COMPUTER-SIMULATION AND EXPERIMENTAL VALIDATION OF THE ELECTROPHORETIC BEHAVIOR OF PROTEINS .3. USE OF TITRATION DATA PREDICTED BY THE PROTEINS AMINO-ACID-COMPOSITION

To simulate the electrophoretic behavior of a protein, a diffusion coefficient and a tabular representation of net charge vs. pH (titration curve) are required. So far data taken from the literature have been employed, the tables being extracted from experimentally determined titration curves. The construction of data tables from the amino acid composition of proteins is reported and compared with those from the literature. The predicted data serve as a rough approximation only, because pK values are dependent on the local environment. Shifting the curve along the pH axis to match the experimentally determined pl is shown to yield simulation data which is in better agreement with experimental data. However, the predicted protein charge numbers are typically too large. Reduction by a pH-independent factor is shown to provide meaningful data for computer simulation. The utility of the titration data employed is documented with good agreement between simulation and experimental data obtained by capillary isotachophoresis.