ON and melanin photoprotection against mammalian collagen photodamage in solution.

Previous results indicated that cuttlefish sepia (eu)melanin appears to protect against UVC-induced loss (fading) of acid-soluble collagen fluorescence emission at 360 nm. Reinvestigation of this question with both eu- and pheomelanin underscores the double-edged nature of melanin-collagen interaction. Both melanins appear to provide significant protection against photochemical fluorescence fading via optical absorption/scattering. On the other hand, SDS-PAGE results indicate that they provide minimum protection or might actually enhance collagen cross-linking and chain degradation by short and long wavelength UV. Thus, the latter processes do not appear to be directly linked to collagen photochemical fluorescence fading. Photochemical formation of melanin-derived radicals and/or active oxygen species, could conceivably react with nearby collagen molecules. H2O2, a long-lived product of melanin photolysis can react with collagen, but is efficiently scavenged by melanin, and has little effect on collagen fluorescence.