School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore.
Centre for Biomimetic Sensor Science , Nanyang Technological University , 50 Nanyang Drive , 637553 , Singapore.
Langmuir. 2018 Nov 13;34(45):13745-13753. doi: 10.1021/acs.langmuir.8b02536. Epub 2018 Nov 5.
Fatty acids and monoglycerides are single-chain lipid amphiphiles that interact with phospholipid membranes as part of various biological activities. For example, they can exhibit membrane-disruptive behavior against microbial pathogens on the human skin surface. Supported lipid bilayers (SLBs) provide a useful experimental platform to characterize these membrane-disruptive behaviors, although related studies have been limited to neutral pH conditions. Herein, we investigated how lauric acid (LA) and glycerol monolaurate (GML) interact with SLBs and cause membrane morphological changes under acidic pH conditions that are representative of the human skin surface. Although LA induces tubule formation under neutral pH conditions, we discovered that LA causes membrane phase separation under acidic pH conditions. By contrast, GML induced membrane budding in both pH environments, although there was more extensive membrane remodeling under acidic pH conditions. We discuss these findings in the context of how solution pH affects the ionization states and micellar aggregation properties of LA and GML as well as its effect on the bending stiffness of lipid bilayers. Collectively, the findings demonstrate that solution pH plays an important role in modulating the interaction of fatty acids and monoglycerides with phospholipid membranes, and hence influences the scope and potency of their membrane-disruptive activities.
脂肪酸和单甘油脂是单链脂质两亲物，作为各种生物活性的一部分与磷脂膜相互作用。例如，它们可以针对人类皮肤表面的微生物病原体表现出破坏膜的行为。支撑脂质双层（SLB）为表征这些破坏膜的行为提供了一个有用的实验平台，尽管相关研究仅限于中性 pH 条件。在此，我们研究了月桂酸（LA）和甘油单月桂酸酯（GML）在酸性 pH 条件下与 SLB 相互作用并导致膜形态变化的方式，该酸性 pH 条件代表了人类皮肤表面的情况。尽管 LA 在中性 pH 条件下诱导管形成，但我们发现 LA 在酸性 pH 条件下导致膜相分离。相比之下，GML 在两种 pH 环境下都诱导了膜出芽，但在酸性 pH 条件下，膜重塑更为广泛。我们根据溶液 pH 如何影响 LA 和 GML 的离子化状态和胶束聚集特性及其对脂质双层弯曲刚度的影响来讨论这些发现。总之，这些发现表明，溶液 pH 在调节脂肪酸和单甘油脂与磷脂膜的相互作用方面起着重要作用，因此影响它们破坏膜的活性的范围和效力。
