Fluorogenic tagging of peptides via Cys residues using thiol-specific vinyl sulfone affinity tags

Fluorescent tagging of Cys-containing peptides is presented herein. The procedure follows a two-step sequential reaction scheme using thiol specific bifunctional chemical reporters and fluorogenic labels. Vinyl-sulfone bearing chemical reporters have been synthesized and demonstrated to selectively modify cysteine under physiological conditions in the presence of other nucleophilic amino acids. Bifunctional chemical reporters decorated with a terminal alkyne moiety, suitable for modification with azide containing fluorogenic labels were also synthesized. Such fluorogenic (turn on) labels in combination with these new vinyl-sulfone tags can be used generally in fluorescent modulation schemes of thiol-bearing biomolecules.