Radiation biochemistry

Radiation Biochemistry of Carbohydrates. Normal autolytic processes are not affected by pasteurizing doses of ionizing radiation. The principal source of volatile base in irradiated and unirradiated or sterile fish or shellfish tissues is through enzymatic amination of adenosine monophosphate to the flavor-active compound inosine monophosphate. 

Radiation Biochemistry of Proteins and Amino Acids. Up to the levels of 500 krads the changes in pigment properties of heme proteins are similar to those caused by oxidation or reduction. Changes in the proteins, in addition to deamination and loss of —SH groups, indicate a partial de-naturation similar to that induced by hydrogen ions. This results in some enhancement of reactivity of the heme portion (2). 

Radiation Biochemistry of Flavor and Odor. Some 17 carbonyl compounds have been isolated in irradiated fish, and 12 have been identified. Nonirradiated clams show an increase in carbonyls during storage. Following irradiation at 450 krads the concentration of carbonyls increases sharply. The use of cryogenic temperatures significantly lowers the production of carbonyls. (2). 

Radiation Biochemistry of Lipids. The rancidity that develops in stored fish is the result of oxidative reactions. Work being done with methyl docosahexaenoate shows that irradiation per se does not cause observable or measurable changes in this long-chain fatty acid ester. However, changes involving fatty acids go on at a higher rate in irradiated fishery products than in the nonirradiated counterparts (16). 

Simic M, Dizdaroglu M (1985) Formation of radiation-induced cross-links between thymine and tyrosine Possible model for cross-linking of DNA and proteins by ionizing radiation. Biochemistry 24 234-236... 

The alkylperoxyl radical can be expected to react with sulfur amino acids by mechanisms similar to those for HOO- and HO-. Reactions of the hydroxyl and hydroperoxyl radicals have been more extensively studied because of their importance in radiation biochemistry. Thus, for cysteine, glutathione, and sulfhydryl proteins,... 

Studies in radiation biochemistry have shown that there is some localization of free radical damage to enzymes and proteins at their sulfur amino acids. In proteins irradiated in solution cysteine, cystine and methionine arc some of the most labile amino acids. Radiation in the dry state allows electron spin resonance measurements and Gordy (1958) has shown the localization of unpaired electrons at sulfur in amino acids and proteins. As described previously in this article, in the damage to cytochrome c by linolenate peroxidation, cystine and methionine are among the most labile amino acids. If damage is localized at a sulfhydryl site on a protein, immediate molecular repair is possible by a sulfur interchange of the unpaired electron,... 

Smerdon MJ, Lieberman MW (1980) Distribution within chromatin of deoxyribonucleic acid repair synthesis occurring at different times after ultraviolet radiation. Biochemistry 19 2992-3000... 

Horgan, V.J., Philpot, J.S.L., Porter, B.W. and Roodyn, D.B. (1957) Toxicity of autox-idized squalene and linoleic acid, and of simple peroxides, in relation to toxicity of radiation. Biochemistry 67, 551-558. 

Introduction - This report is for the most part based on articles selected from the 425 Included in the author s bibliographyl covering 1967. As in the two previous reports in this series no attempt has been made to cover developments in radiobiology or radiation biochemistry such as the effect of radiation on cellular kinetics or the development of a mathematical model for the biological effectiveness of radiation. ... 

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