Molecular-level thermodynamic and kinetic parameters for the self-assembly of apoferritin molecules into crystals.
Molecular-level thermodynamic and kinetic parameters for the self-assembly of apoferritin molecules into crystals.
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DOI：
10.1006/jmbi.2000.4171
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发表时间：
2000-11
影响因子：
5.6
通讯作者：
S. Yau;D. Petsev;B. R. Thomas;P. Vekilov
中科院分区：
文献类型：
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作者：
S. Yau;D. Petsev;B. R. Thomas;P. Vekilov
脱铁铁蛋白分子自组装成晶体是蛋白质结晶和聚集的合适模型;这些过程是几种生物学和生物医学现象以及蛋白质和病毒自组装的基础。我们使用原子力显微镜原位，在脱铁铁蛋白的结晶过程中，在分子水平上可视化和量化负责晶体生长的过程。要评估的热力学参数，我们的图像的配置的掺入网站，“扭结”，在生长的晶体的表面上。我们表明，扭结是由于在晶体-溶液界面的分子的热波动。这允许评价分子间键的自由能phi=3.0 k（B）T=7.3 kJ/mol。从蛋白质溶解度提取的结晶自由能为-42kJ/mol。公布的第二维里系数和蛋白质溶解度在0和40摄氏度之间的测定结果表明，结晶焓接近于零。基于这三个值的分析表明，结晶驱动力的主要组成部分是溶液中与蛋白质分子结合并在结晶时释放的水分子的熵增益。此外，监测掺入的单个分子的扭结，我们确定在一组条件下的单个分子的附着的特征频率。这允许生长的介观动力学系数和这里确定的分子水平的热力学和动力学参数之间的相关性。我们发现，步骤生长速度，缩放的分子尺寸，等于产品的扭结密度和附着频率，即后一对是分子自组装成晶体的分子水平的参数。
The self-assembly of apoferritin molecules into crystals is a suitable model for protein crystallization and aggregation; these processes underlie several biological and biomedical phenomena, as well as for protein and virus self-assembly. We use the atomic force microscope in situ, during the crystallization of apoferritin to visualize and quantify at the molecular level the processes responsible for crystal growth. To evaluate the governing thermodynamic parameters, we image the configuration of the incorporation sites, "kinks", on the surface of a growing crystal. We show that the kinks are due to thermal fluctuations of the molecules at the crystal-solution interface. This allows evaluation of the free energy of the intermolecular bond phi=3.0 k(B)T=7.3 kJ/mol. The crystallization free energy, extracted from the protein solubility, is -42 kJ/mol. Published determinations of the second virial coefficient and the protein solubility between 0 and 40 degrees C revealed that the enthalpy of crystallization is close to zero. Analyses based on these three values suggest that the main component in the crystallization driving force is the entropy gain of the water molecules bound to the protein molecules in solution and released upon crystallization. Furthermore, monitoring the incorporation of individual molecules in to the kinks, we determine the characteristic frequency of attachment of individual molecules at one set of conditions. This allows a correlation between the mesoscopic kinetic coefficient for growth and the molecular-level thermodynamic and kinetic parameters determined here. We found that step growth velocity, scaled by the molecular size, equals the product of the kink density and attachment frequency, i.e. the latter pair are the molecular-level parameters for self-assembly of the molecules into crystals.