Differentiation of the maturity of cataractous human lens capsules according to changes in protein secondary structures determined by Fourier-transformed infrared spectroscopy.

Abstract

Cataract-induced alterations in the protein secondary structure of human lens capsules in different maturity of cataractous patients was investigated. Fourier-transformed infrared (FT-IR) spectroscopy with Fourier self-deconvolution and curve-fitting algorithms was used. Twenty-seven immature and four mature cataractous patients (previously classified through observations of the depth of the shadow cast by the iris on oblique illumination) were investigated in the present study. Two groups with progressive cataract formation could be effectively redifferentiated and re-arranged. In the first group, all the peak positions were the same and the peak at 1651 cm-1 assigned to the alpha-helix structure was predominant, but the structural compositions of the beta-sheet and beta-turn changed with progressive cataractogenesis. In the second group, in which cataract formation was more advanced, the peak at 1651 cm-1 assigned to the alpha-helix structure shifted to 1658 cm-1 and a new peak appeared at 1647 cm-1, due to random coil structure; the structural compositions of triple helix significantly decreased but the compositions of the beta-sheet and beta-turn slightly increased. Amides II and III of the IR spectra seemed to be less changed in secondary structures. These results suggest that FT-IR spectroscopy with Fourier self-deconvolution and curve-fitting programs can be used as a diagnostic tool for the determination of the cataractous maturity of human lens capsules.