An exactly solvable Ogston model of gel electrophoresis: VIII. Nonconducting gel fibers, curved field lines, and the Nernst-Einstein relation

In this article, we examine the low-field electrophoretic migration of infi nitely small analytes in dilute sieving media made of nonconducting gel fib ers. Using an Ogston obstruction model, we show that the electrophoretic mo bility is not affected by the presence of curved field lines. In other word s, the Nernst-Einstein relation between the mobility and the diffusion coef ficient is valid regardless of the electrical properties of the gel fibers. Although this finding may greatly simplify the development of obstruction models of electrophoretic sieving, it also represents a critical test for a ny analytical or computational approach.