Armstrong Clare L, Häussler Wolfgang, Seydel Tilo, Katsaras John, Rheinstädter Maikel C
Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada.
Soft Matter. 2014 Apr 21;10(15):2600-11. doi: 10.1039/c3sm51757h.
Lipid dynamics in the cholesterol-rich (40 mol%) liquid-ordered (lo) phase of dimyristoylphosphatidylcholine membranes were studied using neutron spin-echo and neutron backscattering. Recent theoretical and experimental evidence supports the notion of the liquid-ordered phase in phospholipid membranes as a locally structured liquid, with small ordered 'domains' of a highly dynamic nature in equilibrium with a disordered matrix [S. Meinhardt, R. L. C. Vink and F. Schmid, Proc. Natl. Acad. Sci. U. S. A., 2013, 110(12), 4476-4481, C. L. Armstrong et al., PLoS One, 2013, 8(6), e66162]. This local structure was found to have a pronounced impact on the membranes' dynamical properties. We found that the long-wavelength dynamics in the liquid-ordered phase, associated with the elastic properties of the membranes, were faster by two orders of magnitude as compared to the liquid disordered phase. At the same time, collective nanoscale diffusion was significantly slower. The presence of a soft-mode (a slowing down) in the long-wavelength dispersion relationship suggests an upper size limit for the ordered lipid domain of ≈220 Å. Moreover, from the relaxation rate of the collective lipid diffusion of lipid-lipid distances, the lifetime of these domains was estimated to be about 100 nanoseconds.
利用中子自旋回波和中子背散射技术研究了二肉豆蔻酰磷脂酰胆碱膜中富含胆固醇（40摩尔%）的液态有序（lo）相中的脂质动力学。最近的理论和实验证据支持磷脂膜中液态有序相是一种局部结构化液体的观点，即具有高度动态性质的小有序“域”与无序基质处于平衡状态[S. 迈因哈特、R. L. C. 温克和F. 施密德，《美国国家科学院院刊》，2013年，110(12)，4476 - 4481；C. L. 阿姆斯特朗等人，《公共科学图书馆·综合》，2013年，8(6)，e66162]。发现这种局部结构对膜的动力学性质有显著影响。我们发现，与膜的弹性性质相关的液态有序相中的长波长动力学比液态无序相快两个数量级。同时，集体纳米级扩散明显较慢。长波长色散关系中软模（减速）的存在表明有序脂质域的尺寸上限约为220 Å。此外，根据脂质 - 脂质距离的集体脂质扩散的弛豫率，估计这些域的寿命约为100纳秒。
