67616-42-6Relevant articles and documents
A spectroscopic investigation of the interaction-between nitrogen monoxide and copper sites of the fungal laccase from Rigidoporus lignosus
Bonomo,Castronovo,Santoro
, p. 104 - 112 (2004)
The interaction of NO, with the copper centres of the laccase secreted by Rigidoporus lignosus was studied under both aerobic or anaerobic conditions. The reduction of the T1 site was always observed, as detected by the disappearance of the characteristic optical band at 604 nm (T3 presents probably the same behaviour because of the decreasing of the band at 330 nm) and the absence of its characteristics EPR signal, while T2 undergoes an initial partial and transitory reduction, its EPR signal intensity totally restoring after 24 h interaction. Different magnetic parameters of the T2 site have been detected, evidencing an increase of the hyperfine coupling constant. Furthermore, the number of superhyperfine lines on the fourth line of T2 copper was also found to increase from seven in the native to nine in the NO-treated laccase, this fact implying the coordination of a nitrogenous species to the T2 site. It was also shown that nitrite can be a source of NO, thus, paralleling the behaviour of NO-donor molecules or NO gas, but after longer interaction times. The nitrogenous species coordinated to T2 site is probably NO2-, which arises indirectly by NO oxidation. In order to understand the mechanistic pathway of this interaction, some experiments were also carried out in the presence of azide to study the interaction of NO with this laccase having its trinuclear cluster blocked by the presence of an exogenous ligand as N3-. After the addition of NO-donor molecules to the azide-treated laccase, a new EPR signal appeared at low temperatures, which is ascribable to the partially reduced T3 site, while the T1 and T2 sites were found to be totally reduced. The mechanistic pathway of the NO interaction seems to proceed through the reduction of T1 and T3 copper sites, followed by the coordination of nitrogenous species to T2.
Reactivity of sulfur nucleophiles with N-methyl-N-nitroso-p- toluenesulfonamide
Adam,Garcia-Rio,Leis
, p. 1181 - 1185 (2004)
The transfer of the nitroso group from N-methyl-N-nitroso-p- toluenesulfonamide (MNTS) to cysteine (CYS) and 2-aminoethanethiol (AET) has been studied in a pH range between pH = 7 and pH = 13. Kinetic results clearly indicate that both nucleophiles react through the corresponding thiolate to give the corresponding nitrosothiol. The existence of two (AET) or three (CYS) macroscopic acidity constants has been kinctically evidenced and the nitrosation rates of the corresponding bases have been identified. Nitrosation rate constants of the different species present in the reaction medium have been determined and a Bronsted-type plot has been established giving a βnuc value ? 0.08 clearly different from the values of βnuc ? 0.7 obtained in the nitrosation of primary and secondary amines by MNTS. The low βnuc value has been attributed to the need for previous desolvation of the nucleophile.
Equilibrium and kinetics studies of transnitrosation between S-nitrosothiols and thiols
Wang, Kun,Wen, Zhong,Zhang, Wei,Xian, Ming,Cheng, Jin-Pei,Wang, Peng George
, p. 433 - 436 (2007/10/03)
Using UV-vis spectrometrical measurements, equilibrium constants for NO transfer between S-nitroso-N-acetyl-penicillamine (SNAP) and different thiols as well as kinetic data for NO transfer from S-nitroso bovine serum albumin (BSANO) to thiols have been obtained. NO transfer from SNAP to other primary/secondary thiols are thermodynamically favorable, whereas other S-nitrosothiols exhibit similar NO transfer potential. The obtained Gibbs free energy, enthalpy and entropy data indicated that NO transfer reactions from SNAP to four thiols are exothermic with entropy loss. The kinetic behavior of BSANO/RSH transfer can be related to both the acidity of sulfhydryl group and the electronic structure in thiol.
