Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 May 21;51(10):5637-41.
doi: 10.1021/ic202561f. Epub 2012 May 3.

Nitrosation, thiols, and hemoglobin: energetics and kinetics

Willem H Koppenol  1
Affiliations
Free PMC article

Nitrosation, thiols, and hemoglobin: energetics and kinetics

Willem H Koppenol. Inorg Chem. .
Free PMC article

Abstract

Nitrosothiols are powerful vasodilators. Although the mechanism of their formation near neutral pH is an area of intense research, neither the energetics nor the kinetics of this reaction or of subsequent reactions have been addressed. The following considerations may help to guide experiments. (1) The standard Gibbs energy for the homolysis reaction RSNO → RS(•) + NO(•)(aq) is +110 ± 5 kJ mol(-1). (2) The electrode potential of the RSNO, H(+)/RSH, NO(•)(aq) couple is -0.20 ± 0.06 V at pH 7. (3) Thiol nitrosation by NO(2)(-) is favorable by 37 ± 5 kJ mol(-1) at pH 7. (4) N(2)O(3) is not involved in in vivo nitrosation mechanisms for thermodynamic--its formation from NO(2)(-) costs 59 kJ mol(-1)--or kinetic--the reaction being second-order in NO(2)(-)--reasons. (5) Hemoglobin (Hb) cannot catalyze formation of N(2)O(3), be it via the intermediacy of the reaction of Hb[FeNO(2)](2+) with NO(•) (+81 kJ mol(-1)) or reaction of Hb[FeNO](3+) with NO(2)(-) (+88 kJ mol(-1)). (6) Energetically and kinetically viable are nitrosations that involve HNO(2) or NO(•) in the presence of an electron acceptor with an electrode potential higher than -0.20 V. These considerations are derived from existing thermochemical and kinetics data.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Cassoly R.; Gibson Q. H. Conformation, co-operativity and ligand binding in human hemoglobin. J. Mol. Biol. 1975, 91, 301–313. - PubMed
    1. Moore E. G.; Gibson Q. H. Cooperativity in the dissociation of nitric oxide from hemoglobin. J. Biol. Chem. 1976, 251, 2788–2794. - PubMed
    1. Doyle M. P.; Pickering R. A.; Cook B. R. Oxidation of oxymyoglobin by nitric oxide through dissociation from cobalt nitrosyls. J. Inorg. Biochem. 1983, 19, 329–338.
    1. Eich R. F.; Li T.; Lemon D. D.; Doherty D. H.; Curry S. R.; Aitken J. F.; Mathews A. J.; Johnson K. A.; Smith R. D.; Phillips G. N.; Olson J. S. Mechanism of NO-induced oxidation of myoglobin and hemoglobin. Biochemistry 1996, 35, 6976–6983. - PubMed
    1. Herold S. Kinetic and spectroscopic characterization of an intermediate peroxynitrite complex in the nitrogen monoxide induced oxidation of oxyhemoglobin. FEBS Lett. 1998, 439, 85–88. - PubMed
-