Radical nitrogen-based molecules that can act to facilitate nitrosylation reactions; reactive nitrogen species include dioxidonitrogen(•) (nitrogen dioxide, nitryl radical) NO2•, oxidonitrogen(•) (nitrogen monoxide, nitrosyl radical) NO• oxidonitrogen(1+) (nitrosyl cation) NO+, hydroxyoxidonitrogen (nitrous acid) HNO2 and oxidonitrate(1-) NO-.