Membrane Biochemistry & Biophysics, Bijvoet Center for Biomolecular Research, Department of Chemistry, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, the Netherlands.
Membrane Biochemistry & Biophysics, Bijvoet Center for Biomolecular Research, Department of Chemistry, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, the Netherlands.
Biophys J. 2018 Jul 3;115(1):129-138. doi: 10.1016/j.bpj.2018.05.032.
Styrene-maleic acid (SMA) copolymers have attracted interest in membrane research because they allow the solubilization and purification of membrane-spanning proteins from biological membranes in the form of native-like nanodisks. However, our understanding of the underlying SMA-lipid interactions is hampered by the fact that SMA preparations are very polydisperse. Here, we obtained fractions of the two most commonly used SMA preparations: SMA 2:1 and SMA 3:1 (both with specified M ∼10 kD), with different number-average molecular weight (M) and styrene content. The fractionation is based on the differential solubility of styrene-maleic anhydride (SMAnh) in hexane and acetone mixtures. SMAnh fractions were hydrolyzed to SMA and added to lipid self-assemblies. It was found that SMA fractions inserted in monolayers and solubilized vesicles to a different extent, with the highest efficiency being observed for low-M SMA polymers. Electron microscopy and dynamic light scattering size analyses confirmed the presence of nanodisks independent of the M of the SMA polymers forming the belt, and it was shown that the nanodisks all have approximately the same size. However, nanodisks bounded by high-M SMA polymers were more stable than those bounded by low-M polymers, as indicated by a better retention of the native lipid thermotropic properties and by slower exchange rates of lipids between nanodisks. In conclusion, we here present a simple method to separate SMAnh molecules based on their M from commercial SMAnh blends, which allowed us to obtain insights into the importance of SMA length for polymer-lipid interactions.
苯乙烯-马来酸酐（SMA）共聚物因其能够将生物膜中的膜跨膜蛋白以类似天然的纳米盘形式溶解和纯化而引起了人们对膜研究的兴趣。然而，由于 SMA 制剂非常多分散，我们对其与脂质相互作用的基础理解受到了阻碍。在这里，我们获得了两种最常用的 SMA 制剂（SMA 2:1 和 SMA 3:1，均具有指定的 M∼10 kD）的不同数均分子量（M）和苯乙烯含量的分数。分级是基于苯乙烯-马来酸酐（SMAnh）在正己烷和丙酮混合物中的不同溶解度。将 SMAnh 级分水解为 SMA 并添加到脂质自组装体中。结果发现，SMA 级分在单层膜和溶胀囊泡中插入的程度不同，低分子量 SMA 聚合物的效率最高。电子显微镜和动态光散射尺寸分析证实了纳米盘的存在，与形成带的 SMA 聚合物的 M 无关，并且表明纳米盘的大小大致相同。然而，由高分子量 SMA 聚合物形成的纳米盘比由低分子量聚合物形成的纳米盘更稳定，这表明天然脂质热性质的保留更好，并且纳米盘之间的脂质交换速率更慢。总之，我们在这里提出了一种简单的方法，根据其 M 将 SMAnh 分子从商业 SMAnh 混合物中分离出来，这使我们能够深入了解 SMA 长度对聚合物-脂质相互作用的重要性。
