Dye-sensitized photo-oxidation of amino acids in reversed micellar membrane mimetic system

Abstract

The photochemistry of a novel photosensitizer H[TBC(OiPr)4P(OH) 1, and the photo-oxidation of amino acids sensitized by H[TBC(OLPr)4P(OH)] have been investigated in the AOT/HzO/toluene reversed micellar system. Absorption and fluorescence measurements indicate that H[TBC(OiPr)4(OH)1 can interact with the reversed micelles by adsorption to the micellar surface, resulting in the disaggregation of the sensitizer and the enhancement of its photoactivity. In micellar solutions, H[TBC(OiPr)4P(OH)] can efficiently photo-generate1O2(Type II mechanism) and\( O_2^{\mathop .\limits^\_ } \) (Type 1 mechanism) as shown by stationary photolysis and ESR spin-trapping techniques. Amino acids dissolved in water pools of reversed micelles can be photo-oxidized via Type ll mechanism as sensitized by H[TBC(Oi'Pr)4P(OH) ]. The photo-oxidation of tryptophan follows the first-order kinetics, while that of tyrosine is much slower. Kinetic studies of the photodynamic behavior in this microheterogeneous system shows that the microheterogeneity can alter the mechanism and the kinetic-controlling factors of photosensitization reaction.