The reaction of cysteine with the pentacyanonitrosylferrate(2–) ion

Abstract

The title reaction has been studied and it has been found that in the presence of oxygen a catalytic path for the oxidation of cysteine to cystine is established. The rate law is presented, and the mechanism is discussed on the basis of observed effects of the reagent concentrations on the extrapolated initial absorbance of the solution at 522 nm, and on the experimental pseudo-first-order rate of disappearance of colour. Cyanide ion has a remarkable influence on the course of the reaction.'rHE: ion pentacyanonitrosylferrate(2 -) (nitroprusside) is known to react with a wide variety of b a ~e s . l -~ Several types of interaction have been described, involving either direct reaction of the NO group with the incomiEg base or previous reaction with hydroxide ion to generate a reactive intermediate. In a number of cases, penta-c3.."x~onitritoferrate(Ris first generated by reaction wit 1-1 hydroxide and subsequently aquated .4Tlic reaction of cysteine with pentacyanonitrosylferrate(2-1 was first described over 40 years ago,5 and lias b t ~: ~ proposed as a test for this amino-acid. Reactions with other sulphur-containing bases have also beeu described, namely HS-,6 thioglycolic acid,7 other

Overview and New Insights into the Thiol Reactivity of Coordinated NO in {MNO}6/7/8 (M = Fe, Co) Complexes

“…38,48−50 This report was followed by an investigation into the products and kinetics of the decomposition of RP in the reaction of SNP and RSH (RSH = CysSH, N-acetylcysteine, EtSH, and GSH) in alkaline, anaerobic conditions. 51 Consistent with previous studies, 38,48 the products formed were highly condition-dependent. 51,52 In acidic or nonaqueous conditions, the blue [Fe(CN) 4 (NO)] 2− ion results from the corresponding loss of one CN − ligand.…”

Characterization of the Bactericidal Effects of Sodium Nitroprusside and Other Pentacyanonitrosyl Complexes on the Food Spoilage BacteriumClostridium sporogenes

“…The chemistry of SNP has been studied extensively. The nitrosyl ligand functions as a nitrosating agent and is readily attacked (at the nitrogen atom of the nitrosyl ligand) by a range of nucleophiles including amines (5,20), azide (33), hydroxylamine (19), carbanions (6), and thiols (7,23). These reactions parallel those of nitrous acid.…”

Mechanism and biological implications of the NO release of cis-[Ru(bpy)2L(NO)]n+ complexes: A key role of physiological thiols

“…Either in substoichiometric or in excess conditions of thiolate, the [Fe(CN) 5 NO] 3− ion appears as the main product of this reaction, which in the pH range of 8-10 it releases cyanide leading predominantly to [Fe(CN) 4 NO] 2− as final product. This has been found for cysteine, glutathione, and other thiolates [12,13]. At pH 6-8, free NO has been claimed to be released from [Fe(CN) 4 NO] 2− [14] and even bound NO − (nitroxyl) has been reported as an intermediate in the NP-cysteine reaction as a two-electron process [15][16][17][18].…”

“…On the other hand, the reactions of metallonitrosyl with thiolates have been addressed almost exclusively with NP [10][11][12][13][14][15][16]. Adduct intermediates strongly absorbing around 520 nm have been observed for the fast reactions of NP with several thiolates [10,11], with ensuing decomposition processes involving the reduction of NO + and the oxidation of the thiolates [12][13][14][15][16]. Remarkably, one-or two-electron reduction products have been detected in different circumstances with NP ([Fe(CN) 5 NO] 2− ).…”