Electrophoresis of DNA adsorbed to a cationic supported bilayer

We report fluorescence microscopy studies of the electrophoresis of individ ual DNA molecules electrostatically adsorbed to a cationic supported lipid bilayer. Obstacles to uniform electrophoretic flow cause the 2-D chains to adopt hooked conformations similar to those previously observed in 3-D elec trophoresis experiments. Analysis of the stretch-contraction dynamics allow s for an estimate of the obstacle density in the bilayer. Increasing the el ectric field causes the DNA molecules to become more highly stretched and i ncreases the electrophoretic mobility substantially. A comparison of the Ro use relaxation time of the polymers and the average time between chain-obst acle collisions reveals that a single-obstacle model is insufficient to des cribe the observed dynamics but the obstacles are not dense enough to use a reptative model. Analysis of the unhooking dynamics reveals an 80% increas e in hydrodynamic drag as compared to free chains. Finally, we observe anom alous diffusion of the DNA chains, with a large increase in the diffusion c oefficient after the repeated application of high electric fields. Implicat ions of the flow obstacles in the engineering of separation applications ar e discussed.