Diverted natural Lossen rearrangement for bioconjugation through in situ myrosinase-triggered isothiocyanate synthesis.

The fluorescein isothiocyanate FITC is one of the most extensively used fluorescent probe for the labelling of biomolecules. The isothiocyanate function reacts with lysine residues of proteins to provide a chemically stable thiourea linkage without releasing any by-product. However, diversification of isothiocyanate-based reagents is still hampered by the lack of mild conditions to generate isothiocyanate chemical functions, as well as by their poor stability and limited solutions available to increase water solubility, restricting the use of isothiocyanate labelling to highly water soluble fluorophores. Inspired by plant biological processes, we report a safe and biocompatible myrosinase-assisted in situ formation of isothiocyanate conjugates from a highly water soluble and stable glucosinolate precursor. This method was applied for the fluorescence labelling of a plasmatic protein and fluorescence imaging of living cells.