Stability of Crystal Growth Face and Dissolution Face in Crystallization from Solution under Microgravity

The stability of the shapes of crystal growth face and dissolution face in a two-dimensional mathematical model of crystal growth from solution under microgravity is studied. It is proved that the stable shapes of crystal growth face and dissolution face do exist, which are suitably shaped curves with their upper parts inclined backward properly.The stable shapes of crystal growth faces and dissolution faces are calculated for various values of parameters, Ra, Pr and Sc. It is shown that the stronger the convection relative to the diffusion in solution is, the more backward the upperparts of the stable crystal growth face and dissolution face are inclined. The orientation and the shape of dissolution face hardly affect the stable shape of crystal growth face and vice versa.

Crystal Growth of Nitrogenase CrFe Protein and MnFe Protein in Space

Nitrogenase CrFe protein and MnFe protein were purified from a mutant strain UW3 of Azotobacter vinelandii Lipmann grown on a medium containing Cr and Mn, respectively. In order to meet the requirement for crystal growth Of O-2-susceptible proteins including nitrogenase in space, crystallization conditions were optimized for the proteins using a simple and suitable device, as a replacement for the cumbersome anaerobic box (dry box), for anaerobic addition of the protein samples. In all used precipitant and protein solutions added in the simplified plexi glass box, CrFe protein and MnFe protein could be crystallized on the spacecraft in one week by the liquid/liquid diffusion method and vapor diffusion by the sitting drop method, respectively. All formed crystals were single on the spacecraft, but under the same condition twin crystals appeared on the ground. The size of the largest crystal grown in space from CrFe protein was 2-fold larger than that on the ground. But the size of the largest crystal grown in space from MnFe protein was not larger than that on the ground. The difference in crystal growth in space between CrFe protein and MnFe protein could be resulted from the crystallization method, rather than the kind of protein.

Effect of non-uniform magnetic field on crystal growth by floating-zone method in microgravity

The magnetic damping effect of the non-uniform magnetic field on the floating-zone crystal growth process in microgravity is studied by numerical simulation. The results show that the non-uni-form magnetic field with designed configuration can effectively reduce the flow near the free surface and then in the melt zone. At the same time, the designed magnetic field can improve the impurity concen-tration non-uniformity along the solidification interface. The primary principles of the magnetic field con-figuration design are also discussed.

Protein Crystal Growth in Microgravity

Protein crystal growth is quite important for the determination of protein structureswhich are essential to the understanding of life at molecular level as well as to the development of molecu-lar biotechnology.The microgravity environment of space is an ideal place to study the complicated pro-tein crystallization and to grow good-quality protein crystals.A number of crystal-growth experiments of10 different proteins were carried out in August,1992 on the Chinese re-entry satellite FSW-2 in spaceusing a tube crystallization equipment made in China.A total of 25 samples from 6 proteins producedcrystals,and the effects of microgravity on protein crystal growth were observed,especially for an acidicphospholipase A2 and henegg-white lysozyme which gave better crystals in space than earth-grown crys-tals in ground control experiments.The results have shown that the microgravity in space favors the im-provement of the size,perfection,morphology and internal order of the grown protein crytals.

Imaging protein crystal growth behaviour in batch cooling crystallisation

The temporal and spatial growth behaviour of protein crystals, subject to different cooling strategies in protein crystallisation was investigated. Although the impact of temperature and cooling rate on crystal growth of small molecules was well documented, much less has been reported on their impact on the crystallisation of proteins. In this paper, an experimental set-up is configured to carry out such a study which involves an automatic temperature controlled hot-stage crystalliser fitted with a real-time imaging system. Linbro parallel crystallisation experiments(24-well plate) were also conducted to find the suitable initial conditions to be used in the hot-stage crystallisation experiments, including the initial concentration of HEW lysozyme solutions, precipitate concentration and pH value. It was observed that fast cooling rates at the early stage led to precipitates while slow cooling rates produced crystal nuclei, and very slow cooling rates, much smaller than for small molecules are critical to the growth of the nuclei and the crystals to a desired shape. The interesting results provide valuable insight as well as experimental proof of the feasibility and effectiveness of cooling as a means for achieving controlled protein crystallisation, compared with the evaporation approach which was widely used to grow single large crystals for X-ray diffraction study. Since cooling rate control can be easily achieved and has good repeatability, it suggests that large-scale production of protein crystals can be effectively achieved by manipulating cooling rates.

RECENT DOMESTIC PROGRESS IN SPACE CRYSTALLIZATION OF PROTEINS

The advances of protein crystal growth in microgravity are limited by its low success rate of space crystallization experiments. Our recent efforts have concentrated on exploration of the ways to increase the success rate of the experiments.The corresponding studies include structural comparisons of space- and Earthgrown protein crystals, numerical simulations of solute transport in protein crystallizer, optimization of protein crystailization conditions and improvement of crystallization techniques used. These studies show that the success rate of space protein crystallization could be improved by different ways.

A Statistical Rate Theory of Interface Concentration during Solution ZeoliteCrystal Growth

A theoretical model is developed using statistical rate theory to determine the rate of molecular transport across the interface of a growing spherical zeolite crystal. The model is expressed in terms of the interface concentration. Two model constants appear in the expression for the equilibrium exchange rate. In order to validate the model, zeolite crystallization is investigated for a system for which experimental data exist. The model constants were first established using the measured growth rates at a specific temperature. Then the model was used to predict the growth rate at other temperatures.

Solidification and Crystal Growth on the SJ-10 Recoverable Scientific Experiment Satellite

The low-gravity environment aboard the space provides a unique platform for understanding crystal-growth-related phenomena that are masked by gravity on the Earth and for exploring new crystal growth techniques. We have characterized the wetting behavior of metal alloys and carried out melt growth of compound semiconductors under the support of materials science program in the SJ-10 recoverable satellite. We found that interfacial reaction plays a significant role in the interfacial evolution of Sn-based alloys. Detached growth of InAsSb was realized under microgravity, whereas during the terrestrial experiment the crystal and the crucible wall contact with each other. Moreover, the suppression of buoyancy-driven convection results in a more uniform composition distribution in the InGaSb and Bi_2Te_3-based semiconductor alloys.

Progress of Microgravity Material Research During the Period of 2007-2009

Orbital experimental researches on crystal growth of Mn-doped GaSb and Bi2Se0.21Te2.79 are briefly summarized.The space experiments were completed in September of 2007 on broad the Foton-M3 satellite of Russia.Ground-based researches on the solidification behaviors of Al-Al3Ni,AlAl2Cu,Ag-Cu eutectic,Al-Pb monotectic and Cu-Co peritectic alloys in a 50-meter-high drop tube were investigated.New experimental results on the ultrasonic field and the temperature recycling induced to chiral symmetry breaking of NaClO3 crystal also were reported in the present paper.

Influence of microgravity on protein crystal structures

Structural determination and comparison of microgravity and ground grown protein crystals have been carried out in order to investigate the effect of microgravity on the structure of protein crystals. Following the structural studies on the hen egg-white lysozyme cystals grown in space and on the ground, the same kind of comparative studies was performed with acidic phospholipase A2 crystals grown in different gravities. Based on the results obtained so far, a conclusion could be made that microgravity might not be strong enough to change the conformation of polypeptide chain of proteins, but it may improve the bound waters’ structure, and this might be an important factor for microgravity to improve the protein crystal quality. In addition, the difference in the improvement between the two kinds of protein crystals may imply that the degree of improvement of a protein crystal in microgravity may be related to the solvent content in the protein crystal.

Influence of curved interfaces of phase change on the radial segregation of crystal growth

THE radial uniformity of components is an important parameter for crystal growth of a semiconductor of binary alloy. Radial segregation may be influenced by many factors, such as the convection, curved solidification interface, curved melting interface and others.

Growth of Large Single Crystals of Nitrogenase CrFe Protein and MnFe Protein

By using the liquid/liquid diffusion method at a suitable crystallization conditions, large single and dark brown crystals (the sides of the largest crystals were 0.20 mm x 0.20 mm x 0.07 min and 0.18 mm x 0.18 mm x 0.05 mm, respectively) could be obtained from the solutions of nitrogenase CrFe protein and MnFe protein purified from a mutant UW3 of Azotobacter vinelandii Lipmarm grown in Cr- or Mn-containing but NH3-free medium. The time of crystal formation, as well as the number, size, shape and quality of crystals obviously depended on the concentrations of PEG, MgCl2 and NaCl. The liquid/liquid diffusion method seems to benefit CrFe protein and MnFe protein for the growth of large single crystals for X-ray diffraction analysis.

Study of Growth Mechanism of Lysozyme Crystal by Batch Crystallization Method

The lysozyme crystals were made by batch crystallization method and the distribution of aggregate in solution were measured by dynamic light scattering. The results showed that the dimension of aggregate increased with the increase of the concentration of lysozyme and NaCl, lysozyme molecules aggregated gradually in solution and finally arrived at balance each other. The higher the concentrations of lysozyme and NaCl were, the faster the growth rate of （110） face was. The growth rates of lysozyme crystal were obtained by a Zeiss microscope, and the effective surface energy （a） of growing steps were calculated about 4.01×10^-8s J·cm^-2 according to the model of multiple two-dimensional nucleation mechanism.

The fluid phenomena in the crystallization of the protein crystal

This paper reports that an optical diagnostic system consisting of Mach-Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect the outcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement.

微重力下生长的蛋白质晶体的溶剂结构研究

为了考察微重力在分子水平上的效应，特别是对水溶剂结构的影响，测定了空间和地面生长的多个鸡蛋清溶菌酶晶体和蝮蛇毒酸性磷脂酶Ａ２晶体的结构，并做了结构比较研究。结果表明，虽然微重力不足以改变蛋白质肽链的构象及与蛋白质分子联系较强的溶剂分子的结合状况，但微重力可能改善与蛋白质分子联系较弱的有序水分子结构。这两种蛋白质晶体的结构测定结果也提示，微重力下蛋白质晶体质量改善的显示程度可能与蛋白质晶体的溶剂含量相关。这些发现从一个方面揭示了微重力改进蛋白质晶体质量的机理。另外，考虑到水分子对生命活动的重要性，这一初步结论的确认可能会对深入开展微重力生命科学研究有所启示。

碲化铋基热电半导体晶体研究

碲化铋基热电半导体是中低温区高性能热电转换材料,在微电子、计算机以及航天等领域广泛用于局部致冷与精确温控,在工业余废热回收温差发电等领域具有良好的应用前景。通过合金化和掺杂的方法,可以增强声子散射降低晶格热导率,优化载流子浓度提高电性能,从而提高碲化铋基材料的热电性能。在简述碲化铋晶体结构和能带结构基础上,综述了合金化和掺杂提高碲化铋基半导体的热电性能、碲化铋基半导体晶体生长的方法及空间微重力对碲化铋基晶体区熔生长的影响,并展望了利用天宫二号空间实验室开展碲化铋基晶体生长及其相关研究。

硅酸铋(BSO)晶体的空间生长

BSO晶体首次在飞船上进行了空间晶体生长.本文对空间和地面生长的BSO晶体进行了X射线摇摆曲线、位错腐蚀和透过率的测试.实验结果表明:在微重力环境下能明显提高BSO晶体的光学质量.

碘酸锂晶体的空间生长（2）

本文报道了在空间环境下进行碘酸锂晶体生长的实验结果。空间实验是在我国第１６颗科学探测与技术试验卫星上进行的，卫星在近地轨道运行１５天。本次空间实验共生长α－ＬｉＩＯ２单晶体２２块。实验表明：对于掺有１×１０－５ｍｏｌ／Ｌ的Ｃａ２＋离子的碘酸锂过饱和溶液，微重力条件下所生长的α－ＬｉＩＯ３晶体，具有均匀的宏观完整性。

配液结晶法制备溶菌酶蛋白质晶体的生长机理研究

采用配液结晶法制取了溶菌酶蛋白质晶体,使用动态光散射测量了溶液中聚集体的颗粒度几率分布;使用Zeiss显微镜测定了溶菌酶(110)晶面的生长速度.实验表明:随着蛋白质和NaCl浓度的增加,溶液中聚集体的颗粒尺寸也相应增加.随着反应时间的增加,溶菌酶分子在溶液中的聚集反应,逐渐达到平衡;在蛋白质和NaCl浓度较高时,溶菌酶晶体的(110)面生长较快,而在蛋白质和NaCl浓度较低时,该晶面生长较慢.基于二维成核生长机理,从晶体生长动力学理论方程出发,计算了二维成核的形成能α=4.01×10-8J?cm-2.

磁场在晶体生长中的应用研究进展

综述了磁场影响晶体生长的两种机制，磁场的产生和构型，在半导体材料硅、砷化镓、磷化铟晶体生长中的应用，在蛋白质及氧化物晶体生长方面的新进展．