Lewis Acid-Assisted Reduction of Nitrite to Nitric and Nitrous Oxide via the Elusive Nitrite Radical Dianion

Reduction of nitrite anions [NO2]- takes place in a myriad of environments such as in the soil as part of the biogeochemical nitrogen cycle as well as in acidified nuclear waste. Nitrite reduction typically takes place within the coordination sphere of a redox active transition metal. Lewis acid coordination, however, can dramatically modify the reduction potential of this polyoxoanion to allow for reduction under non-aqueous conditions (-0.74 V vs. NHE). This strategy enables the isolation of a borane-capped nitrite dianion [NO2]2- along with its spectroscopic study consistent with reduction to the N(II) oxidation state. Protonation of the nitrite dianion results in facile loss of nitric oxide (NO) while reaction of the nitrite dianion with nitric oxide results in disproportionation to nitrous oxide (N2O) and nitrite, connecting three redox levels in the global nitrogen cycle.

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Identification of nitric oxide and nitrous oxide as products of nitrite reduction by Pseudomonas cytochrome oxidase (nitrite reductase)

Biochemical and Biophysical Research Communications ◽

10.1016/s0006-291x(80)80159-8 ◽

1980 ◽

Vol 97 (1) ◽

pp. 236-242 ◽

Cited By ~ 43

Author(s):

David C. Wharton ◽

Susan T. Weintraub

Keyword(s):

Nitric Oxide ◽

Nitrous Oxide ◽

Cytochrome Oxidase ◽

Nitrite Reductase ◽

Nitrite Reduction

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Microbiological Nitrous-Oxide Production: Implications for the Global Nitrogen Cycle

Biogeochemistry of Ancient and Modern Environments ◽

10.1007/978-3-662-26582-6_28 ◽

1980 ◽

pp. 267-278

Author(s):

T. Rosswall

Keyword(s):

Nitrous Oxide ◽

Nitrogen Cycle ◽

Oxide Production ◽

Nitrous Oxide Production ◽

Global Nitrogen Cycle

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Microbiological Nitrous-Oxide Production: Implications for the Global Nitrogen Cycle

Biogeochemistry of Ancient and Modern Environments ◽

10.1007/978-3-642-48739-2_28 ◽

1980 ◽

pp. 267-278

Author(s):

T. Rosswall

Keyword(s):

Nitrous Oxide ◽

Nitrogen Cycle ◽

Oxide Production ◽

Nitrous Oxide Production ◽

Global Nitrogen Cycle

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A QM/MM Study of Nitrite Binding Modes in a Three-Domain Heme-Cu Nitrite Reductase

Molecules ◽

10.3390/molecules23112997 ◽

2018 ◽

Vol 23 (11) ◽

pp. 2997

Author(s):

Kakali Sen ◽

Michael Hough ◽

Richard Strange ◽

Chin Yong ◽

Thomas Keal

Keyword(s):

Nitric Oxide ◽

Nitrite Reductase ◽

Binding Mode ◽

Nitrite Reduction ◽

Quantum Mechanical ◽

Binding Modes ◽

Crystallographic Study ◽

Nitrite Reductases ◽

Global Nitrogen Cycle ◽

Oxygen Mode

Copper-containing nitrite reductases (CuNiRs) play a key role in the global nitrogen cycle by reducing nitrite (NO2−) to nitric oxide, a reaction that involves one electron and two protons. In typical two-domain CuNiRs, the electron is acquired from an external electron-donating partner. The recently characterised Rastonia picketti (RpNiR) system is a three-domain CuNiR, where the cupredoxin domain is tethered to a heme c domain that can function as the electron donor. The nitrite reduction starts with the binding of NO2− to the T2Cu centre, but very little is known about how NO2− binds to native RpNiR. A recent crystallographic study of an RpNiR mutant suggests that NO2− may bind via nitrogen rather than through the bidentate oxygen mode typically observed in two-domain CuNiRs. In this work we have used combined quantum mechanical/molecular mechanical (QM/MM) methods to model the binding mode of NO2− with native RpNiR in order to determine whether the N-bound or O-bound orientation is preferred. Our results indicate that binding via nitrogen or oxygen is possible for the oxidised Cu(II) state of the T2Cu centre, but in the reduced Cu(I) state the N-binding mode is energetically preferred.

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Experimental evidence for plasmid-bornenor-nirgenes inSinorhizobium melilotiJJ1c10

Canadian Journal of Microbiology ◽

10.1139/w04-062 ◽

2004 ◽

Vol 50 (9) ◽

pp. 657-667 ◽

Cited By ~ 7

Author(s):

Yiu-Kwok Chan ◽

Wayne A McCormick

Keyword(s):

Nitric Oxide ◽

Nitrous Oxide ◽

Sinorhizobium Meliloti ◽

Nitrite Reduction ◽

Nucleotide Sequence Analysis ◽

Gene Products ◽

Oxide Reduction ◽

Accessory Gene ◽

Genes Encoding ◽

Denitrification Genes

In denitrification, nir and nor genes are respectively required for the sequential dissimilatory reduction of nitrite and nitric oxide to form nitrous oxide. Their location on the pSymA megaplasmid of Sinorhizobium meliloti was confirmed by Southern hybridization of its clones with specific structural gene probes for nirK and norCB. A 20-kb region of pSymA containing the nor-nir genes was delineated by nucleotide sequence analysis. These genes were linked to the nap genes encoding periplasmic proteins involved in nitrate reduction. The nor-nir-nap segment is situated within 30 kb downstream from the nos genes encoding nitrous oxide reduction, with a fix cluster intervening between nir and nos. Most of these predicted nor-nir and accessory gene products are highly homologous with those of related proteobacterial denitrifiers. Functional tests of Tn5 mutants confirmed the requirement of the nirV product and 1 unidentified protein for nitrite reduction as well as the norB-D products and another unidentified protein for nitric oxide reduction. Overall comparative analysis of the derived amino acid sequences of the S. meliloti gene products suggested a close relationship between this symbiotic N2fixer and the free-living non-N2-fixing denitrifier Pseudomonas G-179, despite differences in their genetic organization. This relationship may be due to lateral gene transfer of denitrification genes from a common donor followed by rearrangement and recombination of these genes.Key words: denitrification genes, nitric oxide reductase, nitrite reductase, Rhizobiaceae, Sinorhizobium meliloti.

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