Trp is one of the 20 naturally occurring aromatic amino acids and is electroactive, meaning it can be readily oxidized or reduced. Nguyen et al. demonstrated that Trp undergoes an initial 2-electron, 2-proton oxidation, a step that was attributed to the observed anodic peak at 0.9 V on a pyrolytic graphite electrode vs. SCE. Others 60 have attributed the loss of the pyrrolic double bond and addition of a ketone adjacent to the secondary amine as the primary oxidation event observed on glassy carbon (vs. Ag/AgCl (3M KCl)). Trp oxidation was observed using FSCV at CFM by Ross and colleagues 56 at 1.06 V, and we observe a similar oxidation peak at 1.0 V on the forward scan (Figure ).