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Kinetics and mechanism of the reversible binding of nitric oxide to reduced cobalamin $B_{12r}$ (Cob(II)alamin)


Kinetics and mechanism of the reversible binding of nitric oxide to reduced cobalamin $B_{12r}$ (Cob(II)alamin)

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dc.contributor.author Wolak, Maria pl
dc.contributor.author Zahl, Achim pl
dc.contributor.author Schneppensieper, Thorsten pl
dc.contributor.author Stochel, Grażyna [SAP11011061] pl
dc.contributor.author van Eldik, Rudi [SAP14007947] pl
dc.date.accessioned 2015-09-22T11:06:46Z
dc.date.available 2015-09-22T11:06:46Z
dc.date.issued 2001 pl
dc.identifier.issn 0002-7863 pl
dc.identifier.uri http://ruj.uj.edu.pl/xmlui/handle/item/15758
dc.language eng pl
dc.title Kinetics and mechanism of the reversible binding of nitric oxide to reduced cobalamin $B_{12r}$ (Cob(II)alamin) pl
dc.type JournalArticle pl
dc.description.physical 9780-9791 pl
dc.abstract.en The reduced form of aquacobalamin binds nitric oxide very effectively to yield a nitrosyl adduct, Cbl(II) - NO. UV - vis, 1 H-, 31 P-, and 15 N NMR data suggest that the reaction product under physiological conditions is a six-coordinate, “base-on” form of the vitamin with a weakly bound R -dimethylbenzimidazole base and a bent nitrosyl coordinated to cobalt at the ‚ -site of the corrin ring. The nitrosyl adduct can formally be described as Cbl(III) - NO - . The kinetics of the binding and dissociation reactions was investigated by laser flash photolysis and stopped-flow techniques, respectively. The activation parameters, ¢ H q , ¢ S q , and ¢ V q , for the forward and reverse reactions were estimated from the effect of temperature and pressure on the kinetics of these reactions. For the “on” reaction of Cbl(II) with NO, the small positive ¢ S q and ¢ V q values suggest the operation of a dissociative interchange ( I d ) substitution mechanism at the Co(II) center. Detailed laser flash photolysis and 17 O NMR studies provide evidence for the formation of water-bound intermediates in the laser flash experiments and strongly support the proposed I d mechanism. The kinetics of the “off” reaction was studied using an NO-trapping technique. The respective activation parameters are also consistent with a dissociative interchange mechanism. pl
dc.description.volume 123 pl
dc.description.number 40 pl
dc.identifier.doi 10.1021/ja010530a pl
dc.identifier.eissn 1520-5126 pl
dc.title.journal Journal of the American Chemical Society pl
dc.language.container eng pl
dc.affiliation Wydział Chemii : Zakład Chemii Nieorganicznej pl
dc.subtype Article pl

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