Dispersion coefficients of lambda DNA in agarose gels during electrophoresis by fringe recovery after photobleaching.

By combining an electrophoretic cell with a fringe recovery after photobleaching setup, we have measured both the electrophoretic mobility mu and the dispersion coefficient D of double-stranded lambda-DNA in agarose gel as a function of the applied electric field E. Besides the determination of the mobilities, the analysis of the exponential decay of the signal gives, for the first time, experimental values of the longitudinal Dx and transverse Dy dispersion coefficients (field E perpendicular and parallel to the light fringes, respectively). Time dispersion measurements are complicated by the existence of a bleached area drift time. We present an analysis of their different contributions. Both dispersion coefficients increase linearly with increasing field E and, in the range of field we used, Dx is larger than Dy. Our results are consistent with the recent theoretical predictions of Slater (Electrophoresis 1993, 14, 1-7) and Duke et al. (Biopolymers 1994, 94, 239-247).