Heat-induced structural transitions of alpha- crystallin studied by small-angle neutron scattering
نویسندگان
چکیده
Alpha-crystallin from the bovine eye lens was studied by small-angle neutron scattering (SANS) in 90% D2O buffer solution at 20, 50, 60, 65, 75, 85 and 95 o C. The temperature points for this study were specified on the basis of differential scanning calorimetric analysis of alpha-crystallin solutions which has shown two endothermic transitions with midpoints at 64.5 and 86 o C. The SANS study revealed no significant alphacrystallin quaternary structure alterations at 50 o C as compared with 20 o C. At 60-65 o C the SANS data confirmed substantial alpha-crystallin quaternary structure rearrangements which resulted in the formation of alpha-crystallin oligomers with a similar shape but approximately twofold increased molecular weight as compared to the native state at 20 o C. At higher temperatures (75, 85 and 95 o C) the SANS patterns were very similar and were consistent with the scattering by rod-like particles with a cross-section radius of gyration ~55 Ǻ. This transformation of alpha-crystallin to the rod-like particles was evidently irreversible as these particles remained in solution after cooling to 20 o C. Ab initio shape models of the native and high-temperature alpha-crystallin were retrieved with DAMMIN and DAMAVER software. Schematic model of alpha-crystallin heat-induced quaternary structure transitions was
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