In contrast to the ionic pathway the kinetic barrier for the homolytic dissociation of the O-O is merely 1.4 kcal/mol, enabling the system to avoid the formation of the sulfinic acid. A broken-symmetry was used for these calculations. The resultant hydroxyl radical can then easily strip a proton from the amine moiety with whom it was interacting, with a barrier of 2.2 kcal/mol, and form a radical species on the nitrogen atom of the lysine residue. Finally, the radical at the oxygen of the cysteine residue and the nitrogen recombine, with an activation barrier of 8.2 kcal/mol, forming the NOS bond. An overview of all the involved reactions (and also other reaction possibilities, which are not mentioned directly in the text) are given in Figure . Beside the advantage of overcoming the threat of the sulfinic acid formation, another vital property of the homolytic pathway is its validity in expanding the NOS to the double-NOS (SONOS), sharing the same nitrogen.