α,α-Dehydrophenylalanine containing cecropin-melittin hybrid peptides: conformation and activity

Abstract

Synthesis and conformational studies of a cecropin-melittin hybrid pentadecapeptide CA(1-7)MEL(2-9), and its three α, β-dehydrophenylalanine (ΔPhe) containing analogs in water-TFE mixtures are described. ΔPhe is placed at strategic positions in order to preserve the amphipathicity of the molecule. The wild type CAMEL0 and its three analogs, containing one, two and three ΔPhe residues namely CAMELΔPhe1, CAMELΔPhe2 and CAMELΔPhe3 respectively were synthesized in solid phase and their conformation determined by CD and NMR. CAMELΔPhe2 and CAMELΔPhe3 peptides exhibit the presence of 3₁₀-helix and β-turns in the former and only turns in the latter. CAMELΔPhe1 peptide was found to have a largely extended conformation. Antibacterial and hemolytic activities of the peptides were also evaluated. CAMELΔPhe2 peptide is maximally potent against both Staphylococcus aureus ATCC 259230 and Escherichia coli ATCC 11303. CAMELΔPhe1 with a single ?Phe at the center shows minimal hemolysis.