Determination of macroion diffusion coefficients using an analytical electrophoresis apparatus

Abstract

Methods are presented to determine the effective macroion diffusion coefficient in the presence or absence of an electric field, using a unique analytical electrophoresis apparatus in which both electrophoretic mobility and steady-state electrophoresis may be studied. Approximate analytic solutions to the differential equations and boundary conditions describing diffusion are derived. These solutions are shown to be good approximations to numerial simulations of the differential equations, and provide a good phenomenological description of experimental data for the oligonucleotide p(dA)₂₀⋅p(dT)₂₀ in 100 mM KCl, 20 mM Tris-HCl, pH 8.0 buffer. Diffusion and electrophoresis measurements are made on a single sample without changing the buffer or the macroion concentration, thus the data are directly comparable.