Lipid bilayers assembled on solid substrates have been extensively studied with single-molecule resolution as the constituent molecules diffuse in 2D; however, the out-of-plane motion is typically ignored. Here we present the subnanometer out-of-plane diffusion of nanoparticles attached to hybrid lipid bilayers (HBLs) assembled on metal surfaces. The nanoscale cavity formed between the Au nanoparticle and Au film provides strongly enhanced optical fields capable of locally probing HBLs assembled in the gaps. This allows us to spectroscopically resolve the nanoparticles assembled on bilayers, near edges, and in membrane defects, showing the strong influence of charged lipid rafts. Nanoparticles sitting on the edges of the HBL are observed to flip onto and off of the bilayer, with flip energies of ∼10 meV showing how thermal energies dynamically modify lipid arrangements around a nanoparticle. We further resolve the movement of individual lipid molecules by doping the HBL with low concentrations of Texas Red (TxR) dye-labeled lipids.

中文翻译：

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等离子体光谱揭示的脂质分子和纳米粒子的平面外纳米尺度重组。

组装在固体基质上的脂质双层已经以单分子分辨率进行了广泛研究，因为构成分子以二维扩散。但是，通常会忽略平面外运动。在这里，我们介绍了附着在金属表面组装的混合脂质双层（HBLs）的纳米粒子的亚纳米平面外扩散。在Au纳米颗粒和Au膜之间形成的纳米级腔提供了增强的光场，能够局部探测装配在间隙中的HBL。这使我们能够在光谱上分辨组装在双层，边缘附近和膜缺陷中的纳米颗粒，从而显示带电脂质筏的强大影响。观察到位于HBL边缘的纳米粒子会翻转到双层上或从双层上掉下来，翻转能量约为10 meV，显示了热能如何动态改变纳米粒子周围的脂质排列。我们通过用低浓度的德克萨斯红（TxR）染料标记的脂质掺杂HBL，进一步解决单个脂质分子的运动。