Affinity electrophoresis in gels containing hydrophobic substituents

The electrophoresis of a number of proteins was studied in poly(N,N-dimethylacrylamide) gels containing entrapped linear copolymers of N,N-dimethylacrylamide with N-alkyl-substituted acrylamides. The mobility of soybean trypsin inhibitor, carbonic anhydrase, ovalbumin, and myoglobin were unaffected by the hydrophobic residues in the gel. The mobilities of bovine serum albumin and beta-lactoglobulin A were sharply reduced, with the effect increasing as the alkyl side chain on the acrylamide residue was extended from dodecyl to octadecyl. The effect of the octadecyl ligand could be further increased by interposing a spacer between it and the polymer chain backbone. The retardation of the mobilities was used to obtain protein association constants with the alkyl residues. Interaction with the hydrophobic ligand produced a separation of beta-lactoglobin A into two fractions.