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Light emission from tryptophan oxidation by hypobromous acid.
MedLine Citation:
PMID:  23034821     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The emission of ultraweak light from cells is a phenomenon associated with the oxidation of biomolecules by reactive oxygen species. The indole moiety present in tryptophan, serotonin and melatonin is frequently associated with the emission of light during the oxidation of these metabolites. This study presents results for hypobromous acid (HOBr) oxidation of tryptophan as a putative endogenous source of ultraweak light emission. We found that chemiluminescence elicited by the oxidation of tryptophan by HOBr was significantly higher than by hypochlorous acid (HOCl). This difference was related to secondary oxidation reactions, which were more intense using HOBr. The products identified during oxidation by HOCl, but depleted by using HOBr, were N-formylkynurenine, kynurenine, 1,2,3,3a,8,8a-hexahydro-3a-hydroxypyrrolo[2,3-b]-indole-2-carboxylic acid, oxindolylalanine and dioxindolylalanine. The emission of light is dependent on the free α-amino group of tryptophan, and hence, the indole of serotonin and melatonin, although efficiently oxidized, did not produce chemiluminescence. The emission of light was even greater using taurine monobromamine and dibromamine as the oxidant compared to HOBr. A mechanism based on bromine radical intermediates is suggested for the higher efficiency in light emission. Altogether, the experimental evidence described in the present study indicates that the oxidation of free tryptophan or tryptophan residues in proteins is an important source of ultraweak cellular emission of light. This light emission is increased in the presence of taurine, an amino acid present in large amounts in leukocytes, where this putative source of ultraweak light emission is even more relevant. Copyright © 2012 John Wiley & Sons, Ltd.
Authors:
Maicon Segalla Petrônio; Valdecir Farias Ximenes
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-4
Journal Detail:
Title:  Luminescence : the journal of biological and chemical luminescence     Volume:  -     ISSN:  1522-7243     ISO Abbreviation:  Luminescence     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100889025     Medline TA:  Luminescence     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 John Wiley & Sons, Ltd.
Affiliation:
Departamento de Química, Faculdade de Ciências, Universidade Estadual Paulista, Bauru, Sao Paulo, Brazil; Departamento de Análises Clínicas, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, Araraquara, Sao Paulo, Brazil.
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