Orädd Greger, Lindblom Göran
Department of Biophysical Chemistry, Umeå University, Umeå, Sweden.
Magn Reson Chem. 2004 Feb;42(2):123-31. doi: 10.1002/mrc.1338.
This mini-review focuses on the utilization of pulsed magnetic field gradients to measure diffusional motion in systems of macroscopically oriented lipid bilayers. The NMR diffusion technique is proposed to have appreciable potential for future biophysical investigations in the field of membrane biology. Topics such as transport of molecules both across and in the plane of the membrane can be successfully studied, and the formation of lipid domains and their intrinsic dynamics can also be scrutinized. First, a short introduction to the NMR technique is given together with a brief discussion on methods of obtaining a good bilayer orientation. Then, a number of recent results on biophysical/biological membrane systems of great interest is presented, in which some unique conclusions on so-called 'raft membranes' are reached. It is shown for systems with large two-phase areas of liquid disordered and liquid ordered phases that lipid lateral diffusion is faster in the former phase and has a smaller apparent activation energy. Further, on the time-scale of the experiments (50-250 ms), exchange between the two phases is fast in the phospholipid-cholesterol-water ternary system, whereas it is slow in the sphingomyelin-dioleoylphosphatidylcholine-cholesterol-water quaternary system.
本综述聚焦于利用脉冲磁场梯度来测量宏观取向脂质双层系统中的扩散运动。核磁共振扩散技术被认为在膜生物学领域未来的生物物理研究中具有可观的潜力。诸如分子在膜平面内和跨膜运输等主题能够得到成功研究，脂质结构域的形成及其内在动力学也能受到审视。首先，给出了核磁共振技术的简短介绍，并对获得良好双层取向的方法进行了简要讨论。然后，展示了一些关于备受关注的生物物理/生物膜系统的近期研究成果，从中得出了关于所谓“筏膜”的一些独特结论。结果表明，对于具有大面积液相无序和液相有序相的系统，脂质在液相无序相中的横向扩散更快，且表观活化能更小。此外，在实验时间尺度（50 - 250毫秒）上，磷脂 - 胆固醇 - 水三元体系中两相之间的交换很快，而在鞘磷脂 - 二油酰磷脂酰胆碱 - 胆固醇 - 水四元体系中则很慢。
