QUENCHING OF CHEMICALLY and ENZYMICALLY-GENERATED TRIPLET ACETONE BY TYROSINE and 3,5-DIHALOGENODERIVATIVES |
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| Authors: | Edy Rivas-Suárez Luiz H Catalani Etelvino J H Bechara Giuseppe Cilento |
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| Institution: | Department of Biochemistry, Instituto de Quimica, Universidade de Sāo Paulo, C.P. 20780, Sao Paulo, S.P., Brazil |
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| Abstract: | Tyrosine and especially its 3,5-dihalogenoderivatives quench acetone triplets. When the excited acetone is generated free in solution, the Stern-Volmer plots for the quenching by these species, monitored via the sensitized emission of the 9,10-dibromoanthracene-2-sulfonate ion, are linear. When triplet acetone is generated enzymically by the peroxidase-catalyzed aerobic oxidation of isobutyral-dehyde, the Stern-Volmer plots for the quenching of the acetone phosphorescence curve upwards in the case of 3,5-dibromotyrosine and even more markedly with 3,5-diiodotyrosine. Quenching appears likely to occur by triplet-triplet energy transfer and especially in the case of the phenoxide form, also by electron transfer. The curvature denotes a static contribution to quenching favoured by the enzyme. |
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