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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.

High-throughput methods for the preparation of nonmevalonate terpene biosynthesis enzymes, which can be effectively used as antiinfective drugs, are described. Enzyme-assisted methods for the preparation of the required substrates in multigram amounts, with or without (13.Super)C labels in various positions that enable monitoring of enzyme reaction by (13.Super)C NMR, are presented.

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.

The role of amphipathicity using an analogue of tachyplesin 1(TP-1), CDT (KWFRVYRGIYRRR-N[H.sub.2]), in which all four cysteines were deleted were investigated. The properties help to explain that cysteine residues may not contribute to antimicrobial activity and that the loss of hemolytic activity is due to lack of hydrophobicity and amphipathicity.

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.

Sum frequency generation (SFG) vibrational spectroscopy is employed to study the molecular interactions between a single substrate supported lipid bilayer and an amphiphilic antibiotic compound with a designed based on the common structural motif of natural antimicrobial peptides. The interfacial sensitivity of SFG allows real-time in situ monitoring of ordering changes in both leaflets of the bilayer and orientation of the compound simultaneously.

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.

Novel analogues of melittin were designed by substituting the leucine residue(s) at the 'd' and 'a' positions of its previously identified leucine zipper motif to understand the lytic activities of melittin antimicrobial peptide against bacteria and mammalian cells. The data revealed that the substitution of hydrophobic leucine residue(s) by lesser hydrophobic alanine residue(s) in the leucine zipper sequence of melittin disturbed its pore-forming activity and mechanism only in hRBCs but not in the tested bacteria.

The structure of the par toxin Fst, the first atomic resolution structure of a component of an antisense regulated toxin-antitoxin system, is described. The studies have shown that Fst has displayed neither hemolytic nor antimicrobial activity when applied externally to a series of bacteria, fungal cells and erythrocytes and also its charge distribution, orientation in the membrane and structure has distinguished it from antimicrobial peptides.

[Super 31]P and [super 19]F solid-state NMR spectroscopy are applied to study the the lipid interaction, depth of insertion, orientation, and dynamics of an arylamide, PMX30016 and gain better insight into the mechanism of action of the antimicrobial arylamide foldamers. The results suggested that antimicrobial arylamides destabilize anionic lipid membranes primarily by altering the membrane electric potential profile, and the spinning molecular knife might additionally create transient defects in the lipid membrane.

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.

The article presents a new approach, where in the measurements of diffusion times can be employed for studying the antimicrobial peptide (AMP)-membrane interactions. The methodology is shown to be extremely beneficial in studying the membrane structures at extremely low peptide ratios.

A paramagnetic copper-chelated lipid is used to enhance the spin-lattice relaxation and thereby speed up solid-state NMR measurements. The results have shown a 6.2-fold speed increase and a 2.7-fold improvement in signal-to-noise ratio for solid-state NMR experiments under magic-angle spinning and static conditions.

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 article presents a new approach, which employs a modified nonwoven fabric as a thin film detection/response system for the pathogenic bacteria. The systems are shown to be widely used as responsive dressings with the release of antimicrobials.

The role of the leader peptide of McjA is examined and is shown that only the eight C-terminal amino acids of this leader peptide are needed for maturation of the antimicrobial peptide microcin J25 (MccJ25). Alanine scanning mutagenesis studies have shown that the Thr-35 residue in the leader peptide is vital for correct processing of McjA into mature MccJ25, whereas the charged amino acids have not played a major role in the maturation of MccJ25.

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.

A new method is described for obtaining information about the conformational dynamics of membrane-proteins by using solid-state NMR experiments of oriented samples. The method is shown for the antimicrobial peptaibol alamethicin for which combined analysis of anisotropic interactions for the [Aib.sub.8] residue has given information about helix-tilt angle, wobbling and oscillatory rotation around the helix axis in the membrane bound state.

The secondary metabolites platensimycin and platencin, isolated from the bacterial strain Streptomyces platensis, have represented a novel class of natural products displaying potent antimicrobial activity. The syntheses of platecin have shown the power of the cobalt-catalyzed asymmetric Diels-Alder reaction and the one-pot reductive rearrangement of [3.2.1] bicyclic ketones to [2.2.2] bicyclic olefins.

One member of a prototypical class of antimicrobial oligomers is used for studying pore formation in cardiolipin-rich membranes and both vesicle dye-leakage assays and small-angle X-ray scattering are used for studying bilayer remodeling. The results have shown that the presence of negative intrinsic curvature lipids is necessary for pore formation by this class of molecules.

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.

A biosynthetic study on spiro-mamakone A, a potently cytotoxic and antimicrobial compound from an endophytic fungus isolated from the New Zealand native tree Knightia excelsa is reported. The biosynthesis proceeds via an unprecedented symmetric enedione with the two halves of the molecule formed from two separate pentaketide units connected by oxidative coupling and have confirmed the origin of polyketide to the spirobisnaphthalene class of compounds.

A method is described for converting tert-butyl benzoates or tert-butyl 1-naphthoates into derivatives having an alkyl or substituted alkyl group. The method can be applied to the synthesis of the antimicrobial fungal metabolite culpin.

A method based on selected amino acid alterations in the peptide template was used to identify novel C3a peptide variants with enhanced antimicrobial effects. The results provide insights into the structure-activity relationships associated with the function and specificity of antimicrobial C3a and related analogues and also into the forces that drive evolution of antimicrobial peptides.

The studies and synthesis of cateslytin, a positively charged (5+) arginine-rich antimicrobial peptide that mimic bacterial or mammalian systems is presented. The results shed light onto the mode of action of cateslytin on systems modeling mammalian and bacterial membranes.

A series of guidelines useful for the future design of short cationic antimicrobial peptides with high resilience against tryptic degradation are presented. The guidelines can also be applied to generate stabilization of other small cationic peptides against tryptic degradation.

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.

A novel strategy is developed for the total synthesis of sceptrin from the initial failure of an allyl urocanate dimerization route to a successful oxaquadricyclane fragmentation strategy. The exploration of 2-aminoimidazole heterocycle has led to the total synthesis of oxysceptrin and nakamuric acid and a successful construction of the carbon skeleton of axinellamine.

Polymers based on m-phenylene ethylenes (mPE) were designed and synthesized to mimic the amphiphilic, cationic, and rigid structure of antimicrobial peptides (AMPs) and were found to be good mimics of AMPs in terms of their high potency toward microbes and low hemolytic activities. Two mPEs were found to readily insert into anionic model bacterial membranes but to differ in the degree of selectivity between bacterial and mammalian erythrocyte model membranes, demonstrating that mPEs can mimic AMPs' membrane disordering.

The steps taken toward the development of nontoxic antimicrobial synthetic polymers to determine the structure-activity relationship of amphiphilic polymethacrylate derivatives as measured via antimicrobial and hemolytic activities are described. This class of synthetic polymers is inexpensive and easy to prepare, allowing the production of antimicrobial materials on industrial scales.

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.

A solid-state NMR (ssNMR) was employed to study the structure and topology of isotopically labeled piscidins in the membrane-bound state. The results from the NMR restraints established that the piscidins were alpha-helical and oriented parallel to the bilayer surface and topology observed indicates that partitioning of amphipathic, cationic, antimicrobial peptides at the water-bilayer interface allows for favorable peptide-lipid interactions and it might be related to the mechanism of action of piscidins.