DYNAMICS OF A DNA MOLECULE HANGING OVER AN OBSTACLE IN GEL-ELECTROPHORESIS

Direct observation of a DNA molecule in gel electrophoresis indicates that the DNA repeats a stretch-contraction cycle every time when it is hooked by a gel fiber. The dynamics of this process is analyzed for a simple situation that a DNA is hooked by a single obstacle. It is shown that in the weak field limit, the characteristic time of the stretch-contraction process is independent of the electric field, while in the strong field limit, it is proportional to L/v(0), where L is the contour length of DNA and v(0) is the migration velocity of DNA in free space. The experimental result of Oana et al. (submitted to Macromolecules) is interpreted by this result.