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AGE‐RELATED CHANGES IN THE HUMAN LENS AS MONITORED BY DETECTION OF PORPHYRIN EXCITED STATES
Author(s) -
Roberts Joan E.,
Atherton Stephen J.,
Gaillard Elizabeth R.,
Dillon James
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb05278.x
Subject(s) - porphyrin , lens (geology) , excited state , triplet state , chemistry , homogeneous , fluorescence , flash photolysis , photochemistry , crystallin , optics , atomic physics , kinetics , physics , reaction rate constant , biochemistry , quantum mechanics , thermodynamics
— Previous studies have shown that the triplet state lifetimes of various porphyrins are increased by several orders of magnitude when they are bound to lens proteins. Flash photolysis studies of me‐sotetra ( p ‐sulfonatophenyl)porphyrin (TPPS) on intact bovine lenses indicated a biexponential decay of the triplet state with lifetimes of 160 μs and 1.6 ms. Here we extend those measurements to TPPS associated with intact human lenses. Steady‐state fluorescence measurements indicate that TPPS binds to both young and old human lenses. In an intact young human lens, the TPPS triplet state is observed to decay biexponentially with lifetimes of 50 and 680 μs. As the age of the lens increases, the lifetime of the shorter‐lived component lengthens while that of the longer‐lived component decreases slightly. In older human lenses, the two lifetimes coalesce and the triplet decay exhibits purely monoexponential behavior. These photophysical characteristics apparently are due to age‐related modification(s) of the protein in the human lens resulting in an increasingly more homogeneous environment around the porphyrin.