Download or read book New Methodologies of Solid State NMR and Biophysical Studies of Antimicrobial and Designed Peptides in Model and Natural Membranes written by Barbara Perrone and published by . This book was released on 2011 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solid-state NMR (SS-NMR) spectroscopy is a powerful tool to investigate structural details of membrane-associated peptides. In particular, the tilt angle of helical peptides reconstituted in non-oriented membranes can be derived by line-shape analysis of ^{15}N powder patterns. This approach allow a better control on several parameters with respect oriented SS-NMR spectroscopy. The spectra of peptides undergoing to fast uniaxial rotation diffusion around the membrane normal are characterized by distortions close to the isotropic chemical shift (Magic Angle Hole, MAH) that prevent to reach a satisfying fit quality. We developed a method that recovers the theoretical powder pattern line-shape based on ROtor-Directed Exchange of Orientations Cross-Polarization (RODEO). The method was successfully applied to designed peptides in unoriented membranes resulting in tilt angles values in agreement with published data. RODEO was applied also to complex membrane systems, such as lipid mixture extracted from natural membranes, and, for the first time, we obtained an estimation of the alignment of an antimicrobial peptide in vivo. In the second part of this work, we report some unexpected results of biophysical investigations conducted to elucidate the insertion mechanism of the antimicrobial peptide LAH4 in zwitterionic membranes. It was previously shown that the LAH4-helix adopts an in-plane orientation in acidic conditions, while, at neutral pH, the peptide adopts a trans-membrane orientation. In contrast, we found that when citrate buffer is added to regulate the pH at 5, the peptide inserts in a transmembrane manner. Some possible explanations are suggested.