Minton A P
Section on Physical Biochemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830, USA.
Biophys J. 2000 Jan;78(1):101-9. doi: 10.1016/S0006-3495(00)76576-3.
An equilibrium statistical-thermodynamic model for the effect of volume exclusion arising from high concentrations of stable macromolecules upon the stability of a trace globular protein with respect to denaturation by heat and by chaotropes is presented. The stable cosolute and the native form of the trace protein are modeled by effective hard spherical particles. The denatured state of the trace protein is represented as an ensemble of substates modeled by random coils having the same contour length but different rms end-to-end distances (i.e., different degrees of compaction). The excess or nonideal chemical potential of the native state and of each denatured substate is calculated as a function of the concentration of stable cosolute, leading to an estimate of the relative abundance of each state and substate, and the ensemble average free energy of the transition between native and denatured protein. The effect of the addition of stable cosolute upon the temperature of half-denaturation and upon the concentration of chaotrope required to half-denature the tracer at constant temperature is then estimated. At high cosolute concentration (>100 g/l) these effects are predicted to be large and readily measurable experimentally, provided that an experimental system exhibiting a fully reversible unfolding equilibrium at high total macromolecular concentration can be developed.
本文提出了一个平衡统计热力学模型，用于研究高浓度稳定大分子引起的体积排除效应，对痕量球状蛋白质热变性和离液剂变性稳定性的影响。稳定共溶质和痕量蛋白质的天然形式用有效硬球形颗粒建模。痕量蛋白质的变性状态表示为一个子状态集合，这些子状态用具有相同轮廓长度但不同均方根端到端距离（即不同压缩程度）的无规线团建模。计算天然状态和每个变性子状态的过量或非理想化学势作为稳定共溶质浓度的函数，从而估计每个状态和子状态的相对丰度，以及天然蛋白质和变性蛋白质之间转变的系综平均自由能。然后估计添加稳定共溶质对半变性温度以及在恒定温度下半变性示踪剂所需离液剂浓度的影响。在高共溶质浓度（>100 g/l）下，预计这些影响很大且易于通过实验测量，前提是能够开发出在高总大分子浓度下表现出完全可逆展开平衡的实验系统。
