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TitleThe fluorescent oxidation products of dihydroxyphenylalanine and its esters
Publication TypeJournal Article
Year of Publication2000
AuthorsSmith, G.J., and Haskell T.G.
JournalJournal of Photochemistry and Photobiology B: Biology
Pagination103 - 108
Date Published2000
ISSN10111344 (ISSN)
Keywordsalkalinity, aqueous solution, article, caffeic acid, Caffeic Acids, Dihydroxyphenylalanine, DOPA, ester, Esters, excitation, fluorescence, Hydrogen-Ion Concentration, nonhuman, Oxidation, Oxidation-Reduction, phenol, priority journal, proton transport, Spectrometry, Fluorescence, Spectrophotometry
AbstractDihydroxyphenylalanine (DOPA), its methyl ester (DOPAM) and the N-acetylated derivative of the ester (DOPAMNA) are found to undergo rapid oxidation in air-saturated alkaline solution. Some of the products of oxidation exhibit fluorescent emission in the 300-500 nm spectral range and their excitation-emission spectra have been determined in acidic and alkaline aqueous solutions. The spectral distributions and positions of the maxima depend on the pH of the solution. Excitation-emission maxima associated with the protonated phenolic form of the compounds occur at shorter wavelengths than those of the conjugate base. At some pH values the phenolic forms of these molecules are excited and undergo rapid deprotonation in the excited state; as a consequence, emission is observed from the phenolate anion. The fluorescence excitation-emission spectrum of an authentic sample of 3,4-dihydroxycinnamic (caffeic) acid has also been determined and features of the fluorescence spectra of the principal oxidation products are consistent with the presence of 3,4-hydroxycinnamoyl compounds in solutions of oxidized DOPAM and DOPAMNA. (C) 2000 Elsevier Science S.A. All rights reserved.

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