CHANGES IN TERTIARY STRUCTURE OF CALF‐LENS α‐CRYSTALLIN BY NEAR‐UV IRRADIATION: ROLE OF HYDROGEN PEROXIDE

The effect of 300 nm irradiation on the three lens crystallins, α‐, β‐, and γ‐, was studied by using fluorescence and circular dichroism techniques. α‐Crystallin showed a pronounced change in tertiary structure as manifested in fluorescence and circular dichroism measurements. This finding is in agreement with our earlier findings that the tryptophan residues of α‐crystallin are more exposed than those of the other two crystallins. The results of studies using inhibitors specific for the different active species of oxygen suggest that H₂O₂‐mediated damage is involved in the change of tertiary structure of the proteins. Analyses of circular dichroism spectra indicate that, upon irradiation, the secondary structure of α‐crystallin remains virtually unaltered, and that the change in tertiary structure results primarily from photoinduced damage to the tryptophan residues.