In interfaces between inorganic and biological materials relevant for technological applications, the general challenge of structure determination is exacerbated by the high flexibility of bioorganic components, chemical bonding, and charge rearrangement at the interface. In this paper, we investigate a chemically complex building block, namely, the arginine (Arg) amino-acid interfaced with Cu, Ag and Au (111) surfaces. We investigate how the environment changes the accessible conformational space of this amino acid, by building and analyzing a database of thousands of structures optimized with the PBE functional including screened pairwise van der Waals interactions. When in contact with metallic surfaces, the accessible space for Arg is dramatically reduced, while the one for Arg-H$^+$ is instead increased if compared to the gas-phase. This is explained by the formation of strong bonds between Arg and the surfaces and by their absence and charge screening on Arg-H$^+$ upon adsorption. We also observe protonation-dependent stereoselective binding of the amino acid to the metal surfaces: Arg adsorbs with its chiral C$_\alpha$H center pointing H away from the surfaces while Arg-H$^+$ adsorbs with H pointing toward the surface.

中文翻译：

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金属表面柔性氨基酸的构象空间

在与技术应用相关的无机和生物材料之间的界面中，生物有机成分的高度灵活性、化学键和界面处的电荷重排加剧了结构确定的普遍挑战。在本文中，我们研究了一种化学复杂的构件，即精氨酸 (Arg) 氨基酸与 Cu、Ag 和 Au (111) 表面界面。我们通过构建和分析数以千计的结构数据库来研究环境如何改变这种氨基酸的可及构象空间，该数据库使用 PBE 功能优化，包括筛选的成对范德华相互作用。当与金属表面接触时，Arg 的可及空间显着减少，而与气相相比，Arg-H$^+$ 的可及空间反而增加。这可以通过在 Arg 和表面之间形成强键以及它们在吸附时在 Arg-H$^+$ 上的缺失和电荷筛选来解释。我们还观察到氨基酸与金属表面的质子化依赖性立体选择性结合：Arg 吸附时其手性 C$_\​​alpha$H 中心指向远离表面的 H，而 Arg-H$^+$ 吸附时 H 指向表面。