The Research Of 3-hydroxyflavons’ Substituent Effect And Their Application In The Design Of Sensitive Fluorescent Probes

Fluorescence probes have become powerful tools for quantitative,noninvasive and real-time monitoring of interactions among proteins,biomolecules and enzymes in biological systems.As many target molecules are present in only trace amounts,high sensitivity is indispensable for their probe development.A usual method to improve the sensitivity of fluorescence probes is to improve the affinity between probes and target molecules.Based on this strategy,many highly sensitive fluorescence probes have been designed and synthesized.Nevertheless,some of them are highly sensitive for vitro test,but insufficiently sensitive for cell and in vivo experiment.One of the reasons is their short intracellular residence,which means the fluorophores escape from cells fast,and it may reduce their actual sensitivity.In the previous work,we found that there is strong interaction between the 3-hydroxyflavone derivatives and the a-helix structure in protein.a-helix is a common secondary structure in protein,and there are a large number of a-helix-containing proteins in cells that can delay the escape of the fluorescence probes,so that this type of molecules can be used as mother molecules to develop high-sensitivity fluorescence probes for long-term and real-time monitoring of intracellular active species.With this idea in mind,we synthesized a series of 3-hydroxychromones by introducing varied substituents on 4’ and 7 positions.By comparing their fluorescence performance in solvents of different polarities and when interacting with BSA(protein rich in a-helix structure),we found that the substituents’ stronger electron-donating power can shift the absorption and fluorescence spectra to the red,increase fluorescence quantum yield and inhibitor ESIPT effect.By studying their residence time,we found that the residence time of 3-hydroxyflavones could be greatly increased.Finally,we screened out the molecules that are more suitable for design of sensitive fluorescence probes.