Redox conversions of dinitrosyl iron complexes with natural thiol-containing ligands
2013; Elsevier BV; Volume: 35; Linguagem: Inglês
10.1016/j.niox.2013.07.004
ISSN1089-8611
AutoresR. R. Borodulin, Lyudmila N. Kubrina, В. А. Сереженков, Dosymzhan Sh. Burbaev, V. D. Mikoyan, А. Ф. Ванин,
Tópico(s)Redox biology and oxidative stress
ResumoUsing 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 640 nm and a bend at 450 nm. 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 310 nm, respectively. Treatment of bovine serum albumin (BSA) solutions with gaseous NO in the presence of Fe2+ 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 (d7 ({Fe(NO)2}7) and d7–d7 ({Fe(NO)2}7–{Fe(NO)2}7), respectively).
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