Versatility of thiourea dioxide as redox agent in globins: Case study with myoglobin

Abstract

This work focuses on understanding the versatile chemical properties of thiourea dioxide (TDO). The electronic structure of TDO is clarified, based on DFT and NBO population analysis calculations. We demonstrate that the most probable structure is the carbenoid one, with charge delocalization. The reduction of myoglobin with TDO was studied under different conditions in the pH range between 5 and 13, anaerobic/aerobic conditions and in the presence/absence of cysteine. Depending on the conditions, deoxy-, oxy-, carboxy-, and, in some cases, sulf-Mb species were obtained. To understand the influence of compounds containing S, N, and O functional groups on the decomposition kinetics of TDO in basic media, experiments and DFT calculations were performed. Adducts of cysteine and glycine with TDO identified in these investigations are deemed unlikely to be involved in protein reduction by TDO in short-term room-temperature UV–vis experiments.