Polymer stabilized nanodiscs are self-assembled structures composed of a polymer belt that wraps around a segment of lipid bilayer, and as such are capable of encapsulating membrane proteins directly from the cell membrane. To date, most studies on these nanodiscs have used poly(styrene-co-maleic acid) (SMA) with the term SMA-lipid particles (SMALPs) coined to describe them. In this study, we have determined the physical and thermodynamic properties of such nanodiscs made with two different SMA copolymers. These include a widely used and commercially available statistical poly(styrene-co-maleic acid) copolymer (coSMA) and a reversible addition–fragmentation chain transfer synthesized copolymer with narrow molecular weight distribution and alternating styrene and maleic acid groups with a polystyrene tail, (altSMA). We define phase diagrams for each polymer, and show that, regardless of polymer topological structure, self-assembly is driven by the free energy change associated with the polymers. We also show that nanodisc size is polymer dependent, but can be modified by varying polymer concentration. The thermal stability of each nanodisc type is similar, and both can effectively solubilize proteins from the E. coli membrane. These data show the potential for the development of different SMA polymers with controllable properties to produce nanodiscs that can be optimized for specific applications and will enable more optimized and widespread use of the SMA-based nanodiscs in membrane protein research.

中文翻译：

---

聚（苯乙烯的影响共-马来酸）的性质和SMALP纳米圆盘自组装共聚物结构

聚合物稳定的纳米光盘是由聚合物带组成的自组装结构，该聚合物带围绕脂质双层的一部分包裹，因此能够直接从细胞膜包封膜蛋白。迄今，这些纳米盘大多数研究使用聚（苯乙烯-共-马来酸）（SMA）与用来形容他们的术语SMA-脂质颗粒（SMALPs）。在这项研究中，我们确定了由两种不同的SMA共聚物制成的纳米光盘的物理和热力学性质。这些措施包括广泛使用和市售的统计聚（苯乙烯共-马来酸）共聚物（coSMA）和可逆的加成-断裂链转移合成的共聚物，该共聚物具有窄的分子量分布，并且苯乙烯和马来酸基团交替且带有聚苯乙烯尾巴（altSMA）。我们定义了每种聚合物的相图，并表明，不管聚合物的拓扑结构如何，自组装都是由与聚合物相关的自由能变化驱动的。我们还表明，纳米光盘的尺寸取决于聚合物，但是可以通过改变聚合物浓度来进行修改。每种纳米光盘的热稳定性都相似，并且两者都可以有效地溶解大肠杆菌中的蛋白质膜。这些数据显示了开发具有可控制特性的不同SMA聚合物以生产可以针对特定应用进行优化的纳米光盘的潜力，这将使基于SMA的纳米光盘在膜蛋白研究中得到更优化和广泛的应用。