A near infrared fluorescent probe for one-step detection of histone deacetylase activity based on an intramolecular FRET

It is urgent to implement ideal fluorophores to detect enzymatic activity of histone deacetylases (HDACs) because of their important roles in many cellular metabolisms such as transcription regulation and tumorigenesis. However, the emission wavelength of reported one-step fluorescent probes for the detection of HDACs is limited at visible region. In this paper, we construct a near infrared (NIR) fluorescent probe Lys-OBD for detecting the activity of sirtuin 1 (SIRT1), one of the most important HDACs, with NIR emission based on an intramolecular FRET effect. Lys-OBD contains a non-emissive O-aryl NBD group (OBD) and a NIR emissive Cy5 fluorophore. After reaction with SIRT1, non-fluorescence OBD in Lys-OBD was changed to green emissive nitrobenzoxadiazole (NBD) through a deacetylation reaction followed by a backbone rearrangement. An intramolecular FRET between the energy donor NBD and the energy acceptor Cy5 was thus happened and the NIR emission of Cy5 could be detected. This FRET mechanism could further decrease the interference of high-concentration amino acid that are abound in living system in the process of SIRT1 detection. Thus, this probe can not only detect SIRT1 in vitro, but also image SIRT1 in live cells that high express SIRT1 with NIR fluorescence for the first time.