Theory and Modeling of Specific Ion Effects in Chemistry and Biology

辛辛那提大学的Thomas Beck由化学部的理论、模型和计算方法计划支持，对特定离子或阴离子的霍夫迈斯特效应进行计算研究。这项工作采用了一种新的液体统计力学理论方法--准经典理论(QCT)。QCT通过实施具有硬球约束的空间分配，将多余的化学势划分为三个贡献：1)在溶剂中挖洞的空穴自由能；2)将溶质放入空穴的自由能；以及3)释放硬球约束的自由能，允许溶质和溶剂之间的直接接触。对于离子溶剂化问题，上述步骤2)对水合自由能的贡献最大。研究发现，对这一项的平均场估计是相当准确的。特定的离子或霍夫迈斯特效应在许多化学、物理和生物系统中是非常重要的，例如生物膜的膨胀、自由溶剂化的能量和活性、表面张力增量、气泡相互作用、离子通道传输、胶体相互作用、pH测量、缓冲行为以及蛋白质的折叠和稳定性。贝克教授参与组织了一个关于化学和生物中的离子的研讨会，该研讨会将在科罗拉多州的特勒里德举行。他还积极参与本科生和研究生课程的开发。

Thomas Beck of the University of Cincinnati is supported by the Theory, Models and Computational Methods program in the Chemistry Division to carry out computational studies of specific ion or Hofmeister effects for anions. This work employs a novel theoretical approach for the statistical mechanics of liquids, the quasi-classical theory (QCT). The QCT partitions the excess chemical potential into three contributions by enacting a spatial partitioning with a hard-sphere constraint: 1) the cavity free energy for digging a hole in the solvent 2) the free energy for placing the solute into the cavity, and 3) the free energy to release the hard-sphere constraint, allowing direct contact between the solute and solvent. For ion solvation problems, step 2) above yields the largest contribution to the hydration free energy. It was found that a mean-field estimate of this term is quite accurate. This method permits computations of free energies at the quantum mechanical level, and in binding sites in proteins.Specific ion or Hofmeister effects are very important in a wide array of chemical, physical, and biological systems, for example the swelling of biological membranes, solvation free energies and activities, surface tension increments, bubble interactions, ion channel transport, colloid interactions, pH measurements, buffer behavior and protein folding and stability. Professor Beck is involved in organizing a workshop on ions in chemistry and biology to be held in Telluride CO. He is also heavily involved in undergraduate and graduate curriculum development.