Viscoelastic behavior of fractionated ovine submaxillary mucins

Solution properties of fractionated ovine submaxillary mucin (OSM) and asialo OSM (aOSM) in aqueous guanidine hydrochloride have been investigated using light scattering and rheological methods. For the first time we present viscometric evidence in both dilute and concentrated solution that the molecular structure of OSM is that of a wormlike chain. The intrinsic viscosity shows molecular weight dependence consistent with the linear extended chain conformation observed by light scattering measurements. The viscoelastic behavior of the OSM fractions in aqueous guanidine hydrochloride was further examined above the overlap concentration as a function of molecular weight and temperature. Under these solvent conditions in which the role of nonbonding intermolecular interactions is minimized, OSM shows predominantly fluid like behavior. However, high molecular weight OSM shows evidence of the existence of an entanglement network at high concentration. The frequency-dependent shear storage and loss moduli at all concentrations and molecular weights can be scaled to yield a master curve by incorporating typical viscoelastic shift parameters. The entanglement molecular weight and concentration are consistent with literature data for extended, semiflexible wormlike chains. The behavior of aOSM is similar to that of intact OSM at comparable degrees of coil overlap, indicating that the terminal sialic acid residue on the carbohydrate side chain has no effect on the rheology of concentrated OSM solutions beyond that due to an increase in the hydrodynamic volume.