Removable Backbone Modification (RBM) Strategy for the Chemical Synthesis of Hydrophobic Peptides/Proteins

Chemical synthesis can provide hydrophobic proteins with natural or man-made modifications (e.g. S-palmitoylation, site-specific isotope labeling and mirror-image proteins) that are difficult to obtain through the recombinant expression technology. The difficulty of chemical synthesis of hydrophobic proteins stems from the hydrophobic nature. Removable backbone modificaiton (RBM) strategy has been developed for solubilizing the hydrophobic peptides/proteins. Here we take the chemical synthesis of a S-palmitoylated peptide as an example to describe the detailed procedure of RBM strategy. Three critical steps of this protocol are: (1) installation of Lys6-tagged RBM groups into the peptides by Fmoc (9-fluorenylmethyloxycarbonyl) solid-phase peptide synthesis, (2) chemical ligation of the peptides, and (3) removal of the RBM tags by TFA (trifluoroacetic acid) cocktails to give the target peptide.