Crystal Growth In Microgravity Research Articles

Equilibration of precipitants in a counter-diffusion apparatus for protein crystallization.

A cost-effective capillary dialysis apparatus (Toledo Capillary Box, TCB) developed for biomacromolecule crystal growth in microgravity and unit gravity environments can provide slow equilibration between the precipitant reservoir and capillary solutions, nurturing growth of neutron-diffraction-quality crystals. Under microgravity conditions, mass transfer of precipitants and biomacro-mol-ecules occurs under diffusion-controlled conditions, promoting slow growth and suppressing defect formation. The equilibration of common precipitants (polyethyl-ene glycol and salts such as ammonium sulfate) between capillary and reservoir solutions was measured for capillaries oriented horizontally or vertically with respect to the gravitational field at unit gravity. Precipitants equilibrated less rapidly in the vertical orientation when capillary solution densities were lower than those of the reservoir solutions. A plug filled with agarose gel was introduced in the TCB apparatus for salt precipitants since salts often exhibit relatively high free diffusion. Equilibration of the capillaries with reservoir solutions was significantly delayed for many of the salt precipitants tested. Analytical and semi-analytical models allow the prediction of precipitant equilibration of capillary and reservoir solutions under diffusion-controlled transport and show good agreement with experimental results.

Tracing transport of protein aggregates in microgravity versus unit gravity crystallization

Microgravity conditions have been used to improve protein crystallization from the early 1980s using advanced crystallization apparatuses and methods. Early microgravity crystallization experiments confirmed that minimal convection and a sedimentation-free environment is beneficial for growth of crystals with higher internal order and in some cases, larger volume. It was however realized that crystal growth in microgravity requires additional time due to slower growth rates. The progress in space research via the International Space Station (ISS) provides a laboratory-like environment to perform convection-free crystallization experiments for an extended time. To obtain detailed insights in macromolecular transport phenomena under microgravity and the assumed reduction of unfavorable impurity incorporation in growing crystals, microgravity and unit gravity control experiments for three different proteins were designed. To determine the quantity of impurity incorporated into crystals, fluorescence-tagged aggregates of the proteins (acting as impurities) were prepared. The recorded fluorescence intensities of the respective crystals reveal reduction in the incorporation of aggregates under microgravity for different aggregate quantities. The experiments and data obtained, provide insights about macromolecular transport in relation to molecular weight of the target proteins, as well as information about associated diffusion behavior and crystal lattice formation. Results suggest one explanation why microgravity-grown protein crystals often exhibit higher quality. Furthermore, results from these experiments can be used to predict which proteins may benefit more from microgravity crystallization.

Effect of macromolecular mass transport in microgravity protein crystallization

Abstract To investigate the effect of macromolecular transport and the incorporation of protein aggregate impurities in growing crystals, experiments were performed on the International Space Station (ISS) and compared with control experiments performed in a 1G laboratory environment. Crystal growth experiments for hen egg-white lysozyme (HEWL) and Plasmodium falciparum glutathione S-transferase (PfGST) were monitored using the ISS Light Microscopy Module (LMM). Experiments were performed applying the liquid–liquid counter diffusion crystallization method using rectangular, optically transparent capillaries. To analyze the quantity of impurity incorporated into growing crystals, stable fluorescently labeled protein aggregates were prepared and subsequently added at different percent concentrations to nonlabeled monomeric protein suspensions. For HEWL, a covalent cross-linked HEWL dimer was fluorescently labeled, and for PfGST, a stable tetramer was prepared. Crystallization solutions containing different protein aggregate ratios were prepared. The frozen samples were launched on 19.02.2017 via SpaceX-10 mission and immediately transferred to a -80°C freezer on the ISS. Two series of crystallization experiments were performed on ISS, one during 26.02.2017 to 10.03.2017 and a second during 16.06.2017 to 23.06.2017. A comparison of crystal growth rate and size showed different calculated average growth rates as well as different dimensions for crystals growing in different positions along the capillary. The effect of macromolecular mass transport on crystal growth in microgravity was experimentally calculated. In parallel, the percentage of incorporated fluorescent aggregate into the crystals was monitored utilizing the fluorescent LMM and ground-based fluorescent microscopes.

Homogeneous InGaSb crystal grown under microgravity using Chinese recovery satellite SJ-10

Microgravity crystal growth experiment for the growth of In0.11Ga0.89Sb was performed at the Chinese recoverable satellite through the space program SJ-10. This experiment is aimed to understand the melt formation and growth kinetics of InxGa1−xSb solid solution with higher indium composition, because their segregation coefficient was higher than the crystals with lower indium compositions. The target composition and uniformity were achieved with higher growth rate under microgravity, whereas the uniformity in composition was not achieved under normal gravity. The growth and dissolution were affected mainly by the steady state equilibrium in the melt composition because of the convection under normal gravity. The non-steady state equilibrium in the melt composition under microgravity helped to achieve a higher growth rate and compositional homogeneity at higher indium composition of InxGa1−xSb solid solution.

Crystal growth in microgravity for neutron diffraction studies

Crystal growth in microgravity for neutron diffraction studies

30 Years of Crystal Growth Under Microgravity Conditions in Freiburg: An Overview of Past Activities

AbstractIn the framework of this overview, the past four decades of research activities from the Freiburg Crystallography in the field of crystal growth in microgravity (µg) environments is presented. Crystal growth from the melt and solution phases of different materials was investigated onboard various manned and unmanned µg platforms such as parabolic flights, shuttle missions, satellite missions, and sounding rocket flights. The focus of material research in Freiburg was and is still in semiconducting materials; elemental semiconductors like Si, Ge, and GeSi as well as various compound semiconductors like InP, GaAs, and CdTe. The objectives of the single experiments, the results, and their further application and utilizations are summarized in this overview.

Terrestrial development of the experiments on the fullerite C60 crystal growth in microgravity

Terrestrial development of the experiments on the fullerite C60 crystal growth in microgravity

JAXA protein crystallization in space: ongoing improvements for growing high-quality crystals

The Japan Aerospace Exploration Agency (JAXA) started a high-quality protein crystal growth project, now called JAXA PCG, on the International Space Station (ISS) in 2002. Using the counter-diffusion technique, 14 sessions of experiments have been performed as of 2012 with 580 proteins crystallized in total. Over the course of these experiments, a user-friendly interface framework for high accessibility has been constructed and crystallization techniques improved; devices to maximize the use of the microgravity environment have been designed, resulting in some high-resolution crystal growth. If crystallization conditions were carefully fixed in ground-based experiments, high-quality protein crystals grew in microgravity in many experiments on the ISS, especially when a highly homogeneous protein sample and a viscous crystallization solution were employed. In this article, the current status of JAXA PCG is discussed, and a rational approach to high-quality protein crystal growth in microgravity based on numerical analyses is explained.

Homogeneous SiGe crystal growth in microgravity by the travelling liquidus-zone method

Homogeneous SiGe crystal growth experiments will be performed on board the ISS "Kibo" using a gradient heating furnace (GHF). A new crystal growth method invented for growing homogeneous mixed crystals named "travelling liquidus-zone (TLZ) method" is evaluated by the growth of Si0.5Ge0.5 crystals in space. We have already succeeded in growing homogeneous 2mm diameter Si0.5Ge0.5 crystals on the ground but large diameter homogeneous crystals are difficult to be grown due to convection in a melt. In microgravity, larger diameter crystals can be grown with suppressing convection. Radial concentration profiles as well as axial profiles in microgravity grown crystals will be measured and will be compared with our two-dimensional TLZ growth model equation and compositional variation is analyzed. Results are beneficial for growing large diameter mixed crystals by the TLZ method on the ground. Here, we report on the principle of the TLZ method for homogeneous crystal growth, results of preparatory experiments on the ground and plan for microgravity experiments.

Recombinant formate dehydrogenase from Arabidopsis thaliana: Preparation, crystal growth in microgravity, and preliminary X-ray diffraction study

Crystals of high-purity recombinant NAD+-dependent formate dehydrogenase from the higher plant Arabidopsis thaliana (AraFDH) were grown in microgravity in the Modul’-1 protein crystallization apparatus on the International Space Station. The space-grown crystals have larger sizes than those grown on Earth. X-ray diffraction data suitable for determining the three-dimensional structure were collected from the space-grown crystals to a resolution of 1.22 A using an X-ray synchrotron source. The crystals belong to sp. gr. P43212; the unit-cell parameters are a = b = 107.865 A, c = 71.180 A, α = β = γ = 90°.

Melt Structural Self-Organization and Viscosity within the Transient Layer during a Single Crystal Growth in Microgravity

A brief review is given of the results obtained and published in 2003–2007 by IChPM and IPPE during their joint study and modeling of Ge:Ga, Ge:Sb, GaSb:Te, InP:S single crystal growth from stoichiometric and non-stoichiometric melts on board the Photon satellite series. The use of microgravity is shown to be justified and holding promise for research into the structural self-organization processes (cluster forming) taking place within the transient layer of the melt during the solidification. The mathematical model of convective heat and mass transfer taking into account the dual-phase character of matter in the boundary layers near the interface has been created and used as an independent tool for the study of such processes. Prospects are discussed for this new area of space material science.

Simple Geometry for Diffusion Limited Protein Crystal Growth: Harnessing Gravity to Suppress Convection

A new upside-down geometry is proposed to achieve the beneficial effects of microgravity crystal growth by making use of buoyant forces instead of compensating for them. We show by growth experiments on sodium chlorate and lysozyme that crystal growth in an upside-down geometry leads to the formation of a buoyancy assisted depletion zone where convection is suppressed. The effects on growth rate and morphology that are observed are all indicative of diffusion limited growth, just as would happen in the absence of gravity. The optical quality of the lysozyme crystals clearly improved, but no effects of the growth method on X-ray diffraction quality could be observed. The simplicity of the growth geometry offers the possibility to perform large scale protein crystal growth experiments under microgravity-like conditions, without the requirement of compensating for gravity.

A Comparison between Simulations and Experiments for Microgravity Crystal Growth in Gradient Magnetic Fields

Experiments on microgravity crystal growth in gradient magnetic fields for nickel sulfate and lysozyme are compared with finite element simulations. These simulations include the inhomogeneous effective gravity that accompanied the magnet experiments. An excellent agreement between the simulations and the experiments was found. Methods to reduce the adverse effects of the inhomogeneous effective gravity and to optimize the growth conditions are discussed.

Melt Structural Self-Organization and Viscosity within the Transient Layer during Crystal Growth in Microgravity

Melt Structural Self-Organization and Viscosity within the Transient Layer during Crystal Growth in Microgravity

Using Gradient Magnetic Fields to Suppress Convection during Crystal Growth

Using in situ schlieren microscopy, we have studied the growth process of nickel sulfate hexahydrate crystals in a gradient magnetic field under conditions where convection is suppressed, to investigate whether the features that occur here are the same as those that occur during microgravity crystal growth. An expansion of the depletion zone with decreasing effective gravity was observed. If convection is suppressed, the depletion zone keeps expanding and the crystal growth rate decreases significantly, reaching a constant value. Although there remains some residual flow, it is very slow and does not affect the depletion zone. We find that homogeneity of the effective gravity in the milligravity range is sufficient to suppress convection. The results show that crystal growth in gradient magnetic fields is a good alternative for microgravity crystal growth in space.

Convection Effects on Crystallinity in the Growth of In0.3Ga0.7 as Crystals by the Traveling Liquidus Zone Method

The influence of convection in a melt on the crystallinity of the TLZ-grown In(0.3)Ga(0.7)As crystals has been investigated by growing crystals with various shapes and dimensions on the ground. No single crystals have been grown when the crystal diameter was 10 mm, but we were successful in growing single crystals by reducing crystal diameter to 2 mm. These results suggested the importance of suppressing convection in the melt during alloy crystal growth because constitutional supercooling tends to occur at the freezing interface or ahead of the interface by the segregation effect. Large area is required for substrate use in various applications. This requirement can be fulfilled by the crystal growth in microgravity because density difference-induced convection is suppressed in microgravity. Another means for suppressing convection without deteriorating area is plate-shape crystal growth with reduced thickness. The latter can be applied on the ground and we succeeded in growing single crystals of plate-shaped In(0.3)Ga(0.7)As by the traveling liquidus zone (TLZ) method. Dimensions of obtained single crystals were 10 mm in width and 2 mm in thickness and lengths ranged from 20 to 40 mm. Compositional uniformity was good and 0.3 +/- 0.02 in InAs mole fraction was achieved.

Upside‐Down Protein Crystallization

The benefits of protein crystal growth in microgravity are well documented. The crystallization vessels currently employed for microgravity crystallization are far from optimal with regards to cost, sample volume, size, and ease of use. The use of microbatch experiments is a favorable alternative in each respect: 96 experiments of 0.5-2 microL volumes can be performed in a single microtiter tray measuring 5 x 8 cm and costing 1 pound sterling each. To date, the use of microbatch has not been pursued on account of concerns of oil leakage. To address this issue, a novel approach to microbatch crystallization experiments is described, where the microbatch plates are inverted throughout the duration of the experiment. The findings intimate the application of the microbatch method to space flight and the potential to drastically increase the output of microgravity crystallization research .

Developing Quantitative, Multiscale Models for Microgravity Crystal Growth

Crystal growth conducted under microgravity conditions has had a profound impact on improving our understanding of melt crystal growth processes. Here, we present a brief history of microgravity crystal growth and discuss the development of appropriate models to interpret and optimize these growth experiments. The need for increased model realism and predictive capability demands new approaches for describing phenomena important at several disparate length scales. Of special importance is the ability to represent three-dimensional and transient continuum transport (flows, heat, and mass transfer), phase-change phenomena (thermodynamics and kinetics), and system design (such as furnace heat transfer during melt growth). An overview of mathematical models and numerical algorithms employed to represent such multiscale effects is presented.

G-jitter-induced motion of a protein crystal under microgravity

Direct numerical simulations have been carried out to examine the nature of g-jitter induced convective flows during a typical protein crystal growth experiment in a microgravity environment. The numerical investigations identified six parameters of importance for the motion of a spherical crystal particle in a microgravity environment subjected to single frequency vibrations in one direction: frequency ( f) and amplitude ( A) of the applied vibration, particle radius ( R) and density ( ρ p), fluid density ( ρ f) and fluid viscosity ( ν). In the Stokes regime, the numerical results were found to be in good agreement with the analytical results of Coimbra and Rangel [AIAA J. 39(9)(2001)]. Beyond the Stokes regime (1< Re p<300), the particle motion amplitude was found to approach the cell vibration amplitude to within 1% when the ratio α 2/ S ( α= ρ f / ρ p, S= f R 2/9 ν) becomes greater than about 20. Most importantly, the present results show that the g-jitter-induced convective flows are likely to occur during the microgravity crystal growth on space platforms. In a typical protein crystal growth process involving a crystal of ρ p=1.2 g/cm 3 and 10–1000 μm diameter in an aqueous solution, g-jitter-induced crystal motion and convection have been predicted to occur even at acceleration levels as low as 1.0 μG.

Microgravity crystal growth in a magnet

Polymer crystallization is notoriously difficult to control at a local scale because the growth of polymeric crystals is complicated by the need for cooperativemovements of a large number of connected monomers, resulting in a lack of long-range order and rapid loss of orientational correlation over short distances. Typically, polymeric crystals organize intomicroscale, isotropic, spherical superstructures (spherulites), which are comprised of splaying and branching thin lamellae interleaved with amorphous layers. Here, we report on a fast and easy method to control the orientation of crystals of semicrystalline polymers at the nanometer scale by using nanoimprint lithography [1]. Whenever a hardmold that contains nanoscale features defined on its surface (typical lateral size 50-250 nm; typical height 100 nm), is pressed against a molten film of a crystallizable polymer cast on a substrate under controlled temperature and pressure conditions, themolten polymer is forced to flow into the cavities of the mold. The isolation of polymer in separate nano-cavities, which strongly decreases the importance of nucleation by impurities; the confinement of the polymer in nano-sized cavities, which hinders the transport of polymer chains between cavities and controls the fast crystal growth direction; the partial orientation of polymer chains near the vertical walls on themold due to elongational flow, which eases the formation of nuclei with the crystallographic c axis parallel to the vertical walls on the mold, lead to a fine control over crystallographic orientation, crystal size and shape of polymer crystals. This is shown for a series of geometries, from simple straight lines tomore complex shapes, such as concentric circles and small squares, and for a variety of polymers.