Buffer properties of biopolymer solutions, as related to their behaviour in electrokinetic methodologies

The buffer properties of biopolymers (proteins and nucleic acids), with special reference to electrokinetic methodologies, are considered. The action of biopolymers as potential titrants is also analyzed. Since the 'buffering capacity' value (beta), that is conventionally used, is a local value, we propose to use the concept of 'buffer reserve'. The latter is obtained by integrating the beta value over the necessary pH interval, and thus coincides with the concentration of strong titrant needed to induce the appropriate pH shift. With this parameter any buffer system may be characterized and its value will be a function of the Delta pH shift. The theoretical calculations performed for two real amphoteric substances show that the resistivity limit of such two buffers with the same initial beta level may be quite different even in case of rather small pH shifts (several tenths of pH unit). (C) 1999 Elsevier Science B.V. All rights reserved.