Hexafluoro-2-propanol as a potent cosolvent for chemical ligation of membrane proteins

The study on membrane proteins is an important challenge mainly because of their very poor solubility in various solvents. The traditional recombinant expression strategy and the native chemical ligation method both have difficulty in generating sufficient amounts of desired proteins with high efficiency. Previous studies have shown that multiply fluorinated alcohols exhibit good ability to dissolve difficult peptide sequences, especially hexafluoro-2-propanol (HFIP). In the present study we systematically studied the capability of solvents containing different percentage of HFIP in dissolving transmembrane peptides. Through both HPLC and UV analyses we concluded that 60% HFIP/8 M urea constituted a good solvent system. In this solvent system we also optimized conditions to perform native chemical ligation (NCL). Under the optimized conditions we successfully achieved NCL’s for both dipeptide formation and the synthesis of a model protein (Trifolitoxin). These results suggested that HFIP was a potential cosolvent that could be used in the ligation of poorly soluble peptides for the generation of membrane proteins.