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Biophys J, December 1998, p. 2732-2742, Vol. 75, No. 6

Electrostatic Potential of B-DNA: Effect of Interionic Correlations

Sergei Gavryushov and Piotr Zielenkiewicz

Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warszawa, Poland

Modified Poisson-Boltzmann (MPB) equations have been numerically solved to study ionic distributions and mean electrostatic potentials around a macromolecule of arbitrarily complex shape and charge distribution. Results for DNA are compared with those obtained by classical Poisson-Boltzmann (PB) calculations. The comparisons were made for 1:1 and 2:1 electrolytes at ionic strengths up to 1 M. It is found that ion-image charge interactions and interionic correlations, which are neglected by the PB equation, have relatively weak effects on the electrostatic potential at charged groups of the DNA. The PB equation predicts errors in the long-range electrostatic part of the free energy that are only ~1.5 kJ/mol per nucleotide even in the case of an asymmetrical electrolyte. In contrast, the spatial correlations between ions drastically affect the electrostatic potential at significant separations from the macromolecule leading to a clearly predicted effect of charge overneutralization.

Biophys J, December 1998, p. 2732-2742, Vol. 75, No. 6
© 1998 by the Biophysical Society   0006-3495/98/12/2732/11  $2.00




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Copyright © 1998 by the Biophysical Society.