title: Redox conversions of dinitrosyl iron complexes with natural thiol-containing ligands.
abstract: Using the electron paramagnetic resonance (EPR) and optical spectrophotometric methods, it has been established that biologically active, water-soluble dinitrosyl iron complexes (DNIC) with glutathione are predominantly represented by the diamagnetic binuclear form (B-DNIC) even in the presence of a 10-fold excess of glutathione non-incorporated into DNIC at neutral pH. With the increase in рН to 10-11, B-DNIC are fully converted into the paramagnetic mononuclear form (М-DNIC) with a characteristic EPR signal at g⊥=2.04, g‖=2.014 and gaver.=2.03. After treatment with a strong reducing agent sodium dithionite, both М- and B-DNIC are converted into the paramagnetic form with a characteristic EPR signal at g⊥=2.01, g‖=1.97 and gaver.=2.0. Both forms display similar absorption spectra with absorption bands at 960 and 640nm and a bend at 450nm. After oxidation by atmospheric oxygen, this situation is reversed, which manifests itself in the disappearance of the EPR signal at gaver.=2.0 and complete regeneration of initial absorption spectra of М- or B-DNIC with characteristic absorption bands at 390 or 360 and 310nm, respectively. Treatment of bovine serum albumin (BSA) solutions with gaseous NO in the presence of Fe(2+) and cysteine yields BSA-bound М-DNIC (М-DNIC-BSA). After treatment with sodium dithionite, the latter undergo transformations similar to those established for low-molecular М-DNIC with glutathione. Based on the complete coincidence of the optical and the EPR characteristics of sodium dithionite-treated М- and B-DNIC and other findings, it is suggested that sodium dithionite-reduced B-DNIC are subject to reversible decomposition into М-DNIC. The reduction and subsequent oxidation of М- and B-DNIC are interpreted in the paradigm of the current concepts of the initial electronic configurations of М- and B-DNIC (d(7) ({Fe(NO)2}(7)) and d(7)-d(7) ({Fe(NO)2}(7)-{Fe(NO)2}(7)), respectively).
authors.affiliation: Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Rostislav R
authors.initials: RR
authors.lastname: Borodulin
authors.forename: Lyudmila N
authors.initials: LN
authors.lastname: Kubrina
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Serezhenkov
authors.forename: Dosymzhan S
authors.initials: DS
authors.lastname: Burbaev
authors.forename: Vasak D
authors.initials: VD
authors.lastname: Mikoyan
authors.forename: Anatoly F
authors.initials: AF
authors.lastname: Vanin
mesh_terms: D000818:Animals; D002417:Cattle; D004227:Dithionite; D004578:Electron Spin Resonance Spectroscopy; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D009569:Nitric Oxide; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D012710:Serum Albumin, Bovine; D013438:Sulfhydryl Compounds / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008024:Ligands; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D013438:Sulfhydryl Compounds; D004227:Dithionite; D012710:Serum Albumin, Bovine; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D007501:Iron; D005978:Glutathione
keywords: BSA; Dinitrosyl iron complexes; EPR; M- or B-DNIC; NO and NO(+) donors; Redox conversions; bovine serum albumin; electron paramagnetic resionance; mononuclear- or binuclear dinitrosyl iron complex