%0 Journal Article
%T Electronic and Spatial Structures of Water-Soluble Dinitrosyl Iron Complexes with Thiol-Containing Ligands Underlying Their Ability to Act as Nitric Oxide and Nitrosonium Ion Donors
%A Anatoly F. Vanin
%A Dosymzhan Sh. Burbaev
%J Journal of Biophysics
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/878236
%X The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe+(NO+)2] core ({Fe(NO)2}7 according to the Enemark-Feltham classification). Similarly, the {(RS£¿)2Fe+(NO+)2}+ structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin ( ) state with a d7 electron configuration of the iron atom and predominant localization of the unpaired electron on MO( ) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC. By present, endogenous dinitrosyl iron complexes (DNICs) with thiol-containing ligands, that is, DNICs having a Fe(NO)2 core, were detected in a vast majority of animal tissues and cell cultures [1¨C8]. These DNIC are generated in the presence of nitric oxide (NO) released from endogenous or exogenous sources (L-arginine or nitrite, resp.). In biological systems, DNIC are predominantly represented by protein-bound mononuclear forms with characteristic anisotropic EPR signals at and , commonly termed as ¡°the 2.03 signal¡± in accordance with the average value of the -factor [9]. The 2.03 signal was recorded at both low and ambient temperatures. One of the first records of the 2.03 signal in yeast cells and animal tissues obtained by three independent groups of investigators in the USSR, Great Britain, and the USA as early as mid-1960s are shown in Figure 1 [10¨C14]. Figure 1: The first recordings of 2.03 signal: dry yeast cells (A) [ 10]; wet yeast cells and rabbit liver (B, spectra a, and b, c). Three components of hyperfine structure of EPR signal of Mn ions in MgO sample are shown in spectrum c [ 14]; rat liver carcinoma induced by p-dimethylaminoazobenzene (butter yellow) (C, spectrum b; (a) spectrum from normal liver) [ 11]; (D) livers from rats maintaining 7, 14, 21, 35, and 49 days on a diet containing butter
%U http://www.hindawi.com/journals/jbp/2011/878236/