title: Acidity and hydrogen exchange dynamics of iron(II)-bound nitroxyl in aqueous solution.
abstract: Nitroxyl-iron(II) (HNO-Fe(II)) complexes are often unstable in aqueous solution, thus making them very difficult to study. Consequently, many fundamental chemical properties of Fe(II)-bound HNO have remained unknown. Using a comprehensive multinuclear ((1)H, (15)N, (17)O) NMR approach, the acidity of the Fe(II)-bound HNO in [Fe(CN)5(HNO)](3-) was investigated and its pK(a) value was determined to be greater than 11. Additionally, HNO undergoes rapid hydrogen exchange with water in aqueous solution and this exchange process is catalyzed by both acid and base. The hydrogen exchange dynamics for the Fe(II)-bound HNO have been characterized and the obtained benchmark values, when combined with the literature data on proteins, reveal that the rate of hydrogen exchange for the Fe(II)-bound HNO in the interior of globin proteins is reduced by a factor of 10(6).
authors.affiliation: Department of Chemistry, Queen's University, Kingston, Ontario, K7L 3N6 (Canada).
authors.forename: Yin
authors.initials: Y
authors.lastname: Gao
authors.forename: Abouzar
authors.initials: A
authors.lastname: Toubaei
authors.forename: Xianqi
authors.initials: X
authors.lastname: Kong
authors.forename: Gang
authors.initials: G
authors.lastname: Wu
mesh_terms: D000143:Acids / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009589:Nitrogen Oxides / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D000143:Acids; D009589:Nitrogen Oxides; D012996:Solutions; D014867:Water; D006859:Hydrogen; D007501:Iron; C039900:nitroxyl
keywords: NMR spectroscopy; acidity; density functional calculations; isotopic labeling; nitroxyl