The normal growth rates R and apparent step velocities (lateral growth rates of a spiral hillock) V of tetragonal hen egg-white lysozyme (HEWL) crystals were for the first time measured by Michelson interferometry in the international space station (as part of the NanoStep project) using commercialized HEWL samples containing 1.5% impurities. A significant increase in V under microgravity was confirmed compared to step velocities Vstep on the ground, while a decrease in R was also confirmed compared to that in the purified solution under microgravity as expected. Because of exact measurement of growth rates, kinetic analyses of R were conducted as a function of supersaturation, σ (σ ≡ ln(C/Ce), where C is the concentration; Ce is the solubility), using a spiral growth model and a two-dimensional (2D) nucleation growth model. For both models over a wide range of σ, R in the impure solution was significantly lower than that in the purified solution. The degree of the suppression of impurity effects was also evaluated using the difference in Vp and Vi, where Vp is the apparent step velocity in the purified solution, and Vi is that in the impure solution. The difference between Vp and Vi was smaller than the difference in step velocities on the ground, Vstep,p and Vstep,i, where Vstep,p is the step velocity in the purified solution, and Vstep,i is the step velocity in the impure solution.
Research Containing: International Space Station
Expression of p53-Regulated Proteins in Human Cultured Lymphoblastoid TSCE5 and WTK1 Cell Lines during Spaceflight
The aim of this study was to determine the biological effects of space radiations, microgravity, and the interaction of them on the expression of p53-regulated proteins. Space experiments were performed with two human cultured lymphoblastoid cell lines: one line (TSCE5) bears a wild-type p53 gene status, and another line (WTK1) bears a mutated p53 gene status. Under 1 gravity or microgravity conditions, the cells were grown in the cell biology experimental facility (CBEF) of the International Space Station for 8 days without experiencing the stress during launching and landing because the cells were frozen during these periods. Ground control samples were simultaneously cultured for 8 days in the CBEF on the ground for 8 days. After spaceflight, protein expression was analyzed using a PanoramaTM Ab MicroArray protein chips. It was found that p53-dependent up-regulated proteins in response to space radiations and space environment were MeCP2 (methyl CpG binding protein 2), and Notch1 (Notch homolog 1), respectively. On the other hand, p53-dependent down-regulated proteins were TGF-β, TWEAKR (tumor necrosis fac- tor-like weak inducer of apoptosis receptor), phosho-Pyk2 (Proline-rich tyrosine kinase 2), and 14-3-3θ/τ which were affected by microgravity, and DR4 (death receptor 4), PRMT1 (protein arginine methyltrans- ferase 1) and ROCK-2 (Rho-associated, coiled-coil containing protein kinase 2) in response to space radi- ations. ROCK-2 was also suppressed in response to the space environment. The data provides the p53- dependent regulated proteins by exposure to space radiations and/or microgravity during spaceflight. Our expression data revealed proteins that might help to advance the basic space radiation biology.
Dust particles of micro-meter size are levitated around a sheath in discharges. Gravity pushes the dust particles from a bulk of plasma to the sheath on the ground. Microgravity conditions brought by sounding rockets, parabolic flights of aircract and the International Space Station allow the dust particles to suspend in the bulk of plasma. Many researches have required phenomena of the dust particles under microgravity to be understood with connected to plasma parameters. Here several examples estimating the plasma parameters of microgravity experiments were shown, and described as manners to elucidate the phenomena in dusty plasmas with the plasma parameters. A rough estimation of ion density was obtained in observing wave propagation, and spatial distribution of the dust particles changed by a discharge control was understood in measuring electron density.
Rapid Access:Dream Chaser® Space Traffic Management and Operations to Enable Near-Immediate Payload Access for Responsive Mission and Payload Support
As research institutions all over the world are placing a higher value on space-based science, the need for rapid access to vehicles returning from space carrying experiments grows more important. One of the challenges of enhanced science utilization is rapid access to space vehicles post-flight, which is significantly enabled by effective space traffic management and integration of space operations into a mature commercial aviation system to achieve radically improved orbit to researcher timelines. Sierra Nevada Corporation’s (SNC) Space Systems’ Dream Chaser® reusable spacecraft is designed for multiple applications including cargo and/or crew resupply to the International Space Station and independent long duration science missions. The Dream Chaser is an optionally-piloted, reusable lifting-body spacecraft that lands horizontally on a runway, similar to the Space Shuttle. Unlike the Space Shuttle, the Dream Chaser design supports the unique capability of being able to land at many domestic and international commercial and public-use airports, and offers access to cargo and/or crew almost immediately thereafter. Though this capability presents a unique opportunity for researchers in the field of microgravity science, there are challenges when considering the current landscape of regulation, public risk, and autonomous flight. The potential opportunities associated with landing the Dream Chaser at public-use airports to enable globally convenient and rapid access to crew, cargo, and time critical microgravity experiments post-flight are identified and addressed in this paper.
Manned space flight induces a reduction in immune competence among crew and is likely to cause deleterious changes to the composition of the gastrointestinal, nasal, and respiratory bacterial flora, leading to an increased risk of infection. The space flight environment may also affect the susceptibility of microorganisms within the spacecraft to antibiotics, key components of flown medical kits, and may modify the virulence characteristics of bacteria and other microorganisms that contaminate the fabric of the International Space Station and other flight platforms. This review will consider the impact of true and simulated microgravity and other characteristics of the space flight environment on bacterial cell behavior in relation to the potential for serious infections that may appear during missions to astronomical objects beyond low Earth orbit.
Three-dimensional structure of phosphoribosyl pyrophosphate synthetase from E. coli at 2.71 Å resolution
Phosphoribosyl pyrophosphate synthetase from Escherichia coli was cloned, purified, and crystal- lized. Single crystals of the enzyme were grown under microgravity. The X-ray diffraction data set was col- lected at the Spring-8 synchrotron facility and used to determine the three-dimensional structure of the enzyme by the molecular-replacement method at 2.71 Å resolution. The active and regulatory sites in the molecule of E. coli phosphoribosyl pyrophosphate synthetase were revealed by comparison with the homol- ogous protein from Bacillus subtilis, the structure of which was determined in a complex with functional ligands. The conformations of polypeptide-chain fragments surrounding and composing the active and reg- ulatory sites were shown to be identical in both proteins.
Three-dimensional structure of carboxypeptidase T from Thermoactinomyces vulgaris in complex with N-BOC-L-leucine
The 3D structure of recombinant bacterial carboxypeptidase T (CPT) in complex with N-BOC-L-leucine was determined at 1.38 A resolution. Crystals for the X-ray study were grown in microgravity using the counter-diffusion technique. N-BOC-L-leucine and SO4(2-) ion bound in the enzyme active site were localized in the electron density map. Location of the leucine side chain in CPT-N-BOC-L-leucine complex allowed identification of the S1 subsite of the enzyme, and its structure was determined. Superposition of the structures of CPT-N-BOC-L-leucine complex and complexes of pancreatic carboxypeptidases A and B with substrate and inhibitors was carried out, and similarity of the S1 subsites in these three carboxypeptidases was revealed. It was found that SO4(2-) ion occupies the same position in the S1′ subsite as the C-terminal carboxy group of the substrate.
Combustion of clear cast polymethylmethacrylate (PMMA) samples 10 cm long by either 1 or 2 cm wide with thicknesses ranging from 1-5 mm was investigated in opposed flow. Tests included both one sided and two sided burns. The samples were burned in a flow duct within the Microgravity Science Glovebox (MSG) on the International Space Station (ISS) to ensure true microgravity conditions. The experiment took place in opposed flow with a varying oxygen concentration (uncontrolled) and varying flow;velocities (controlled). Flames are recorded on two cameras and later tracked to determine spread rate.;Assuming a linear profile between oxygen concentration at the start and the end of each test we made graphs of oxygen concentration vs. time for each test. From these we created flammability maps showing the flame behavior at different oxygen concentrations and flow velocities. Additionally we have conducted an extinction analysis, plotting the oxygen concentration against the flow velocity at;the time of extinction with respect to type of test (one sided or two sided).;Currently we are modeling combustion of flat PMMA;samples in microgravity using Fire Dynamic Simulator (FDS 5.5.3). The entire modeling for BASS-II is done in DNS mode because of the laminar conditions and small domain. The model employs the same test sample and MSG geometry as the experiment. The model predicts a higher flame spread rate than that observed in experiments. So we look to modify the chemical kinetics and materials;properties to improve the model. Also we plan to do a domain study and grid sensitivity analysis in future.
We examine the dynamics of a binary mixture in a cubic cell subjected to a temperature differential and oscillatory forcing. The Soret effect, which is negative in the present study, provides a coupling mechanism by which a temperature gradient establishes a concentration gradient in a mixture. We present the results of experiments that were performed on the International Space Station (ISS) and compare the observations with the results of direct numerical simulations. The evolution of temperature and concentration fields is investigated by optical digital interferometry. One advantage of the experimental technique is the observation of the fields along two perpendicular directions of the cell, allowing us to restore the three-dimensional field. Experimental evidence disproves speculations that the ISS microgravity environment always affects diffusion-controlled processes. Furthermore, we demonstrate that imposed vibrations with constant frequency and amplitude create slow mean flows and that they do influence the diffusion kinetics. The perturbation of the diffusive fields scales as the square of the vibrational velocity. In addition to calculations of the full three-dimensional Navier–Stokes equations, a two-time-scale computational methodology is used for situations in which the forcing period is very small compared to the natural time scales of the problem. The simulations show excellent agreement with experimental observations.
We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both three-dimensional experiments and simulations from realistic noisy initial conditions. In the latter case, erratic tip-splitting events promoted by large-amplitude oscillations contribute to maintaining the long-range array disorder, unlike in thin-sample experiments where long-range coherence of oscillations is experimentally observable.