Off–On Squalene Epoxidase-Specific Fluorescent Probe for Fast Imaging in Living Cells

Abstract

SQLE (squalene epoxidase) is a cell membranebound enzyme. It is a target of fungicides and may become a new target for cancer therapy. Therefore, monitoring the content and distribution of the key enzyme in living cells is very challenging. To achieve this goal, tetraphenyl ethylene-Ter (TPE-Ter) was first designed as a new fluorescent probe to SQLE based on its active cavity. Spectral experiments discovered that SQLE/TPE-Ter shows stronger emission with fast response time and low interference from other analytes. Molecular dynamics simulation clearly confirmed the complex structure of SQLE/TPE-Ter, and the key residues contribute to restriction of TPE-Ter single-molecular motion in the cavity. TPE-Ter-specific response to SQLE is successfully demonstrated in living cells such as LO2, HepG2, and fungi. Imaging of TPE-Ter-treated fungi indicates that it can be used to rapidly assess antifungal drug susceptibility (30 min at least). The present work provides a powerful tool to detect content and distribution of SQLE in living cells.

Molecular Design Strategy of Protein Isoform-Specific Fluorescent Probes by Considering Molecule in Its Entirety

“…As a result, there has been a lack of feasible molecular design strategies. According to previous literature, the detection properties of the fluorescent probe in this category are affected by the interaction between the AIE or TICT fluorophore and amino acid residues. − More than that, some of the fluorophores could be fluorescent probes, which can respond to a protein isoform without a binding group . It means that the detection properties of the fluorescent probe could be affected by any part of the fluorescent molecule.…”