Experimental and theoretical dynamics of isoelectric focusing: IV. Cathodic, anodic and symmetrical drifts of the pH gradient.

The production of anodic, cathodic and symmetrical drifts of a pH 3.5-10 gradient formed by isoelectric focusing in polyacrylamide gels is demonstrated experimentally by manipulation of the electrolyte concentrations. Experimental behavior is reproduced by computer simulation of a model mixture of 15 hypothetical carrier ampholytes whose pIs span the pH range 3-10. The mechanism which produces the drifts is elucidated and approaches to minimize such drifts are discussed. The data suggest why most experimentally observed drifts are cathodic.