Ionizing radiation on biological systems

Several studies have reported the influence of nitroimidazole derivatives on biological systems. Thus the influence of Misonidazole, l-(2-nitro-l-imidazoyl)-3-methoxy-propan-2-ol, on strand breaking in calf thymus DNA under ionizing radiation conditions has been assessed70. Pulse-radiolysis studies of nitroheterocyclic compounds have examined... 

A more reliable means of providing a reference of -OH in a biological system maybe by means of irradiation with ionizing radiation (von Sonntag et al. 2000). The action of ionizing radiation on an aqueous medium gives rise to OH whose yield/dose relationship (G value) is known (Chap. 2). Apart from this, since biological media are concentrated solutions the formation of the indicator product, e.g., a phenol (ArOH), via the direct effect [expressions (69) and (70)] must in principle be taken into account as well. It can be shown that with k4i [probe]/ k42 [cellular components] above 10 4 the direct effect contributes less than 10%... 

The effects of ionizing radiations on chemical and biological systems may be minimized by the addition of certain chemical compounds to the system to be irradiated. These compounds react either directly with the radiation or, more often, with the reactive species produced by the radiations. In so doing, they are themselves transformed into other substances, but their transformation results in the preservation of the integrity of the original chemical or biological system. 

Effects of ionizing radiation on lipid molecules have been understood by studying model systems which are simpler than the real biological membranes, such as PUFA micelles and liposomes. The formation of lipid oxidative modifications of PUFAs appears as a dynamic process initiated by hydroxyl free radicals generated by water radiolysis, amplified by a propagating-chain mechanism involving alkyl and peroxyl free radicals, and leading not only to hydroperoxides but also to a lot of other lipidic oxidized end-products. Kinetic data, such... 

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