Preliminary Study on Cataractous Human Lenses Using Near‐Infrared Fourier Transform Raman Spectroscopy

Abstract

Raman vibrations of the fingerprint of aromatic amino acid residues were analyzed to study the changes of cataractous 'ens protein in the cortex and nucleus at various ages, Tryptophan content, analyzed by the quantification of I m /l l44 g ratio, shows the damage (modification) of tryptophan residue in the nucleus is caused primarily by the formation of cataracts, not by the aging process, Microenvironmental changes of tryptophan and tyrosine were analyzed by the intensity ratios of Il!7Jl m and 1 829/1m, respectively. The decrease of the ratio of 1 819 /1758' from 0.9 to 0.6 in the nucleus and from 0.7 to 0.6 for the cortex, reveal that more buried tryptophan residues become exposed in the cortex than in the nucleus during cataractogenesis, especially for non-senile cataractous lenses. The ratio of 1829/lm is around 1,0for both cortical and nuclear proteins at various ages, indicating some tyrosine residues have undergone a change in their hydrogen bonding environment. When compared to previous studies, we found that a normal (clear) lens bas a higher peak at 1617em:' than at 1604em", while a dense opaque or brunescent lens shows stronger intensity at 1604 em:' than at 1617 em", suggesting the ratio of 116l7/J1604 can be used to evaluate the human lens morphology.