AGE-RELATED-CHANGES IN THE HUMAN LENS AS MONITORED BY DETECTION OF PORPHYRIN EXCITED-STATES

Previous studies have shown that the tripler state lifetimes of variou s porphyrins are increased by several orders of magnitude when they ar e bound to lens proteins. Flash photolysis studies of mesotetra (p-sul fonatophenyl)porphyrin (TPPS) on intact bovine lenses indicated a biex ponential decay of the triplet state with lifetimes of 160 mu s and 1. 6 ms. Here we extend those measurements to TPPS associated with intact human lenses. Steady-state fluorescence measurements indicate that TP PS binds to both young and old human lenses. In an intact young human lens, the TPPS tripler state is observed to decay biexponentially with lifetimes of 50 and 680 mu s As the age of the lens increases, the li fetime of the shorter-lived component lengthens while that of the long er-lived component decreases slightly. In older human lenses, the two Lifetimes coalesce and the tripler decay exhibits purely monoexponenti al behavior. These photophysical characteristics apparently are due to age-related modification(s) of the protein in the human lens resultin g in an increasingly more homogeneous environment around the porphyrin .