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Related Concept Videos

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...
Electrophilic Aromatic Substitution: Nitration of Benzene01:20

Electrophilic Aromatic Substitution: Nitration of Benzene

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.
Rate-Determining Steps03:08

Rate-Determining Steps

Relating Reaction Mechanisms
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...
Overview of Nitrogen Metabolism01:20

Overview of Nitrogen Metabolism

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.
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Free Energy Changes for Nonstandard States03:25

Free Energy Changes for Nonstandard States

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Microbes and the Nitrogen Cycle01:26

Microbes and the Nitrogen Cycle

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Related Experiment Video

Updated: Jun 5, 2026

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
10:01

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase

Published on: December 4, 2017

Electron transfer and half-reactivity in nitrogenase.

Thomas A Clarke1, Shirley Fairhurst, David J Lowe

  • 1Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK. tom.clarke@uea.ac.uk

Biochemical Society Transactions
|January 27, 2011
PubMed
Summary

Nitrogenase

Area of Science:

  • Biochemistry
  • Enzymology
  • Nitrogen Cycle

Background:

  • Nitrogenase catalyzes essential dinitrogen reduction to ammonia.
  • The nitrogenase complex involves a molybdenum-iron (MoFe) protein and an iron (Fe) protein.
  • Current electron transfer models are based on spectrophotometry.

Purpose of the Study:

  • Investigate the stoichiometry and mechanism of electron transfer between Fe protein and MoFe protein.
  • Clarify the apparent half-activity of the Fe protein in electron transfer.

Main Methods:

  • Stopped-flow spectrophotometry to determine reaction rates.
  • Rapid-quench electron paramagnetic resonance (EPR) to study pre-steady-state kinetics.

Main Results:

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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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Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction
10:57

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Published on: April 10, 2018

Related Experiment Videos

Last Updated: Jun 5, 2026

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
10:01

Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase

Published on: December 4, 2017

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
08:05

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

Published on: October 7, 2020

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction
10:57

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Published on: April 10, 2018

  • Four Fe protein molecules are needed to saturate one MoFe protein, suggesting half-activity.
  • Pre-steady-state electron transfer shows Fe protein becomes only half-oxidized.
  • MoFe protein with one active site occupied is saturated by three Fe protein equivalents.

Conclusions:

  • The Fe protein exhibits a second, non-electron transfer interaction with the MoFe protein.
  • This interaction occurs during initial mixing stages and influences observed stoichiometry.