An efficient method for the solid-phase synthesis of fluorescently labelled peptides

Fluorescent labelling of peptides is necessary in a wide range of cell biological applications. In the last decade, the application of cell-penetrating molecules has been advanced by the use of peptides, which have proven efficient in aiding nonpermeant molecules to cross the cell membrane. Currently, the development of new cell-penetrating peptides based on the design and synthesis of labelled peptide libraries is becoming critically important. Here we report an improved method for the solid-phase labelling of peptides, mediated by the activation of 5(6)-carboxyfluorescein with PyAOP/ HOAt.