The epinephrine assay for superoxide: Why dopamine does not work
| Autor: | David Njus, Roba S Alhasan |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Epinephrine
Semiquinone Dopamine Biophysics Disproportionation Photochemistry Biochemistry Chemical kinetics Adrenochrome chemistry.chemical_compound Catecholamines Superoxides Benzoquinones medicine Indolequinones Molecular Biology Superoxide Cell Biology Hydrogen-Ion Concentration Quinone Kinetics chemistry Yield (chemistry) Catecholamine Biological Assay Oxidation-Reduction medicine.drug |
| Zdroj: | Analytical Biochemistry. 381:142-147 |
| ISSN: | 0003-2697 |
| Popis: | Superoxide oxidizes epinephrine to a semiquinone, initiating a series of reactions leading to the colored product adrenochrome. This popular assay for superoxide is more sensitive at higher pH, and it does not work if dopamine is used instead of epinephrine. A kinetic analysis shows that these effects can be explained by competing reactions that lower the yield of the observed product. The catecholamine quinone may cyclize to form the absorbing product, or it may be reduced back to the semiquinone by superoxide. For epinephrine, the quinone cyclizes quickly and adrenochrome formation dominates, but for dopamine, the quinone cyclizes slowly and the back reaction prevails. The yield of adrenochrome increases if the epinephrine semiquinone reacts with O2 to form more superoxide, but this reaction competes with disproportionation of the semiquinone. Because disproportionation slows as pH increases, both superoxide formation and the yield of adrenochrome increase at higher pH. |
| Databáze: | OpenAIRE |
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