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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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Electrophilic Aromatic Substitution: Nitration of Benzene01:20

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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meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H01:13

meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H

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All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
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2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

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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.
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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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1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism01:37

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

4.7K
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
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An Efficient Viologen-Based Electron Donor to Nitrogenase.

Artavazd Badalyan1, Zhi-Yong Yang1, Bo Hu1

  • 1Department of Chemistry and Biochemistry , Utah State University , 0300 Old Main Hill , Logan , Utah 84322 , United States.

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Researchers developed a new sulfonated viologen derivative that efficiently donates electrons to nitrogenase, overcoming limitations of previous electron donors for studying and applying nitrogen fixation. This advance enables better spectrophotometric assays and electrocatalysis 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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Area of Science:

  • Biochemistry and Bioinorganic Chemistry
  • Enzyme Catalysis
  • Nitrogen Fixation Research

Background:

  • Nitrogenase is crucial for biological nitrogen fixation, converting N2 to NH3.
  • Existing electron donors like ferredoxin, flavodoxin, and sodium dithionite have limitations for spectrophotometric studies and electrocatalysis.
  • Methyl viologen, a common electron donor, shows decreased nitrogenase activity at higher concentrations due to dimer formation.

Purpose of the Study:

  • To investigate the concentration-dependent decrease in nitrogenase activity with methyl viologen.
  • To synthesize and evaluate novel viologen derivatives as improved electron donors for nitrogenase.
  • To establish a robust method for studying nitrogenase activity and its potential in electrocatalysis.

Main Methods:

  • Synthesis of functionalized viologen derivatives (sulfonated and positively charged).
  • Spectroscopic analysis and cyclic voltammetry to characterize the viologen derivatives.
  • Assays measuring nitrogenase activity using the novel viologen derivatives as electron donors under argon and N2.

Main Results:

  • The sulfonated viologen derivative, [(SPr)2V]-, supported full nitrogenase activity up to 3 mM, unlike methyl viologen.
  • A positively charged viologen derivative was inefficient due to a high standard redox potential.
  • The study demonstrated a sensitive spectrophotometric assay for nitrogenase activity using [(SPr)2V]-, confirming ammonia formation under N2.

Conclusions:

  • The formation of methyl viologen dimers explains its inhibitory effect on nitrogenase at higher concentrations.
  • The sulfonated viologen derivative [(SPr)2V]- is a superior electron donor for nitrogenase, enabling accurate activity measurements.
  • [(SPr)2V]- shows significant promise for nitrogenase electrocatalysis and bioelectrosynthetic N2 reduction due to its efficiency and low overpotential.