Rate of viscosity changes in five salivary protein fractions following pH alterations

The change of viscosity with time following alteration of pH was studied in five protein fractions isolated from human parotid saliva. The results indicate that sudden pH changes may cause rapid charge alterations leading to shock-like expansion or compression of the molecules. This quick reaction seems to be followed by more slowly proceeding conformational alterations probably involving folding, intermingling, and other types of chain interactions. The content of proline residues may influence the rate and extent of such conformational changes.