Research into Formation and Structure of Helical Superstructure formed from Synthetic Bilayer Membrane

由两亲化合物在水中形成的双层聚集体有时会在低于凝胶温度下孵化形成螺旋超结构，从而发生液晶相变。我们使用20多个两亲性分子来研究螺旋超结构，以阐明螺旋形成的驱动力和螺旋中的分子取向或堆积结构，并获得了以下结果。具有较短疏水链的手性双链铵两亲物优先于具有较长疏水链的手性双链铵两亲物形成螺旋超结构；十二烷基和十四基；十五烷和十六烷基。虽然在含有氢键基团的非手性单链两亲铵的水溶液中观察到螺旋聚集体的形成，但螺旋超结构主要是由手性两亲而不是非手性两亲形成的。结果表明，不对称碳键和氢键的存在促进了螺旋的形成。这些结构基团协同作用于螺旋的形成。在低于Tc.4的恒定温度下，热处理比恒温孕育更有利于螺旋超结构的形成。两亲分子的电子光谱和红外光谱没有改变，而与两亲分子是否形成大螺旋或碎裂螺旋无关。因此，大螺旋和小螺旋的分子取向和堆积在局部是相同的。水相双层膜的电子光谱和红外光谱随疏水链上碳原子数的变化而交替变化，与螺旋的形成无关。由此可见，奇偶链效应是双层体系中的普遍现象。

Bilayer aggregate which formed from amphiphilic compound in water sometimes transforms into helical superstructure by incubation at temperatures below the gel to liquid-crystal phase transition (Tc). We investigated the helical superstructure by using more than 20 amphiphiles to elucidate driving force of the helix-formation and molecular orientation or packing structure in the helices, and obtained following results.1. Chiral, double-chain ammonium amphiphiles possessing shorter hydrophobic chain formed the helical superstructures in preference to those possessing longer hydrophobic chain; dodecyl > tridecyl > tetradecyl > pentadecyl > hexadecyl.2. Although the formation of the helical aggregates were observed in aqueous solution of an achiral, single-chain ammonium amphiphile which contained a hydrogen bonding group, the helical superstructure was predominantly formed from chiral amphiphiles rather than achiral amphiphiles. The result means that the helix-formation is promoted by the presence of an asymmetric carbon and hydrogen bonding groups. And these structural moieties cooperatively act on the helix-formation.3. Annealing was more effective to form the helical superstructure than incubation at a constant temperature below Tc.4. Electronic and infrared spectra of the amphiphiles were not changed without respect to whether the amphiphiles formed large helices or fragmental helices. Thus the molecular orientation and packing is locally identical between large and small helices.5. Electronic and infrared spectra of aqueous bilayer membranes were alternatively changed with number of carbon atoms in the hydrophobic chain, which was independent of the helix-formation. Therefore, it became apparent that the even-odd-chain effect was an general phenomenon in the bilayer systems.