Step velocity in tetragonal lysozyme growth as a function of impurity concentration and mass transport conditions
Step velocity in tetragonal lysozyme growth as a function of impurity concentration and mass transport conditions
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DOI：
10.1016/j.jcrysgro.2006.04.116
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发表时间：
2006-07-15
影响因子：
1.8
通讯作者：
Sazaki, G.
中科院分区：
文献类型：
--
作者：
Dold, P.;Ono, E.;Sazaki, G.
用高分辨相差显微镜原位测量了四方溶菌酶晶体{110}面上的台阶速度。台阶的运动在生长速度和与杂质的相互作用方面表现出明显的各向异性。在高纯度条件下(使用99.99%纯度的溶菌酶)，沿<；110>；方向的步速nu(Step)比沿<；001>；方向的步速高6倍。螺旋丘和2D岛显示出拉长的透镜状形态，在<；110&>；方向有明显的尖端。当使用商品级溶菌酶(纯度：98.5%)时，Nu(Step)<；1110>；/Nu(Step)<；001>；的比例降至约2-4。山丘/岛屿的形态由透镜状变为圆形。进入快速生长的<lt；110>方向的台阶速度受杂质的影响比进入<lt；001&>方向的影响大得多。在测量精度上，单层岛(5.6 nm高)、多层岛和生长螺旋的阶跃速度相似。在顶部，晶体暴露在宽度约为0.5 mm的蛋白质溶液中。这导致了对流质量传输条件。在晶体的背面，有一个几百纳米的小缺口。在这个间隙内，晶体在扩散传输条件下生长。改变聚焦位置从晶体的顶部到背面，在对流和扩散条件下都可以在同一晶体上观察到生长。使用商品级溶菌酶，扩散条件下的生长速度高于对流优势条件下的生长速度。在扩散质量传输条件下，从商业级溶液中生长的岛的形态与仅从高纯度溶液中获得的岛的形态相似。使用高纯度溶液时，阶跃速度和岛的形态并不随传质条件的变化而变化。这些结果证明了在扩散输运条件下，杂质的耗尽区扩大，杂质向生长界面的输运减少。(C)2006爱思唯尔B.V.保留所有权利。
The step velocity on {110} faces of tetragonal lysozyme crystals has been measured in situ by high-resolution phase contrast microscopy. The movement of the steps shows a distinct anisotropy with respect to the growth velocity and the interaction with impurities. Under high-purity conditions (using lysozyme of 99.99% purity), the step velocity nu(step) in the < 110 > direction exceeds the one in the < 001 > direction by a factor of 6. Spiral hillocks as well as 2D islands show an elongated, lens shaped morphology with pronounced tips in the < 110 > direction. The ratio of nu(step) < 1110 >/nu(step) < 001 > is reduced to approximate to 2-4 when commercial grade lysozyme (purity: 98.5%) is used. The morphology of the hillocks/islands changes from the lens-shaped one to a rounded one. The step velocity into the fast growing < 110 > direction is significantly more affected by impurities than the growth into the < 001 > direction. The step velocity of monolayer islands (5.6 nm in height), of multilayer islands and of growth spirals is similar within the accuracy of the measurements.On the topside, the crystal is exposed to protein solution of approximate to 0.5 mm width. This results in convective mass transport conditions. On the backside of the crystal, there is a small gap of a few hundred nanometers. Within this gap, the crystal is growing under diffusive transport conditions. Changing the focus position from the topside of the crystal to the backside, the growth can be observed on the same crystal under convective as well as under diffusive conditions. Using commercial grade lysozyme, the growth velocity is higher under diffusive conditions than under convectively dominated ones. The morphology of the islands grown from a commercial grade solution under diffusive mass transport conditions is similar to the island morphology obtained otherwise only from high-purity solutions. Using high-purity solution, the step velocity and the island morphology does not differ as a function of the mass transport conditions. These results prove the extension of the depletion zone of the impurities and the reduced transport of impurities toward the growing interface under diffusive transport conditions. (c) 2006 Elsevier B.V. All rights reserved.