Proton tunnelling and promoting vibrations during the oxidation of ascorbate by ferricyanide?

A combination of the temperature- and pressure-dependencies of the kinetic isotope effect on the proton coupled electron transfer during ascorbate oxidation by ferricyanide suggests that this reference reaction may exploit vibrationally assisted quantum tunnelling of the transferred proton. The combined temperature/pressure-dependencies of the KIE on ascorbate oxidation show H-tunnelling is a general feature of the reaction.