Assessing accumulated solvent near a macromolecular solute by preferential interaction coefficients.
Assessing accumulated solvent near a macromolecular solute by preferential interaction coefficients.
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通过优先相互作用系数评估大分子溶质附近累积的溶剂。
DOI：
10.1016/s0006-3495(02)75629-4
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Bloomfield,VictorA
中科院分区：
文献类型：
--
作者：
Tang,KarenES;Bloomfield,VictorA
生物大分子常在混合溶剂中进行研究。为了理解助溶剂-大分子相互作用，优先相互作用系数Γ 3可以帮助确定表面溶剂组成。Γ 3测量"局部区域"内的水B1和助溶剂B3的量，"局部区域"是围绕大分子的（可能是深远的）区域，其中溶剂是非块状的。然而，局部区域的边界是模糊的，并且不清楚哪些分子被计算在Bi中。探索一个简单的模型系统是有用的，它可以使Bimore具体化，并理解表面溶剂分布ρ（x）的哪些方面由Γ 3采样。我们进行了计算机模拟的二维（2D）系统组成的硬壁溶质（大分子）在混合溶剂（不同半径的硬盘）。我们同时计算了Γ 3和ρ（x）。我们发现：1）在实际中，局域区域的边界是由第一个共溶剂（而不是水）层的外边界来划分的; 2）B1主要计算大分子附近的溶剂; 2）假设B1只计算第一个水层内的沃茨是一个很差的近似; 3）当确定B1和B3时，水和共溶剂分子必须从同一空间区域来计算。我们推测，这些二维结果可以作为一个一级近似的优势贡献，甚至在三维，只要助溶剂是不是强烈地排除在大分子表面，有没有显着的长程溶剂结构。
Biological macromolecules are often studied in mixed solvents. To understand cosolvent-macromolecule interactions, the preferential interaction coefficient, Γ3, may help determine surface solvent compositions. Γ3measures the amounts of water,B1, and cosolvent,B3, within the "local domain," the (possibly far-reaching) region surrounding the macromolecule where the solvent is nonbulk-like. The local domain's boundary is, however, vague and it is unclear which molecules are counted inBi. It is useful to explore a simple model system to makeBimore concrete and to understand which aspects of the surface solvent distribution,ρ(x), are sampled by Γ3. We performed computer simulations on a two-dimensional (2D) system consisting of a hard-wall solute (the macromolecule) in a mixed solvent (hard disks of different radii). We simultaneously calculated Γ3andρ(x). We found that 1) in practice, the local domain's boundary is demarked by the outer limit of the first cosolvent (not water) layer;Bimainly counts the solvent near the macromolecule; 2) assumingB1to count only the waters within the first water layer is a poor approximation; 3) when determiningB1andB3, water and cosolvent molecules must be counted from the same region of space. We speculate that these 2D results may serve as a first-order approximation for the dominant contributions to Γ3even in three dimensions, so long as the cosolvent is not strongly excluded from the macromolecular surface and there is no significant long-ranged solvent structure.
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