Dynamic twisting correlations in a model DNA with uniform torsion elastic constant

The extent to which the twisting motions of two separate subunits (base pairs) in an elastic filament are correlated is discussed in terms of the two-point correlation function of their azimuthal angular displacements C(Delta,t) identical with <(phi(m)(t) - phi(m)(0))(phi(n)(t) - phi(n)(0))>, where m,n are the sequential subunit indices and Delta = |m - n| is their absolute difference. An approximate expression is derived for C(Delta,t) for an infinitely long model DNA from the analytical theory developed previously to treat the decay of the fluorescence polarization anisotropy of intercalated ethidium. C(Delta,t) is numerically evaluated as a function of Delta for a range of times (20, 40, 60, 80, 100, and 120 ns) for a model DNA with a typical torsion elastic constant. By t = 120 ns, significant dynamic correlations are observed to extend over a domain (Delta) several hundred base pairs. Copyright 1999 John Wiley & Sons, Inc.