Chiral elasticity of DNA

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DNA is a chiral semiflexible polymer, so its bending Hamiltonian may contain nonlinear terms coupling the curvature κ to the torsion τ, leading to an average torsion independent of curvature, with variance scaling as 1/κ2. We perform atomistic MD simulations of 31 base-pair DNA sequences with explicit solvent, in which thermal fluctuations cause the DNA to bend. We extract bending moduli by fitting to bending and torsional angle distributions. We find that chiral elasticity matters whenever DNA bends on a radius less than about 5 nm.