ELECTROPHORETIC MOBILITY OF DNA IN GELS. I. NEW BIASED REPTATION THEORY INCLUDING FLUCTUATIONS

In weak electric fields, the motion of DNA molecules undergoing gel electrophoresis may be described by biased reptation. We argue that the degree of molecular orientation induced by the field is determined by a competition between longitudinal fluctuations and drift of the molecule along the tube. A self-consistent calculation shows that the end-to-end vector of long molecules varies with the square root of the field strength, and not linearly as previously supposed. This leads to a number of new predictions about the field dependence of the molecular mobility and the size limit of resolution. We present the results of computer simulations that support the predictions of the theory of biased reptation including fluctuations. Finally, we discuss the correspondence with experimental data and the implications of our findings for the optimization of DNA electrophoresis. (C) 1994 John Wiley & Sons, Inc.