Electrocatalytic monitoring of peptidic proton-wires

The transfer of protons or proton donor/acceptor abilities is an important phenomenon in many biomolecular systems. One example is the recently proposed peptidic proton-wires (H-wires), but the ability of these His-containing peptides to transfer protons has only been studied at the theoretical level so far. Here, for the first time the proton transfer ability of peptidic H-wires is examined experimentally in an adsorbed state using an approach based on a label-free electrocatalytic reaction. The experimental findings are complemented by theoretical calculations at the ab initio level in a vacuum and in an implicit solvent. Experimental and theoretical results indicated Ala3(His–Ala2)6 to be a high proton-affinity peptidic H-wire model. The methodology presented here could be used for the further investigation of the proton-exchange chemistry of other biologically or technologically important macromolecules.