(569e) Multiple Regimes of Collisions of a Single Electrophoretically Translating Polymer Chain against a Thin Post

We use a previously developed bead-spring Brownian dynamics model for simulating the topological interactions between polymers and thin obstacles to study electrophoretically translating DNA strands interacting with an immovable post over a wide range of chain lengths and field strengths. The field strength is quantified by the Peclet number based on the Kuhn length, which is the ratio of the rates of field-induced polymer motion to diffusive transport at the level of the Kuhn segment length. We quantify the effect of the post by using the "delay distance" between the position of the post after its encounter with the post and the position it would have had if it had translated at uniform rate in the absence of the post. We find that the "delay distance" induced by the entanglement interaction increases with higher fields, encompassing four distinct regimes. Two regimes exhibit the classic rope-and-pulley dynamics. One of these is a very high field strength regime in which the dimensionless delay distance induced by interactions with the post reaches its upper limit, and the other is a moderately high field strength regime in which the chain is not able to fully extend. In the two slower regimes, the polymer retains a coil-like shape as it diffuses laterally and eventually clears the post without deforming. We develop models that describe both the average delay and the distribution of delays for all regimes, except the slowest one, which is distinguished by a peculiar fractional power law relationship between delay distance and Peclet number. We also develop models that quantititively predict the distribution in decay distances and hence are of relevance to band broadening and separation efficiency.