Electrophoretic mobilities of proteins and protein mixtures

Electrophoretic mobilities of bovine serum albumin (SA), haemoglobin (Hb) and ovalbumin (OA) have been determined by direct ultramicroscopic observation of the velocities of individual particles in a particle electrophoresis apparatus, and of SA and Hb in a free-flow apparatus of the type described independently by Hannig and by Strickler. Agreement between the results obtained by the two methods for SA and Hb over wide pH ranges covering both sides of the respective isoelectric points was surprisingly good. Runs were also conducted in the free-flow cell in which SA was transported in buffer containing Hb, and vice versa; these showed clear evidence of interactions between the motions of the two proteins, as occurs in the parallel case of multicomponent diffusion, but the results could not be quantified in terms of the Maxwell-Stefan theory. Finally, the single protein data were compared with predictions made on the basis of the Debye-Huckel-Henry theory, and showed reasonable agreement.