Electron-paramagnetic resonance spectroscopy using N-methyl-D-glucamine dithiocarbamate iron cannot discriminate between nitric oxide and nitroxyl: implications for the detection of reaction products for nitric oxide synthase


Komarov, Andrei M., Wink, David A., Feelisch, Martin and Schmidt, Harald H.H.W. (2000) Electron-paramagnetic resonance spectroscopy using N-methyl-D-glucamine dithiocarbamate iron cannot discriminate between nitric oxide and nitroxyl: implications for the detection of reaction products for nitric oxide synthase. Free Radical Biology and Medicine, 28, (5), 739-742. (doi:10.1016/S0891-5849(00)00156-8). (PMID:10754269).

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Description/Abstract

Purified neuronal nitric oxide synthase (NOS) does not produce nitric oxide (NO) unless high concentrations of superoxide dismutase (SOD) are added, suggesting that nitroxyl (NO(-)) or a related molecule is the principal reaction product of NOS, which is SOD-dependently converted to NO. This hypothesis was questioned by experiments using electron paramagnetic resonance spectroscopy and iron N-methyl-D-glucamine dithiocarbamate (Fe-MGD) as a trap for NO. Although NOS and the NO donor S-nitroso-N-acetyl-penicillamine produced an electron paramagnetic resonance signal, the NO(-) donor, Angeli's salt (AS) did not. AS is a labile compound that rapidly hydrolyzes to nitrite, and important positive control experiments showing that AS was intact were lacking. On reinvestigating this crucial experiment, we find identical MGD(2)-Fe-NO complexes both from S-nitroso-N-acetyl-penicillamine and AS but not from nitrite. Moreover, the yield of MGD(2)-Fe-NO complex from AS was stoichiometric even in the absence of SOD. Thus, MGD(2)-Fe directly detects NO(-), and any conclusions drawn from MGD(2)-Fe-NO complexes with respect to the nature of the primary NOS product (NO, NO(-), or a related N-oxide) are invalid. Thus, NOS may form NO(-) or related N-oxides instead of NO.

Item Type: Article
ISSNs: 0891-5849 (print)
Keywords: nitric oxide, nitroxyl, EPR, nitric oxide synthase, superoxide dismutase, free radical
Subjects: Q Science > QP Physiology
Q Science > QR Microbiology > QR180 Immunology
Divisions: Faculty of Medicine > Infection, Inflammation and Immunity
ePrint ID: 337875
Date Deposited: 29 Jun 2012 10:31
Last Modified: 27 Mar 2014 20:21
URI: http://eprints.soton.ac.uk/id/eprint/337875

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