Biophysics Program and Department of Chemistry, Macromolecular Science and Engineering, Biomedical Engineering , University of Michigan , Ann Arbor , Michigan 48109-1055 , United States.
Department of Fine Chemistry , Seoul National University of Science and Technology , Seoul 01811 , Republic of Korea.
Langmuir. 2020 Feb 11;36(5):1258-1265. doi: 10.1021/acs.langmuir.9b03538. Epub 2020 Jan 30.
The ability of amphipathic polymers to self-assemble with lipids and form nanodiscs has been a boon for the field of functional reconstitution of membrane proteins. In a field dominated by detergent micelles, a unique feature of polymer nanodiscs is their much-desired ability to align in the presence of an external magnetic field. Magnetic alignment facilitates the application of solid-state nuclear magnetic resonance (NMR) spectroscopy and aids in the measurement of residual dipolar couplings via well-established solution NMR spectroscopy. In this study, we comprehensively investigate the magnetic alignment properties of styrene maleimide quaternary ammonium (SMA-QA) polymer-based nanodiscs by using P and N solid-state NMR experiments under static conditions. The results reported herein demonstrate the spontaneous magnetic alignment of large-sized (≥20 nm diameter) SMA-QA nanodiscs (also called as macro-nanodiscs) with the lipid bilayer normal perpendicular to the magnetic field direction. Consequently, the orientation of macro-nanodiscs is further shown to flip the alignment axis parallel to the magnetic field direction upon the addition of a paramagnetic lanthanide salt. These results demonstrate the use of SMA-QA polymer nanodiscs for solid-state NMR applications including structural studies on membrane proteins.
两亲聚合物与脂质自组装形成纳米盘的能力是膜蛋白功能重建领域的福音。在以胶束为主导的领域中，聚合物纳米盘的一个独特特征是它们在外部磁场存在下能够进行排列，这是人们所期望的。磁定向有助于应用固态核磁共振（NMR）光谱，并通过成熟的溶液 NMR 光谱法辅助测量残磁偶合。在这项研究中，我们通过静态条件下的 P 和 N 固态 NMR 实验，全面研究了基于苯乙烯马来酰亚胺季铵（SMA-QA）聚合物的纳米盘的磁定向性质。本文报道的结果表明，大尺寸（≥20nm 直径）的 SMA-QA 纳米盘（也称为大纳米盘）具有自发的磁定向性，其脂质双层的法向垂直于磁场方向。因此，进一步表明，在添加顺磁镧系盐后，大纳米盘的取向会翻转，使其排列轴与磁场方向平行。这些结果表明 SMA-QA 聚合物纳米盘可用于固态 NMR 应用，包括膜蛋白的结构研究。
