Related Experiment Video
Updated: Jun 17, 2026
09:18
Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics
Published on: April 17, 2017
Radical sequestration by protein-bound 3,4-dihydroxyphenylalanine
Michelle Nelson1, A Ruth Foxwell, Peter Tyrer
1Faculty of Applied Science, University of Canberra, Canberra, ACT 2601, Australia. michelle.nelson@canberra.edu.au
The International Journal of Biochemistry & Cell Biology
|January 20, 2010
Summary
Protein-bound 3,4-dihydroxyphenylalanine (PB-DOPA) and free DOPA protect cells from oxidative stress. This suggests DOPA
Area of Science:
- Biochemistry
- Cell Biology
- Oxidative Stress Research
Background:
- Protein oxidation generates redox-active 3,4-dihydroxyphenylalanine (PB-DOPA).
- Free DOPA is studied for Parkinson's disease, but PB-DOPA's physiological activity is less understood.
- PB-DOPA occurs beyond neurological tissues, e.g., in atherosclerotic plaques, necessitating broader research.
Purpose of the Study:
- To investigate the antioxidant capacity of free and protein-bound DOPA.
- To determine if PB-DOPA enhances cellular antioxidant defense systems.
- To explore DOPA's potential therapeutic applications in oxidative stress-related diseases.
Main Methods:
- Luminol-enhanced chemiluminescence assay to assess radical scavenging.
- In vitro experiments using monocytes and macrophages exposed to peroxyl radicals.
- Comparison of DOPA's effects with tyrosine.
Main Results:
- Free DOPA directly scavenges peroxyl radicals, distinct from tyrosine.
- Both free and PB-DOPA protect monocytes and macrophages from oxidative damage.
- PB-DOPA generation may enhance cellular antioxidant defenses.
Conclusions:
- Free and PB-DOPA possess significant antioxidant properties.
- DOPA contributes to cellular antioxidant defense mechanisms.
- DOPA shows potential as a therapeutic agent for oxidative stress-related conditions.
Related Concept Videos
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...
00:51Radical 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...
01:19Allosteric Proteins-ATCase
Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
01:17Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
01:29Drugs Affecting Neurotransmitter Synthesis
Drugs affecting neurotransmitter synthesis can impact the adrenergic neuron and the synthesis of neurotransmitters. For example, α-methyltyrosine and carbidopa target specific enzymes involved in catecholamine synthesis. α-methyltyrosine inhibits the enzyme tyrosine hydroxylase, which converts tyrosine into dopamine. By blocking this enzyme, α-methyltyrosine reduces dopamine production and other catecholamines. Carbidopa, on the other hand, inhibits the enzyme dopa decarboxylase, which converts...
01:29Drug Distribution: Plasma Protein Binding
Drugs predominantly attach to plasma proteins, with only a small percentage remaining unbound. The unbound portion can be calculated as one minus the bound fraction. Acidic drugs form large, inactive complexes by reversibly binding to plasma albumin, which prevents them from diffusing across biological barriers. These drug-protein complexes act as reservoirs for the drugs. As the concentration of unbound drugs decreases, these complexes quickly dissociate to release the free drug, maintaining...