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Related Concept Videos

Nitric Oxide Signaling Pathway01:28

Nitric Oxide Signaling Pathway

Nitric oxide (NO), an inorganic gas, acts as a potent second messenger in most animal and plant tissues. NO diffuses out of the cells that produce it and enters the neighboring cells to generate a downstream response. NO synthase (NOS) catalyzes NO production by the deamination of the amino acid arginine. There are three isoforms of NOS. Endothelial cells have endothelial NOS (eNOS), nerve and muscle cells have neuronal NOS (nNOS), and macrophages produce inducible NOS (iNOS) upon exposure to...
Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
Phase II Reactions: Miscellaneous Conjugation Reactions01:19

Phase II Reactions: Miscellaneous Conjugation Reactions

Phase II biotransformations are detoxification mechanisms that conjugate xenobiotics with endogenous substances, neutralizing their toxicity.
A key example involves the conjugation of cyanide ions, which impair cellular respiration and alter hemoglobin into non-oxygen-carrying cyanmethemoglobin. To neutralize this threat, a sulfur atom from thiosulphate is transferred to the cyanide ion, catalyzed by the enzyme rhodanese, resulting in an inactive compound called thiocyanate. The production of...
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by water loss...
Structural Isomerism02:34

Structural Isomerism

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...

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Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
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Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds

Published on: February 16, 2022

Heme/copper assembly mediated nitrite and nitric oxide interconversion.

Shabnam Hematian1, Maxime A Siegler, Kenneth D Karlin

  • 1Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.

Journal of the American Chemical Society
|November 8, 2012
PubMed
Summary
This summary is machine-generated.

Cytochrome c oxidase

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Area of Science:

  • Biochemistry
  • Enzyme kinetics
  • Redox chemistry

Background:

  • Cytochrome c oxidase's heme(a3)/Cu(B) active site mediates cellular nitrite reduction to nitric oxide.
  • This active site also oxidizes nitric oxide back to nitrite.

Purpose of the Study:

  • To investigate the specific roles of the heme and Cu(II) ions in the redox reactions involving nitrite and nitric oxide at the heme(a3)/Cu(B) active site.

Main Methods:

  • Spectroscopic analysis of a partially reduced heme/Cu assembly.
  • Monitoring of reaction products under controlled conditions.

Main Results:

  • A partially reduced heme/Cu assembly was shown to reduce nitrite ions to nitric oxide, requiring both heme and Cu(II).
  • A μ-oxo heme-Fe(III)-O-Cu(II) complex was identified as facilitating nitric oxide oxidation to nitrite.

Conclusions:

  • The heme(a3)/Cu(B) active site exhibits bidirectional redox chemistry with nitrogen oxides.
  • This dual capability highlights the site's crucial role in regulating nitric oxide metabolism.