l‑Cysteine Interaction with Au₅₅ Nanoparticle

Abstract

Simulations of l-cysteine molecules attaching on Au nanoparticles provide insight on how larger biomolecules (such as proteins and peptides) can interact with Au nanoparticles. The attaching mode is still in debate and of strong impact on the fundamental research in biosensors and biomedicine. We used a density functional theory (DFT) approach to calculate the interactions between l-cysteine molecules and the quantum sized Au nanoparticle Au₅₅. Our results support the attaching mode recognized in solid-state NMR studies, which indicate that a double layer of l-cysteine molecules is the likely configuration. A strong electronic interaction between gold and sulfur atoms establishes a strong-bonding inner layer, while a hydrogen-bond network between zwitterion-structured cysteine molecules stabilizes the existence of a second layer with thiol (−SH) groups oriented outward. Such a structure has high potential for further biofunctionalization