Cross-linking of dermal collagen induced by singlet oxygen.

Changes were studied in dermal collagen induced by singlet oxygen, which was generated by a bilirubin-photosensitized reaction. An increase in the ratio of high-molecular-weight components (beta- and r-components) against the alpha-chain of collagen after irradiation manifested in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sodium azide, a singlet oxygen quencher, inhibits the alteration of the molecular size by the photochemical reaction. These data suggest that chronic sunlight irradiation may contribute to cross-links of dermal collagen.