Influence of Polymer Concentration and Electric Field Experimental Study and Comparison with Theory

Abstract

DNA molecules cannot be separated by free-solution electrophoresis [1], because in free solution the ratio of net molecular charge to friction coefficient (the electrophoretic mobility) is nearly equal for all DNA molecules regardless of their chain length [2, 3]. However, it was discovered in 1967 [4] that if electrophoresis is performed within a properly-formulated slab gel matrix (e.g., agarose or crosslinked Polyacrylamide), it is possible to separate differently-sized DNA molecules into distinct zones, where electrophoretic mobility is a decreasing function of DNA chain length. In addition to providing size-based separation of DNA, the crosslinked Polyacrylamide or agarose network of a slab gel serves as a physical support during electrophoresis, substantially reducing diffusion and convection of migrating DNA molecules. This allows the separated zones of differently-sized DNA molecules to remain relatively sharp, if gel formulation and electrophoresis conditions are chosen properly.