The Effect of Gamma Radiation on Collagen

Collagen was irradiated with 5- and 50-Mrad doses of gamma rays under various conditions. Such doses lead to loss of crystallinity, as indicated by the x-ray-diffraction pattern, increase in solubility, and other changes in physical properties indicative of extensive loss of molecular structure and breakdown to smaller units. Determination of N-terminal residues using fluorodinitrobenzene indicates that there was relatively little hydrolytic scission of peptide bonds. Increase in amide nitrogen and in carbonyl groups indicates that --N-- C-- bonds were broken by a previously suggested mechanism. On irradiation with doses of 50 Mrad there was some loss of nitrogen and an over- all loss of some l0 to 20% of amino acids. The formation of carbonyl compounds accounts for only a small proportion of this loss, and large amounts of breskdown products remain unidentified. Relative losses of amino acids varied with the conditibns of irradiation, but in general the acidic and basic amino acids and those having a ring structure were the most radiosensitive. The chemical changes occurring as a result of gamma radiation are compared with those caused by other forms of degradation. (auth)