Boden N, Jones S A, Sixl F
School of Chemistry, The University, Leeds, U.K.
Biochemistry. 1991 Feb 26;30(8):2146-55. doi: 10.1021/bi00222a019.
The packing of hydrocarbon chains in the bilayers of lamellar (L alpha) phases of soap/water and phospholipid/water mixtures has been studied by deuterium NMR spectroscopy and X-ray diffraction. A universal correlation is shown to exist between the average C-D bond order parameter SCD of hydrocarbon chains and the average area per chain ach, irrespective of the chemical structure of the surfactant (hydrophilic group, number of chains per molecule, and chain length), composition, and temperature. The practical utility of the correlation is illustrated by its application to the characterization of the distribution of various hydrophobic and amphiphilic solutes in bilayers. The distribution of hydrocarbons within a bilayer is shown to depend upon their molecular structure in a manner which highlights the nature of the molecular interactions involved. For example, benzene is shown to be fairly uniformly distributed across the bilayer with an increasing tendency to distribute into the center at high concentrations. In contrast, the more complex hydrocarbon tetradecane preferentially distributes into the center of the bilayer at low concentrations, while at higher concentrations it intercalates between the surfactant chains. Alcohols such as benzyl alcohol, octanol, and decanol all interact similarly with the bilayer in so far as they are pinned to the polar/apolar interface, presumably by involvement of the hydroxyl group in a hydrogen bond. But the response of the surfactant chains to the void volume created in the center of the bilayer is dependent upon the distance of penetration of the alcohol into the bilayer. For benzyl alcohol, the shortest molecule, this void volume is taken up by the disordering of the chains, while for decanol, the longest molecule, it is absorbed by interdigitation of the chains of apposing monolayers. For octanol, the chain interdigitation mechanism is dominant at low concentrations, but there is a transition to chain disordering at high concentrations. Finally, it is shown that the correlation provides a useful test for statistical mechanical models of chain ordering in lipid bilayers.
已通过氘核磁共振光谱法和X射线衍射研究了肥皂/水和磷脂/水混合物的层状（Lα）相双层中烃链的堆积情况。结果表明，无论表面活性剂的化学结构（亲水基团、每个分子的链数和链长）、组成和温度如何，烃链的平均C-D键序参数SCD与每条链的平均面积ach之间都存在普遍的相关性。通过将该相关性应用于表征双层中各种疏水和亲水溶质的分布，说明了其实际用途。双层内烃类的分布显示出取决于它们的分子结构，这突出了所涉及的分子相互作用的性质。例如，苯在双层中分布相当均匀，在高浓度时向中心分布的趋势增加。相比之下，更复杂的烃十四烷在低浓度时优先分布到双层的中心，而在高浓度时它插入表面活性剂链之间。诸如苄醇、辛醇和癸醇之类的醇与双层的相互作用方式相似，因为它们大概通过羟基参与氢键而固定在极性/非极性界面上。但是表面活性剂链对双层中心产生的空隙体积的响应取决于醇进入双层的穿透距离。对于最短的分子苄醇，这个空隙体积被链的无序化所占据，而对于最长的分子癸醇，它被相对单层的链的相互穿插所吸收。对于辛醇，链相互穿插机制在低浓度时占主导，但在高浓度时会转变为链无序化。最后，结果表明该相关性为脂质双层中链排序的统计力学模型提供了有用的检验。
