Wills Peter R, Winzor Donald J
Department of Physics, Univeristy of Auckland, Private Bag 92019, Auckland 1020, New Zealand.
Acta Crystallogr D Biol Crystallogr. 2005 Jun;61(Pt 6):832-6. doi: 10.1107/S0907444905013569. Epub 2005 May 26.
The van der Waals equation of state for imperfect gases is applied to solutions of macromolecules, especially to explain the fluid-fluid phase transition in protein solutions, a phenomenon of much interest in relation to protein crystallization. The van der Waals b parameter corresponds to the total excluded volume per pair of molecules and can be calculated from independently known molecular properties. It is comprised of terms resulting from hard-sphere and net charge-charge interactions. The experimentally determined second virial coefficient B2 can then be used to obtain the equilibrium constant for dimerization K2, a phenomenologically accessible measure of the van der Waals a parameter. Sedimentation equilibrium is recommended as the technique for measuring B2 most accurately. More general results are used to make a minor quantitative correction to the van der Waals prediction concerning the criterion for the fluid-fluid phase transition. Calculations of the effect of inert co-solutes on the phase transition may prove useful in choosing crystallization conditions.
非理想气体的范德华状态方程被应用于大分子溶液，特别是用于解释蛋白质溶液中的液-液相转变，这是一种与蛋白质结晶密切相关且备受关注的现象。范德华b参数对应于每对分子的总排斥体积，可根据独立已知的分子性质计算得出。它由硬球相互作用和净电荷-电荷相互作用产生的项组成。然后，通过实验测定的第二维里系数B2可用于获得二聚化平衡常数K2，这是一种从现象学角度可获取的范德华a参数的度量。建议采用沉降平衡法作为最准确测量B2的技术手段。运用更通用的结果对范德华关于液-液相转变判据的预测进行了微小的定量修正。计算惰性共溶质对相变的影响可能有助于选择结晶条件。
