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Tryptophan Quenching of Zinc‐Phthalocyanine and Porphycene Fluorescence in Micellar CTAC
Author(s) -
Daraio Marta E.,
Völker Axel,
Aramendia Pedro F.,
Román Enrique San
Publication year - 1998
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1998.tb05213.x
Subject(s) - chemistry , quenching (fluorescence) , photochemistry , fluorescence , tryptophan , flash photolysis , triplet state , zinc , electron transfer , singlet state , phthalocyanine , structural isomer , excited state , reaction rate constant , kinetics , organic chemistry , molecule , biochemistry , physics , amino acid , quantum mechanics , nuclear physics
Singlet excited state deactivation of a zinc phthalocyanine (ZnPc), porphycene (Po) and tetrapropyl‐porphycene (PrPo) by anionic tryptophan (Trp − ) were investigated in cetyltrimethylammonium chloride (CTAC) micelles at pH 9.2 ± 0.1, regulated by a Tris buffer. Data obtained from steady‐state experiments over a wide range of detergent and added NaCl concentrations were analyzed by using a pseudophase ion‐exchange model (Abuin et al., J. Phys. Chem . 87, 5166–5172, 1983). The model was applied to derive singlet quenching rate constants for ZnPc and the porphycenes by Trp − and the selectivity coefficient for Trp/Cl exchange at the micellar surface. The results point to an electron transfer quenching. Neutral tryptophan also quenches efficiently ZnPc fluorescence in CTAC without added buffer and Trp − does not deactivate the triplet state of these dyes. By flash photolysis, only the absorption of the triplet species was detected.