Gavryushov S, Zielenkiewicz P
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warszawa, Poland.
Biophys J. 1998 Dec;75(6):2732-42. doi: 10.1016/S0006-3495(98)77717-3.
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 approximately 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.
为了研究具有任意复杂形状和电荷分布的大分子周围的离子分布和平均静电势，已对修正的泊松-玻尔兹曼（MPB）方程进行了数值求解。将DNA的结果与通过经典泊松-玻尔兹曼（PB）计算获得的结果进行了比较。在离子强度高达1 M的情况下，对1:1和2:1电解质进行了比较。研究发现，PB方程忽略的离子镜像电荷相互作用和离子间相关性，对DNA带电基团处的静电势影响相对较弱。即使在不对称电解质的情况下，PB方程预测的自由能远程静电部分的误差也仅约为每核苷酸1.5 kJ/mol。相比之下，离子之间的空间相关性会极大地影响与大分子有显著距离处的静电势，导致明显预测到的电荷过中和效应。
