Quantitative generation of singlet (1Δg) oxygen from acidified aqueous peroxynitrite produced by the reaction of nitric oxide and superoxide anion

Abstract

Simple acidification of aqueous alkaline peroxynitrite quantitatively generates singlet (¹Δ_g) molecular oxygen, detected and quantitated spectroscopically (1270 nm). This observation provides a chemical basis for physiological cytotoxicity of ONOO⁻ generated in the diffusion ‐ controlled reaction of cellular NO^• and O . The experiments consist of (i) chemical generation of ONOO⁻ from NO^• gas and KO₂ powder in alkaline aqueous solution; (ii) absorption spectral identification of ONOO⁻ in the near‐UV with maximum at 302 nm; (iii) spectroscopic identification of ¹O₂ by its emission band at 1200–1340 nm with maximum at 1275 nm; and (iv) quantitation of ¹O₂ generated in ONOO⁻/H⁺ reaction by comparison of the chemiluminescence intensity at 1270 nm with that from H₂O₂/OCl⁻ reaction that generates ¹O₂ with unit efficiency at alkaline pH. ¹O₂ was generated with unit efficiency with respect to ONOO⁻ concentration by the ONOO⁻/H⁺ reaction.