Photodegradation of melanin by an interferometric technique.

Photodegradation of melanin thin films is investigated for a UVA wavelength of 355 nm and a UVC wavelength of 244 nm. The technique involves interferometric exposure of melanin with two coherent beams from a low-power UV laser. The periodic photodegradation-grating pattern is monitored by diffraction of a second low-power He-Ne laser. Dependence of the photodegradation rate on UV intensity as well as the effect of ambient humidity is investigated and explained with a simple model. The technique has promise for investigating photo-induced effects in other biomolecular substrates as well.