| againins and PGLa are natural defense peptides produced in frog skin in response to injury. These 21-23 residue cationic peptides, which show a broad spectrum of antibiotic activity but are not harmful to host cells at antimicrobial concentrations, kill bacteria by increasing the permeability of the plasma membrane. Permeability may be caused by the formation of discrete ion channels in the membrane or by detergent-like disruption. The conformation of these peptides when bound to membranes is also not well understood. The purpose of this research is to perform experiments which provide a better understanding of the basis of selectivity between bacterial and plasma membranes as well as the mechanism by which these peptides kill bacteria. Three model peptides, MSI-103, MSI-144, and MSI-1425, were studied by Fourier transform infrared (FTIR) spectroscopy to monitor structural changes in lipid-peptide mixtures. The orientation of the peptides with respect to the membrane was estimated by polarized attenuated total reflectance (PATR) infrared spectroscopy. MSI-103, MSI-144, and MSI-1425 contain a mixture of... |
