Some hydrodynamic properties of native and modified serum orosomucoids

Human and bovine serum orosomucoids and their neuraminidase (EC 3.2.1.18) treated counterparts were characterized with respect to their sedimentation, diffusion, viscosity, and optical rotatory properties at pH 7 in cacodylate buffer. The human and bovine orosomucoids had molecular weights of 41600 and 37000 respectively by the sedimentation diffusion method. Calculations involving the frictional coefficient and viscosity increment indicated that the two orosomucoids were highly hydrated prolate shaped molecules with an axial ratio of 2.5. The removal of sialic acid caused a loss of the water of hydration with an increase of the axial ratio to 5 and no loss of helical structure.