Synthesis,Properties And Functions Of Peptide Based Cu²⁺?Hg²⁺ Fluorescent Probe

With the rapid development of science and technology,the demand for chemical and electronic products in human society has increased sharply.The problem of heavy metal ion pollution caused by unreasonable use and discharge of human beings has become more and more serious,and the living environment of human beings has been seriously threatened.Therefore,how to quickly and effectively detect heavy metal ions in the environment is of great significance to biochemistry,environmental science and life medicine.The research of heavy metal ion chemical probes in the field of analytical chemistry is developing rapidly.An ideal chemical probe should have good selectivity,high sensitivity,easy synthesis and good reversibility.Peptide based chemical probes have attracted much attention due to their many advantages.Among peptide based chemical probes,fluorescent peptide sensing,peptide based colorimetric sensing and electrochemical sensing are more popular.In addition,peptide based chemical probes are widely used in biomedical research due to their good water solubility and biocompatibility.Based on the principle of chemical probes,three peptide-based Cu²⁺and Hg²⁺fluorescent chemical probes were designed and synthesized,and their ion selectivity and function of sensing were studied.The main contents are as follows:1.The research background and design principle of peptide-based heavy metal ion chemical probes are briefly introduced.The research progress of peptide based chemical probes in recent years is summarized.Finally,the research significance of this topic is put forward.2.Study on Cu²⁺,Hg²⁺,and S^2-probe based on fluorescent pentapeptide?D-GHGGW-COOH,D-P5?.Fluorescent pentapeptide?D-GHGGW-COOH,D-P5?was synthesized by Fmoc solid phase peptide synthesis using dansyl chloride as the fluorescent group.The interaction of D-P5 with 17 metal ions and 6 anions was studied by fluorescence spectroscopy.The results show that D-P5 has a special selective effect on Cu²⁺and Hg²⁺,and exhibit"Turn off"and"Turn on"fluorescence responses for Cu²⁺and Hg²⁺,respectively.The interaction of D-P5 with Cu²⁺and Hg²⁺was also characterized by UV-visible absorption spectroscopy.The fluorescence sensing properties of D-P5 on Cu²⁺and Hg²⁺and their influencing factors were further studied.The bonding ratio of D-P5 to Cu²⁺and Hg²⁺was 2:1,and the binding constants were 11.23×10⁵ M^-1/21/2 and 6.54×10⁴ M^-1/2,respectively,and the detection limits were 85.0 nM and 25.0 nM,respectively.In addition,both D-P5-Cu and D-P5-Hg systems showed better selectivity for S^2-,and the detection limits were 0.22?M and 0.38?M,respectively.3.Detection of peptide based Cu²⁺,Hg²⁺and biothiol?GSH,Hcy and Cys?fluorescent chemical probe?D-HPGW-NH₂,D-P4?.By further optimizing the fluorescent pentapeptide?D-GHGGW-COOH?,the peptide based probe Dansyl-HPGW-NH₂?D-P4?for the detection of Cu²⁺and Hg²⁺was synthesized by Fmoc solid phase peptide synthesis.The interaction of D-P4 with 17 metal ions and 6 anions was studied by fluorescence spectroscopy.Similarly,the fluorescent tetrapeptide D-P4 exhibits a good specific binding ability with Cu²⁺and Hg²⁺,while other ions do not interferance its detection.The addition of Cu²⁺leads to fluorescence quenching of the fluorescent peak of D-P4,and the addition of Hg²⁺causes the fluorescence peak of this peptide to undergo a blue shift from 550 nm to505 nm?the fluorescence intensity at 550 nm is gradually decreased,and the fluorescence intensity at 505 nm is gradually increased?.The interaction between D-P4 and Cu²⁺and Hg²⁺was studied by UV-visible absorption spectroscopy and circular dichroism?CD?.The fluorescence sensing properties of D-P4 on Cu²⁺and Hg²⁺and their influencing factors were further studied.The bonding ratios of D-P4 to Cu²⁺and Hg²⁺were 1:1 and 3:1,respectively,and the binding constants were 8.82×10⁴ M^-11 and 2.87×10⁵ M^-1/3,respectively.The detection limits were 105.0 nM and 37.0 nM,respectively.More importantly,the D-P4-Hg system can be used to detect biothiol?GSH,Hcy,and Cys?.The detection limit of Cys in D-P4-Hg system is 82.0 nM.4.Peptide-based fluorescence probe?Dansyl-ECEW-NH₂,DP-4?for detecting Hg²⁺based on fluorescence resonance energy transfer mechanism.Peptide-based probe Dansyl-ECEW-NH₂,D-P4 which specifically detect Hg²⁺,were synthesized by Fmoc solid phase peptide synthesis.DP-4 utilizes a thiol group on a cysteine residue and free carboxyl group on both sides of glutamate to interact with Hg²⁺,resulting in folding of DP-4,shortening the distance between Dansyl and tryptophan residues,resulting in fluorescence resonance energy transfer occurs between the two.Therefore,the addition of Hg²⁺leads to a decrease in the fluorescence peak of tryptophan and an increase in the fluorescence peak of the fluorophore dansyl.The interaction between DP-4 and Hg²⁺was characterized by UV-Vis absorption spectroscopy,circular dichroism and electrochemical methods.The bonding ratio of DP-4 to Hg²⁺was 1:1,the binding constant was 9.09×10⁴ M^-1,and the detection limit was 23.0 nM.The addition of Cys and other biothiol groups will cause the fluorescence peak of the DP-4-Hg system to re-enhance,rather than the"On-Off"regeneration mechanism,which may be the interaction between the biothiol group and the DP-4-Hg system.The detection limit of Cys in the DP-4-Hg system was 52.0 nM.The DP-4-Hg system was more sensitive to the detection of Cys by circular dichroism,and the detection limit was 8.8 nM.