title: Involvement of ferryl in the reaction between nitrite and the oxy forms of globins.
abstract: The reaction between nitrite and the oxy forms of globins has complex autocatalytic kinetics with several branching steps and evolves through chain reactions mediated by reactive species (including radicals) such as hydrogen peroxide, ferryl and nitrogen dioxide, starting with a lag phase, after which it proceeds onto an autocatalytic phase. Reported here are UV-Vis spectra collected upon stopped-flow mixing of myoglobin with a supraphysiological excess of nitrite. The best fit to the experimental data follows an A → B → C reaction scheme involving the formation of a short-lived intermediate identified as ferryl. This is consistent with a mechanism where nitrite binds to oxy myoglobin to generate an undetectable ferrous-peroxynitrate intermediate, whose decay leads to nitrate and ferryl. The ferryl is then reduced to met by the excess nitrite. DFT calculations reveal an essentially barrierless reaction between nitrite and the oxy heme, with a notable outer-sphere component; the resulting metastable ferrous-peroxynitrate adduct is found to feature a very low barrier towards nitrate liberation, with ferryl as a final product-in good agreement with experiment.
authors: Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, 11 Arany Janos Street, 400028, Cluj-Napoca, Romania.
authors: Denisa
authors: D
authors: Hathazi
authors: Sonia Diana
authors: SD
authors: Mahuţ
authors: Florina-Violeta
authors: FV
authors: Scurtu
authors: Cristina
authors: C
authors: Bischin
authors: Corina
authors: C
authors: Stanciu
authors: Amr Ali
authors: AA
authors: Attia
authors: Grigore
authors: G
authors: Damian
authors: Radu
authors: R
authors: Silaghi-Dumitrescu
mesh_terms: D000818:Animals; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism*; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000737:chemistry / Q000378:metabolism*; D050661:Sperm Whale / Q000378:metabolism*
chemical_list: D009211:Myoglobin; D009573:Nitrites; C017595:oxymyoglobin; C066317:ferryl iron; D030421:Peroxynitrous Acid; D007501:Iron