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Related Concept Videos

Radical Reactivity: Electrophilic Radicals01:02

Radical Reactivity: Electrophilic Radicals

Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a low‐energy SOMO, which interacts...
Radical Reactivity: Overview01:11

Radical Reactivity: Overview

Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...
Radical Reactivity: Nucleophilic Radicals01:16

Radical Reactivity: Nucleophilic Radicals

Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For instance, consider...
Radical Formation: Overview01:03

Radical Formation: Overview

A bond can be broken either by heterolytic bond cleavage to form ions or homolytic bond cleavage to yield radicals. A fishhook arrow is used to represent the motion of a single electron in homolytic bond cleavage. There are two main sources from which radicals can be formed:
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the latter, also known...
Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Radicals: Electronic Structure and Geometry01:07

Radicals: Electronic Structure and Geometry

This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...

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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
14:22

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development

Published on: April 15, 2013

Radicals in flavoproteins.

Erik Schleicher1, Stefan Weber

  • 1Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.

Topics in Current Chemistry
|November 22, 2011
PubMed
Summary

Electron paramagnetic resonance (EPR) spectroscopy advances the study of photoactive flavoproteins, revealing diverse photochemistry and reaction mechanisms. This technique is crucial for understanding how protein-cofactor interactions fine-tune flavin catalysis in vital photobiological processes.

Area of Science:

  • Biophysics
  • Spectroscopy
  • Photobiology

Background:

  • Electron paramagnetic resonance (EPR) spectroscopy is vital for studying paramagnetic states in proteins with organic cofactors.
  • Flavoproteins, abundant in nature, utilize flavins as prosthetic groups and are amenable to EPR analysis.
  • Understanding protein-flavin interactions is key to flavin's catalytic fine-tuning.

Purpose of the Study:

  • To highlight recent advancements in EPR spectroscopy for photoactive flavoproteins.
  • To explore the diverse photochemistry and reaction mechanisms of these proteins.
  • To elucidate the role of protein-cofactor interactions in flavin-mediated catalysis.

Main Methods:

  • Utilizing various Electron Paramagnetic Resonance (EPR) spectroscopy techniques.

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Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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  • Analyzing stationary and short-lived paramagnetic states in photoactive flavoproteins.
  • Characterizing photoexcited triplet states, radical pairs, and stationary radicals.

    • Main Results:

    • EPR spectroscopy effectively probes flavin electronic structure and protein-cofactor interactions.
    • Diverse photochemistry, including triplet states and radical pairs, was observed.
    • Paramagnetic intermediates were characterized, aiding mechanistic investigations.

    Conclusions:

    • EPR is the premier method for characterizing paramagnetic intermediates in photoactive flavoproteins.
    • This research advances the understanding of photobiological processes mediated by flavoproteins.
    • Further EPR studies will unravel the complex mechanisms of these essential proteins.