Are nucleation kinetics of protein crystals similar to those of liquid droplets?
Are nucleation kinetics of protein crystals similar to those of liquid droplets?
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DOI：
10.1021/ja9930869
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发表时间：
2000-01-12
影响因子：
15
通讯作者：
Vekilov, PG
中科院分区：
文献类型：
--
作者：
Galkin, O;Vekilov, PG
我们已经研究了从水溶液中的模型蛋白质的晶体的成核，使用从未技术，允许直接测定均匀的成核速率。在12.6摄氏度的恒定温度下，我们通过改变蛋白质和沉淀剂的浓度来改变热力学过饱和度。我们发现了一个打破依赖的均匀成核速率的过饱和度，这是超出了经典的成核理论的预测。成核定理允许我们将其与晶核尺寸随过饱和度增加的离散变化联系起来，如（10或11）->（4或5）->（1或2）。此外，我们观察到，在高蛋白质浓度下第二液相的存在强烈影响晶体成核动力学：（i）在液-液分层的相区，晶体成核速率低于预期。(ii)在该区域的紧邻处，在相同的实验中，成核速率变化高达2倍。由于该区域的理论预测一个尖锐的速率最大值，我们将这种动力学不稳定性的实验条件朝向或远离相边界的微小变化。
We have studied the nucleation of crystals of a model protein from aqueous solutions using a never technique that allows direct determinations of homogeneous nucleation rates. At a constant temperature of 12.6 degrees C we varied the thermodynamic supersaturation by changing the concentrations of protein and precipitant. We found a broken dependence of the homogeneous nucleation rate on supersaturation that is beyond the predictions of the classical nucleation theory. The nucleation theorem allows us to relate this to discrete changes of the size of the crystal nuclei with increasing supersaturation as (10 or 11) -> (4 or 5) -> (1 or 2). Furthermore, we observe that the existence of a second liquid phase at high protein concentrations strongly affects crystal nucleation kinetics: (i) Crystal nucleation rates are lower than expected in the phase region of liquid-liquid demixing. (ii) In the immediate proximity of this region, nucleation rates vary by factors of up to 2 in identical experiments. Since for this region theory predicts a sharp rate maximum, we attribute this kinetic instability to minor shifts of the experimental conditions toward or away from the phase boundary.