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Mechanistic studies on the binding of nitric oxide to a synthetic heme-thiolate complex relevant to cytochrome P450

Mechanistic studies on the binding of nitric oxide ...

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dc.contributor.author Franke, Alicja pl
dc.contributor.author Stochel, Grażyna [SAP11011061] pl
dc.contributor.author Suzuki, Noriyuki pl
dc.contributor.author Higuchi, Tsunehiko pl
dc.contributor.author Okuzono,, Kimiko pl
dc.contributor.author van Eldik, Rudi [SAP14007947] pl
dc.date.accessioned 2014-12-20T07:39:47Z
dc.date.available 2014-12-20T07:39:47Z
dc.date.issued 2005 pl
dc.identifier.issn 0002-7863 pl
dc.identifier.uri http://ruj.uj.edu.pl/xmlui/handle/item/2364
dc.language eng pl
dc.title Mechanistic studies on the binding of nitric oxide to a synthetic heme-thiolate complex relevant to cytochrome P450 pl
dc.type JournalArticle pl
dc.description.physical 5360-5375 pl
dc.abstract.en The synthetic heme−thiolate complex (SR) in methanol binds nitric oxide (kon = (2.7 ± 0.2) × 106 M-1 s-1 at 25 °C) to form SR(NO). The binding of NO to the SR complex in a noncoordinating solvent, such as toluene, was found to be almost 3 orders of magnitude faster than that in methanol. The activation parameters ΔH⧧, ΔS⧧, and ΔV⧧ for the formation of SR(NO) in methanol are consistent with the operation of a limiting dissociative mechanism, dominated by dissociation of methanol in SR(MeOH). In the presence of an excess of NO, the formation of SR(NO) is followed by subsequent slower reactions. The substantially negative activation entropy and activation volume values found for the second observed reaction step support an associative mechanism which involves attack of a second NO molecule on the thiolate ligand in the initially formed SR(NO) complex. The following slower reactions are strongly accelerated by a large excess of NO or by the presence of NO2- in the SR/NO reaction mixture. They can be accounted for in terms of dynamic equilibria between higher nitrogen oxides (NOx) and reactive SR species, which lead to the formation of a nitrosyl−nitrite complex of SR(FeII) as the final product. This finding is clearly supported by laser flash photolysis studies on the SR/NO reaction mixture, which do not reveal simple NO photolabilization from SR(FeIII)(NO), but rather involve the generation of at least three photoinduced intermediates decaying with different rate constants to the starting material. The species formed along the proposed reaction pathways were characterized by FTIR and EPR spectroscopy. The results are discussed in terms of their relevance for the biological function of cytochrome P450 enzymes and in context of results for the reaction of NO with imidazole- and thiolate-ligated iron(III) hemoproteins. pl
dc.description.volume 127 pl
dc.description.number 15 pl
dc.identifier.doi 10.1021/ja047572u 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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