Binary liquid phase separation and critical phenomena in a protein/water solution.
Binary liquid phase separation and critical phenomena in a protein/water solution.
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DOI：
10.1073/pnas.84.20.7079
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发表时间：
1987-10
影响因子：
11.1
通讯作者：
J. Thomson;P. Schurtenberger;G. Thurston;G. Benedek
中科院分区：
文献类型：
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作者：
J. Thomson;P. Schurtenberger;G. Thurston;G. Benedek
我们研究了牛晶状体蛋白γ II-晶状体蛋白水溶液的相图。当温度 T 小于 Tc = 278.5 K 时，我们发现这些溶液在蛋白质浓度不同的两个各向同性液相之间表现出可逆共存。通过测量两个共存浓度 c(T) 和测量不同初始浓度的云温度，一致地表征了共存曲线的稀释和浓缩分支。我们估计临界浓度 cc 为每毫升溶液 244 毫克蛋白质。共存曲线可以用 (c - cc)/cc = 5.2 平方根 (Tc - T)/Tc 的绝对值很好地表示。利用沿着与临界等容线平行的等容线的散射光强度的温度依赖性，我们估计了旋节线的位置，发现其形式为 (c - cc)/cc = 3.0 平方根 (Tc - T)/Tc。共存曲线与旋节线宽度之比(5.2/3.0)接近平均场值平方根3。我们还在其中一些水溶液中观察到了γ II-晶状体蛋白大晶体的生长，并对促进或延迟结晶开始的因素进行了初步观察。这些发现表明，选定的蛋白质/水系统可以作为研究相变和关键现象的优秀模型系统。
We have investigated the phase diagram of aqueous solutions of the bovine lens protein gamma II-crystallin. For temperatures T less than Tc = 278.5 K, we find that these solutions exhibit a reversible coexistence between two isotropic liquid phases differing in protein concentration. The dilute and concentrated branches of the coexistence curve were characterized, consistently, both by measurements of the two coexisting concentrations, c(T), and by measuring the cloud temperatures for various initial concentrations. We estimate that the critical concentration, cc, is 244 mg of protein per ml solution. The coexistence curve is well represented by the absolute value of (c - cc)/cc = 5.2 square root (Tc - T)/Tc. Using the temperature dependence of the scattered light intensity along isochores parallel to the critical isochore, we estimated the location of the spinodal line and found it to have the form (c - cc)/cc = 3.0 square root (Tc - T)/Tc. The ratio of the widths of the coexistence curve and the spinodal line, (5.2/3.0), is close to the mean-field value square root 3. We have also observed the growth of large crystals of gamma II-crystallin in some of these aqueous solutions and have made preliminary observations as to the factors that promote or delay the onset of crystallization. These findings suggest that selected protein/water systems can serve as excellent model systems for the study of phase transitions and critical phenomena.