SEQUENCE-DISORDER EFFECTS ON DNA ENTROPIC ELASTICITY

DNA stretching experiments are usually interpreted using the wormlike chain model; the parameter A appearing in the model is then interprete d as giving the elastic bend stiffness of the double helix. Actually, however, the value of A obtained by this method is a combination of be nd stiffness and intrinsic bend effects reflecting sequence informatio n, just as at zero stretching force. This observation resolves the dis crepancy between the value of A measured in these experiments and the larger ''dynamic persistence length'' measured by other means. On the other hand, the twist stiffness deduced from torsionally constrained s tretching experiments suffers no such correction. The calculation is v ery simple and analytic; it explains the success of the naive wormlike chain model over the entire force range of DNA stretching experiments . [S0031-9007(98)06015-3].