Fluorescence quenching of tryptophan, 4-methyl- 2,6-diformylphenol and 5-hydroxytetracycline by ethylene trithiocarbonate at high pH

Abstract

Ethylene trithiocarbonate (ETTC) s shown to quench the fluorescence of tryptophan (Trp), 4-methyl-2,6-diformylphenol (Mfp) and 5-hydroxytetracycline (Htc) in aqueous alkaline medium at 300K. Rate constant measurements indicate that in all the three cases the quenching process is not entirely deactivation of the excited state, but in part may be due to association between fluorescers and quencher in its ground state, as shown by positive curvatures in Stern-Volmer plots. Bimolecular rate constants (<em>k</em>_q) are obtained from steady-state measurements leading to a modified form of the Stern-Volmer equation.