Electrophoretic collision of a DNA molecule with an insulating post.

We study the dynamics of single DNA molecules driven by an electric field into a stationary obstacle. These collisions are broadly classified as "hook" and "roll-off" events. We show that obstacle-induced electric field gradients stretch impacting DNA and thus greatly influence the hooking probability. Consequently, in addition to collision geometry, determination of the hooking probability depends on the Deborah number (De) for 0.5<De<40. Individual DNA impact dynamics are highly configuration sensitive, characteristic of polymers in elongational flows and fields.