Influence of chain length on the diffusion and electrophoresis of DNA adsorbed on heterogeneous supported lipid bilayers.

This manuscript describes the influence of chain length on the diffusion and electrophoresis of single stranded DNA (ssDNA) adsorbed on heterogeneous cationic supported lipid bilayers. These studies are motivated by the increasing interest in developing novel strategies for the separation of DNA. We studied ssDNA molecules with the number of bases (N) varying from 21 to 84. Fluorescence recovery after photobleaching (FRAP) studies revealed that the diffusivity (D) of adsorbed ssDNA varied with N as D approximately N(-1), similar to a trend previously observed for the diffusion of double stranded DNA on homogeneous supported lipid bilayers. In contrast, the electrophoretic mobility of the adsorbed ssDNA in the presence of an applied tangential electric field was independent of N. Our studies indicated that the motion of ssDNA in the presence of an applied electric field was primarily due to electrophoresis and was not influenced significantly by electro-osmotic flow. Our results also suggest that the use of asymmetric diffusion barriers or other tunable obstacles may assist DNA separation on supported lipid bilayers.