INFRARED MICROSPECTROSCOPIC SAMPLING TECHNIQUES TO DETERMINE THE SECONDARY CONFORMATIONS OF α-CRYSTALLIN IN DIFFERENT STATES

The secondary structure of α-crystallin was examined in powder, film, and aqueous solution by different sampling techniques (specular reflectance, direct or KBr pellet transmission and attenuated total reflectance) using microscopic Fourier transform infrared (FT-IR) spectroscopy. The conformation of α-crystallin was quantitatively estimated from the vibrational analysis of amide I band achieved by second-derivative analysis, Fourier self-deconvolution and curve fitting program. The results indicate that all the α-crystallin samples did not show a large different composition in α-helix structure (12.06%–15.95%). Except in aqueous solution or in KBr pellet, the β-turn (32.05%–34.77%), β-sheet (38.22% –%) or random coil (13.98%–14.96%) structures of α-crystallin was, respectively, found to be similar, indicating that α-crystallin in powder and film states exhibited similar IR spectra and secondary structure determined by specular reflectance and transmission techniques. Once the powder or film of α-crystall...