QUANTITATIVE GENERATION OF SINGLET ((1)DELTA(G)) OXYGEN FROM ACIDIFIED AQUEOUS PEROXYNITRITE PRODUCED BY THE REACTION OF NITRIC-OXIDE AND SUPEROXIDE ANION

Simple acidification of aqueous alkaline peroxynitrite quantitatively generates singlet ((1) Delta(g)) molecular oxygen, detected and quanti tated spectroscopically (1270nm). This observation provides a chemical basis for physiological cytotoxicity of ONOO- generated in the diffus ion - controlled reaction of cellular NO. and O-2(-). The experiments consist of (i) chemical generation of ONOO- from NO. gas and KO2 powde r in alkaline aqueous solution; (ii) absorption spectral identificatio n of ONOO- in the near-UV with maximum at 302nm; (iii) spectroscopic i dentification of O-1(2) by its emission band at 1200-1340 nm with maxi mum at 1275 nm: and (iv) quantitation of O-1(2) generated in ONOO-/Hreaction by comparison of the chemiluminescence intensity at 1270 nm w ith that from H2O2/OCI- reaction that generates O-1(2) With unit effic iency at alkaline pH. O-1(2) was generated with unit efficiency with r espect to ONOO- concentration by the ONOO-/H+ reaction.