. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 230 THE EFFECT OF IONIZING RADIATIONS in vitro, will oxidize thiol compounds; the experiments in which H2O2 or other peroxides produced mutations or chromosome breaks show only that oxidation reactions are responsible for these phenomena. There is no plausible reason, however, to attribute such oxidations to H2O2 when there are two other more powerful oxidation products formed on irradiation of water, namely, the radicals OH and O2H. Radiations and Coenzymes Ionizing radiations attack not only easily
. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 230 THE EFFECT OF IONIZING RADIATIONS in vitro, will oxidize thiol compounds; the experiments in which H2O2 or other peroxides produced mutations or chromosome breaks show only that oxidation reactions are responsible for these phenomena. There is no plausible reason, however, to attribute such oxidations to H2O2 when there are two other more powerful oxidation products formed on irradiation of water, namely, the radicals OH and O2H. Radiations and Coenzymes Ionizing radiations attack not only easily oxidizable systems, but also a number of substances of biological importance. The adenine residue of adenosinetriphosphoric acid can be oxidized by x-ray irradiation,. X 10''r Fig. 10. The x-ray efficiency on the destruction of adenosinetriphosphoric acid as measured by the absorption spectrum at 2600 A. Abscissa: X-ray dose in roentgen units; ordinate: per cent difference in the absorption spectrum. although the ionic yield is rather low, about (Fig. 10). That the measured change (height of the absorption spectrum at 2600 A) (Fig. 11) is due to oxidation is demonstrated by the reduction produced by catalase (46 per cent) and by the exclusion of oxygen (70 per cent). The pyrimidine-pyridine residues of diphosphopyridine nucleotide, how- ever, are more resistant to the action of ionizing radiations (Fig. 12) (ionic yield ). If the intensity of irradiation is increased, there will be more profound alterations, as has been shown by Scholes et al. (14). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Symposium on Radiobiology (1950 : Oberlin College); Nickson, James J. New York, Wiley
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