(269e) Scaling of Entropic Trapping Transport in Weak Electric Fields: A Monte Carlo Study

Authors: 
Shi, N., Texas A&M University
Ugaz, V. M., Texas A&M University

Electrophoretic transport of long DNA molecules through networks containing alternating nanoslits and deep wells (i.e., nanofilters) is of interest in separation applications. The activation process associated with escaping the energy barrier imposed by the narrow slits is characterized by a scaling theory which predicts the maximum free energy of the transition state is inversely proportional to the applied electric field strength. But the majority of experiments and simulations investigating these phenomena have been limited to the high electric field regime, with comparatively few studies addressing the low field limit. Here, we use Monte Carlo simulation and biased Rosenbluth sampling to study DNA activation processes in 3D nanofilter geometry over an expanded range of electric fields covering both high and low strength regimes. Modeling the DNA with segment lengths much smaller than slit depth (approximately equal to the Kuhn length) allows us to capture sub Kuhn length behavior associated with the transport.  We also employ biased sampling of a large ensemble of DNA configurations in the nanofilter to reveal new features of both entropic and enthalpic contributions to the free energy change as DNA escapes the energy barrier. Our simulations are able to recover the expected scaling of activation energy in high electric field strength, and further reveal a transition of the scaling as the electric field strength becomes small.