DNA condensation by field-induced non-equilibrium noise.

DNA molecules under good solvent conditions condense when subjected to strong AC electrical fields. It is shown that AC electrical fields couple charge fluctuations to molecular shape fluctuations, which produces a non-equilibrium noise source that can dominate over equilibrium thermal noise in the long-wavelength limit. The field-induced excess charge fluctuations amplify the Asakura-Oosawa fluctuation attraction force between neighboring chains, providing a mechanism for field-induced DNA condensation.