Studies On The Synthesis And Biological Application Of Peptide-based Fluorescence Chemosensors

In the cell,protein and metal ions binding motifs play important roles in maintaining the normal biological functions.For example,Zinc-finger protein,a finger-shaped protein fold that is formed by Histidine?His?and Cysteine?Cys?in the protein binding to a Zn²⁺,is related to gene transcription and regulation;EF-hand,a helix-loop-helix structural motif which Aspartic acid?Asp?and Glutamic acid?Glu?offer the chelating sites with calcium,plays an important role in cell proliferation,differentiation and apoptosis;Metalloproteinase contains metal ions in the active sites and the loss of these metal ions can lose its enzymatic activity;Fe3+ and Cu²⁺ is an important part of photosynthesis and oxidative phosphorylation of the electron transport chain.The characteristics of these binging motifs from the biological macromolecules provide a large amount of chemical information to mimic the natural protein and metal ion binding motifs.The peptide-based fluorescence chemosensor is designed by this idea and offers a powerful tool to disclose the key roles of metal ions in the cell.Recently,design and application of peptide-based fluorescence chemosensors has been widely concerned,a number of domestic and foreign research groups reported many peptide-based fluorescence chemosensors.Compared to other chemosensors,peptide-based fluorescence chemosensors have special advantages,?1?solid phase peptide synthesis?SPPS?technique is a mature method for the modification of peptide chains with different fluorophores,thus the sensitivity and selectivity of peptide fluorescence chemosensors can be optimized by changing the peptide backbones;?2?the water solubility,biocompatibility and low toxicity of peptide-based fluorescence chemosensors are superior to organic ones,pure water detection and biological applications can be successfully actualized;?3?the response type of peptide chemosensors can be easily created by different mechanisms,such as photoinduced electron transfer?PET?,fluorescence resonance energy transfer?FRET?and chelation enhanced fluorescence?CHEF?.In views of these advantages,we have successfully designed and synthesized a series of novel peptide-based fluorescence chemosensors for monitoring several analytes including Zn²⁺,Cd²⁺,Cu²⁺,S2-and H2 S,and the realization of pure water detection and biological applications.This dissertation can be divided into seven parts.Chapter I: The design principles and research background of fluorescence chemosensors have been concisely reviewed.In particular,the development and application of peptide-based fluorescence chemosensors have been summarized.Chapter II: A novel multifunctional peptide fluorescence chemosensor?L1?base on Fmoc-Lys?Fmoc?-OH backbone has been designed and synthesized,L1 is a promising analytical tool for detecting Zn²⁺,Cu²⁺,and S2-based on different mechanisms in 100% aqueous solutions,and intracellular biosensing has been successfully actualized.Chapter III: On the basis of L1,we has been synthesized a novel peptide-based fluorescence chemosensor L2 for detecting Cd²⁺ based on photo-induced electron transfer?PET?effect by changing the amino acid in 100% aqueous solution,L2 showed excellent cell permeation and low biotoxicity,can be applied to detect Cd²⁺ effectively in He La cells.Chapter IV: We report a novel tetra-peptide fluorescence chemosensor L3 for detecting Zn²⁺based on the photo-induced electron transfer?PET?effect by turn-on response in 100% aqueous solution.Furthermore,we replacement out Zn²⁺ in L3-Zn complex system by chelating agent EDTA,thus detecting EDTA by L3-Zn complex system.L3 can penetrate live HeLa cells and detect intracellular Zn²⁺ and EDTA.Chapter V: A novel peptide-based fluorescence chemosensor L4 for detecting Zn²⁺ based on different excitation wavelengths in 100% aqueous solution and living cells have been designed and synthesized.One is the fluorescence resonance energy transfer?FRET?effect by ratiometric response at an excitation wavelength of 290 nm,while the other is the chelation enhanced fluorescence?CHEF?effect by turn-on response at an excitation wavelength of 330 nm.Chapter VI: We successfully developed a novel multifunctional peptide fluorescence chemosensor L5 based on tetra-peptide.The chemosensor L5 displays “On-Off-On” response type fluorescence change with added Cu²⁺ and S2-to the aqueous media.In addition,L5 showed excellent cell permeation and low biotoxicity,can be applied to continuity detection by“On-Off-On” response in live He La cells.Chapter VII: On the basis of L5,we have presented a novel peptide-based fluorescence chemosensor L6 by changing the fluorophore,which offer binding sites to coordinated with copper ions?L6-Cu?.After a fast fluorescence quench by Cu²⁺ coordinated with L6 by Cu²⁺-removal sensing mechanism,the fluorescence of L6 is recovered by adding hydrogen sulfide to form insoluble copper sulfide,thus L6-Cu system can detecting H2 S in aqueous media and can be used for imaging both in living cell and zebrafish larvae.