Fluorescence polarization and circular dichroism studies on aging human lens proteins

The tryptophan residues within the alpha, beta and gamma crystallins (derived from normal human lenses ranging in age from the 1st through the 7th decade) were examined by fluorescence polarization (FP) and near UV circular dichroism (CD) techniques. These experiments demonstrate an age-related difference mainly in the gamma crystallin fraction in which the polarization and CD data demonstrate changes in the old gamma (7th decade) compared with the young gamma fraction (1st-3rd decade). Young gamma has the highest stability and is one of the most compact of the lens crystallins, as reflected by the FP and CD studies, and these parameters decrease significantly in the old gamma fraction. The loss of one of the gamma fractions as the lens ages may also be correlated with these age-related changes. There were no significant aging changes in the beta crystallins, while the alpha crystallins demonstrated a moderate FP change with age.