1.D.47 The Pore-forming Synthetic Cyclic Peptide (PSCP) Family
Amino acid composition determines the ability of cyclic peptides to form transmembrane channels in lipid bilayers. The self-assembly of alt-(l,d)-alpha-cyclic octapeptides has been investigated (Danial et al., 2015). Cyclic peptides comprising d-leucine, alternating with different combinations of l-azidolysine, l-lysine (Alloc), l-lysine and l-tryptophan were synthesized, and the sizes of pores formed via self-assembly of these molecules in lipid bilayers was elucidated using large unilamellar vesicle fluorescence assays and dynamic light scattering. Pore formation was examined in large unilamellar vesicles made up of egg yolk phosphatidylcholine or Escherichia coli total lipid extracts. Cyclic peptides with charged side chains form large pores while those with neutral side chains form unimeric pores. Cyclic peptides that consist of non-symmetric amino acid configurations possess higher membrane activity than the cyclic peptides with a symmetric amino acid configuration. Peptide amphiphilicity plays vital roles in selective partitioning between bilayers that consist of different lipid compositions (Danial et al., 2015).