A near-infrared Raman spectroscopic study on the bovine lens applied to the solar radiation in Antarctica

The near-infrared Raman spectral measurements, of the bovine lenses transported to the Syowa station at the mid-summer in Antarctica and exposed to the solar radiation, were performed to suggest that the photolysis of tryptophan residues developed. The Raman spectra excited at 785 nm showed that little changes in the conformation of crystallin molecules occurred by the low temperature in Antarctica. Dehydration of crystallin molecules and the change of the environments of tyrosyl residues might have proceeded to some extent. The Raman spectral measurements were impossible for those lenses exposed to the solar radiation of the mid-summer in Antarctica excited at 785 nm, due to the strong fluorescence background emitted from some decomposed compounds produced by the exposure. Raman measurements excited at 1064 nm gave fair spectra for those exposed lenses as well as those stored at 4 °C or masked lenses. The Raman bands due to tryptophan residues specifically disappeared, while those signals due to phenylalanyl and tyrosyl residues persisted. These results were interpreted that the photo-induced decomposition of tryptophan residues developed by the exposure to the solar radiation of the mid-summer in Antarctica.