We have also considered the thio-(hydro)peroxy acid as a potential intermediate candidate. Note that the reduction potential is now higher than for the sulfenic (1.00-1.30 V) and sulfinic (0.70-0.90 V) acids, but similar to the thyil radical formation, about 1.60 V. Its dissociation could lead to the formation of the sulfenic acid, while at the same time, oxidising any residue nearby. Moreover, the extended "arm" of the peroxy moeity would allow to reach the neighbouring lysine residue, establishing contact between the residues prior to covalent bond formation. Herein, the formation of the thio-(hydro)peroxy acid species is considered, taking into account probable oxidant agents, present in the experimental assays. This can be seen in Figure , where the explored pathways for the formation of the thio-(hydro)peroxy acid from a thiol moiety are schematically represented.