Аннотация
Understanding proton-coupled charge transport in extracellular biopolymers is essential, as proton transport underlies extracellular electron transfer (EET), microbial electromethanogenesis, and the development of sustainable bioelectronic materials. Inspired by the structural and functional similarity to the mechanochondroitin (MC) layer of Methanosarcina species, this study utilises hyaluronic acid (HA) as a biomimetic model to elucidate coupled proton-electron transport in hydrated polymer networks. Electrochemical measurements on HA films in various aqueous media were performed. Results show a hybrid conductivity driven by hydrogen-bonded networks and functional-group-mediated mobility. Specifically, the role of carboxylic and acetoamido groups of HA films is identified as instrumental in facilitating proton conduction. A notable hydrogen/deuterium (H/D) isotope effect supports the involvement of proton-coupled charge transfer/transport and quantum-assisted transport mechanisms. Furthermore, Density Functional Theory (DFT) calculations confirm these findings, showing that isotopic substitution alters the zero-point energy and hydrogen-bond strength. This provides a molecular explanation for the observed shifts in the conductivity of extracellular biopolymers that mediate complex charge-transport processes, such as Extracellular Electron Transfer (EET), thereby advancing sustainable wastewater treatment and resource-conversion technologies.