Biological methane activation involves the intermediacy of carbon‐centered radicals

The spin‐trapping technique has demonstrated that carbon‐centered radicals are produced during soluble‐methane‐monooxygenase catalysis of the hydroxylation of several different types of substrate. The resulting spin‐adducts were identified from the hyperfine splitting constants in their EPR spectra. Isotopic labelling showed unequivocally that the trapped radicals were derived from substrate. The carbon‐centered substrate radicals are believed to result from hydrogen‐atom abstraction by a ferryl species in a cytochrome‐P‐450‐like mechanism. No hydroxy radical nor an oxygen‐based radical of any kind was detected in any of the spin‐trapping experiments.