Design of highly stabilized beta-hairpin peptides through cation-pi interactions of lysine and n-methyllysine with an aromatic pocket.

Two tryptophan residues were incorporated on one face of a beta-hairpin peptide to form an aromatic pocket that interacts with a lysine or N-methylated lysine via cation-pi interactions. The two tryptophan residues were found to pack against the lysine side chain forming an aromatic pocket similar to those observed in trimethylated lysine receptor proteins. Thermal analysis of methylated lysine variant hairpin peptides revealed an increase in thermal stability as the degree of methylation was increased, resulting in the most thermally stable beta-hairpin reported to date.