Phospholipid reorientation at the lipid/water interface measured by high resolution 31P field cycling NMR spectroscopy.
Phospholipid reorientation at the lipid/water interface measured by high resolution 31P field cycling NMR spectroscopy.
复制标题
通过高分辨率 31P 场循环 NMR 光谱测量脂质/水界面处的磷脂重新取向。
DOI：
10.1016/j.bpj.2009.03.057
复制
发表时间：
2009
影响因子：
3.4
通讯作者：
Mohanty,Udayan
中科院分区：
文献类型：
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作者：
Roberts,MaryF;Redfield,AlfredG;Mohanty,Udayan
磷脂的31 P自旋-晶格弛豫速率R1的磁场依赖性可用于区分这些分子在各种单层囊泡中的运动。特别是，内部运动与5- 10-ns的相关时间已被归因于扩散在锥的磷酸二酯区域，类似于运动的圆柱体中的液态烃。我们利用低场（0.03-0.08 T）下31 PR 1的温度依赖性（它反映了这种关联时间）来探索与这种运动相关的能垒。大多数磷脂在高于与其凝胶至液晶转变（Tm）相关的温度时表现出13.2 ± 1.9 kJ/mol的类似能垒;在低于Tm的温度下，该能垒急剧增加至68.5 ± 7.3 kJ/mol。这种温度依赖性被广泛地解释为在空间上粗糙的势能景观中的脂质轴的扩散运动所产生的。在这些囊泡中包含胆固醇在高于其Tm的温度下对磷脂仅具有中等影响，但在低于纯脂质的Tm的温度下显著降低能垒（至17 ± 4kJ/mol）。非常低的场R1数据表明，胆固醇夹杂物改变了平均处置的磷甘油质子矢量（其平均长度和相对于膜法线的平均角度），决定了31 P松弛。
The magnetic field dependence of the31P spin-lattice relaxation rate,R1, of phospholipids can be used to differentiate motions for these molecules in a variety of unilamellar vesicles. In particular, internal motion with a 5- to 10-ns correlation time has been attributed to diffusion-in-a-cone of the phosphodiester region, analogous to motion of a cylinder in a liquid hydrocarbon. We use the temperature dependence of31PR1at low field (0.03–0.08 T), which reflects this correlation time, to explore the energy barriers associated with this motion. Most phospholipids exhibit a similar energy barrier of 13.2 ± 1.9 kJ/mol at temperatures above that associated with their gel-to-liquid-crystalline transition (Tm); at temperatures belowTm, this barrier increases dramatically to 68.5 ± 7.3 kJ/mol. This temperature dependence is broadly interpreted as arising from diffusive motion of the lipid axis in a spatially rough potential energy landscape. The inclusion of cholesterol in these vesicles has only moderate effects for phospholipids at temperatures above theirTm, but significantly reduces the energy barrier (to 17 ± 4 kJ/mol) at temperatures below theTmof the pure lipid. Very-low-fieldR1data indicate that cholesterol inclusion alters the averaged disposition of the phosphorus-to-glycerol-proton vector (both its average length and its average angle with respect to the membrane normal) that determines the31P relaxation.