Human cytochrome c (hCyt c) contains a covalently attached heme group with six-coordination (Met/His) and plays vital biological functions, including electron transfer and peroxidase activity by structural alterations, as well as other functions by interactions with partners such as neuroglobin (Ngb). In this study, we designed and engineered an artificial disulfide bond in hCyt c via double mutations (A51C/G77C) which bridges the Ω-loops C and D. The formation of the intramolecular disulfide bond (Cys51-Cys77) was confirmed by mass spectromet...