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The effect of substituting two glycine residues, Gl[y.sup.8] and Gl[y.sup.13] with Ala or Pro on the peptide's structure and biological activities is examined to develop novel antibiotic peptides with selectivity for bacterial cells. It is demonstrated that the Gly-Pr[o.sup.8] is an excellent candidate lead compound for the development of novel antimicrobial agents.

The rotational-echo double-resonance solid-state NMR distance measurements are employed to the intermolecular packing and the membrane-bound dimer structure of a [beta]-hairpin antimicrobial peptide, Protegrin-1 (PG-1) in various lipid bilayers. The analysis shows that the peptide is parallely packed in the lipid bilayer and may be stabilized by strong amphipathic character and hence facilitates its insertion in the amphipathic lipid bilayer.

Antimicrobial peptides (AMPs) are old components of innate immunity found in all living pluricellular organisms. The study highlights the importance of a single alpha-amino acid epimerization as a tool used by nature to modulate the activity of AMPs and the findings suggest bombinins H as potential templates for the development of new drugs with a new mode of action against Leishmania.

An observation about SigB that contributes positively to Listeria monocytogenes tolerance of the bacteriocins nisin and lacticin 3147 and of the antibiotics ampicillin and penicillin G. is presented. The results showed that SigB might contribute to the survival of Listeria monocytogenes both in the food-processing environment and in vivo during infection which might represent an attractive target for the development of new control and treatment strategies for this important pathogen.

A three-dimensional computer model of bio-film dynamics was developed as a tool for investigating mechanisms of protection from antimicrobial agents in bio-films. The differences between the protective mechanisms predicted in these simulations could guide the design of experiments to discriminate antimicrobial tolerance mechanisms in biofilms.

Several studies are conducted to explain the formation and properties of the bifunctional layer-by-layer (LbL) construct made by the combination of permanent microbicidal polyelectrolyte multilayered (PEM) base film with a hydrolytically degradable PEM top film. These films are shown to be extremely efficient and hence can be used as coatings for different implantable devices.

Extensive 2D NMR and MS techniques were used for structural characterization of eight new antimicrobial natural products named chrysophaentins A-H belonging to a new structural class isolated from the marine chrysophyte alga Chrysophaeum taylori. Chrysophaentin A, identified as one of the most potent antibiotic, inhibited the growth of clinically relevant gram-positive bacteria including methicillin-resistant Staphylococcus aureus, multidrug-resistant S. aureus and vancomycin-resistant Enterococcus faecium.

[Super 19]F NMR solid-state analysis was performed to isolate native membranes from erythrocyte ghosts and bacterial protoplasts and prepare them as macroscopically oriented samples. The characteristic fingerprint splitting of the membrane-bound antimicrobial peptide PGLa detected by [super 19]F reporter group indicated that the peptide helix binds to the native membranes in a surface alignment, although with a higher affinity in the prokaryotic than the eukaryotic system.

A study was conducted to gain insight into the toxic properties and the role of anionic lipid clustering of five antimicrobial peptides which consists of peptides that form cationic amphipathic helices on membranes. Gram-positive bacteria showed a predominance of anionic lipids in the cytoplasmic membrane while gram-negative bacteria, which exhibit clustering of anionic lipids away from zwitterionic ones, could contribute significantly to the mechanism of bacterial toxicity for some antimicrobial agents.

The various effects of the linear cationic antimicrobial peptide structures on the inhibition of the planktonic growth and biofilm formation in Escherichia coli are discussed. The hexameric, as well as the octameric peptides are shown to be the best inhibitors of the discussed growth.

Two members, temporin A (TA) and temporin L (TL) from temporins which constitute a family of amphipathic [alpha]-helical antimicrobial peptides (AMPs) and contain some of the shortest cytotoxic peptides are examined to understand their spectra of antimicrobial activity and toxicity. NMR studies indicated that strongly hemolytic [Gln.sup.3]-TA exhibited stable helical conformation along the entire sequence, while weakly hemolytic but antimicrobial [Pro.sup.3]-TL showed conformational averaging at the N-terminus.

The biological activity of the selected peptides from the combinatorial library in bacteria, fungi and mammalian cells is studied to characterize the selected peptides and to compare the activity of antimicrobial peptides (AMPs) in vitro and in vivo. The analysis has shown that the methods focusing on screening peptide libraries in vitro for membranes with the appropriate interfacial activity has enabled the design, selection and discovery of novel, potent and broad-spectrum membrane-active antibiotics.

A detailed characterization of peptide-membrane interactions of dermaseptin (Drs B2), which is a 33-residue-long cationic, [alpha]-helical antimicrobial peptide endowed with membrane-damaging activity against a wide range of microorganisms such as bacteria, yeast, fungi, and protozoa is described. The results showed that Drs B2 could adopt a flexible helix-hinge-helix structure in a membrane environment with a strong positive curvature strain that permits the concomitant insertion of the strongly hydrophobic N- and C-termini of the peptide into the acyl core of the membrane.

The development of a concise route for the preparation of new tetra-orthogonally protected (2S,6R)-lanthionines is described. The new orthogonally protected lanthionines could be used to study the lantibiotic family of antimicrobial peptides.

Nuclear magnetic resonance (NMR) study was conducted to study and compare the dynamics and depth of insertion of two tachyplesin-I (TP-I) linear analogs, TPF4 and TPA4, in lipid bilayers. The active TP-I and TPF4 were found to exhibit large-amplitude motions on the NMR timescales, while the inactive TPA4 was immobilized.

Rational designing of antimicrobial peptides is described using indolicidin analogue CP-11 peptide with the sequence of ILKKWPWWPWRRK-NH(sub)2 and its cyclic disulfide-bonded version cyclo-CP-11 bearing the sequence ICLKKWPWWPWRRCK-NH(sub)2. Results reveal that the cyclo peptide exhibits higher resistance to trypsin which may be due to compact packing of lysine and tryptophan side chains.