ELECTROPHORESIS BETWEEN SIEVING AND REPTATION - AN INVESTIGATION OF THE ROLE OF SHAPE FLUCTUATIONS IN ELECTROPHORESIS

We present numerical simulation results of electrophoretic mobilities of flexible polyelectrolytes over a wide molecular size range moving t hrough gels with various pore sizes. The data are compared to existing models for different molecular size regimes and to experimental resul ts. We observe rather pronounced shape fluctuations of the polyelectro lytes which, especially for larger gel pores or small molecules, have a strong impact on the dynamics of the molecules. Electrophoretic sepa ration, as is used e.g. for DNA sequencing, is best achieved for polye lectrolytes with a radius of gyration of the order of the average pore radius of the gel, i.e. in a molecular size regime where the polyelec trolyte interacts with only a few gel fibers at a given time. A decrea se of the gel pore size leads to a systematic decrease of the electrop horetic mobility, but does not lead to a qualitative change in the mol ecular size dependence, as long as the pore size is larger than the pe rsistence length of the polyelectrolyte.