PH EFFECTS ON NONIDEAL PROTEIN SIZE-EXCLUSION CHROMATOGRAPHY ON SUPEROSE-6

The retention behavior of five globular proteins (ribonuclease, lysozyme, beta-lactoglobulin, serum albumin, gamma-globulin) was determined on Superose 6 in low ionic strength (0.0-0.04 M) mobile phases of high, intermediate and [ow pH (110.0, 7.0, 4.3). Quantitative assessments of attractive or repulsive solute-packing interactions were made by comparing the chromatographic partition coefficient to the value obtained for non-interacting, spherical solutes on the same column. The dependence of this ''non-ideal'' adsorption or exclusion on net protein charge is complex, but not very sensitive to protein type. The results suggests that on size-exclusion chromatography packings that behave as weak cation-exchange resins the electrostatic solute-packing interaction is not governed by a highly localized set of a few charged sites