Styrene-maleic acid (SMA) copolymers have recently gained attention for their ability to facilitate the detergent-free solubilization of membrane protein complexes and their native boundary lipids into polymer-encapsulated, nanosized lipid particles, referred to as SMALPs. However, the interfacial interactions between SMA and lipids, which dictate the mechanism, efficiency, and selectivity of lipid and membrane protein extraction, are barely understood. Our recent finding has shown that SMA 1440, a chemical derivative of the SMA family with a functionalized butoxyethanol group, was most active in galactolipid-rich membranes, as opposed to phospholipid membranes. In the present work, we have performed X-ray reflectometry (XRR) and neutron reflectometry (NR) on the lipid monolayers at the liquid–air interface followed by the SMA copolymer adsorption. XRR and Langmuir Π–A isotherms captured the fluidifying effect of galactolipids, which allowed SMA copolymers to infiltrate easily into the lipid membranes. NR results revealed the detailed structural arrangement of SMA 1440 copolymers within the membranes and highlighted the partition of butoxyethanol group into the lipid tail region. This work allows us to propose a possible mechanism for the membrane solubilization by SMA.

中文翻译：

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苯乙烯-马来酸共聚物与含半乳糖脂单层的相互作用的X射线和中子反射率研究。

苯乙烯-马来酸（SMA）共聚物最近因其促进膜蛋白复合物及其天然边界脂质的无洗涤剂增溶作用而成为聚合物封装的纳米级脂质颗粒（称为SMALP）的能力而受到关注。然而，人们几乎不了解SMA与脂质之间的界面相互作用，该相互作用决定了脂质和膜蛋白提取的机理，效率和选择性。我们最近的发现表明，SMA 1440是具有官能化丁氧基乙醇基团的SMA家族的化学衍生物，与富含磷脂的膜相比，在富含半乳糖脂的膜中活性最高。在目前的工作中，我们对液-气界面处的脂质单层进行了X射线反射法（XRR）和中子反射法（NR），然后进行了SMA共聚物吸附。甲等温线捕获半乳糖脂的流化作用，这使得SMA共聚物很容易地渗入到脂质膜。NR结果揭示了SMA 1440共聚物在膜内的详细结构排列，并突出了丁氧基乙醇基团在脂质尾部区域的分配。这项工作使我们能够提出一种通过SMA溶解膜的可能机制。