Reassessment of the viscosity behavior of sodium dodecyl sulfate-protein polypeptide complexes

A reassessment study was made on the viscosity behavior of SDS-protein polypeptide complexes, since information about the nature of the complexes is important in establishing the principles of SDS-polyacrylamide gel electrophoresis. Measurements were made under two conditions, i.e., in a buffer of low concentration, and in a buffer of high concentration (usually used in standard SDS-polyacrylamide gel electrophoresis). Results in the former case were not consistent with viscometric data previously reported and widely accepted [Reynolds, J.A. and Tanford, C. (1970) J. Biol. Chem. 245, 5161-5165], and indicated that the complexes did not behave as a series of pseudo-homopolymers under the former conditions. Results in the latter case indicated that the complexes behaved much more like homologous polymers, but their viscosity behavior can only be interpreted in terms of flexible chains rather than a series of rigid rods with a constant diameter and variable lengths depending on their molecular weights.