Jennings James, Carter Matthew C D, Son Chang Yun, Cui Qiang, Lynn David M, Mahanthappa Mahesh K
Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Langmuir. 2020 Jul 21;36(28):8240-8252. doi: 10.1021/acs.langmuir.0c01369. Epub 2020 Jul 10.
We report the aqueous lyotropic mesophase behaviors of protonated amine-based "lipidoids," a class of synthetic lipid-like molecules that mirrors essential structural features of the multitail bacterial amphiphile lipid A. Small-angle X-ray scattering (SAXS) studies demonstrate that the protonation of the tetra(amine) headgroups of six-tail lipidoids in aqueous HCl, HNO, HSO, and HPO solutions variably drives their self-assembly into lamellar (L) and inverse micellar (I) lyotropic liquid crystals (LLCs), depending on acid identity and concentration, amphiphile tail length, and temperature. Lipidoid assemblies formed in HSO(aq) exhibit rare inverse body-centered cubic (BCC) and inverse face-centered cubic (FCC) micellar morphologies, the latter of which unexpectedly coexists with zero mean curvature L phases. Complementary atomistic molecular dynamics (MD) simulations furnish detailed insights into this unusual self-assembly behavior. The unique aqueous lyotropic mesophase behaviors of ammonium lipidoids originate in their dichotomous ability to adopt both inverse conical and chain-extended molecular conformations depending on the number of counterions and their identity, which lead to coexisting supramolecular assemblies with remarkably different mean interfacial curvatures.
我们报道了质子化胺基“类脂质”的水致溶致液晶相行为，这是一类合成的类脂分子，反映了多尾细菌两亲性脂质A的基本结构特征。小角X射线散射（SAXS）研究表明，在HCl、HNO₃、H₂SO₄和H₃PO₄水溶液中，六尾类脂质的四胺头基质子化会根据酸的种类和浓度、两亲分子的尾长以及温度，以不同方式驱动它们自组装成层状（L）和反胶束（I）溶致液晶（LLC）。在H₂SO₄（aq）中形成的类脂质聚集体呈现出罕见的反体心立方（BCC）和反面心立方（FCC）胶束形态，其中后者意外地与零平均曲率L相共存。互补的原子分子动力学（MD）模拟为这种不寻常的自组装行为提供了详细的见解。铵类脂质独特的水致溶致液晶相行为源于它们具有二分性的能力，即根据抗衡离子的数量及其种类，既能采取反锥形又能采取链延伸的分子构象，这导致了具有显著不同平均界面曲率的超分子聚集体共存。
