Role of Surface Coordination and Thiol–Amine Cooperative Interactions in Cysteine Adsorption on Nanostructured Gold

The interaction of cysteine and related amino acid thiols with metal substrates has applications in several fields of science, technology and health. Despite widespread interest in these systems, the relationship between thiol adsorption and surface coarsening, including the effects of surface adatoms and other defect sites, has not been systematically addressed. Here, the effect of binding site unsaturation on the adsorption strength of l-cysteine on gold substrates is examined using density functional theory. Adsorption sites with a full range of in-surface coordination numbers are generated using surface adatoms or pitting structures. The configurational space of the adsorbate on the nanostructured surface is sampled extensively using Born–Oppenheimer molecular dynamics simulation. Our results indicate that binding strength is primarily determined by a combination of surface site reactivity to the mercapto group and the availability of additional sites for amino group coordination. The study aims to further our understanding of amino acid binding to substrates with defects and low-coordinated nanoparticle sites, and to provide a basis for the development of coordination-dependent force fields that may be used in classical simulations of these systems.半胱氨酸及其相关氨基酸巯基（thiol）化合物与金属基底的相互作用，在科学、技术与健康等多个领域均具有应用价值。尽管此类体系已受到广泛关注，但巯基吸附与表面粗化之间的关联——包括表面吸附原子（surface adatoms）及其他缺陷位点的影响——尚未得到系统性研究。本文采用密度泛函理论（density functional theory），探究了结合位点不饱和性对L-半胱氨酸（L-cysteine）在金基底上吸附强度的影响。研究通过表面吸附原子或蚀坑结构，构建了覆盖全部表面内配位数区间的吸附位点。借助玻恩-奥本海默分子动力学（Born–Oppenheimer molecular dynamics）模拟，对纳米结构表面上吸附质的构型空间开展了广泛采样。研究结果表明，结合强度主要由两大因素共同决定：一是表面位点对巯基的反应活性，二是氨基（amino group）配位的额外位点可用性。本研究旨在加深对氨基酸与带缺陷及低配位纳米颗粒位点基底结合过程的理解，并为开发依赖于配位作用的力场（force fields）提供理论基础，此类力场可用于此类体系的经典模拟（classical simulations）。