Hydrodynamic properties of proteoglycan subunit from bovine nasal cartilage. Self-association behavior and interaction with hyaluronate studied by laser light scattering.

Abstract

AbstractMeasurements of translational diffusion coefficients by quasielastic laser light scattering, sedimentation coefficients, and intrinsic viscosities at zero shear of proteoglycan subunit fraction A1‐D1‐D1 isolated from bovine nasal septa are reported. Molecular weights and hydrodynamic dimensions are compared with those expected on the basis of structural models previously proposed. Comparison of the concentration dependence of the diffusion coefficient in the presence of NaCl and GdnHCl leads to the conclusion that significant self‐association behaviour of subunit occurs in the absence of GdnHCl. In the absence of added salt, anomalous nonlinear concentration dependence of Dt estimated from wide‐angle light‐scattering experiments is observed. In addition, Dt apparently becomes angle dependent. These results are interpreted in terms of the perturbation of normal translational diffusion of the monomer by strong repulsive intermolecular interactions due to the combined effects of long‐range electrostatic forces and macromolecular congestion at higher concentrations. By carrying out experiments at small scattering angles, it is possible to determine D for proteoglycan subunit in the absence of supporting electrolyte. Titration of a dilute solution of subunit with hyaluronic acid results in a sigmoidal behaviour of the Stokes radius, indicating the formation of complexes of higher molecular weight results from the noncovalent association of proteoglycan subunits with hyaluronate. Observation of Dt appears to provide a useful method for studying the proteoglycan subunit–hyaluronate interactions.