Related Experiment Video
Updated: Jul 11, 2026
13:21
Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps
Published on: August 18, 2012
Lipid radicals: properties and detection by spin trapping
1Institute of Pharmacology and Toxicology, Veterinary University of Vienna, Austria. Hans.Nohl@vu-wien.ac.at
Acta Biochimica Polonica
|May 9, 2002
Summary
Iron (Fe2+) rapidly oxidizes unsaturated lipids, forming toxic products. Researchers used spin traps to detect lipid radicals, identifying secondary carbon-centered radicals under anaerobic conditions and oxygen-centered radicals aerobically.
Area of Science:
- Biochemistry
- Oxidative Stress Research
- Analytical Chemistry
Background:
- Unsaturated lipids readily oxidize to toxic products, accelerated by transition metals like iron.
- Lipid hydroperoxides are converted to short-lived lipid alkoxyl radicals via Fenton-type reactions.
Purpose of the Study:
- To investigate and detect lipid radical species generated during the oxidation of unsaturated lipids.
- To characterize the radicals formed in Fenton-type reactions involving iron and lipid hydroperoxides.
Main Methods:
- Electron Spin Resonance (ESR) spectroscopy utilizing various spin traps (MNP, DMPO, DEPMPO).
- Synthesis of lipophilic spin trap derivatives for lipid phase radical detection.
- Anaerobic and aerobic incubation systems with linoleic acid hydroperoxide (LOOH) and Fe2+.
Main Results:
- Detection of secondary radical adducts, including methinyl fragments, carbon-centered lipid radicals, acyl radicals, and hydroxyl radicals.
- Identification of a lipid-derived carbon-centered radical under anaerobic conditions (Fe2+/LOOH).
- Formation of an SOD-insensitive oxygen-centered radical adduct under aerobic conditions using DEPMPO derivatives.
Conclusions:
- Spin trapping ESR successfully detected lipid radicals, primarily secondary products, in iron-catalyzed lipid oxidation.
- Lipophilic DEPMPO derivatives are effective for detecting radicals within the lipid phase.
- Distinct radical adducts are formed under anaerobic and aerobic conditions, providing insights into lipid oxidation pathways.
Related Concept Videos
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
01:03Radical 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...
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...
01:11Radical 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...
01:10Radical 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...
Along with electronic factors, steric factors also account...
01:16Radical 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...
01:20Radical Autoxidation
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...