Mobility-molecular weight relationships of small proteins and peptides in acrylamide-gel electrophoresis

Abstract

Previous results have shown that the mobility of proteins and peptides in acrylamide-gel electrophoresis is strongly dependent on the concentration of the gel (1,2). Generally, the more concentrated the gel, the lower is the mobility. In presenting our earlier results (2) for proteins of molecular weight 10,000 to 700,000 we tried to arrive at a relationship between mobility and molecular weight in this range. A reasonably good empirical relationship was found, though it did not agree with that suggested by a theoretical approach. Calculations of the diameters of peptides of the order of 1000 molecular weight suggested that they were of the same order as the pore sizes in acrylamide gels and could be expected to show some retardation, especially at high gel concentration. This paper presents some data for peptides of molecular weight 1200 upward and derives an empirical relationship similar to that previously described (2).