IR spectra of lens crystallins.

The IR technique has been applied to investigate secondary structure of the crystallins from the normal bovine eye. Crystallins have been isolated by column chromatography. IR spectra were recorded for the solid phase of proteins. From these spectra, especially amide I, amide II and amide V bands, the presence of alpha-helix, beta-sheet, beta-chain and unordered structures is stated. It was elucidated that alpha-crystallins are present mainly in a beta-sheet conformation but they also contain a considerable quantity of alpha-helix and a slight quantity of unordered and beta-chain forms. In beta H-crystallins, alpha-helix and, in a lesser percentage, beta-structures predominante. beta-sheet, alpha-helix and a low content of beta-chain forms are present in beta L-crystallins. In gamma-crystallins all forms secondary structure have been found, with predominance of beta-sheet and alpha-helix forms. A satisfactory agreement has been noticed between the forms of secondary structures in crystallins investigated by the IR technique and the results obtained by means of other methods. In conclusion IR spectroscopy has been suggested to be applied to observe crystallin structure during formation and development of a cataract.