Crystallization of the EGF receptor ectodomain on US space mission STS-47

Although biochemists working in the field of biological signal transduction have characterized cell surface receptors for numerous growth factors within the past ten years, none of the three-dimensional structures could be obtained for these important proteins which represent major components of the cells' growth control system. Now, the extracellular ligand binding domain of the EGF receptor was crystallized in the presence of EGF under microgravity on US Shuttle mission STS-47. In 8 out of 9 experiments prepared under different conditions crystal growth was observed. One of these space-grown crystals showed higher diffraction quality than all crystals previously obtained in the laboratory. It allowed, for the first time, evaluation of the real space group by partial data collection.     

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.     

A型分子筛生长的理论模型

以XRD，TEM，电子衍射对A型分子筛水热晶化过程中晶体生长作了实时观察，分析了晶体生长过程中晶体的聚集行为与演化特征，提出了A型分子筛生长的叠合生长模型，认为，水热体系经过一个晶化诱导阶段后，大量的纳米晶形成，纳米晶作为生长基元，相互迅速了聚集直接叠合演化为微米多晶体，叠合过程不同于邻位面生长所描述的生长基元一个个按次序嵌入晶面，而是许多纳米晶同时相互按一定方向叠合而形成微晶。     

Does Microgravity Influence Self-Assembly??

The templated syntheses of TMA₂Sn3S7 and TBA2Sn4S9 (where TMA is tetramethylammonium and TBA is n-tetrabutylammonium) microporous layered tin(iv) sulfides have been carried out under both microgravity (μG) and earth (1G) conditions in order to elucidate the influence of gravity on the self-assembly and crystal-growth processes of this class of materials. The μG experiments were conducted on board the May 1996 Endeavour STS-77 NASA space-shuttle flight. It was determined that the long-range ordering of the porous layers and the population of defects but not the short-range ordering within the layers is influenced by gravity. Bulk and surface crystallinity, smoothness of crystal faces, optical quality, crystal habits, registry of the porous layers, and accessible void volume to adsorbates were found to be improved in the space-grown crystals. This is probably because the forces associated with the organization of the porous layers are expected to be weak and sensitive to the elimination of buoyancy-driven convective flows and Stokes sedimentation effects in a microgravity environment. One can draw an analogy to the weak forces between protein macromolecules and the established effect of microgravity on improving the diffraction quality of crystals harvested in space.     

A Compact Device for Colloidal Crystal Studies on Tiangong-1 Target Spacecraft

An experimental device with three crystallization cells, each with two working positions, was designed to study growth kinetics and structural transformation of colloidal crystals under microgravity condition. The device is capable of remote control of experimental procedures. It uses direct-space imaging with white light to monitor morphology of the crystals and reciprocal-space laser diffraction (Kossel lines) to reveal lattice structure. The device, intended for colloidal crystal growth kinetics and structural transformation on Tiangong-1 target spacecraft, had run on-orbit for more than one year till the end of the mission. Hundreds of images and diffraction patterns were collected via the on-ground data receiving station. The data showed that single crystalline samples were successfully grown on the orbit. Structural transformation was carefully studied under electric and thermal field. Using a backup device, control experiments were also performed on the ground under similar conditions except for the microgravity. Preliminary results indicated that the on-orbit crystals were more stable than the on-ground ones.     

空间微重力环境下蛋白质晶体生长的研究进展

空间微重力环境可消除或减弱常重力场下溶液中存在的对流和沉降,为蛋白质晶体生长提供一个相对均一和稳定的环境,有利于得到尺寸更大、衍射分辨率更高的蛋白质晶体。通过对这些高质量空间晶体进行X射线衍射分析,可获得多种蛋白质的精细三维结构。从空间蛋白质晶体生长的发展历史、研究成果、生长机理、存在的问题与对策等方面总结了空间微重力环境下蛋白质晶体生长的研究进展,展望了空间蛋白质结晶的未来。     

Effects of a microgravity environment on the crystallization of biological macromolecules

Macromolecules crystals are indispensable intermediates in the analysis of macromolecular structure, are essential for the application of x-ray diffraction methods, and are at the same time the greatest obstacle to success. Protein crystals are generally difficult to grow, often of imperfect form or small size, and frequently lack sufficient order. Their growth has become the rate limiting step in x-ray crystallography. Evidence has emerged from protein crystallization experiments carried out in space that suggests macromolecular crystals of improved order and quality can be grown in a microgravity environment. Presumably the absence of density driven convection and sedimentation permits a more deliberate and graceful entry of individual molecules into the crystal lattice. This in turn results in improvements in both morphology and the diffraction patterns of the crystals. The precise mechanisms for these improvements and the means for their optimization are, however, not understood at more than a rudimentary level. I attempt here to review microgravity effects that may play a role in protein crystal growth, sedimentation, convection and surface contact, and suggest their possible mechanisms.     

Secondary grain growth in ammonium nitrate crystallization

Crystallization and ageing of pure ammonium nitrate crystals was studied by scanning electron microscopy. Ageing the crystals beyond 1 h led to the growth of secondary grains along the grain boundaries of primary grains (140–200 m). After 6 h ageing secondary growth along grain boundaries was not observed; instead, distinct clusters with morphologies similar to the secondary grains were formed. The ancillary growth obeys approximately the parabolic relation L=(Kt)^1/n+1 where n=1 justifies grain growth in the pure crystals, and its formation is ascribed to the dissolution of dendrites, edges and corners. The high interfacial activity and interparticle voids can affect the storage and mechanical properties of the material.     

Recrystallization of the ODS superalloy PM-1000

The primary recrystallization of a 1 0 0-fiber textured coarse-grained oxide dispersion strengthened nickel-based superalloy (PM-1000) has been investigated by high-resolution electron backscatter diffraction. The annealing behavior of this alloy is quite complex. Even at high annealing temperatures (e.g. 1200 °C), recrystallization is only partial. The microstructure of this superalloy in the annealed state consists of a blurred subgrain structure, coarse grains with sizes of about 10–20 μm at the pre-existing grain boundaries and a significant fraction of small crystals in the interior of the recovered grains. These small grains are elongated and display anisotropic growth. In the present paper we present a detailed explanation for this peculiar microstructure. Particular focus is placed on the origin of the new grains in the recovered structure in a [1 0 0]-oriented grain.     

Deformation behaviour of aluminium macrocrystals in the grain boundary region

Lattice distortions of deformed aluminium macrocrystals were observed by Electron-microprobe-Kossel techniques. Grain boundary effects due to deformation appeared in various ways such as extraordinary separation and branching of Kossel lines, and as intergranular rotation of the grains in pseudo-Kossel X-ray diffraction patterns obtained from the grain boundary regions of the specimens. Such distortions of the patterns peculiar to the grain boundary regions were attributed to the effect of local slipping induced by the active slip systems of the neighbouring crystals. By the interpretation of these patterns and the orientation relationships between neighbouring grains, it was found that the local slipping was induced towards the slip direction of the active slip plane in the neighbouring crystals, or induced by a type of local stress along the slip direction of the active slip planes in the neighbouring crystals. It was also recognised that at an early stage of stressing, deformation bands were produced in the grain boundary region as a result of a grain boundary effect.     

Can intergranular force transmission be identified in sand?

This work tackles the challenge of assessment of force distributions in granular media. Spatially resolved neutron and x-ray diffraction are used to measure internal strains of sand grains under load. These approaches are sensitive to the crystallographic strains of the sand grains (quartz crystals) such that each grain acts as a local 3D strain gauge and so, for elastic deformations, a force gauge. First results are presented from recent experiments that provide tantalising indications of the potential of these techniques in the investigation of the mechanics of granular media.     

High Resolution Synchrotron X-Radiation Diffraction Imaging of Crystals Grown in Microgravity and Closely Related Terrestrial Crystals

Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.     

汽相转化法制备纳米晶组成的块状ZSM-5多孔沸石

在ZSM-5沸石前驱体中加入羧甲基纤维素钠并制得干胶, 然后通过蒸汽相转化制得了大块状ZSM-5沸石。由于羧甲基纤维素钠与硅铝物种之间的相互作用干扰了沸石晶体的正常生长, 这种干扰所产生的“键阻断”作用导致合成的大块状ZSM-5沸石由100~150 nm的初级ZSM-5沸石晶体组成, 在这些初级粒子之间存在2~20 nm的二次介孔结构。异丙苯催化裂化结果表明, 由于纳米沸石具有较高的外表面积和较大的介孔孔容, 比参比催化剂表现出更高的异丙苯转化率。     

Microwave synthesis of metallosilicate zeolites with fibrous morphology

In this paper, we report syntheses of silicalite (Si-MFI) zeolite crystals with tetravalent metal ions incorporated to synthesize metallosilicalite (M-MFI; M = Sn, Zr, Sn/Zr, Ti/Zr) zeolite crystals by using microwave irradiation reactions. Beta-Diketonate (acetylacetone) was used as a chelating ligand of the metal precursors, in order to reduce their hydrolysis rates and, therefore, to enhance framework incorporation of each metal in the syntheses of M-MFI zeolites. The zeolite crystals formed show puck-like morphology, and these crystals are stacked to form fibers with the degree of self-assembly varied depending on the nature of the tetravalent metal ion used. Importantly, the self-assembly of the zeolite crystals and the resultant fibrous morphology are observed only when the substituting metal ions are present. Powder X-ray diffraction, infrared and ultraviolet diffuse reflectance spectroscopic data all indicate that Sn and Ti atoms are well substituted for Si, but Zr is not well incorporated in the resulting MFI crystals. These results are discussed in terms of the ionic sizes and bulk dielectric constants of the corresponding metal oxides of the substituting metal ions.     

Abnormal grain growth via the migration of planar growth interfaces

Nanocrystalline nickel electrodeposits undergo a sequence of morphologically distinct grain growth stages during annealing. The nanostructure initially undergoes a rapid sequence of abnormal grain growth, followed by a much slower normal grain growth stage. Out of this uniformly growing structure comes a second stage of abnormal grain growth which not only accelerates the overall growth rate, but the transformation also occurs by the migration of planar reaction fronts. These planar growth interfaces are composed of many individual grain boundary segments, migrating together at essentially the same velocity. Grain shape was studied from intergranular fracture surfaces; it was found that the abnormally growing grains were cuboidal in shape and were present either as individually growing grains or as cuboid clusters. Electron backscatter diffraction showed numerous twin-related cuboidal grain clusters having complex compound planes.     

Low Resistance Polycrystalline Diamond Thin Films Deposited by Hot Filament Chemical Vapour Deposition

Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH4) highly diluted with H2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications.     

Effect of Ambient Temperature on Stress Measurement Method Using Copper Foil

The copper electroplating stress measurement method uses the grain growth in the copper on a machine element that has been subjected to repeated loads. Because this growth is also caused by thermal energy, the effect of the ambient temperature on grain growth density and grain orientation was investigated. Cyclic torsion tests were carried out at temperatures from 293 to 353 K. The relationship among the grain growth density, maximum shear stress, number of cycles, and ambient temperature was formulated to measure the maximum shear stress occurring on the machine element. Moreover, cyclic bending–torsion tests were also performed, and the orientations of grown grains were analysed by electron backscatter diffraction. The slip directions of grown grains corresponded closely with the direction of shear stress in spite of the ambient temperatures. This means that principal stresses can be measured by using the pole figure or the inverse pole figure of grown grains at temperatures up to 353 K.     

Spherulitic growth and recrystallization in barium silicate glasses

The growth and recrystallization of spherulites formed in barium disilicate glasses between 700 and 900° C has been studied by electron microscopy and electron diffraction. Spherulites formed at 700° C consist of fibrillar (～ 100 Å diameter) monoclinic crystals in confocal arrangement with preferred crystallographic growth axes. High temperature (900° C) spherulites are composites of radially oriented plate-shaped orthorhombic crystals with lateral growth of epitaxially nucleated fibrillar monoclinic crystals. At intermediate temperatures “axialites”, consisting of a single orthorhombic “midrib” crystal with monoclinic fibrillar side-growths, grow in competition with the low temperature spherulite morphology. The monoclinic fibrillar phase is believed to be an intermediate metastable structure which is able to grow more rapidly than the orthorhombic phase via cellular transformation in the presence of impurities. Brief comparison is made between the observed morphologies and theories for interface instability and cellular crystallization. Recrystallization, induced mainly by the large interfacial area of spherulite fibrils, produces faulted and twinned monoclinic grains which transform slowly to the orthorhombic stable crystal phase. A glassy intercrystalline residue becomes more prominant with grain growth.     

In situ measurement of crystal growth rate of zeolite

To clarify the growth behavior of zeolite crystals under hydrothermal synthesis conditions, the growth process of ZSM-5 type zeolite crystals was studied using two kinds of in situ observation apparatus. Direct observation of ZSM-5 crystals from amorphous gels during steaming and silicalite crystals from clear aqueous solutions was performed. During the stationary growing stage, a constant rate of crystal growth of zeolites was observed directly for both zeolite crystals. In the case of ZSM-5 zeolites from gels, it was also found that after a certain induction time, crystals grew to 10–20 μm in size, after which no further growth was observed. On the other hand, in the case of silicalite crystals from aqueous solutions, the induction time hardly existed. The size distribution of crystals and the activation energy for crystal growth are also discussed.