English: FSLs can be easily created from cysteine-containing peptides, proteins or any other thiols of biological interest. The mixing of a cysteine containing peptide with FSL-RFG(Maleimide), in 4MMF buffer, allows the peptide to react with the maleimide residue of the FSL (through the well-known Michael nucleophilic addition reaction). Following overnight incubation then vacuum drying, an FSL peptide is created. No purification is required.