title: Length effects in antimicrobial peptides of the (RW)n series.
abstract: A class of antimicrobial peptides involved in host defense consists of sequences rich in Arg and Trp-R and -W. Analysis of the pharmacophore in these peptides revealed that chains as short as trimers of sequences such as WRW and RWR have antimicrobial activity (M. B. Strom, B. E. Haug, M. L. Skar, W. Stensen, T. Stiberg, and J. S. Svendsen, J. Med. Chem. 46:1567-1570, 2003). To evaluate the effect of chain length on antimicrobial activity, we synthesized a series of peptides containing simple sequence repeats, (RW)n-NH2 (where n equals 1, 2, 3, 4, or 5), and determined their antimicrobial and hemolytic activity. The antimicrobial activity of the peptides increases with chain length, as does the hemolysis of red blood cells. Within the experimental error, longer peptides (n equals 3, 4, or 5) show similar values for the ratio of hemolytic activity to antibacterial activity, or the hemolytic index. The (RW)3 represents the optimal chain length in terms of the efficacy of synthesis and selectivity as evaluated by the hemolytic index. Circular dichroism spectroscopy indicates that these short peptides appear to be unfolded in aqueous solution but acquire structure in the presence of phospholipids. Interaction of the peptides with model lipid vesicles was examined using tryptophan fluorescence. The (RW)n peptides preferentially interact with bilayers containing the negatively charged headgroup phosphatidylglycerol relative to those containing a zwitterionic headgroup, phosphatidylcholine.
authors.affiliation: Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Liu
authors.forename: Anna
authors.initials: A
authors.lastname: Brady
authors.forename: Anne
authors.initials: A
authors.lastname: Young
authors.forename: Brian
authors.initials: B
authors.lastname: Rasimick
authors.forename: Kang
authors.initials: K
authors.lastname: Chen
authors.forename: Chunhui
authors.initials: C
authors.lastname: Zhou
authors.forename: Neville R
authors.initials: NR
authors.lastname: Kallenbach
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D017433:Protein Structure, Secondary; D013211:Staphylococcus aureus / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D000890:Anti-Infective Agents; D010446:Peptide Fragments