DIRECT NMR EVIDENCE FOR ETHANOL BINDING TO THE LIPID-WATER INTERFACE OF PHOSPHOLIPID-BILAYERS
DIRECT NMR EVIDENCE FOR ETHANOL BINDING TO THE LIPID-WATER INTERFACE OF PHOSPHOLIPID-BILAYERS
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DOI：
10.1021/bi00192a013
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发表时间：
1994-07-05
期刊：
影响因子：
2.9
通讯作者：
GAWRISCH, K
中科院分区：
文献类型：
--
作者：
BARRY, JA;GAWRISCH, K
乙醇的膜介导的影响背后的机制进行了检查，通过在10-12水分子/脂质的水化水平的乙醇与磷脂双层的相互作用。H-2和P-31核磁共振（NMR）光谱用于监测氘代水和乙醇以及中性磷脂的头基和酰基链。乙醇被发现强烈相互作用与磷脂酰胆碱（PC）和磷脂酰乙醇胺（PE）双层，给H-2 NMR四极分裂为CH 3CD 2 OH之间的6.3和9.4 kHz。凝胶相脂质中乙醇的四极分裂仍然很好地解决，并没有显着大于那些在L（α）相，这表明很少或没有乙醇被绑定在碳氢化合物内部的双层。乙醇结合显着改变了脂质头基的方向，如所示的头基氘代PC双层。整个长度的酰基链显着无序的乙醇相互作用，证明了显着减少的H-2 NMR的顺序参数的链。无序对应于每脂质的面积增加了估计6%，每脂质一个乙醇分子，和第二个乙醇每脂质的总18%。这种明显的面积增加可能是由于甘油骨架的刚性区域中而不是酰基链中的脂质包装的破坏引起的，因为烃链的顺序不会受到烷烃和长链醇并入烃内部的显著程度的影响。从这些数据可以得出结论，乙醇与磷脂双层在脂-水界面（由头基，甘油骨架，和最高链亚甲基），而不是在烃内部相互作用。乙醇的界面结合，也能够无序的整个长度的酰基链可以解释小乙醇诱导的流化膜脂质，已在文献中频繁报道。
The mechanisms behind the membrane-mediated effects of ethanol were examined via the interaction of ethanol with phospholipid bilayers at hydration levels of 10-12 water molecules per lipid. H-2 and P-31 nuclear magnetic resonance (NMR) spectroscopy was used to monitor deuterated water and ethanol and the headgroups and acyl chains of neutral phospholipids. Ethanol was found to interact strongly with both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) bilayers, giving H-2 NMR quadrupolar splittings for CH3CD2OH between 6.3 and 9.4 kHz. The quadrupolar splittings for ethanol in gel-phase lipids remained well resolved and were not significantly larger than those in the L(alpha) phase, suggesting that little or no ethanol was bound in the hydrocarbon interior of the bilayer. Ethanol binding significantly altered the orientation of the lipid headgroups, as shown with headgroup-deuterated PC bilayers. The entire lengths of the acyl chains were significantly disordered by the ethanol interaction, evidenced by significant reductions in the H-2 NMR order parameters of the chains. The disordering corresponds to an increase in the area per lipid by an estimated 6% with one ethanol molecule per lipid, and a total of 18% with a second ethanol per lipid. This pronounced area increase is presumably caused by the disruption of lipid packing in the rigid region of the glycerol backbone rather than in the acyl chains, since the order of hydrocarbon chains is not affected to a significant degree by incorporation of alkanes and long-chain alcohols into the hydrocarbon interior. From these data it was concluded that ethanol interacts with phospholipid bilayers at the lipid-water interface (consisting of the headgroup, glycerol backbone, and uppermost chain methylene groups) rather than in the hydrocarbon interior. An interfacial binding of ethanol that is also capable of disordering the entire length of the acyl chains could explain the small ethanol-induced fluidization of membrane lipids that has been reported frequently in the literature.