Formation and Properties of Peroxynitrite as Studied by Laser Flash Photolysis, High-Pressure Stopped-Flow Technique, and Pulse Radiolysis

Abstract

Flash photolysis of alkaline peroxynitrite solutions results in the formation of nitrogen monoxide and superoxide. From the rate of recombination it is concluded that the rate constant of the reaction of nitrogen monoxide with superoxide is (1.9 +/- 0.2) x 10(10) M-1 s-1. The pKa of hydrogen oxoperoxonitrate is dependent on the medium. With the stopped-flow technique a value of 6.5 is found at millimolar phosphate concentrations, while at 0.5 M phosphate the value is 7.5. The kinetics of decay do not follow first-order kinetics when the pH is larger than the pKa, combined with a total peroxynitrite and peroxynitrous acid concentration that exceeds 0.1 mM. An adduct between ONOO- and ONOOH is formed with a stability constant of (1.0 +/- 0.1) x 10(4) M. The kinetics of the decay of hydrogen oxoperoxonitrate are not very pressure-dependent: from stopped-flow experiments up to 152 MPa, an activation volume of 1.7 +/- 1.0 cm3 mol-1 was calculated. This small value is not compatible with homolysis of the O-O bond to yield free nitrogen dioxide and the hydroxyl radical. Pulse radiolysis of alkaline peroxynitrite solutions indicates that the hydroxyl radical reacts with ONOO- to form [(HO)ONOO].- with a rate constant of 5.8 x 10(9) M-1 s-1. This radical absorbs with a maximum at 420 nm (epsilon = 1.8 x 10(3) M-1 cm-1) and decays by second-order kinetics, k = 3.4 x 10(6) M-1 s-1. Improvements to the biomimetic synthesis of peroxynitrite with solid potassium superoxide and gaseous nitrogen monoxide result in higher peroxynitrite to nitrite yields than in most other syntheses.

Endothelial cell respiration is affected by the oxygen tension during shear exposure: role of mitochondrial peroxynitrite

“…3B) provides evidence that the enhanced suppression of respiration for ECs sheared at 21% O 2 is due to mitochondrial ONOO Ϫ formation. O 2 ⅐ Ϫ is known to react with NO at a faster rate [k 1 ϭ 1.9 ϫ 10 10 M Ϫ1 s Ϫ1 (38)] than with MnSOD [k 2 ϭ 2.3 ϫ 10 9 M Ϫ1 s Ϫ1 (39)]. Although there is a 10-fold difference in the rate constants and NO levels may be in the low M range inside the mitochondria, it is the local concentration of MnSOD that determines whether NO will outcompete MnSOD and react with O 2 ⅐ Ϫ to generate ONOO Ϫ or MnSOD will outcompete NO and prevent ONOO Ϫ formation.…”

Oxygen radical inhibition of nitric oxide-dependent vascular function in sickle cell disease

“…Pretreatment of aortic vessels with the more cell-avid and membranepermeable SOD mimetic MnTE-2-PyP (54, 55) had a greater impact on scavenging O 2 ⅐Ϫ , giving a 33% and 50% reduction in rates of O 2 ⅐Ϫ release in control and sickle vessels, respectively. XO-derived O 2 ⅐Ϫ will react with ⅐ NO at diffusion-limited rates to impair ⅐ NO signaling and concomitantly yield secondary oxidizing species, such as ONOO Ϫ , that can further propagate tissue injury (25,56,57). A challenge for the future is the delineation of acute versus chronic actions of XO on vascular function in SCD.…”

Red cell membrane and plasma linoleic acid nitration products: Synthesis, clinical identification, and quantitation

“…• NO exerts a particularly broad influence on oxidative inflammatory reactions by reacting at diffusion-limited rates with superoxide ( • O 2 Ϫ , k ϭ 1.9 ϫ 10 10 M Ϫ1 ⅐sec Ϫ1 ) to yield peroxynitrite (ONOO Ϫ ) and its conjugate acid, peroxynitritrous acid (ONOOH), the latter of which undergoes homolytic scission to nitrogen dioxide ( • NO 2 ) and hydroxyl radical ( • OH) (2,6). Also, biological conditions favor the reaction of ONOO Ϫ with CO 2 , generating nitrosoperoxycarbonate (ONO-OCO 2 Ϫ ; k ϭ 3 ϫ 10 4 M Ϫ1 ⅐sec Ϫ1 ), which yields • NO 2 and carbonate ( • CO 3 Ϫ ) radicals by means of homolysis or rearranges to NO 3 Ϫ and CO 2 (7).…”