(4-24)-ply(a) and 1-palmitoyl-2-oleoylphosphatidylcholine

The histidine-rich peptides of the LAH4 family were designed using cationic antimicrobial peptides such as magainin and PGLa as templates. The LAH4 amphipathic helical sequences exhibit a multitude of interesting biological properties such as antimicrobial activity, cell penetration of a large variety of cargo and lentiviral transduction enhancement. The parent peptide associates with lipid bilayers where it changes from an orientation along the membrane interface into a transmembrane configuration in a pH-dependent manner. Here we show that LAH4 adopts a transmembrane configuration in fully saturated DMPC membranes already at pH 3.5, i.e. much below the pK

Topics: Amino Acid Sequence; Antimicrobial Cationic Peptides; Dimyristoylphosphatidylcholine; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Lipid Bilayers; Magainins; Magnetic Resonance Spectroscopy; Phosphatidylcholines; Phosphatidylglycerols

Dynamic Nuclear Polarization (DNP) has been introduced to overcome the sensitivity limitations of nuclear magnetic resonance (NMR) spectroscopy also of supported lipid bilayers. When investigated by solid-state NMR techniques the approach typically involves doping the samples with biradicals and their investigation at cryo-temperatures. Here we investigated the effects of temperature and membrane hydration on the topology of amphipathic and hydrophobic membrane polypeptides. Although the antimicrobial PGLa peptide in dimyristoyl phospholipids is particularly sensitive to topological alterations, the DNP conditions represent well its membrane alignment also found in bacterial lipids at ambient temperature. With a novel membrane-anchored biradical and purpose-built hardware a 17-fold enhancement in NMR signal intensity is obtained by DNP which is one of the best obtained for a truly static matrix-free system. Furthermore, a membrane anchor sequence encompassing 19 hydrophobic amino acid residues was investigated. Although at cryotemperatures the transmembrane domain adjusts it membrane tilt angle by about 10 degrees, the temperature dependence of two-dimensional separated field spectra show that freezing the motions can have beneficial effects for the structural analysis of this sequence.

Topics: Amino Acid Sequence; Anti-Infective Agents; Antimicrobial Cationic Peptides; Cold Temperature; Dimyristoylphosphatidylcholine; Hydrophobic and Hydrophilic Interactions; Lipid Bilayers; Magnetic Resonance Spectroscopy; Phosphatidylcholines; Phosphatidylglycerols