Syntheses And Spectral Properties Of Cyanine Dyes As Fluorescent Probe Molecules

Cyanine dyes are widely used for the labelling of biological molecules especially for nucleic acids as biological fluorescent probes. These dyes demonstrate high molar extinction coefficient and low fluorescent background. Their fluorescent excitation and emission wavelength ranges from visible region to near-infrared region, which can be suitable for different excitation sources. Cyanine dyes are now one of the newest and most studied ones in fluorescent probes.Benzyl bromide is used to simulate chloro-resin which has the same functional group to synthesize fluorescent dyes of thiazole orange series. This method provides a reference for solid-phase synthesis using chloro-resin. Two different synthetic routes are used to embellish the fluorescent dyes and three dyes of thiazole orange series with different substituents are gained. Their synthetic conditions and influencing factors are discussed.An indole fluorescent dye with polymethine is synthesized. UV-VIS spectra of four dyes are studied and the influences of the substituents'introduction to the dyes are discussed. References of the embellishing of the thiazole orange dyes are provided. The introduction of methyl widens theπconjugated system and makes the absorption maximum red shift of 10 nm, while the introduction of chlorine has no influences with the absorption maximum. Dye 4 has larger absorption maximum compared with thiazole orange dyes and its additional methine in the bridge structure has great significance.According to the labelling characteristic of cyanine dyes and nucleic acid, different dyes are used to labelled proteins. UV-VIS and fluorescent spectra of the 4 dyes bound with proteins are studied. After the binding, absorption maximum of each dye has a red shift compared with their free state in water solution and fluorescent maximum reaches 600 nm.