Department of Chemistry, University of Oslo, Sem Sælandsvei 26, 0371 Oslo, Norway.
Department of Biosciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway.
Langmuir. 2021 May 25;37(20):6178-6188. doi: 10.1021/acs.langmuir.1c00304. Epub 2021 May 12.
Lipid nanodiscs formed by mixtures of styrene maleic acid (SMA) copolymers and lipid membranes are important tools for studying membrane proteins in many biotechnological applications. However, molecular interactions leading up to their formation are not well understood. Here, we elucidate the nanodisc formation pathways for SMA/lipid vesicle mixtures using small-angle X-ray scattering (SAXS) that allows detailed in situ nanostructural information. SMA copolymer that is initially aggregated in solution inserts its styrene units into the lipid bilayer hydrocarbon region, leading to fractures in the membrane. The initial copolymer-lipid interactions observed in the vesicles are also present in the formed discs, with excess copolymer distributed along the normal of the bilayer. The size and SMA distribution in the resulting discs strongly depend on the temperature, lipid/copolymer ratio, and lipid type. We find that the solubilization limit increases for membranes above the melting point, suggesting that defects in gel-like lipid membranes play a significant role in membrane fracturing and nanodisc formation. These findings provide unique insights into the formation of nanodiscs as well as into the microscopic mechanism of solubilization, which plays an important role in many applications and products ranging from household goods to biotechnology and medicine.
由苯乙烯马来酸（SMA）共聚物和脂质膜组成的脂质纳米盘是许多生物技术应用中研究膜蛋白的重要工具。然而，导致其形成的分子相互作用尚不清楚。在这里，我们使用小角 X 射线散射（SAXS）阐明了 SMA/脂质囊泡混合物的纳米盘形成途径，该方法允许进行详细的原位纳米结构信息。最初在溶液中聚集的 SMA 共聚物将其苯乙烯单元插入脂质双层烃区，导致膜破裂。在囊泡中观察到的初始共聚物-脂质相互作用也存在于形成的盘片中，多余的共聚物沿双层的法向分布。所得盘片中的大小和 SMA 分布强烈依赖于温度、脂质/共聚物比和脂质类型。我们发现，高于熔点时，膜的增溶极限增加，这表明凝胶状脂质膜中的缺陷在膜破裂和纳米盘形成中起着重要作用。这些发现为纳米盘的形成以及在许多应用和产品中起着重要作用的增溶的微观机制提供了独特的见解，这些应用和产品范围从家居用品到生物技术和医学。
