A fluorogenic probe for SNAP-tag protein based on ESPT ratiometric signals

Protein self-labeling tags achieve selective fusion and labeling of target proteins through genetic coding technology,but require exogenous fluorescent probes with fluorogenicity for protein tag binding to have the performance of wash-free fluorescence imaging in live cells.In this paper,we reported a fluorogenic probe 1 capable of ratiometric fluorescence recognition of SNAP-tag proteins.In this probe,the O6-benzylguanine derivative of 3-hydroxy-1,8-naphthalimide underwent a selective covalent linkage reaction with SNAP-tag protein.The hydroxyl group on the naphthalimide fluorophore formed a hydrogen bond with the functional group near the protein cavity.The excited state proton transfer occurred after illumination,to obtain the ratio fluorescence signal from blue emission to red emission,realizing the wash-free fluorescence imaging of the target proteins.