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Related Concept Videos

Redox Reactions01:24

Redox Reactions

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another atom must lose an electron, meaning oxidation and reduction must occur together. Since the redox occurs in pairs, the atom that gets oxidized is also called the reducing agent or reductant, and the atom that is reduced is also called the oxidizing agent or oxidant. A straightforward way to remember the definitions of oxidation and reduction is...
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Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
The Supercomplexes in the Crista Membrane01:41

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The mitochondrial cristae membrane is the primary site for the oxidative phosphorylation (OXPHOS) process of energy conversion mediated through respiratory complexes I to V. These complexes have been widely studied for decades, and it has been proven that they form supramolecular structures called respiratory supercomplexes (SC). These higher-order complexes may be crucial in maintaining the biochemical structure and improving the physiological activity of the individual complexes while...
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The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the para position.
Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
Redox Reactions01:27

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Redox reactions are vital biochemical processes that underpin energy metabolism in cells. These reactions involve the transfer of electrons between molecules, occurring in tandem as oxidation and reduction. Oxidation refers to the loss of electrons, while reduction denotes their gain. This coupling ensures the seamless flow of electrons through metabolic pathways. For example, in bacterial metabolism, glucose undergoes oxidation to carbon dioxide, while oxygen is simultaneously reduced to...

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Related Experiment Video

Updated: Jul 17, 2026

Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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Published on: March 18, 2012

Redox-state-dependent complex formation between pseudoazurin and nitrite reductase.

Antonietta Impagliazzo1, Anneloes J Blok, Matthew J Cliff

  • 1Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.

Journal of the American Chemical Society
|January 4, 2007
PubMed
Summary

Researchers studied how pseudoazurin binds to bacterial nitrite reductase. Reduced pseudoazurin shows two binding modes, while oxidized pseudoazurin shows one, revealing insights into electron transfer in denitrification.

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Published on: February 16, 2022

Area of Science:

  • Biochemistry
  • Microbiology
  • Enzymology

Background:

  • Bacterial copper-containing nitrite reductase is crucial for denitrification, converting nitrite to nitric oxide.
  • Pseudoazurin acts as an electron donor to nitrite reductase, facilitating this process.
  • Understanding their interaction is key to elucidating the denitrification pathway.

Purpose of the Study:

  • To investigate the redox-state dependence of complex formation between pseudoazurin and nitrite reductase.
  • To characterize the binding modes and affinities of pseudoazurin to nitrite reductase.
  • To explore the role of metal charge and specific amino acid residues in the binding interaction.

Main Methods:

  • Nuclear magnetic resonance (NMR) spectroscopy was employed to study complex formation.
  • Isothermal titration calorimetry (ITC) was used to determine binding affinities.
  • Metal-substituted proteins were utilized to assess the influence of the metal center.

Main Results:

  • Reduced pseudoazurin exhibits two binding modes (fast and slow exchange) with a K(d)(app) of 100 microM.
  • Oxidized pseudoazurin binds in a single fast exchange mode with similar affinity.
  • Binding mode is independent of nitrite reductase's metal charge; His81 protonation is not directly involved in dual binding.

Conclusions:

  • Pseudoazurin displays distinct binding behaviors depending on its redox state.
  • A model involving a minor pseudoazurin form is proposed to explain the reduced state's dual binding.
  • These findings offer insights into electron transfer mechanisms in bacterial denitrification.