This is a proposal to document the nature of photochemical changes in lens crystallin proteins in solution. In the living lens, there are several potential mechanisms of UV damage, including: Direct crystallin photolysis, DNA photolysis, and damage to lens cell metabolism. Our experiments are designed to study crystallin photolysis separately. The hypothesis is that molecular changes in the crystallins, caused by UV radiation, can trigger a series of events, which finally lead to protein aggregation and insolubilization in solution, and to lens opacity in vivo. Molecular effects of UV radiation which we will study include: Crystallin crosslinking, protein conformational changes, and losses of specific amino acids in the peptide chains. Solution opacification is used as a marker of altered intermolecular interactions which lead to protein aggregation. The proposed experiments use UV wavelengths and doses which are comparable to those present in the human ambient environment. UV photodamage to human skin and eyes is presently of particular interest because of the reported trend toward decreased ozone-layer protection in the earth's atmosphere and recent epidemiological studies which indicate a positive correlation between UV exposure and human cataracts.