Study of α-Crystallin Structure by Small Angle Neutron Scattering with Contrast Variation

The structure of the oligomeric protein alpha-crystallin from bovine eye lens was investigated by small-angle neutron scattering (SANS) with contrast variation. Based on the SANS curves, the match point for alpha-crystallin (43% (DO)-O-2) and its average scattering length density at this point (2.4aEuro cent 1010 cm(-2)) were evaluated. The radius of gyration and the distance distri- bution functions for alpha-crystallin were calculated. On the basis of these calculations, it was concluded that alpha-crystallin is characterized by homogeneous distribution of scattering density in the domains inaccessible for water penetration, and all polypeptide subunits in alpha-crystallin oligomers undergo equal deuteration. The latter indicates that all alpha-crystallin subunits are equally accessible for water and presumably for some other low molecular weight substances. These conclusions on the alpha-crystallin structure (homogeneous distribution of scattering density and equal accessibility of all subunits for low molecular weight substances) should be taken into account when elaborating a-crystallin quaternary structure models.