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Related Concept Videos

Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

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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...
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Carbon-dioxide Fixation01:28

Carbon-dioxide Fixation

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Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...
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Metabolism of Chemolithotrophs01:15

Metabolism of Chemolithotrophs

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Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation.
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Overview of Nitrogen Metabolism01:20

Overview of Nitrogen Metabolism

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Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of  ammonia, ammonium ions, nitrate, nitrite, or  nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
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The Nitrogen Cycle01:49

The Nitrogen Cycle

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Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
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Electrophilic Aromatic Substitution: Nitration of Benzene

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The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.
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Related Experiment Video

Updated: Jul 29, 2025

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
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Nitrogen Fixation and Hydrogen Evolution by Sterically Encumbered Mo-Nitrogenase.

Cécile Cadoux1,2, Daniel Ratcliff1,2, Nevena Maslać3

  • 1Department of Inorganic and Analytical Chemistry, Faculty of Sciences, University of Geneva, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland.

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Summary

Biological nitrogen fixation involves complex protein interactions. This study reveals that nitrogenase enzymes exhibit negative cooperativity, where one functional half inhibits the other, highlighting long-range communication critical for ammonia production.

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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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Area of Science:

  • Biochemistry
  • Enzymology
  • Nitrogen Fixation

Background:

  • Nitrogenases (MoFe, VFe, FeFe) are α2ß2(γ2) protein complexes with two functional halves.
  • The dimeric organization may enhance in vivo stability, but cooperativity in enzymatic activity remains debated.

Purpose of the Study:

  • To investigate the cooperativity of nitrogenase activity.
  • To elucidate the role of protein-protein interactions in biological nitrogen fixation.

Main Methods:

  • A 1.4 kDa peptide with a Strep-tag was covalently attached near the P cluster of the MoFe protein.
  • This modification sterically inhibited electron transfer and allowed isolation of partially inhibited MoFe proteins.
  • Assessed N2 reduction to NH3 and H2 formation in partially functional MoFe proteins.

Main Results:

  • Partially functional MoFe proteins retained N2 reduction ability without altered selectivity for H2 formation.
  • Wild-type nitrogenase demonstrated negative cooperativity in steady-state H2 and NH3 formation.
  • One half of the MoFe protein was found to inhibit the turnover of the other half.

Conclusions:

  • Biological nitrogen fixation in Azotobacter vinelandii involves significant long-range (>95 Å) protein-protein communication.
  • The study confirms negative cooperativity in wild-type nitrogenase, with implications for understanding enzyme regulation and efficiency.
  • The findings underscore the importance of intermolecular communication for efficient ammonia synthesis.