Study On The Synthesis And Spectral Properties Of PH Fluorescence Probe Based On Imidazopyridine

Hydrogen ion is one of the important intracellular substances.Many diseases are related to the abnormal concentration of hydrogen ion in cells.Therefore,it is of great significance to build an excellent pH fluorescence probe to accurately track and monitor the fluctuation of pH in cells.At present,most fluorescent pH probes are suitable for weakly acidic organelles or nearly neutral cytoplasm,but the pH probes used in extremely acidic environment(pH<4)are very rare.Although the extremely acidic environment is fatal to most organisms,some prokaryotic cells can not only survive in the extremely acidic environment,but also break the defense mechanism of organisms and lead to many diseases.In this paper,imidazo[1,2-a]pyridine compounds are selected as receptors,double bonds are used as bridges to connect different strength donors,and two novel pH fluorescence probes are designed and synthesized,which are suitable for extremely acidic environment.Their spectral properties and biological imaging in extremely acidic environment are studied.The specific contents include the following two aspects:1.Synthesis and spectral properties of a pH fluorescence probe based on imidazolidineUsing imidazo[1,2-a]pyridines as acceptors and double bond as bridge to connect phenothiazine,10-(2-(2-methoxyethoxy)ethyl)-3-(2-(2-phenylimidazo[1,2-a]pyridine-7-yl)vinyl)-10h phenothiazine was designed and synthesized.The results of pH titration showed that with the decrease of pH in the system(7.0-0.4),the UV absorption intensity of the compounds decreased at 399 nm,and increased at 419 nm.The fluorescence emission intensity at 573 nm decreased with the decrease of pH value.In addition,the p K_aof the compound is 3.07.The experimental data show that the compound can be used as a new pH fluorescence probe in extremely acidic environment.However,because the emission spectrum of the probe is single emission wavelength,it is not a ratio probe,and the fluorescence monitoring signal is easily affected by environmental factors,so it is not further applied to biological imaging,but it provides data support for the design and synthesis of fluorescent probes suitable for extremely acidic pH.2.Synthesis and application of imidazolylpyridine ratio based pH fluorescence probe to track and monitor pH fluctuation in E.coliUsing N,N-dimethylaniline as donor and 2-(4-methoxyphenyl)imidazo[1,2-a]pyridine as electron acceptor,the compound(E)-4-(2-(2-(4-methoxyphenyl))imidazo[1,2-a]pyridine-7-yl)vinyl)-N,N-dimethylaniline was designed and synthesized by ethylene bridge.The results of pH titration showed that with the decrease of pH(6.5-2.2),the UV absorption intensity of the compound decreased at 385 nm,and increased at 425nm;the fluorescence emission intensity decreased at 500 nm,and increased at 580 nm.The absorption and emission spectra of the compound show obvious changes,showing two emission wavelengths with different ratios.In addition,the p K_aof the compound is 3.3.The experimental data show that the compound can be used as a new ratio type pH fluorescence probe in extremely acidic environment,and can accurately track and monitor the pH fluctuation in E.coli.