ONOO" structure

This yields a value for log k5(ONOO) of 7.78 — 4.1/0, which gives a value for k5 over 3 orders of magnitude smaller than the value calculated by Ashmore and Burnett at 473°K. Extrapolated to room temperature, this gives a value of log kB 4.8. The alternative before us, then, is that either Ashmore and Burnett obtained a value for k5 inexplicably low by about a factor of 15 or a value low by about 105 because of structural differences. More accurate structural data are clearly needed to resolve this problem, although at present we prefer the first possibility. 

Mixtures of NO/O3/O2 also produce NO4+ ions under the conditions described above, but their decomposition products indicate an O3NO coimectivity. Three isomeric NO3+ cations have been detected in the mixtures described above under different conditions one has O2NO connectivity and two share O NO2 coimectivity, but with different structures. One NO3+ cation has a trigonal structure like the radical NOb-, the other corresponds to a weakly bound species that undergoes a near threshold decomposition and is assumed to have ONOO connectivity. Neutralisation-reionization mass spectrometry of this NO3+ isomer shows weak evidence for a neutral ONOO isomer (69) with a lifetime exceeding 1 ts. 

An additional nitrogen oxyanion is peroxynitrite, ONOO" , whose structure has recently been reported." The structure of one conformation of ONOO is shown in Figure 8-25 a twisted form with different bond angles and a different N — O distance is also found in the crystal. Peroxynitrite may play important roles in cellular defense against infection and in environmental water chemistry. ... 

The recent discovery that nitric oxide (NO) is a signaling molecule ubiquitous in tissue has raised the question that one of the pathways contributing to superoxide toxicity in vivo might be the formation of the highly reactive peroxynitrite anion (ONOO") produced by spontaneous reaction of NO with superoxide (77). It has been shown that perox5mitrite is a substrate of SOD (78). The interaction of SOD with peroxynitrite leads to a permanent modification of the enzyme at Tyr-108. The structural determination of the peroxynitrite-modified Cu2Zn2SOD has been conducted on monoclinic crystals (79). The structure confirms that peroxynitrite permanently modifies the Tyr-108 side chain with formation of 3-nitroty-rosine. The modification does not alter active site residues and the enzyme remains fully active. 

Physiological concentrations of Cu/Zn SOD catalyze nitration (Ischiro-poulos etal., 1992b) and enhance nitration yield, whereas similar concentrations of either free or chelated copper do not. These findings indicate that SOD it is not simply acting as an endogenous copper chelator. ONOO bears a structural resemblance to superoxide and may be directed to the... 

Since NO2 is in equilibrium with N2O4, mostly 5ym-N204 (structure 1), we may assume that a form of N2O4 is the actual next intermediate. The most obvious pathway would include the formation of 3 by simple addition of NO to the peroxyl function of ONOO. However, while 1 is the typical form of N2O4 at ambient conditions and spectroscopic evidence for 2 (asym-N204) has been found after photolysis of matrix-isolated 1(58), the isomer 3 has not been unambiguously identified till to date, but ah initio calculations have given its existence some credit (59,60). 

Aldehydes, like CO2, react rapidly with peroxynitrite and catalyse its decompensation (Uppu et al. 1997). The pH dependence of the reaction is consistent with the addition of ONOO" (not ONOOH) to the carbonyl carbon atom of the free aldehyde forming a 1-hydroxyalkylperoxynitrite anion adduct, which structurally resembles the nitrosoper-... 

Write the Lewis structure for the peroxynitrite ion, ONOO". Label each atom with its state of hybridization and specify the composition of each of the different types of bond. 

Escherichia coll plasmid phage (pUC 19) DNA when exposed to ONOO undergoes structural change by converting the circular DNA into single-nicked open circular form and double-nicked circular form. At higher concentration of ONOO , the DNA disappeared. As indicated by the fluorescence DNA bands, canolol (>1 0,M) could prevent DNA breakage in the presence of 1 pM ONOO (Kuwahara et al., 2004). This indicated the DNA protection capacity of canolol. 

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