PHOTOCHEMICAL PROCESSES IN MOLECULES OF POLYMETHINE DYE PROBES IN THE PRESENCE OF BILE SALTS

Abstract

Rimary photochemical processes in molecules of polymethine dye probes 3,3 ¢ -di(g-sulfopropyl)-4,5,4 ¢ ,5 ¢ -dibenzo-9-ethylthiacarbocyanine betaine (DEC) and 3,3 ¢ ,9-trimethylthiacarbocyanine iodide ( Cyan 2) in the micellar systems of bile salts sodium cholate, sodium deoxycholate, and sodium taurocholate, as well as, for comparison, sodium dodecyl sulfate (SDS), have been studied by flash photolysis. Upon flash photolysis of aerated aqueous solutions of the dyes in the presence of micelles of bile salts and SDS, signals due to photoisomerization of the trans-isomers of the dyes and back dark isomerization of cis-photoisomers formed are observed. The lifetimes of the photoisomers are in the range of 60-190 μs. Moreover, upon flash photolysis of deoxygenated solutions of Cyan 2 and DEC in the presence of micelles of bile salts and SDS, in addition to photoisomerization, the transition of the dyes to the excited triplet state and the subsequent backward transition (intersystem crossing) to the initial singlet state occur. For comparison, the triplet-triplet absorption spectra of the isomers of the dyes have been obtained by the method of triplet-triplet energy transfer from anthracene in polar (ethanol, isopropanol) and nonpolar (dioxane) solvents. A conclusion is drawn about the similar photochemical behavior of the dyes in the micellar systems of bile salts and SDS.