We apply the Laplace approximation to a mathematical formulation of DNA cyclization J factors, leading to a formula that involves energies of local minima of the DNA energy, factors coming from the Hessian of the energy near each minimum, and geometric factors arising from the orientational portion of J. The approximation is derived in a quite general setting that encompasses both rigid base and rigid basepair models common in the literature. The approximation is applied to several families of 200–400 bp DNA, some relatively straight (fragments of λ-phage) and others quite bent (constructs that include up to 10 A tracts).

Project opportunity - Molecular resolution of biomolecular assembly by combining neutron scattering and coarse-grained simulation at the University of Leeds