Electric response of DNA hairpins to magnetic fields

We study the electric properties of single-stranded DNA molecules with hairpin-like 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. The current exhibits periodicity for geometries where the flux through the plaquettes of the ladder can be cancelled pairwise (commensurate twist). 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.