Raman Spectroscopic Study of Cataract Formation: Emory Mouse Cataract

Raman spectra of Emory mouse lenses at various stages of cataract formation have been measured and compared with those of normal lenses from ICR-strain mice. The relative intensity of an OH stretching mode of lens water was considerably stronger for the Emory mouse lenses, even in a precataractous stage, suggesting that lens hydration is deeply implicated in the initiation of Emory mouse cataract. The rate of 2SH → S-S conversion, estimated from the intensity decrease of a SH stretching mode, was similar between the Emory and ICR-strain mouse lenses, Accordingly, it seems unlikely that the conversion is a predominant factor for forming large protein aggregates which lead to lens opacification. A significant change was observed for the intensity ratio of a tyrosine doublet near 840 cm−1 during the cataract development, suggesting that the strength of the hydrogen bonding of some tyrosine residues alters upon the formation of the large protein aggregates. Comparison of the Raman spectral changes observed for Emory mouse cataract with those for normal lens aging and other cataract formation leads us to the conclusion that the microenvironmental change of tyrosine residues is only one common specific feature for lens opacification.