Quantum Mechanics of Proteins in Water: The role of Plasmon-like Solute-Solvent Interactions

van der Waals dispersion interactions form a major component of both intra-protein and protein-water interactions. As such, they play an essential role for the spontaneous folding of proteins in water. van der Waals forces arise from long-range electron correlation and are thus inherently quantum-mechanical and many-body in nature. Nevertheless, they are typically only treated in a phenomenological manner via pairwise potentials. Here, we employ an explicit quantum-mechanical framework based on the many-body dispersion formalism, which allows us to highlight the importance of the many-body character of dispersion interactions for protein energetics and protein-water interactions. As such, our study provides insights into the fundamental quantum-mechanics of proteins in water. Contrary to commonly used pairwise approaches, many-body quantum effects significantly affect relative stabilities during protein folding in the gas-phase. Embedding in an aqueous environment leads to a quenching of such effects and stabilizes native conformations. Remarkably, this arises from a high degree of delocalization and collectivity of protein-water dispersion interactions. Our findings are exemplified on several prototypical proteins, emphasizing their broad validity in the biomolecular context.