RADIOLYSIS, PHOTOLYSIS AND SONOLYSIS OF CELLS AND THEIR CONSTITUENTS

点击翻译按钮获取中文摘要

The Photochemistry of the sensitizers N-formylkynurenine(NKF), Kynurenine KU), 3-hydroxykynurenine(OHKU), riboflavin(RF) and flavin mononucleotide(FMN) which are endogenous to human eye lenses has been studied. These sensitizers have been found to act by both type I (electron transfer) and type II (singlet oxygen) photochemical reactions. The singlet oxygen quantum yields and the superoxide quantum yields have been estimated by spectrophotometric methods.and these quantum yields for the kynurenine derivatives were found to be significantly less compared to the flavin derivatives, which is in agreement with their respective triplet state quantum yields. Based on ESR and spin trapping experiments, it was found that the yield of the DMPO-superoxide adduct increased when the photochemical reaction was carried out in the presence of suitable electron donors for all the sensitizers studied. The relative yields of superoxide anion radical have been monitored by the cytochrome c reduction assay in the presence of EDTA and DETAPAC which were found to be suitable electron donors for NFK, RF and FMN. It was found that the superoxide anion radical yields increased 2-5 fold in the presence of millimolar concentrations of either EDTA or DETAPAC. The results indicate that the presence of electron donors could shift the mechanisms of photochemically induced cataract in lens from Type II to Type 1. Our studies of the chemical effects of ultrasound in relation to hypothermia combined with radiation therapy were continued. The 50 kHz sonolysis of argon-saturated water-acetone and water-acetonitrite mixtures was studied by EPR and spin trapping over a wide range of solvent composition. For both systems a single maximum was observed for the spin adduct yield of methyl radicals and of the radicals formed by H-abstraction from acetone and acetonitrile. Methyl radicals from acetone are formed by C-C bond scission in the collapsing argon bubbles. For acetonitrile C-H bond scission at high temperature is followed by H-addition to the triple bond and the decomposition of this intermediate radical to form methyl radicals.