[2P-2] ポスター2（2P-38ー2P-88）

[2P-61(WS5-4)] 中性子散乱により明らかとなった凍結水和水および非凍結水和水がタンパク質ダイナミクス活性化に及ぼす効果

^○山本 直樹 (自治医科大学医学部生理学講座生物物理学部門)

Hydration water plays a crucial role for activating the protein dynamics required for functional expression. In our previous studies, we observed a temperature-hysteresis phenomenon of the rotational dynamics of hydration water only when hydration level was high. This temperature hysteresis, which is due to the supercooling of freezable hydration water, is a key phenomenon to understand which hydration water, unfreezable or freezable hydration water, is crucial for the activation of protein dynamics. For this purpose, we performed neutron scattering experiments on a lysozyme hydrated with D₂O. Using coherent scattering profile, we revealed that the temperature-hysteresis phenomenon is indeed due to the supercooling of freezable hydration water. However, incoherent neutron scattering of protein revealed that protein dynamics did not show any temperature hysteresis. These results show that the protein dynamics is not coupled with freezable hydration water. Rather, unfreezable hydration water is essential for the activation of protein dynamics required for its function. Decoupling of the dynamics between unfreezable and freezable hydration water could be the cause of the distinct contributions of hydration water to protein dynamics.