Nitrogen Oxide Atom-Transfer Redox Chemistry; Mechanism of NO(g) to Nitrite Conversion Utilizing μ-oxo Heme-Fe ^III-O-Cu ^II(L) Constructs

Hematian S, Kenkel I, Shubina T, Dürr M, Liu JJ, Siegler MA, Ivanovic-Burmazovic I, Karlin KD (2015)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2015

Journal

Publisher: American Chemical Society

Book Volume: 137

Pages Range: 6602-6615

Journal Issue: 20

DOI: 10.1021/jacs.5b02174

Abstract

(Chemical Equation Presented) While nitric oxide (NO, nitrogen monoxide) is a critically important signaling agent, its cellular concentrations must be tightly controlled, generally through its oxidative conversion to nitrite (NO2^-) where it is held in reserve to be reconverted as needed. In part, this reaction is mediated by the binuclear heme a3/CuB active site of cytochrome c oxidase. In this report, the oxidation of NO(g) to nitrite is shown to occur efficiently in new synthetic μ-oxo heme-Fe^III-O-Cu^II(L) constructs (L being a tridentate or tetradentate pyridyl/alkylamino ligand), and spectroscopic and kinetic investigations provide detailed mechanistic insights. Two new X-ray structures of μ-oxo complexes have been determined and compared to literature analogs. All μ-oxo complexes react with 2 mol equiv NO(g) to give 1:1 mixtures of discrete [(L)Cu^II(NO2^-)]⁺ plus ferrous heme-nitrosyl compounds; when the first NO(g) equiv reduces the heme center and itself is oxidized to nitrite, the second equiv of NO(g) traps the ferrous heme thus formed. For one μ-oxo heme-Fe^III-O-Cu^II(L) compound, the reaction with NO(g) reveals an intermediate species ("intermediate"), formally a bis-NO adduct, [(NO)(porphyrinate)Fe^II-(NO2^-)-Cu^II(L)]⁺ (λmax = 433 nm), confirmed by cryo-spray ionization mass spectrometry and EPR spectroscopy, along with the observation that cooling a 1:1 mixture of [(L)Cu^II(NO2^-)]⁺ and heme-Fe^II(NO) to -125°C leads to association and generation of the key 433 nm UV-vis feature. Kinetic-thermodynamic parameters obtained from low-temperature stopped-flow measurements are in excellent agreement with DFT calculations carried out which describe the sequential addition of NO(g) to the μ-oxo complex.

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How to cite

APA:

Hematian, S., Kenkel, I., Shubina, T., Dürr, M., Liu, J.J., Siegler, M.A.,... Karlin, K.D. (2015). Nitrogen Oxide Atom-Transfer Redox Chemistry; Mechanism of NO(g) to Nitrite Conversion Utilizing μ-oxo Heme-Fe ^III-O-Cu ^II(L) Constructs. Journal of the American Chemical Society, 137(20), 6602-6615. https://doi.org/10.1021/jacs.5b02174

MLA:

Hematian, Shabnam, et al. "Nitrogen Oxide Atom-Transfer Redox Chemistry; Mechanism of NO(g) to Nitrite Conversion Utilizing μ-oxo Heme-Fe ^III-O-Cu ^II(L) Constructs." Journal of the American Chemical Society 137.20 (2015): 6602-6615.

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