Neutron-scattering probe of complexes of sodium dodecyl sulfate and serum albumin during polyacrylamide gel electrophoresis.

ABSTRACT

Small-angle neutron scattering (SANS) is used to probe the conformation of SDS-BSA protein surfactant complexes during electrophoresis in cross-linked polyacrylamide gels. Contrast variation permits independent probing of the structure of protein-surfactant complexes with negligible scattering contributions from the polyacrylamide matrix. The conformation of the protein complexes in the gel is found to be independent of the electric fields that are applied in this work (10 V/cm). Furthermore, there are no signs of large-scale macromolecular orientation (anisotropy) in the scattering patterns. However, the scattering shows that there are significant interparticle correlations between the protein-surfactant complexes that are electrophoretically inserted into the gel. These interactions develop when the total concentration of protein in the gels reaches values that are larger than approximately 1 mg/mL. The correlations are due to molecular crowding in the small fraction of pores that are available for protein migration.