Protection of Oxygen-Sensitive Enzymes by Peptide Hydrogel

Molecular oxygen (O₂) is a highly reactive oxidizing agent and is harmful to many biological and industrial systems. Although O₂ often interacts via metals or reducing agents, a binding mechanism involving an organic supramolecular structure has not been described to date. In this work, the prominent dipeptide hydrogelator fluorenylmethyloxycarbonyl-diphenylalanine is shown to encage O₂ and significantly limit its diffusion and penetration through the hydrogel. Molecular dynamics simulations suggested that the O₂ binding mechanism is governed by pockets formed between the aromatic rings in the supramolecular structure of the gel, which bind O₂ through hydrophobic interactions. This phenomenon is harnessed to maintain the activity of the O₂-hypersensitive enzyme [FeFe]-hydrogenase, which holds promising potential for utilizing hydrogen gas for sustainable energy applications. Hydrogenase encapsulation within the gel allows hydrogen production following exposure to ambient O₂. This phenomenon may lead to utilization of this low molecular weight gelator in a wide range of O₂-sensitive applications.