Synthesis and characterization of fluorescent oligo(3,4,5-triethoxycarbonyl-2-pyrazoline)

Pseudopeptide oligomers as newly developing fluorescent macromolecules are of significant importance and fairly attractive in bioimaging of living cells. We report that a type of efficient fluorescent pseudopeptide oligo(3,4,5-triethoxycarbonyl-2-pyrazoline) is prepared by the novel cyclo-polycondensation of 3,4,5-triethoxycarbonyl-2-pyrazoline that is a weakly-fluorescent chromophore. The pseudopeptide oligomer exhibits a strong red-shift and remarkable fluorescence enhancement compared with the monomer 2-pyrazoline and images living cells in good quality, even though it only consists of fewer than 70 glycine residues whereas for the famous green fluorescent protein (GFP) the amount of the various natural amino acid residues is 238. Oligo(3,4,5-triethoxycarbonyl-2-pyrazoline) is a GFP-mimetic but structurally-simplified fluorescent pseudopeptide with simple chemistry, generated from the only natural resource of glycine.