Discovery of a Turn-On Fluorescent Probe for Myeloid Cell Leukemia-1 Protein.

The environment-sensitive probe 2 with turn-on switch for Mcl-1 protein was developed herein. After careful evaluation, this small molecule fluorescent probe revealed a selective binding affinity with Mcl-1 protein with a Ki value of 2.6 μM and can be well applied to imaging Mcl-1 protein or detecting the cellular distribution of Mcl-1 protein inhibitors. Compared with other imaging approaches, such as the immunofluorescence and fluorescent protein-based techniques, this fluorescent method is rapid, convenient, and affordable, especially since a washing procedure is no longer needed. This environment-sensitive "off-on" design strategy may present a case in point for developing small-molecule fluorescent probe of Bcl-2 family proteins.