A disulfide bond of Cys120 and Cys15 was rationally designed in human neuroglobin (Ngb) by A15C mutation, which caused minimal structural alterations, whereas enhanced both chemical and pH stability, with a thermal stability higher than 100 °C.

Neuroglobin (Ngb), with its physiological role not fully understood, was found to be capable of self-oxidation of methionine64 introduced at the heme axial position (H64M Ngb), adopting a high-spin heme state and producing both methionine sulfoxide (SO-Met) and sulfone (SO2-Met), which represents the structure and function of cytochrome c in a non-native state.