Chemoselective Fluorogenic Bioconjugation of Vicinal Dithiol-Containing Proteins for Live Cellular Imaging via Small Molecular Conjugate Acceptors

To develop small molecular fluorogenic tools for the chemoselective labeling of vicinal dithiol-containing proteins (VDPs) in live cells is important for studying intracellular redox homeostasis. With this research, we developed small molecule-based fluorescent probes, achieving selective labeling of VDPs through thiol-thiol substitutions on bisvinylogous thioester conjugated acceptors (IDAs). Initially, IDAs demonstrated its ability to bridge vicinal cysteine-sulfhydryls on a peptide as a mimic. Then, the peptide complex could be decoupled to recover the original peptide-SH in the presence of dithiothreitol. Furthermore, fluorometric signal amplification of the fluorescent probes occurred with high sensitivity, low limit of detection, and selectivity toward vicinal dithiols on reduced bovine serum albumin, as an example of real world VDPs. More importantly, the probes were utilized successfully for labeling of endogenous VDPs at different redox states in live cells. Thus, the bisvinylogous thioester-based receptor as a functional probe represents a new platform for uncovering the function of VDPs in live cells.