(327c) Nonlinear Correlation of Electrophoretic Mobility for Rigorous Estimation of Protein Charges with Highly-Charged Condition

Understanding of electrophoretic mobility and zeta potential is an important issue in charge characteristics of proteins. By exploring long-range electrostatic and electrokinetic principles, we developed a consistent framework that would allow rigorous interpretations. Together with an analytic expression by considering the Henry's formula with Debye-Hückel ansatz [Ohshima, J. Colloid Interface Sci., 1994], the zeta potential is evaluated from an integral expression for the electrophoretic mobility on the basis of nonlinear Poisson-Boltzmann equation. Subsequently, the net charge is evaluated from the corresponding relationships between potential distribution and surface charge. Applying the microchip electrophoresis, experimental mobility data were obtained for model globular proteins with bovine serum albumin and ovalbumin in different pH of buffer solution. To illustrate the usefulness of our framework, experimental data of electrophoretic mobility available in the literature are also included. It is evident that the results by linear correlations are identified to overestimate the zeta potential, while they underestimate the net charge. The discrepancy between linear and nonlinear correlations increases with increasing the surface charge. (This work was supported by the Basic Research Funds R01-2004-000-10944-0 from the Korea Science and Engineering Foundation.)