Hydroxyl-rich beta-sheet adhesion to the gold surface in water by first-principle simulations.

Proteins able to recognize inorganic surfaces are of paramount importance for living organisms. Mimicking nature, surface-recognizing proteins and peptides have also been man-made by combinatorial biochemistry. However, to date the recognition mechanisms remain elusive, and the underlying physicochemical principles are still unknown. Selectivity of gold-binding peptides (cysteine-free and rich in hydroxyl amino acids) is particularly puzzling, since the most relevant gold surface, Au(111), is known to be chemically inert and atomically flat. Using atomistic first-principle simulations we show that weak chemical interactions of dative-bond character confer to a prototype secondary structure (an antiparallel beta-sheet made of hydroxyl amino acids) and its hydration layer the capability of discriminating among gold surface sites. Our results highlight the unexpected role of hydration water in this process, suggesting that hydrophilic amino acids and their hydration shell cooperate to contribute to protein-gold surface recognition.