Locking the GFP Fluorophore to Enhance Its Emission Intensity

Abstract

The Green Fluorescent Protein (GFP) and its analogues have been widely used as fluorescent biomarkers in cell biology. Yet, the chromophore responsible for the fluorescence of the GFP is not emissive when isolated in solution, outside the protein environment. The most accepted explanation is that the quenching of the fluorescence results from the rotation of the aryl–alkene bond and from the Z/E isomerization. Over the years, many efforts have been performed to block these torsional rotations, mimicking the environment inside the protein β-barrel, to restore the emission intensity. Molecule rigidification through chemical modifications or complexation, or through crystallization, is one of the strategies used. This review presents an overview of the strategies developed to achieve highly emissive GFP chromophore by hindering the torsional rotations.

A Molecular Hybrid of the GFP Chromophore and 2,2′-Bipyridine: An Accessible Sensor for Zn2+ Detection with Fluorescence Microscopy

“…However, in its bare form it loses the fluorescence due to non-emissive relaxation via intramolecular rotations [ 22 ]. Locking the conformation permanently or conditionally has been explored creatively to prepare various fluorescent dyes and sensor derivatives of the GFP chromophore [ 20 , 23 , 24 , 25 ].…”

Viscosity-Induced Emission of 5-(Diarylmethylene)imidazolone with Extended Conjugation <i>via</i> Attachment of <i>N</i>-Methylpyrrole at the 2-Position

“…Owing to the rapid nonradiative decay caused by intramolecular bond rotations such as a Z/E-photoisomerization and a twist of the benzylidene single bond, HO-BDI emits fluorescence when conjugated with the β-barrel tertiary structure of proteins but not in the free state. [7][8][9] Therefore, HO-BDI can be applied to ON/OFF switchable fluorescence systems by controlling the bond rotations. To exploit this property of the BDI structure, various synthetic BDI analogs have been developed to date.…”