Electric response of DNA hairpins to magnetic fields

We study the electric properties of DNA molecules with hairpinlike shapes in the presence of a magnetic flux. It is shown that the current amplitude can be modulated by the applied field. The details of the electric response strongly depend on the twist angles. For geometries where the flux through the plaquette of the ladder can be canceled pairwise (commensurate twist), the current exhibits periodicity. Further twisting the geometry and changing its length causes complex aperiodic oscillations. We also study persistent currents. They reduce to simple harmonic oscillations if the system is commensurate, otherwise deviations occur due to the existence of closed paths leading to a washboard shape.