Experimental parameters affecting the ultraviolet-induced tryptophan modification in the lens.

Experimental parameters affecting photolysis of tryptophan in the lens were evaluated, including: (a) the use of previously-frozen vs. freshly excised lenses, (b) the use of lenses in aqueous buffered solutions vs. in air, (c) the species source of the lens, and (d) the effects of oxygen depletion. Lenses were subjected to monochromatic ultraviolet radiation followed by monitoring of the tryptophan fluorescence spectra while exciting at two or more wavelengths. Previously frozen lenses showed faster UV-induced degradation of tryptophan, particularly in aqueous media. A rapid leakage of fluorescent components (including amino acids and peptides) from intact lenses was observed. Evidence for the artifactual production of free radicals during photometric monitoring of samples in solution was obtained. Species dependent differences were also observed.