Influence of a soluble anionic polymer on the electrophoresis of proteins

The influence of a soluble anionic polymer on electrophoresis of proteins was studied in relation to the nonspecific ionic effect of an affinophore on application to affinophoresis. Zone electrophoresis of proteins was carried out in agarose gel in the presence of succinyl-poly-L-lysine (degree of polymerization, 120) by using three electrophoresis buffers differing in ionic strength (0.06, 0.12 and 0.18) and pH (7.0 and 7.9). Proteins migrated as distinct single bands even in the presence of the polymer. The mobility of cationic proteins towards the cathode was first decreased and then increased towards the anode as the polymer concentration increased, while that of anionic proteins was not affected. The dependence of the apparent mobility changes of the proteins on the concentration of the polymer was treated quantitatively in the same way as affinity electrophoresis. The extent of the ionic interaction between a cationic protein and the polymer could be estimated as an apparent dissociation constant. It greatly depended on the ionic strength of the electrophoresis buffer. Except for the extremely cationic proteins such as lysozyme, the ionic interaction with up to 0.1 mM of the polymer could be practically suppressed by the use of 0.1 M sodium phosphate buffer (pH 7.0).