Study on the intermediate ions formed by glutathione peroxidase mimic 2,2'‐ditellurobis(2‐deoxy‐β‐cyclodextrin) by electrospray ionization mass spectrometry

Abstract

2,2'-Ditellurobis(2-deoxy-β-cyclodextrin) (2-TeCD) is one of the most well-known glutathione peroxidase (GPx) mimics. However, because the critical reaction intermediates had not previously been isolated or directly detected due to its short lifetime, the catalytic mechanism of 2-TeCD is not very clear and further experiments are needed to characterize each of the intermediates in the catalytic cycle. Using electrospray ionization mass (and tandem) spectrometry (ESI-MS and ESI-MS/MS) experiments, the decomposition of hydrogen peroxide at the expense of glutathione (GSH) catalyzed by 2-TeCD was monitored on-line. The key intermediates were successfully intercepted and structurally characterized for the first time by coupling a microreactor on-line to the ESI ion source, which permitted the fast screening of intermediates directly from solution. The catalytic mechanism of 2-TeCD catalysis has been elaborated based on mass spectrometric data and exerted its peroxidase activity via tellurol, tellurenic acid, and tellurosulfide, in analogy with natural GPX.