Water permeability of polyunsaturated lipid membranes measured by O-17 NMR
Water permeability of polyunsaturated lipid membranes measured by O-17 NMR
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DOI：
10.1016/s0006-3495(97)78118-9
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发表时间：
1997-08-01
影响因子：
3.4
通讯作者：
Gawrisch, K
中科院分区：
文献类型：
--
作者：
Huster, D;Jin, AJ;Gawrisch, K
通过O-17核磁共振测量了多不饱和磷脂双层中扩散控制的水渗透。在100 nm的挤压脂质体含有50 mM氯化锰，内部和外部的解决方案之间的水交换进行监测，通过外部水的O-17水共振的线宽的变化。脂质体的大小和形状通过光散射法和脂质体捕获体积的测定来表征。在25 ℃下，测定了以下水渗透系数：18：0-18：1 n-9 PC，155 +/- 24 μ m/s; 18：0-18：3 n-3 PC，330 +/- 88 μ m/s;和18：0-22：6 n-3 PC，412 +/- 91 μ m/s。加入1 M乙醇后，18：0-18：1 n-9 PC的渗透系数降低到66 +/- 15 μ m/s，18：0-22：6 n-3 PC的渗透系数降低到239 +/- 67 μ m/s。此外，添加50摩尔%的18：1 n-9-18：1 n-9 PE使水渗透率从纯18：1 n-9-18：1 n-9 PC的122 +/- 21 μ m/s降低到混合物的74 +/- 15 μ m/s。具有多不饱和烃链的膜的水渗透的显着增加与脂质-水界面处的多不饱和脂质的松散堆积以及建议的水更深地渗透到这些双层中相关。乙醇可以通过占据界面处的水进入双层的点来阻断水扩散途径。二油酰磷脂酰乙醇胺的加入增加了脂质堆积密度，因此降低了渗透速率。
Diffusion-controlled water permeation across bilayers of polyunsaturated phospholipids was measured by O-17 nuclear magnetic resonance. In 100-nm extruded liposomes containing 50 mM MnCl2, water exchange between internal and external solutions was monitored via changes in the linewidth of the O-17 water resonance of external water. Liposome size and shape were characterized by light scattering methods and determination of liposome trapped volume. At 25 degrees C, the following water permeability coefficients were determined: 18:0-18:1n-9 PC, 155 +/- 24 mu m/s; 18:0-18:3n-3 PC, 330 +/- 88 mu m/s; and 18:0-22:6n-3 PC, 412 +/- 91 mu m/s. The addition of 1 M ethanol reduced permeability coefficients to 66 +/- 15 mu m/s for 18:0-18:1n-9 PC and to 239 +/- 67 mu m/s for 18:0-22:6n-3 PC. Furthermore, the addition of 50 mol% 18:1n-9-18:1n-9 PE reduced the water permeability from 122 +/- 21 mu m/s for pure 18:1n-9-18:1n-9 PC to 74 +/- 15 mu m/s for the mixture. The significant increase in water permeation for membranes with polyunsaturated hydrocarbon chains correlates with looser packing of polyunsaturated lipids at the lipid-water interface and the suggested deeper penetration of water into these bilayers. Ethanol may block water diffusion pathways by occupying points of water entry into bilayers at the interface. The addition of dioleoylphosphatidylethanolamine increases lipid packing density and, consequently, reduces permeation rates.