Self-assembly of green fluorescent protein chromophore analogue to form microfibers: Inhibited and disassembled by Hg2+ through Z-E isomerization

Abstract

A novel analogue of the green fluorescent protein (GFP) chromophore, named p-DBCI, was synthesized via a 2,3-cycloaddition reaction. The compound was structurally characterized using NMR, HRMS, and single crystal X-ray diffraction, confirming its Z-form conformation in both solid and solution phases. While exhibiting low fluorescence quantum yields in solution, p-DBCI showed strong fluorescence emission in the solid state, indicating aggregation-induced emission (AIE) properties. p-DBCI demonstrated a remarkable ability for self-assembly, forming regular microrods with intense fluorescence through a solvent exchange method. The presence of Hg2+ was found to inhibit and disassemble the self-assembly of p-DBCI, leading to fluorescence quenching via Z-E isomerization driven by strong complexation between p-DBCI and Hg2+. The ability of Hg2+ to induce Z-E isomerization in GFP analogs has been rarely reported. Furthermore, the fluorescence intensity of p-DBCI assemblies in water solution exhibited a highly linear relationship (R2= 0.9992) with increasing concentrations of Hg2+, suggesting that p-DBCI could serve as a sensitive probe for quantitatively detecting Hg2+ in aqueous solutions. These findings offer new theoretical guidance for exploring and utilizing the solid fluorescence properties of GFP analogues.