STRUCTURAL INFORMATION IN THE LOCAL ELECTRIC-FIELD OF DISSOLVED B-DNA

We have developed a theoretical model of the electric potential and field for B-DNA in solution to investigate the persistence of structural information in the local field. A Green-function technique is used to account for the phosphate groups, the dominant charges of the polyelectrolyte DNA, as discrete surface charges exhibiting helical geometry. In addition to the DNA macromolecule, a region of condensed ions and bulk solvent are treated as dielectric media with cylindrical symmetry. We have derived analytical expressions that manifest the symmetry of the system. The leading term is equivalent to that of a continuous line charge and thus only reflects cylindrical symmetry. Information reflecting the helical structure is contained in the terms of higher order. The effective decay length for helical information in the local electric field is approximately 5 Angstrom beyond the surface of DNA. These results have significance for investigations of nucleic-acid-protein interactions and for experimental efforts to image DNA with scanning force microscopies.