BROWNIAN DYNAMICS SIMULATIONS OF DNA ELECTRIC DICHROISM AT HIGH-ELECTRIC-FIELD STRENGTHS

Brownian dynamics simulations have been used to investigate the orient ation dynamics when applying an electric field pulse to a DNA solution . Including only counter ion polarization effects, both the orientatio n and the off-field relaxation are monotonous processes. If, instead, the hydrodynamic coupling between different parts of the molecule is t he dominating mechanism, one observes a small maximum in orientation b efore reaching a steady-state and a pronounced undershoot during the r elaxation back to equilibrium. Such an amplitude inversion, with the D NA molecules transiently perpendicularly oriented relative to the elec tric field, has also been observed in electric dichroism experiments a t high electric fields.