A MOLECULAR-DYNAMICS STUDY OF ELECTRIC-FIELD GRADIENTS IN CONDENSED B-DNA SYSTEMS

Molecular dynamics simulations of the hexagonally packed B-DNA fibre phase at 300 K are reported. A variety of systems containing counterions (Na+ and Ca2+) and coions (Cl-) are studied and the processes contributing to the fast component of quadrupolar relaxation at the counter-ion nuclei investigated. The relaxation rates are found to be strongly dependent on the distance of the ion from the DNA and the extent of solvent structure deformation around the ion. However, the rates are not directly correlated with contributions from the solute sites alone; thus the use of continuum solvent models for the study of quadrupolar relaxation rates in polyelectrolyte systems is called into question.