Study of the protein distribution in the pig lens cross section by Raman spectroscopy

The distribution of proteins in the cross section of a normal pig lens was studied by near-infrared Raman spectroscopy. The Raman spectra were measured in the visual and equatorial axes of this cross section and the protein peak intensities were determined. It was found that along each axis the protein intensities fluctuate. They have a considerable increment along the visual axis with the exception of the C-N bond peak intensities at 1087.2 cm(-1), which decrease, and along the equatorial axis the increment is slight. This increment in protein distribution along the visual axis is related with the refractive gradient of the lens. The classification of pig lens spectra in these axes was performed using principal component analysis (PCA) and linear discriminant analysis (LDA). Cross-validation shows an excellent group separation.