The Schiffer–Edmundson helical wheel showed that the amphipathic α-helical structure (containing hydrophobic residues

on one face of the helix and hydrophilic residues on the opposite face) present in the pleurocidin selleck screening library is also present in the Plc-2 (Fig. 3). Pleurocidin is one of the most noteworthy antimicrobial peptides studied in the past few years. It displays a broad spectrum of activity against bacteria, fungus and some leukemical and eukaryotic cells [17]. In general, the activity of AMP depends on the composition of the membranes with which it interacts together with its structural features; primary structure, conformation, net charge, net hydrophobicity, hydrophobic moment, amphipathicity, size, and polar angle [43]. Therefore, to find the minimal active fragment, Plc was further truncated and assayed against a representative set of Gram-positive (S. aureus and E. faecalis) and Gram negative (P. aeruginosa and E. coli) bacteria and fungi. The bacterium S. aureus has acquired a number of genes that provide antibiotic resistance against

all penicillins, including methicillin and other narrow-spectrum β-lactamase-resistant penicillin antibiotics. Recently, it has become the major cause of hospital-acquired infections [33]. The strain P. aeruginosa typically infects the pulmonary tract, urinary tract, burns, and wounds and also causes other blood infections. It has been reported to be responsible for one in ten hospital-acquired infections are from Pseudomonas [30] and [39]. An important distinction for Gram-positive bacteria is that they possess thicker cell wall than Gram-negative organisms. screening assay This peptidoglycan layer of Gram-positive bacteria remains a relatively porous structure [38]. The essential function of the cell wall is to serve as a selective permeability barrier, protecting bacteria from harmful agents, such as detergents, drugstoxins and degradative enzymes, yet allow the penetration of nutrients to sustain bacterial growth. Evidence from genetic

and chemical experiments have proven that the cell wall plays an essential role in providing a selective permeability barrier for S. aureus and other Gram-positive bacteria. The peptide fragments used here caused cell wall effects such as breaks, thinning, and disintegration Casein kinase 1 as well as abnormal septation. Our experimental results using Plc-1–5, which represent the N-terminal, middle, and C-terminal segments of pleurocidin suggested that only the amino acids present in Plc-2 enhanced the permeability of membrane with a similar potency of the parent molecule, which requires passage through the cell wall. Examining the data in Table 1, the hydrophobicity of the peptides was determined not to be a possible element of influence on the observed activities. Therefore, it was assumed that the structure would be a primary contributing aspect to the mechanism of action.