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TRAPPING OF NITRIC OXIDE FORMED DURING PHOTOLYSIS OF SODIUM NITROPRUSSIDE IN AQUEOUS AND LIPID PHASES: AN ELECTRON SPIN RESONANCE STUDY
Author(s) -
Singh Ravinder Jit,
Hogg Neil,
Neese Frank,
Joseph Joy,
Kalyanaraman B.
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb08616.x
Subject(s) - photodissociation , aqueous solution , sodium nitroprusside , nitric oxide , electron paramagnetic resonance , chemistry , spin trapping , resonance (particle physics) , photochemistry , sodium , electron , oxide , spin (aerodynamics) , nuclear magnetic resonance , inorganic chemistry , atomic physics , organic chemistry , physics , quantum mechanics , thermodynamics
— Photolytic decomposition of sodium nitroprusside (SNP), a widely used nitrovasodilator, produced nitric oxide (NO), which was continuously monitored by electron spin resonance (ESR) spectroscopy. The NO present in the aqueous or the lipid phase was trapped by either a hydrophilic or a hydrophobic nitronyl nitroxide, respectively, to form the corresponding imino nitroxide. The conversion of nitronyl nitroxide to imino nitroxide was monitored by ESR spectrometry. The quantum yield for the generation of NO from SNP, measured from the rate of decay of nitronyl nitroxide, was 0.201 ± 0.007 and 0.324 ± 0.01 (¯± SD, n = 3) at 420 nm and 320 nm, respectively. The action spectrum for NO generation was found to overlap the optical absorption spectrum of SNP closely. A mechanism for the reaction between SNP and nitronyl nitroxide in the presence of light is proposed and computer‐aided simulation of this mechanism using published rate constants agreed well with experimental data. The methodology described here may be used to assay NO production continuously during photoactivation of NO donors in aqueous and lipid environments. Biological implications of this methodology are discussed.