Tryptophan Quenching of Zinc-Phthalocyanine and Porphycene Fluorescence in Micellar CTAC
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 experim...
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| Autores principales: | , , , |
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00318655_v67_n4_p371_Daraio |
| Aporte de: |
| Sumario: | 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. |
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