Solution properties of porcine submaxillary mucin

Porcine submaxillary mucin (PSM) is a glycoprotein composed of a protein core and frequent, short oligosaccharide side chains. We report static and dynamic light scattering experiments and intrinsic viscosities for PSM in aqueous solvent systems. In 0.1 M NaCl solution, the data suggest PSM exists as large, internally branched, highly hydrated, polydisperse aggregates that slowly dissociate to give a stable species of weight‐average molecular weight ( M w ) 7.4 × 10 6 . In 6 M GdnHCl solution, the noncovalent bonds between PSM molecules are broken, giving a highly elongated molecule of M w = 2.0 × 10 6 . The irreversible nature of this dissociation suggests that the forces that stabilize the native aggregates of PSM in 0.1 M NaCl are specific in nature. On reduction of PSM with mercaptoethanol, the polydispersity decreases and M w also decreases to 9 × 10 5 . A discrete change is observed in the solution properties of PSM in 0.1 M NaCl at a concentration of 2mg/mL, manifested by a sudden decrease in the translational diffusion coefficient, an increase in viscosity number, and a decrease in slope of the osmotic compressibility. We tentatively propose that a weak and reversible secondary association process occurs at this concentration, although a purely hydrodynamic interaction cannot be ruled out.