Dynamics of water around F-actin in solution studied by neutron scattering

中性子散乱による溶液中のF-アクチン周辺水分子のダイナミクスの研究

藤原 悟; Plazanet, M.*; 小田 俊郎*

Fujiwara, Satoru; Plazanet, M.*; Oda, Toshiro*

Proteins are constantly fluctuating under the influence of surrounding aqueous environment. These thermal fluctuations, or dynamics, of the protein are indispensable for the structural changes that make the protein function. Ultimate understanding of the protein functions thus requires understanding of the dynamics of the proteins including the hydration water. We have been investigating the dynamics of F-actin. Here we employed quasi-elastic neutron scattering (QENS) to characterize the dynamics of the hydration water as well as the internal dynamics of F-actin. The QENS spectra of the concentrated solutions of F-actin in DO and HO were measured with the instrument IN5 in the Institut Laue-Langevin, Grenoble, France. The spectra arising from the dynamics of the hydration water and those from the internal dynamics of F-actin were extracted from the obtained spectra. The dynamics of the hydration water around the protein in the solution samples is characterized for the first time here, and it is shown that translational diffusion constant of water around F-actin has a similar value to that of the bulk water (2.810 cm/s) but longer residence time (3.3 ps compared to 0.6 ps of the bulk water). The results of the detailed analysis is presented.