Research On Construction And Application Of Polyaryl-Substituted Imidazoles As Organic Fluorescent Molecules

Organic fluorescent molecular probes have the advantages of high sensitivity,simple operation,good reproducibility,good membrane permeability,and in situ detection,and are widely used in in-situ real-time nondestructive testing and monitoring of target molecules and their biological processes in biological systems,and have increasingly become indispensable molecular tools in modern life sciences and disease diagnosis.Imidazole is an important building block of fluorescent materials,and its derivatives have excellent photophysical properties such as narrow spectral characteristics,high quantum efficiency and efficient electrons,and proton transport,and are widely used in fluorescence sensors,light-emitting materials,organic light-emitting diodes,biomarkers and cell imaging.In addition,the structure of imidazole also has unique biological and physiological activities,and has potential application prospects in biomedical fields such as antibacterial,antitumor,anti-inflammatory,and photodynamic therapy.Therefore,the construction of novel imidazole excellent fluorescent organic molecules and the study of their interaction with biological macromolecules are of great significance for the development of biosensing analysis and bioactive applications of novel imidazole probes.This paper designed and synthesized a series of aryl imidazole compounds,and studied their applications in G-quadruplex DNA（G4 DNA）and lipase recognition through spectroscopic studies,molecular docking simulations,and cell imaging methods.The binding mechanisms of different types of imidazole fluorescent molecules to target biomacromolecules were explored.The main results are as follows:（1）Compared with the traditional G4 DNA recognition probe based on large con Jugate planar framework,we first proposed a design strategy of non-planar molecular fluorescent probe for targeted recognition of non-parallel configuration G4 DNA structures.We introduced a G4 DNA groove recognition group into the tetraarylimidazole fluorescence backbone to design a nonplanar molecular probe AI9.The recognition effect of AI9 with various types of DNA was studied spectroscopy,and the results showed that AI9 could specifically target the recognition of G4 DNA with mixed telomere configuration.The binding mechanism study showed that AI9 and 22AG were partially embedded in the ends and grooves of mixed-configuration G4 DNA in a 1:1 ratio.In addition,the cell imaging experiments of AI9 showed that it can be effectively localized to the nucleus,which was expected to become a fluorescent probe for nucleolar telomere G4 DNA.（2）On the basis of the above work,combined with the current defect of false positive signals caused by the interference of external environmental factors in most probe molecules,we designed a new type of molecular probes that are not sensitive to the environment.A novel fluorescent probe ACPS was synthesized by introducing arylimidazole molecular vortex in the traditional D-π-A type molecular unit.The probe was environmentally insensitive and exhibits fluorescence"always off"in a variety of polar environments,avoiding"false"positive signals caused by changes in environmental polarity.The probe ACPS was specifically selective to bind G4 DNA with a limit of detection（LOD）as low as 18 n M and a binding constant（Kd）of 7.09×10⁴ M^-1.Binding site studies have shown that ACPS are mainly stacked at the 5’end of G4 DNA and were associated with partial groove interactions.Meanwhile,ACPS enabled fluorescence visualization in cell imaging and high-fidelity G4 DNA structure sensing in complex systems.（3）Finally,we explored the recognition and application of imidazole derivatives in proteases.Two D-π-A fluorescent molecules LA4 and QL-7 with different side chains were designed with tetraarylimidazole group as electron donor and quinoline salt as electron acceptor.The influence of substituents on the binding mechanism of fluorescent ligands to lipases was studied by spectroscopy,thermodynamics and molecular docking.The results showed that both ligands LA4and QL-7 bound to lipase and entered the hydrophobic domain of lipase,which was enhanced by inhibition of fluorescence due to the TICT process.Binding site studies have shown that ligands LA4 and QL-7 bind to lipases mainly hydrogen bonds and van der Waals forces,which affected the microenvironment around tyrosine and tryptophan residues when bound,but were not enough to change the secondary structure of lipase.Lipase inhibition experiments showed that the ligands LA4 and QL-7 could inhibit lipase activity in vitro,and LA4 had a stronger inhibitory effect on lipase activity.The results showed that the ligand LA4 with flexible amine side chains has a stronger specific sensitivity and binding ability to lipase.