A SMALL-ANGLE NEUTRON-SCATTERING STUDY OF GAMMA-CRYSTALLINS NEAR THEIR ISOELECTRIC POINT

In this paper, a small-angle neutron scattering study of gamma II-crys tallins near their isoelectric point is presented. The experiments wer e carried out using protein concentrations of 5.7-85.7 mg/ml at temper atures in the range 11-60 degrees C. The experimental data were analyz ed using an ellipsoidal model for intraparticle correlations and the m ean spherical approximation for interparticle correlations. Our studie s revealed that gamma II-crystallins have a thick hydration layer, whi ch is possibly due to the special arrangement of polar and ionic group s on their surface. The temperature scan shows that, as a result of re latively strong attractive forces, clusters of two, three, or higher o ligomers are present below 20 degrees C. Our results suggest that prot ein clusters, with a distinctive hydration layer, form a protein-rich phase that separates from a protein-lean phase as the temperature is d ecreased below some threshold value.