Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076Tübingen, Germany.
Interfakultäres Institut für Biochemie, Universität Tübingen, Hoppe-Seyler-Strasse 4, 72076Tübingen, Germany.
Langmuir. 2023 Feb 14;39(6):2450-2459. doi: 10.1021/acs.langmuir.2c03412. Epub 2023 Feb 1.
Membrane proteins are an essential part of signaling and transport processes and are targeted by multiple drugs. To isolate and investigate them in their native state, polymer-bounded nanodiscs have become valuable tools. In this study, we investigate the lipid model system dimyristoyl-phosphocholine (DMPC) with the nanodisc-forming copolymers styrene maleic acid (SMA) and diisobutylene maleic acid (DIBMA). Using small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS), we studied the influence of polymer concentration and temperature on the nanodisc structure. In Tris buffer, the size of nanodiscs formed with SMA is smaller compared to DIBMA at the same polymer ratio. In both cases, the size decreases monotonically with increasing polymer concentration, and this effect is more pronounced when using SMA. Measurements at temperatures () between 5 and 30 °C in phosphate buffer showed an incomplete solubilization at high even at polymer/lipid ratios above that required for complete lipid solubilization. For DIBMA, the nanodiscs developed at lower temperatures are stable and the net repulsion increases, while for SMA, the individual nanodiscs possess smaller sizes and are less affected by . However, using DLS, one can observe SMA agglomerates at low . Interestingly, for both polymers, no drastic changes of the observable parameters (radius and bilayer thickness) are seen upon cooling, which would indicate a sharp (first-order) phase transition from liquid-crystalline to gel, but only gradual changes. Hence, we conclude that the transition from a gel toward a liquid-crystalline lipid phase proceeds over a broad -range compared to a continuous lipid bilayer. These results can pave the way toward the development of better protocols for studying membrane proteins stabilized in this type of membrane mimics.
膜蛋白是信号转导和物质运输过程的重要组成部分，也是多种药物的作用靶点。为了在其天然状态下分离和研究它们，聚合物结合的纳米盘已成为有价值的工具。在这项研究中，我们研究了二肉豆蔻酰磷脂酰胆碱（DMPC）的脂质模型体系，使用形成纳米盘的共聚物苯乙烯马来酸（SMA）和二异丁烯马来酸（DIBMA）。我们使用小角 X 射线散射（SAXS）和动态光散射（DLS）研究了聚合物浓度和温度对纳米盘结构的影响。在 Tris 缓冲液中，与 DIBMA 相比，SMA 形成的纳米盘的尺寸较小，在相同的聚合物比例下。在这两种情况下，随着聚合物浓度的增加，纳米盘的尺寸单调减小，使用 SMA 时这种效应更为明显。在磷酸盐缓冲液中测量 5 至 30°C 之间的温度时，即使在高于完全溶解脂质所需的聚合物/脂质比下，仍存在高 时不完全溶解的情况。对于 DIBMA，在较低温度下形成的纳米盘是稳定的，净排斥力增加，而对于 SMA，单个纳米盘的尺寸较小，受 的影响较小。但是，使用 DLS，可以在低 下观察到 SMA 聚集体。有趣的是，对于两种聚合物，在冷却时，观察到的参数（半径和双层厚度）没有明显变化，这表明从液晶到凝胶的相变是急剧的（一级），但只是逐渐变化。因此，我们得出结论，与连续脂质双层相比，从凝胶到液晶脂质相的转变在较宽的 范围内进行。这些结果为开发用于研究稳定在这种类型的膜模拟物中的膜蛋白的更好方案铺平了道路。
