Foglia Fabrizia, Hazael Rachael, Simeoni Giovanna G, Appavou Marie-Sousai, Moulin Martine, Haertlein Michael, Trevor Forsyth V, Seydel Tilo, Daniel Isabelle, Meersman Filip, McMillan Paul F
Chemistry Department, Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
Sci Rep. 2016 Jan 7;6:18862. doi: 10.1038/srep18862.
Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å(-1) corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.
准弹性中子散射（QENS）是研究皮秒到纳秒时间尺度以及与细胞尺寸相关长度尺度下的水传输和弛豫动力学的理想技术。为了理解地球深部生物圈和生物技术应用，需要对活生物体中的高压动态效应进行研究。在此，我们应用QENS，通过对正常细菌和全氘代细菌以及缓冲溶液进行H/D同位素对比实验，来研究嗜铁还原地杆菌在环境压力（0.1MPa）和高压（200MPa）下的水传输，以区分细胞内和跨膜过程。结果表明，在环境条件下，细胞内水动力学与水性流体中的体扩散速率相当，但在高压下迁移率显著降低。我们将此解释为是由于在纳米受限环境中与大分子的相互作用增强所致。整个细胞包膜的总体扩散速率也以相似的速率发生，但在对应于6 - 9 Å实空间尺寸的动量转移值Q = 0.7 - 1.1 Å⁻¹之间，QENS信号出现了意外变窄。弛豫时间的增加可以通过穿过位于内膜或外膜结构内的水通道蛋白水传输复合物的分子的相关动力学来解释。
