The Effect Of Peroxynitrite And Nitrating Agents On...

Peroxynitrite (ONOO−) is a well known potent oxidant and nitrating agent that is formed through the interaction of (NO†¢) with superoxide ion (O2†¢-) and its production is allied to the superoxide sources (for instance mitochondrial respiratory complexes or NAD(P)H oxidases present on plasma membrane) because superoxide is a shorter lived species and also shows constrained diffusion across biological membranes whereas NO†¢ is quite stable and extremely diffusible free radical. In vivo, the rate of production in particular organelles (such as phagocytic vacuoles in macrophages) is very high as 50–100 ÃŽ ¼M per min. The ability of peroxynitrite to cross cell membranes despite of having short half-life at physiological pH (~10 ms) suggested that peroxynitrite formed could persuade adjoining target cells within one to two cell diameters (~5–20 ÃŽ ¼m) (Denicola et al., 1998). The decomposition of peroxynitrite occur via proton-catalyzed manner to form OH †¢ and NO2†¢ radicals in hydrophobic phases and initiates lipid peroxidation (Radi et al., 1991; Bartesaghi et al., 2006). Peroxynitrite can either oxidize or nitrate different biological molecules like thiols, tyrosine residues in proteins and phospholipids having unsaturated fatty acids. Radicals derived through peroxynitrite carries out one-electron reactions, form sulphilic and sulphonic acid derivatives (Quijano et al., 1997; Bonini and Augusto, 2001). Purine bases, present in DNA, are susceptible to oxidation and adduct formation