Research On Syntesis、spectral Properties And Application Of Polymethine Cyanine Dyes

Cyanine dyes have been widely used as fluorescence probes in biomolecular analysis field due to their large molar extinction coefficient, wavelength turnability and the obvious change of the spectrum when associate with biological moleculars. Recently, more and more literatures reported about the application of cyanine dyes as fluorescent labels in protein determination, analysis of nucleic acid, staining of living cells, the recognition of tumor cells, the detection of pH and ions. To improve the photo-stability and spectra properties of cyanine dyes through the change of the structures is meaningful in bioanalysis.Seven novel asymmetric trimethine benzothiazole cyanine dyes with different N-substituents were synthesized and characterized by MS and 1H-NMR. To get an insight into the photostabilities of the dyes, photodegradation behaviors were determined in ethanol. The results showed that the octyl and benzyl groups on nitrogen atoms of quinoline ring enhanced the photostabilities of the dyes obviously. To study the different influence of the dyes with different substituted groups on the Dye-BSA association,6a-6d were chosen to test the absorption and emission spectra in the presence of BSA. The fluorescent emission enhanced greatly with the increasing concentration of BSA. It showed that dye 6b performed the largest linear range and better linear relationship with short reaction time.A heptamethine indocyanine dye with good water-solubility and a heptamethine indocyanine dye with oil-solubility were synthesized and characterized in this paper. Spectral properties in different solvents and different concentrations of CTAB were measured. This fluorescence mutation gives a direct indication for the micelle forming process and provides a simple and near infrared method for the determination of the critical micelle concentration of the surfactant. Three novel near-infrared N-meso-substituted heptamethine cyanine dyes have been designed and synthesized and their photochemical properties were tested. They have large Stokes shifts of more than 100 nm. We tested their spectra properties in different solvents, dual fluorescence peak occurred in weak polar solvents, while single fluorescence peak occurred in polar solvents. This kind of cyanine dyes may exist excited-state intramolecular charge transfer (ICT) phenomena. We measured their fluorescent emission in weak polar-polar mixed solvents to clarify the relationship between ICT phenomena and the polarity of solvents. We also have measured their absorption and fluorescence spectra in different pH phosphate buffer solutions, and the absorption and fluorescence spectra of piperazine-substituted heptamethine cyanine dye were sensitive to the pH values of the solution, and it is a nice pH label. The photodegradation experiment showed that the introduction of electron withdrawing group on methane chain would improve the photo-stability of the dye, while electron donating group would decrease the photo-stability.