Laboratoire de Physico-Chimie Moléculaire des Protéines Membranaires, UMR 7099, CNRS and Université Paris-7, Institut de Biologie Physico-Chimique, 13, rue Pierre-et-Marie-Curie, F-75005 Paris, France.
Biomacromolecules. 2009 Dec 14;10(12):3317-26. doi: 10.1021/bm900938w.
Amphipols (APols) are short amphipathic polymers designed to adsorb onto the transmembrane surface of membrane proteins, keeping them water-soluble in the absence of detergent. Current APols carry charged groups, which is a limitation for certain types of applications. This has prompted the development of totally nonionic amphiphols (NAPols). In a previous work, glucose-based NAPols synthesized by free-radical cotelomerization of hydrophilic and amphiphilic monomers proved to be able to keep membrane proteins soluble (Sharma et al. Langmuir 2008, 24, 13581-13590). This provided a proof of principle, but the cumbersome synthesis prevented large-scale production and any detailed biochemical studies. In the present work, we describe a new synthesis route for NAPols based on grafting alkyl chains onto a glucosylated homotelomer. The NAPols thus prepared are highly water soluble. In aqueous solutions, they assemble into small, homogeneous particles similar to those formed by ionic APols. Two model membrane proteins, bacteriorhodopsin and the transmembrane domain of OmpA, form with NAPols small, well-defined water-soluble complexes whose size is comparable to that observed with ionic APols. Complexation by NAPols strongly stabilizes bacteriorhodopsin against denaturation. Glucosylated NAPols thus appear as a promising alternative to ionic APols for such applications as ion-exchange chromatography, isoelectrofocusing, and, possibly, structural approaches such as NMR and crystallography.
两亲聚合物（Ampol）是一种短链的两亲性聚合物，设计用来吸附在膜蛋白的跨膜表面，在没有去污剂的情况下保持其水溶性。目前的 Ampol 带有电荷基团，这对于某些类型的应用是一个限制。这促使了完全非离子型两亲聚合物（NAPol）的发展。在之前的一项工作中，通过亲水单体和两亲单体的自由基共聚合成的基于葡萄糖的 NAPol 被证明能够使膜蛋白保持可溶性（Sharma 等人，Langmuir 2008, 24, 13581-13590）。这提供了一个原理上的证明，但繁琐的合成阻碍了大规模生产和任何详细的生化研究。在本工作中，我们描述了一种基于将烷基链接枝到葡糖基同源寡聚物上的 NAPol 的新合成途径。因此制备的 NAPol 具有很高的水溶性。在水溶液中，它们会组装成类似于离子型 Ampol 形成的小而均匀的颗粒。两种模型膜蛋白，细菌视紫红质和 OmpA 的跨膜结构域，与 NAPol 形成小而定义明确的水溶性复合物，其大小与离子型 Ampol 观察到的大小相当。NAPol 的络合强烈稳定了细菌视紫红质免受变性。因此，葡糖基化的 NAPol 似乎是离子型 Ampol 的一种有前途的替代品，可用于离子交换色谱、等电聚焦等应用，并且可能还有结构方法，如 NMR 和结晶学。
