Polyelectrolyte behaviour in mucus glycoproteins.

Mucus glycoproteins isolated from a human ovarian cyst and the sputum of a cystic fibrotic exhibit a significant decrease in reduced viscosity with increase in ionic strength, I. The molecular weights of the glycoproteins showed little variation with I, implying that the change is conformational rather than a dissociation. This change is ascribed to a polyelectrolyte-type contraction rather than to a reduction in particle asymmetry. Guanidine hydrochloride acts as a classical electrolyte in the reversible suppression of charge effects, and not as a denaturing or dissociation agent. These observations help to resolve some discrepancies in earlier studies. The occurrence of polyelectrolyte effects in these glycoproteins is ascribed to flexibility of structure and to their content of N-acetylneuraminic acid. The ionic strength values necessary for different types of physical measurement are discussed.