Design and characterization of peptides with amphiphilic β‐strand structures

Abstract

To extend our studies on peptides and proteins with amphiphilic secondary structures, a series of peptides designed to form amphiphilic β-strand structures was designed, synthesized, and characterized by circular dichroism and infrared spectroscopy. Amphiphilic β-strand conformations may be likely to appear in a variety of surface-active proteins, including apolipoprotein B and fibronectin. In a β-strand conformation, the synthetic peptides will possess a hydrophobia face-composed of valine side chains and a hydrophilic face composed of alternating acidic (glutamic acid) and basic (ornithine or lysine) residues. The peptides studied had a variety of chain lengths (5, 9, and 13 residues), and had the amino groups either free or protected with the trifluoroacetyl group. While the peptides did not possess a high potential for β-sheet formation based on the Chou Fasman parameters, they possessed significant β-sheet content, with up to 90% β-sheet calculated for the 13-residue protected peptide. The driving force for β-sheet formation is the potential amphiphilicity of this conformation. The β-strand conformation of the 13-residue unprotected peptide was stable in 50% trifluoroethanol, 6 M guanidine hydrochloride, and octanol. The peptides are strongly sell-associating in water, which would reduce the unfavorable contacts of the hydrophobic residues with water. It is clear that small peptides can be designed to form stable β-strand conformations.