METHYLENE-BLUE SENSITIZED PHOTOOXIDATION OF COLLAGEN FIBRILS

Isometric tension measurements on rat tail tendons showed that visible light in the presence of Methylene blue led to an increase in the the rmal stability of the collagen. Analysis of CNBr fragments by SDS-poly acrylamide gel electrophoresis showed a decrease in the amounts of low molecular weight fragments and an increase in the formation higher mo lecular components with irradiation time. Amino-acid analysis data ind icated that the relative yields of only tyrosine, methionine and histi dine were reduced by the irradiation, with the loss of histidine being the greatest. The loss of methionine was not sufficient to completely account for the increases in the CNBr fragment sizes. Comparable resu lts were also obtained with ultra-violet light. These thermal and chem ical data were interpreted as being due to the formation of new interm olecular cross-links in the tendon collagen. X-ray fibre diffraction s howed that the irradiation and the induced cross-linking did not lead to a substantial change or disorder in the molecular packing arrangeme nt within the native collagen