Association State, Overall Structure, and Surface Roughness of Native Ovalbumin Molecules in Aqueous Solutions at Various Ionic Concentrations

Abstract

The shape, size, and surface roughness of a globular molecule of ovalbumin (OA) were studied with small angle X-ray scattering over a wide concentration range from 0 to 300 m M of phosphate buffer solution. The Guinier approximation can be sufficiently applied over a relatively wide range of the small scattering angle. The radius of gyration of the native OA molecule can be obtained as ca. 27 Å and it is almost independent of the concentration of the buffer solution. The native OA molecule is spherical and the radius of the molecule is ca. 25 Å over the concentration range from 0 to 300 m M of buffer solution. The specific inner surface, O s, of the native OA molecule, which is obtained at low and high OA concentrations at various buffer concentrations, is approximately 1.8 times that of a sphere with a smooth surface. The value of O s is almost independent of the concentration of the buffer solution. The surface roughness of the OA molecule is also discussed in comparison with that of the micelles and vesicle.