High magnetic field solid-state NMR was performed on amphipathic cationic antimicrobial peptides from fish to characterize their secondary structure and orientation in hydrated phospholipid bilayers. High-resolution distance and orientational restraints on 13C- and 15N-labeled amidated piscidins 1 and 3 provided site-specific information establishing alpha-helicity and an orientation parallel t...

In this thesis, we investigate a variety of problems involving the interaction of cationic peptides with lipid membranes. To this end we adopt Poisson-Boltzmann (PB) theory and coarse-grained models of these molecules. We first examine the electrostatic interaction of a positively-charged peptide with a negatively charged membrane immersed in a salty solution. In particular, we study how this i...

The membrane interaction and solution conformation of two mutants of the beta-hairpin antimicrobial peptide, protegrin-1 (PG-1), are investigated to understand the structural determinants of antimicrobial potency. One mutant, [A(6,8,13,15)] PG-1, does not have the two disulfide bonds in wild-type PG-1, while the other, [Delta(4,18) G10] PG-1, has only half the number of cationic residues. 31P s...

Cationic antimicrobial peptides (AMPs) and host defense peptides (HDPs) show vast potential as peptide-based drugs. Great effort has been made in order to exploit their mechanisms of action, aiming to identify their targets as well as to enhance their activity and bioavailability. In this review, we will focus on both naturally occurring and designed antiviral and antitumor cationic peptides, i...

Host defense peptides (often called cationic antimicrobial peptides) have pleiotropic immunomodulatory functions. The human host defense peptide LL-37 is up-regulated at sites of infection and has little or no antimicrobial activity in tissue-culture media but under the same conditions, demonstrates immunomodulatory effects on epithelial cells, monocytes, and dendritic cells (DC). These effects...

In this study, we develop a novel method for label-free and real-time imaging of molecular interactions between cationic antimicrobial peptides and lipid membranes using liquid crystals (LCs). The optical appearance of LCs changes from bright to dark after transferring phospholipids onto the aqueous/LC interface, representing an orientational transition of LCs from planar to homeotropic state. ...

The antimicrobial action of amphipathic antimicrobial peptides (AMPs) generally depends on perturbation of the bacterial membrane via electrostatic interactions promoting initial binding to the surface and hydrophobic interactions for pore formation into the membrane. Several studies have focused on the structure-activity relationship (SAR) of AMPs by modulation of structural parameters. Howeve...

Many membrane peptides and protein domains contain functionally important cationic Arg and Lys residues, whose insertion into the hydrophobic interior of the lipid bilayer encounters significant energy barriers. To understand how these cationic molecules overcome the free energy barrier to insert into the lipid membrane, we have used solid-state NMR spectroscopy to determine the membrane-bound ...

Antimicrobial peptides (AMPs) have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these...

Antimicrobial peptides (AMPs) are part of the armament that insects have developed to fight off pathogens. Insect AMPs are typically cationic and often made of less than 100 amino acid residues. Although their structures are diverse, most of the AMPs can be assigned to a limited number of families. The most common structures are represented by peptides assuming a alpha-helical conformation in o...