Introducing Rigidity into the GFP Chromophore via a Boron Bridge: Insights and Application in Two-Photon Imaging

A new family of azaborine fluorophores, consisting of ten compounds, has been developed that mimics the chromophore of green fluorescent protein, with conformation locked by a hydroxyboron bridge. These fluorophores exhibit fluorescence Stokes shifts up to 100 nm (0.56 eV) and high brightness (>10⁴ M^-1 cm^-1) in the 408-525 nm range. Their potential utility for sensing applications was demonstrated by constructing zinc sensors capable of detecting 100 micromolar Zn²⁺ concentrations in biological systems with two-photon microscopy.