Electrocatalytic cyclization of dithiothreitol on a chemically modified electrode by analogy with protein action

Abstract

Electrocatalytic oxidative cyclization of dithiothreitol (DTT(SH)₂) to a disulfide product was demonstrated on a Nafion/lead–ruthenium oxide pyrochlore chemically modified electrode (NPyCME). The process at the NPyCME with DTT(SH)₂ is similar to the behaviour of protein in a disulfide linkage, which can be demonstrated by product analysis using HPLC coupled with UV spectroscopy. A possible electrocatalytic mechanism for DTT(SH)₂ oxidation to dihydroxydithiane [i.e. cyclized DTT(S–S)] on the NPyCME was proposed in terms of Py–Ru(IV)/Py–Ru(VI) redox active sites. This physical aspect was further utilized for high precision analytical assays using flow injection analysis (FIA), with a linearity up to 50 µM and a detection limit (S/N = 3) of 28 nM (8.64 pg) in a 20 µL sample loop. This is the most sensitive method ever reported for DTT(SH)₂ detection assays. The interference from dissolved oxygen, disulfide and glucose is almost negligible. The present method offers an easy route for extension to redox-related protein studies.