article nitric oxide chemistry unclassified drug Nitric Oxide Nitrogen Oxides Ligands Models, Molecular chemical structure Kinetics nitroxyl Crystallography, X-Ray Oxidation-Reduction X ray crystallography aqueous solution nitrogen oxide oxidation reduction reaction priority journal Hydrogen bonds Iron Nitric oxide Nitrosyl density functional theory oxygen reaction analysis Animals Chlorine compounds Heme Metalloporphyrins Porphyrins