Pack G R, Wong L, Lamm G
Department of Chemistry, University of Louisville, KY 40292, USA.
Biopolymers. 1999 Jun;49(7):575-90. doi: 10.1002/(SICI)1097-0282(199906)49:7<575::AID-BIP4>3.0.CO;2-J.
The predictions of counterion condensation theory for divalent ions were tested by comparison with the results of Monte Carlo calculations on an all-atom model of DNA. Monovalent-divalent competition at the polyelectrolyte surface was investigated by varying the partial molar volume of divalent ions. To assess the viability of using Poisson-Boltzmann (PB) calculations for determining divalent ion concentrations at DNA surfaces, Monte Carlo (MC) calculations were compared with PB calculations using different models of the dielectric continuum. It was determined that, while standard PB calculations of divalent ion surface densities are about 25-30% below those predicted by MC techniques, and somewhat larger than errors previously determined for monovalent ions, errors due to the use of the mean-field approximation of PB theory are smaller than those arising from common assumptions regarding the dielectric continuum.
通过与DNA全原子模型的蒙特卡罗计算结果进行比较，对二价离子的抗衡离子凝聚理论预测进行了检验。通过改变二价离子的偏摩尔体积，研究了聚电解质表面的一价-二价竞争。为了评估使用泊松-玻尔兹曼（PB）计算来确定DNA表面二价离子浓度的可行性，将蒙特卡罗（MC）计算与使用不同介电连续体模型的PB计算进行了比较。结果表明，虽然二价离子表面密度的标准PB计算值比MC技术预测的值低约25%-30%，且比先前确定的一价离子误差稍大，但由于使用PB理论的平均场近似而产生的误差小于因对介电连续体的常见假设而产生的误差。
