The effects of microgravity on protein crystallization: evidence for concentration gradients around growing crystals |
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Affiliation: | 1. Department of Molecular Biology & Biochemistry, University of California, 560 Steinhaus Hall, Irvine, CA 92697-3900, USA;2. Teledyne Brown Engineering, 300 Sparkman Drive, Huntsville, AL 35805, USA;1. Advanced Material Laboratory, School of Materials Science & Engineering, Tsinghua University, Beijing 100084, PR China;2. Xi’an High Technology Research Center, Xi’an 710025, PR China;1. Division of Food Chemistry, Osaka Prefectural Institute of Public Health, Nakamichi 1-3-69, Higashinari-ku, Osaka, Japan;2. Laboratory of Quantum-Beam Chemistry and Biology, Radiation Research Center, Osaka Prefecture University, 1-2 Gakuen-cho, Sakai, Osaka, Japan;1. Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka, 565-0871, Japan;2. Cellular Function Imaging Team, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies, Kobe, Hyogo, 650-0047, Japan;3. Trinity College Dublin, Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry & Immunology, Dublin 2, Ireland;4. Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan;5. Malvern Instrument Inc., 22 Industrial Drive East, Northampton, MA, 01060, USA;1. Ceramic Department, Imam Khomeini International University, P. O. Box: 34149-16818, Ghazvin, Iran;2. Ceramic Department, Materials and Energy Research Center, Karaj, Iran |
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Abstract: | Atomic force microscopy (AFM) investigations have revealed that macromolecular crystals, during their growth, incorporate an extensive array of impurities. These vary from individual molecules to large particles, and microcrystals in the micron size range. AFM, along with X-ray topology, has further shown that the density of defects and faults in most macromolecular crystals is very high in comparison with conventional crystals. The high defect density is a consequence of the incorporation of impurities, misoriented nutrient molecules, and aggregates of molecules. High defect and impurity density, contributes to a deterioration of both the mechanical and the diffraction properties of crystals. In microgravity, access by impurities and aggregates to growing crystal surfaces is restricted due to altered fluid transport properties. We designed, and have now constructed an instrument, the observable protein crystal growth apparatus (OPCGA) that employs a fused optics, phase shift, Mach–Zehnder interferometer to analyze the fluid environment around growing crystals. Using this device, which will ultimately be employed on the international space station, we have, in thin cells on earth, succeeded in directly visualizing concentration gradients around growing protein crystals. This provides the first direct evidence that quasi-stable depletion zones formed around growing crystals in space may explain the improved quality of macromolecular crystals grown in microgravity. Further application of the interferometric technique will allow us to quantitatively describe the shapes, extent, and magnitudes of the concentration gradients and to evaluate their degree of stability. |
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