Dispersion of protein bands in a horseshoe microchannel during IEF.

Ampholyte-based IEF is simulated for a 2-D horseshoe microchannel. The IEF model takes into account ionic-strength-dependent mobility corrections for both proteins and ampholytes. The Debye-Huckel-Henry model is employed to correct the protein mobilities and the Onsager-Debye-Huckel model is used to obtain effective mobilities of ampholytes from their limiting mobility. IEF simulations are conducted in the presence of 25 ampholytes (DeltapK=3.0) within a pH range of 6-9 under an electric field of 300 V/cm and using four proteins (pIs=6.49, 7.1, 7.93 and 8.6) focused in a 1-cm-long microchannel. The numerical results show that the concentrations of proteins and ampholytes are different when mobility corrections are considered but that the focusing positions remain the same regardless of mobility corrections. Our results also demonstrate that, unlike linear electrophoresis in which the bands deform significantly as they traverse a bend, during the transient portion of IEF racecourse dispersion is mitigated by focusing and, at focused-state, those bands that focus in the bend show no radial concentration dependence, i.e. they completely recover from racecourse dispersion, even within a tight turn.