Numerical analysis of the depletion zone formation around a growing protein crystal
Numerical analysis of the depletion zone formation around a growing protein crystal
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DOI：
10.1196/annals.1324.002
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发表时间：
2004-01-01
期刊：
影响因子：
--
通讯作者：
Yoshitomi, S
中科院分区：
文献类型：
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作者：
Tanaka, H;Inaka, K;Yoshitomi, S
如果晶体周围的扩散场不受干扰，则预期在蛋白质晶体生长期间在晶体周围形成蛋白质耗尽区和杂质耗尽区。如果这些区域不受干扰，则可以降低晶体的生长速率，并且可以抑制杂质的吸收，从而产生高度有序的晶体。众所周知，微重力环境可减少对流流体运动，这被认为会干扰耗尽区。因此，我们期望在太空中生长的晶体能够比在地面上生长的晶体获得更好的质量。在这项研究中，我们估计耗尽区的形成数值和讨论的结晶在空间实验的结果。在α-淀粉酶的情况下，使用PEG 8000作为沉淀剂，大多数晶体在地面上形成簇状形态。然而，在太空中，我们已经从相同的样品成分中获得了单一的高质量晶体。我们已经测量了溶液的粘度、扩散系数和蛋白质晶体在地面上的生长速率。对这些数值进行数值分析，预计主要由于粘度值较高，会形成一个明显的贫化区。这可能是在太空中生长出质量更好的单晶的主要原因之一，因为人们认为耗尽区不会受到干扰。对于蛋白质结晶实验，盐被广泛用作沉淀剂。然而，在这种情况下，由于粘度低，可以预期浓度耗尽区效应降低。因此，如果可以通过添加剂增加蛋白质溶液的粘度，则耗尽区形成效果将增强，以提供在空间中特别有效的技术。
It is expected that a protein depletion zone and an impurity depletion zone are formed around a crystal during protein crystal growth if the diffusion field around the crystal is not disturbed. The growth rate of the crystal may be decreased and the impurity uptake may be suppressed to result in highly ordered crystals if these zones are not disturbed. It is well known that a microgravity environment can reduce convective fluid motion, and this is thought to disturb the depletion zones. Therefore, we expect that crystals grown in space can attain better quality than those grown on the ground. In this study, we estimate the depletion zone formation numerically and discuss the results of crystallization in space experiments. In case of alpha-amylase, most of the crystals form a cluster-like morphology on the ground using PEG 8000 as a precipitant. However, in space, we have obtained a single and high-quality crystal grown from the same sample compositions. We have measured the viscosity of the solution, the diffusion coefficient, and the growth rate of protein crystals on the ground. Applying numerical analysis to these values a significant depletion zone was expected to form mainly due to higher values of the viscosity. This might be one of the main reasons for better quality single crystals grown in space, where the depletion zone is thought to remain undisturbed. For protein crystallization experiments, salts are widely used as a precipitant. However, in that case, reduced concentration depletion zone effects can be expected because of a low viscosity. Therefore, if it is possible to increase the viscosity of the protein solution by means of an additive, the depletion zone formation effect would be enhanced to provide a technique that would be especially effective in space.