We report the first method to calculate a very important molecular level parameter of amphiphilic molecules– the ‘chain splay’. The calculations employed a truncated cone geometry, as it is the most probable configuration adopted by various amphiphiles. This approach utilized known parameters including lipid length, cross-sectional area at the head group and molecular volume. This new parameter, i.e. the area at the chain end, perceived to be more sensitive than Israelachvili’s famous shape factor or critical packing parameter (CPP). With relevant calculations, we demonstrate the fundamental roles of ‘chain splay’ to: a) reveal the critical contribution of molecular structure on average molecular shape and consequent self-assemblies, b) track the finest changes in molecular shapes within different bicontinuous cubic phases, c) obtain non-zero areas at the chain ends of amphiphiles that form normal (type 1) phases, d) back-calculate molecular volumes close to theoretical values, and e) find the link between molecular shapes and global curvatures of self-assemblies. This powerful feature advances our abilities towards quantitative estimation of spatial configurations adopted by amphiphilic molecules; moreover, it has a strong impact on predicting biomembrane structuring and nanoscale design of corresponding self-assemblies for a range of emerging applications.

我们报告了第一种计算两亲分子非常重要的分子水平参数的方法-“链展开”。计算采用了截锥几何形状，因为它是各种两亲物最可能采用的构型。该方法利用了已知的参数，包括脂质长度，头部基团的横截面积和分子体积。该新参数（即链末端的面积）被认为比Israelachvili著名的形状因数或临界填充参数（CPP）更为敏感。通过相关的计算，我们证明了“链张开”的基本作用是：a）揭示分子结构对平均分子形状和随之而来的自组装的关键贡献，b）跟踪不同双连续立方相中分子形状的最佳变化， c）在形成正态的两亲物的链末端获得非零区域（类型1）相，d）反向计算接近理论值的分子体积，e）找到分子形状与自组装整体曲率之间的联系。这一强大的功能提高了我们对两亲分子采用的空间构型进行定量估计的能力；此外，它对预测各种新兴应用的生物膜结构和相应自组装的纳米级设计有很大影响。