Hydrophobic alkyl headgroups strongly promote membrane curvature and violate the headgroup volume correlation due to ''headgroup'' insertion
Hydrophobic alkyl headgroups strongly promote membrane curvature and violate the headgroup volume correlation due to ''headgroup'' insertion
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DOI：
10.1021/bi9517502
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发表时间：
1996-03-26
期刊：
影响因子：
2.9
通讯作者：
Janes, N
中科院分区：
文献类型：
--
作者：
Lee, YC;Zheng, YO;Janes, N
脂质聚集体形成平面双层的能力，而不是高度弯曲的胶束或倒置结构，取决于头基和碳氢化合物区域的相对几何形状。脂质结构的头基体积方法提供了脂质的头基大小与其在磷脂酰乙醇胺(PtdEtn)基质中促进弯曲的、倒置的六边形(H-II)结构的能力之间的定量联系[Lee等人。(1993)生物物理学。J.65,1429-1432]。磷脂酰烷醇(PtdAlk)在这里被显示为促进曲率，其效力远远超过，并且与头基体积方法的预期相反，具有链长依赖性，暗示了非典型的烷基‘’头基‘’构象。3-取代三酰甘油(TAG)的同源系列，其中3-酰基‘’头基‘’插入是建立的，表现出类似于PtdAlk的链长依赖关系，证据是偏离是共同起源的。标签促进曲率的效力是史无前例的，与曲率显著促进平行的饱和开始发生在摩尔分数低至0.0025的地方。PtdAlk或标签促进曲率的效力超过所有被检测的哺乳动物磷脂。热力学分析表明，施加在膜基质上的焓曲应力是主要的能量因素。施加的应力范围从磷脂酰胆碱的-930J·mol(-1)到3-棕榈酰基TAG的+7.5kJ·mol(-1)。结果证实了膜结构的几何考虑，表明烷基头基倾向于插入双分子膜，增大膜内的焓曲应力。
The ability of lipid aggregates to form planar bilayers, rather than highly curved micellar or inverted structures, is dependent on the relative geometries of the headgroup and hydrocarbon regions. The headgroup volume approach to lipid structure provided a quantitative link between a lipid's headgroup size and its ability to promote curved, inverted hexagonal (H-II) structures in a phosphatidylethanolamine (PtdEtn) matrix [Lee et al. (1993) Biophys. J. 65, 1429-1432]. Phosphatidylalkanols (PtdAlks) are shown here to promote curvature with a potency that far exceeds and a chain length dependence contrary to the expectations of the headgroup volume approach, suggestive of an atypical alkyl ''headgroup'' conformation. A homologous series of 3-substituted triacylglycerols (TAGs), for which 3-acyl ''headgroup'' insertion is established, exhibits a chain length dependence similar to the PtdAlks, evidence that the deviation is of common origin. The potency of the TAGs to promote curvature is unprecedented, and the onset of saturation, which parallels the dramatic promotion of curvature, occurs at mole fractions as low as 0.0025. The potency of the PtdAlks or TAGs to promote curvature exceeds that of all mammalian phospholipids examined. Thermodynamic analysis implicates the enthalpic curvature stress imparted upon the membrane matrix as the dominant energetic factor. The imparted stress ranges from -930 J mol(-1) for phosphatidylcholine to +7.5 kJ mol(-1) for 3-palmitoyl TAG. The results affirm the geometric considerations of membrane structure and indicate that alkyl headgroups tend to insert into the bilayer and increase the enthalpic curvature stress within the membrane.