Studies on the mechanism of action of ionizing radiations. IX. The effect of x-irradiation on cytochrome c |
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| Authors: | BARRON E S FLOOD V |
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| Affiliation: | 2. Geisel School of Medicine at Dartmouth, Hanover, New Hampshire;3. Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin;1. Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi di Bari Aldo Moro, Via Orabona 4, Bari 70126, Italy;2. Istituto di Biomembrane e Bioenergetica, CNR, via Amendola 165/A, Bari 70126, Italy;3. Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, Milano 20133, Italy;4. Mitochondrial Biology Unit, Medical Research Council, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, United Kingdom;5. Istituto di Tecnologie Biomediche- Sede di Bari, CNR, Via Amendola 122/D, Bari 70126, Italy |
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| Abstract: | Aqueous dilute solutions of ferrocytochrome c were easily oxidized by x-rays, the oxidation being proportional to the intensity of irradiation. The ionic yield was 0.54. The oxidation produced by 10,000 r. was completely reversed on addition of dithionate. The oxidation seems to be brought about only by OH radicals produced on x-irradiation of water, because catalase offered no protection and the absence of oxygen did not reduce the extent of oxidation.X-Irradiation attacked also the protein and porphyrin components of cytochrome. The protein portion was more sensitive in alkaline solutions, whereas the porphyrin portion was more sensitive in acid solutions. X-irradiation seems to produce an oxidation of the chromophore double bond groups of porphyrin, which is manifested by a decrease of all the absorption bands characteristic of this substance. The ionic yield, as calculated from a decrease of the Soret band, was rather low: 0.015 in neutral solutions, and 0.046 in acid solutions. |
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