Related Experiment Video
Updated: Feb 12, 2026
14:22
Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
20.8K
The photoreactive free radical in eumelanin
Albertus B Mostert1, Shermiyah B Rienecker2,3, Christopher Noble2
1Department of Chemistry, Swansea University, Singleton Park, Swansea, Wales SA2 8PP, UK.
Science Advances
|March 31, 2018
Summary
Melanin
Area of Science:
- Biophysics
- Materials Science
- Biochemistry
Background:
- Melanin acts as a photoprotective pigment in humans.
- Melanin's electrical properties make it a bioelectronic model for proton-to-electron transduction.
- Melanin's spin properties, involving carbon-centered and semiquinone radicals, are key to its functions.
Purpose of the Study:
- To elucidate the distinct photoreactivity of melanin's two radical species.
- To understand the mechanisms behind melanin's electrical and photoprotective properties.
Main Methods:
- Utilized a novel in situ photoinduced electron paramagnetic resonance (EPR) technique.
- Performed simultaneous electrical measurements alongside EPR.
Main Results:
- Demonstrated distinct photoreactivity between carbon-centered and semiquinone radicals.
- Found semiquinone production is driven by light and water.
- Linked semiquinone photoreactivity to melanin's electrical properties.
Conclusions:
- The light- and water-driven production of semiquinone radicals explains melanin's electrical conductivity.
- This photoreactivity is biologically relevant to melanin's functions.
- The study provides new insights into melanin's role in photoprotection and bioelectronics.
Related Concept Videos
01:16Radical Reactivity: Nucleophilic Radicals
2.7K
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...
2.7K
01:27Radicals
762
Roots, often written as radicals, identify the quantity that must be raised to a specific exponent to produce a given value. A radical expression consists of two main components: the radicand, which is the value placed inside the root symbol, and the index, which indicates the degree of the root being taken. The notation n√a indicates the principal nth root of a. If n equals 2, the operation is the square root, while n = 3 defines the cube root. When n is even, a negative radicand does...
762
01:02Radical Reactivity: Electrophilic Radicals
2.5K
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...
2.5K
01:20Radical Autoxidation
3.2K
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...
3.2K
01:26Radical Equations
387
Radical equations are mathematical expressions in which the variable is found within a radical, most commonly a square root or cube root. These equations frequently arise in science, engineering, and real-world measurements involving nonlinear relationships. To solve a radical equation, the standard procedure is to isolate the radical expression and then eliminate the radical by raising each side to a power equal to the index of the radical. This process may lead to extraneous...
387
01:03Radical Formation: Overview
2.7K
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...
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...
2.7K