Department of Chemistry and ‡Weldon School of Biomedical Engineering, Purdue University , West Lafayette, Indiana 47907, United States.
J Am Chem Soc. 2016 Apr 6;138(13):4448-57. doi: 10.1021/jacs.5b13179. Epub 2016 Mar 24.
Precisely tailoring surface chemistry of layered materials is a growing need for fields ranging from electronics to biology. For many applications, the need for noncovalently adsorbed ligands to simultaneously control interactions with a nonpolar substrate and a polar solvent is a particular challenge. However, biology routinely addresses a similar challenge in the context of the lipid bilayer. While conventional standing phases of phospholipids (such as those found in a bilayer) would not provide spatially ordered interactions with the substrate, here we demonstrate formation of a sitting phase of polymerizable phospholipids, in which the two alkyl chains extend along the surface and the two ionizable functionalities (a phosphate and an amine) sit adjacent to the substrate and project into the solvent, respectively. Interfacial ordering and polymerization are assessed by high-resolution scanning probe measurements. Water contact angle titrations demonstrate interfacial pKa shifts for the lipid phosphate but not for the amine, supporting localization of the phosphate near the nonpolar graphite surface.
精准调控层状材料的表面化学是一个日益增长的需求，涵盖了从电子学到生物学等多个领域。对于许多应用而言，需要用到非共价吸附配体来同时控制与非极性基底和极性溶剂的相互作用，这是一个特别的挑战。然而，生物学在脂质双层的背景下，通常会应对类似的挑战。尽管传统的磷脂（如双层中存在的磷脂）的固定相不能提供与基底的空间有序相互作用，但在这里，我们展示了可聚合磷脂的坐定相的形成，其中两个烷基链沿表面延伸，两个可离子化的官能团（一个磷酸基团和一个胺基）分别位于基底相邻的位置，并向溶剂中延伸。通过高分辨率扫描探针测量评估了界面的有序性和聚合。水接触角滴定实验表明，脂质磷酸基团的界面 pKa 发生了变化，但胺基没有，这支持了磷酸基团在非极性石墨表面附近的定位。
