徳島大学 教育・研究者情報データベース(EDB)

1. 徳島大学.大学院ソシオテクノサイエンス研究部.ライフシステム部門.物質機能化学(〜2016年3月31日)

1. 鈴木 良尚([徳島大学.大学院社会産業理工学研究部.理工学域.応用化学系.物質機能化学分野]/[徳島大学.理工学部.理工学科.応用化学システムコース.物質機能化学講座])

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2. 塚本 勝男([大阪大学])

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3. 吉崎 泉(独立行政法人 宇宙航空研究開発機構)

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4. 三浦 均([名古屋市立大学])

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5. 藤原 貴久([徳島大学.総合科学部])

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(英) First Direct Observation of Impurity Effects on the Growth Rate of Tetragonal Lysozyme Crystals under Microgravity as Measured by Interferometry

(英) The suppression of impurity effects on protein crystallization under microgravity would be related to the origin of the higher X-ray resolution limits observed for space-grown crystals, and the mechanism that the impurity effects are suppressed would be useful for producing high-quality protein crystals on the ground. 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 ground, while a decrease in R was also confirmed compared to that in the purified solution under microgravity; therefore, even under microgravity, the purity level influences crystal growth processes as expected. More precisely, 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 of lysozyme, and 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. Thus, the final quality of the crystals would depend on the purity of the solutions even in microgravity environments. The degree of the suppression of impurity effects was also evaluated using the difference between apparent step velocities Vp and Vi, where Vp and Vi are the apparent step velocity in the purified and impure solution, respectively. The difference between Vp and Vi became significantly smaller than the difference in step velocities on the ground, Vstep,p and Vstep,i, where Vstep,p and Vstep,i are the step velocities in the pure and impure solution, respectively. Thus, the suppression of impurity effects under microgravity was confirmed for the first time.

1. 結晶成長(crystal growth)