Kinetics and mechanism of superoxide radical reactions with some biologically important compounds in aqueous solutions. Pulse radiolysis

• Published in: International journal of radiation applications and instrumentation. Part C, Radiation physics and chemistry Radiation physics and chemistry, 1989, Vol.34 (4), p.653-658
• Main Authors: Revina, A.A., Amiragova, M.I., Volod'ko, V.V., Vannikov, A.V.
• Format: Article
• Language: English
• ISSN: 1359-0197; 1878-1020
• DOI: 10.1016/1359-0197(89)90075-1

Microsecond pulse radiolysis of oxygenated aqueous solutions containing 0.02 mol dm -3 sodium formate and 2 mmol dm -3 phosphate buffer at pH 7 was used to generate superoxide anion radicals. The influence of some biologically important compounds upon the rate of O ⨪ 2 decay was monitored spectrophotometrically in the range of 245–300 nm. Hematoporphyrin (HP), hemin C (HC), catalase (Cat), cobalt sulfophthalocyanine (CoTSPc) were studied. Among the investigated compounds only Cat was found to show a high catalytic efficiency towards the self-decay of O ⨪ 2. A red shift of O ⨪ 2 absorption band and slowing down of its decay were observed to take place by adding HP or CoTSPc to the solutions containing formate ions in excess. This effect is associated with the formation of a transient superoxo-complex. An appearance of an intermediate species with absorption maxima at 350 nm and half-life of about 2s was observed to accompany the superoxo-complex of CoTSPc decay. In the aerated solution of HP the intensity of absorbance at 260 nm was found to be independent of the presence of formate ions.