| Budget Amount *help |
¥7,900,000 (Direct Cost: ¥7,900,000)
Fiscal Year 1996: ¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 1995: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Research Abstract |
Crystallization experiement of hen egg-white lysozyme was conducted by using the space shuttle under the microgravity environment in space. The crystallization apparatuses were used according to the principle of the vapor diffusion method.
In the crystallization conditions for growing monoclinic crystals, 2 morphologically different kinds of crystals were obtained. Furthermore, orthorhombic crystal appeared under the same crystallization conditions. On the other hand, crystals which seemed to be the orthorhombic crystal were also grown under the crystallization conditions for growing tetragonal crystals in addition to the tetragonal crystal. Of the two different shapes of monoclinic crystals, one is a rectangular form and the other is an extremely thin plate-like form. They are easily distinguished from each other by their appearances. In the space experiments, there was a strong likelihood of the latter crystals appearing. Since the molecular packing in the crystal of these two monocli
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nic lysozymes, however, revealed to be the same arrangement from the results of X-ray crystallographic analysis, the difference in the morphology between the space- and ground-grown crystals is considered to be derived from difference in the growth rate of the crystal plane. Regarding orthorhombic crystals, in contrast, the molecular packing of the space-grown crystals were quite different from that of the high temperature forms which are transformed under the temperature conditions higher than 30ﾟC from the ground-grown tetragonal or monoclinic crystals. It has been reported that the orthorhombic crystals possessing the same molecular arrangement appearred, but the resolution of the crystals is limited to 6* and no more report has been published thereafter. Next, the space-grown tetragonal crystals had the same molecular packing in the crystals as well as the same morphology as the ground-grown crystals.
As the results, it turned out that crystals of the different space group happened to appear even under the same crystallization conditions in a microgravity environment in space. After X-ray crystallographic analyzes of six crystals from the three different space groups (monoclinic, orthorhombic and tetragonal forms of the space- and earth-grown crystals), their molecular structures were compared. Significant differences among the obtained molecular structures were not found between the space- and ground-grown crystals although they had some relatively fractuated regions in the molecule. Regarding the water structure bound to the protein, three highly ordered water molecules were commonly conserved in the hinge region of lysozyme. These facts suggest that the protein structure itself was not influenced by the microgravity but that the interaction of the protein molecules in the nucleation process was significantly affected. In space, it is assumed that the surface characteristics of the protein molecule e.g.the distributions of the change and the hydrophobic region on the surface of the protein molecule control the intermolecular interactions in the formation of crystal neuclei. Less
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