Electro-optical properties of DNA

摘要

We calculate the steady-state electric birefringence for a flexible bent rod molecule due to free electrophoresis and the interaction of its induced dipole moment with an externally applied electric field. We consider the solution of flexible bent rod as a mixture of rigid bent rod molecules with different angles of conformation. We use the Fok-ker-Planck equation in order to find the orientational and conforma-tional distribution function for the steady state. We first calculate the contribution of the particles having a fixed angle of conformation to the electric birefringence and then, averaging all these values, we obtain the final birefringence value. Using convenient parameters to characterize the DNA restriction fragments we explain the existence of a positive value of the electric birefringence, for low electric fields, and the sign reversal of it when we increase the applied electric field. We also corroborate the order of the inversion field value.