of theexacerbation of gastrointestinal toxicity of(S)flurbiprofen by the noncyclooxygenase inhibiting(R)-flurbiprofen is believed to be associated with itseffect on ICAM-1 up-regulation. This is followed byneutrophil adhesiveness to ICAM-1 via the LFA-1 antigenon its surface and the extravasation ofneutrophils into the tissue. We also examined the effectof high dose (R)-flurbiprofen vs vehicle over 15 days inanimals in which ulcers had been produced by treatment with (S)-flurbiprofen for the previous 15 days.(R)-flurbiprofen did not sustain induced ulcers. Theresults of this study suggest that human studies beconducted to determine if enhanced gastrointestinal toxicity occurs in man. This is at issue sincerac compounds of this class are available over thecounter and others may be introduced.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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