Towards the laser photochemistry of the cornea: studies of the most commonand highly absorbing aliphatic amino acids in collagen

The photochemical properties of various aliphatic amino acid residues commo n in collagen (Gly, Pro, Ala and Hyp), those with high absorption (Arg, Lys and His) and some others, as well as two dipeptides (Gly-Pro and Pro-Gly) have been studied in neutral aqueous solution using 193 nm excimer laser ir radiation. The quantum yields for decomposition and electron ejection (0.02 -0.20) are determined and the relative probability of photochemical damage of specific residues estimated. The peptide bond is likely to be the main t arget in collagen. Its scission could be the most important photochemical r eaction taking place at 193 nm laser irradiation of the cornea. (C) 1998 El sevier Science S.A. All rights reserved.