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Related Concept Videos

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: 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 Formation: Addition00:47

Radical Formation: Addition

Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
Phase II Reactions: Methylation Reactions01:17

Phase II Reactions: Methylation Reactions

Methylation is a phase II biotransformation process involving the attachment of a methyl group to a substrate. Enzymes known as methyltransferases orchestrate this reaction.
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
Radical Anti-Markovnikov Addition to Alkenes: Mechanism01:17

Radical Anti-Markovnikov Addition to Alkenes: Mechanism

The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
Radical Formation: Elimination00:51

Radical Formation: Elimination

Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. For example, as depicted in Figure 1, dibenzoyl peroxide yields a pair of unstable radicals upon homolysis. Given its instability, this radical spontaneously undergoes elimination via a C–C bond cleavage to form a relatively more stable phenyl radical. The mechanism involves cleavage of the bond between the α and β positions with respect to...

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Related Experiment Video

Updated: Jun 1, 2026

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

Methylations: a radical mechanism.

Marc Fontecave1

  • 1Institut de Recherches en Technologie et Sciences pour le Vivant IRTSV-LCBM, UMR 5249 CEA/CNRS/UJF, CEA-Grenoble, France. mfontecave@cea.fr

Chemistry & Biology
|May 26, 2011
PubMed
Summary

Labeling experiments reveal that S-adenosylmethionine-dependent methyltransferases can methylate electrophilic carbons in RNA adenosine via a novel radical mechanism.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • RNA Metabolism

Background:

  • Methylation is a crucial post-transcriptional modification in RNA.
  • S-adenosylmethionine-dependent methyltransferases (SAM-MTs) are key enzymes in methylation.
  • The precise mechanism of methylation by SAM-MTs, particularly involving RNA adenosine, has been an area of investigation.

Discussion:

  • This study investigates the methylation of RNA adenosine by SAM-MTs.
  • Labeling experiments provide evidence for a unique radical mechanism.
  • The findings challenge existing models of enzymatic methylation.

Key Insights:

  • A novel radical mechanism is proposed for the methylation of RNA adenosine.
  • Electrophilic carbon in RNA adenosine serves as the target for methylation.

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Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
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Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues

Published on: November 22, 2014

Related Experiment Videos

Last Updated: Jun 1, 2026

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

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
12:07

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues

Published on: November 22, 2014

  • S-adenosylmethionine acts as the methyl group donor in this radical process.

    • Outlook:

    • Further research is needed to fully elucidate the scope and implications of this radical mechanism.
    • Understanding this pathway could lead to new therapeutic strategies targeting RNA methylation.
    • This discovery opens new avenues for exploring enzymatic radical reactions in biological systems.