Raman spectroscopic evidence for the microenvironmental change of some tyrosine residues of lens proteins in cold cataract.

Reversible "cold cataract" phenomenon of a SD-strain rat lens (29 days old) was studied by Raman spectroscopy in the temperature range of 35-17.5 degrees C. Cold cataract appeared in the lens nucleus below 26 degrees C. The Raman spectra did not show any detectable change in the 300-800 cm-1 and 900-4000 cm-1 regions as the temperature decreased. However lens opacification caused a significant change in the intensity ratio of tyrosine doublet near 840 cm-1, suggesting that some tyrosine residues in lens proteins undergo a change in their hydrogen bonding environment during the cold cataract formation. It was also found that the intensity ratio of the tyrosine doublet band provides a practical indicator of phase transition temperature of cold cataract.