Colloidal structure and properties of bovine serum globulin aqueous systems using SAXS and rheological measurements

Colloidal structure and properties of bovine serum globulin (GLB) aqueous systems have been investigated by means of light scattering, small angle X-ray scattering and rheological measurements. The GLB molecules are dispersed in an association state of ca. 1.7 in a concentration range from 0.02 to 1 wt.%. One GLB molecule can be approximated as an ellipsoidal revolution with a longitudinal semi-axis of 150 Angstrom and a equatorial radius of 22 Angstrom whose volume is ca. 3.1 x 10(5) Angstrom(3). The GLB colloidal systems show a marked yield stress sigma(y) and rigidity G due to a certain solid-like structure even in very dilute systems of 0.005 wt.%. The values of sigma(y) and G increase proportional to the concentration c of GLB in the extremely dilute region from 0.001 to 0.01 wt.% and increase slightly with c(1/4) in the more concentrated region from 0.01 to 1 wt.%.