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首页> 外文期刊>Crystal growth & design >Kinetics and Thermodynamics of Glucose Isomerase Crystallization
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Kinetics and Thermodynamics of Glucose Isomerase Crystallization

机译：葡萄糖异构酶结晶的动力学和热力学

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摘要

A quantitative study using laser confocal microscopy combined with differential interference microscopy on the kinetics and thermodynamics of the crystallization of glucose isomerase is presented. Fundamental crystallization parameters are determined from the kinetics of step advancement and rates of two-dimensional (2D) nucleation. The ruling mass transfer pathway and accompanying activation barriers are discussed. In brief, the solubility exhibits normal temperature dependence and the crystallization enthalpy is the thermodynamic driving force. The diminishing entropic cost for higher PEG concentrations is attributed to water structuring and a decrease in water activity. The prominent step generation mechanism is homogeneous 2D nucleation for high supersaturations. At low driving forces 2D nucleation occurs on anomalously hyperactive sites and the step edge free energies for homogeneous and heterogeneous nucleation are determined. The number of nucleation centers for both mechanisms are estimated and from the density of nucleation centers we obtain for the activation barrier of adsorption similar to 3.8 kJ mol(-1). No step-step interaction is observed for interstep distances >70 nm. Theoretical fits of step velocity data suggest surface diffusion makes a non-negligible contribution to surface kinetics. From the temperature dependence of the step kinetic coefficient the activation barrier for crystallization was determined to be <22.4 kJ mol(-1).
机译：提出了使用激光共聚焦显微镜结合微分干涉显微镜对葡萄糖异构酶结晶动力学和热力学进行定量研究的方法。基本的结晶参数由步骤前进的动力学和二维（2D）成核速率确定。讨论了主要的传质途径和伴随的活化障碍。简而言之，溶解度表现出正常的温度依赖性，并且结晶焓是热力学驱动力。较高的PEG浓度导致的熵成本降低归因于水的结构化和水活度的降低。突出的步进生成机制是用于高过饱和度的均匀2D成核。在低驱动力下，2D形核在异常活跃的位置上发生，并确定了用于均相和异相形核的台阶边缘自由能。估计了两种机制的成核中心数量，并从成核中心的密度获得了类似于3.8 kJ mol（-1）的吸附活化势垒。对于> 70 nm的步距，未观察到步-步相互作用。步速数据的理论拟合表明，表面扩散对表面动力学的贡献不可忽略。根据阶跃动力学系数的温度依赖性，确定结晶的活化势垒为<22.4 kJ mol（-1）。

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