Light-scattering studies of chick limb bud proteoglycan aggregate.

Static and dynamic light-scattering methods have been used to investigate the structure of chick limb bud chondrocyte proteoglycan aggregate in 0.4 M guanidinium chloride. Zimm plot data for proteoglycan aggregate yield a molecular weight of 45 +/- 8 X 10(6) which compares well with a value of approximately 43 X 10(6) obtained by combination of the diffusion and sedimentation data via the Svedberg equation. The molecular weight of the proteoglycan subunit was determined previously to be 1.4 +/- 0.3 X 10(6), which indicates that the average proteoglycan aggregate molecule contains 32 associated subunits. This is in good agreement with electron microscopy which suggests an average of approximately 25.5 subunits/aggregate; it can be concluded that the aggregates visualized by electron microscopy are also present in solution. These data are also compatible with the ratio of the hydrodynamic volumes of proteoglycan aggregate and subunit. The formation of the aggregate structure has little effect on the solvent-binding capacity of the components: both proteoglycan aggregate and subunit have expanded coil conformations that include approximately 99% solvent.