pH transitions in ion-exchange systems:role in the development of a cation-excange process for a recombinant protein

摘要

Unexpectd transient changes in effluent pH canoccur during ion-exchange chromatography.Such changes can occur even if a column that is equilibrated with a buffer receives another solution in the same buffer and of the same pH but of a different salt concentration.An attempt is mde to understand the basis for this phenomenon and apply it to the process purification of a recombinant protein on a strong cation-exchange resin.Incomplete column equilibration was eliminated as a possible cause of these effects.Various buffering species and various salt ions were studied at different solution concentrations to investigate pH transitionson strong cation-exchange resins.A further comparison was made between cation-exchange resinsm is proposed for these phenomena based on competitive equilibria between ions from the buffer salts and H~+/OH~- ions.In addition to the equilibria betwen these ions and the functional groups on the resins,charged groups on theres in backbone were alsofound to contribute to transient pH changes.The results from this study were applied to thecation-exchange step for a recombinant protein that was sensitive to pH excursions to help maintain activity of the protein during the purification process.