The effects of irradiation with high energy electrons on the structure and reactivity of native and cross-linked collagen fibres.

Native and cross-linked rat tail tendon collagen was irradiated with high energy electrons up to a maximum dose of 100 x io J kg" (100 Mrd). Fibres irradiated dry showed greater damage when examined in the electron microscope using negative staining techniques than those irradiated wet. Cross-linking with glutaraldehyde prior to irradiation resulted in the band structure being preserved even at the highest dose but an unequal shrinkage of the bands was noted. Irradiation altered the reactivity of both native and cross-linked collagen with collagenase and elastase. Wetbut not dry-irradiated native collagen became resistant to collagenase. Both wetand dry-irradiated specimens were digested with elastase. Cross-linked collagen, normally resistant to both elastase and collagenase, became sensitive after varying doses of radiation; different results were obtained after irradiation in the wet and dry states. Irradiated collagen reacted abnormally with various histological stains and tended to resemble elastin in tinctorial properties. No marked changes were noted in the amino acid composition of the collagen after irradiation. Solubility in dilute alkali, acetic acid and hot water was decreased after irradiation of collagen in the wet state and increased after irradiation in the dry state. The results were consistent with the hypothesis that electron irradiation of collagen in the dry state results in scission of the polypeptide chains and that, in the presence of water, this is accompanied by the formation of intermolecular bonds. It also appears that changes in the configuration of the polypeptide chains accompany both these processes.