1-2-dioleoyloxy-3-(trimethylammonium)propane and 1-2-dipalmitoylphosphatidylglycerol

Topics: Adsorption; Air; Cations; Fatty Acids, Monounsaturated; Laminaria; Lipids; Membranes, Artificial; Microscopy, Atomic Force; Phosphatidylglycerols; Polysaccharides; Pressure; Quaternary Ammonium Compounds; Surface Properties; Thermodynamics; Water

Dimethyl sulfoxide (DMSO) has been broadly used in biology as a cosolvent, a cryoprotectant, and an enhancer of membrane permeability, leading to the general assumption that DMSO-induced structural changes in cell membranes and their hydration water play important functional roles. Although the effects of DMSO on the membrane structure and the headgroup dehydration have been extensively studied, the mechanism by which DMSO invokes its effect on lipid membranes and the direct role of water in this process are unresolved. By directly probing the translational water diffusivity near unconfined lipid vesicle surfaces, the lipid headgroup mobility, and the repeat distances in multilamellar vesicles, we found that DMSO exclusively weakens the surface water network near the lipid membrane at a bulk DMSO mole fraction (XDMSO) of <0.1, regardless of the lipid composition and the lipid phase. Specifically, DMSO was found to effectively destabilize the hydration water structure at the lipid membrane surface at XDMSO <0.1, lower the energetic barrier to dehydrate this surface water, whose displacement otherwise requires a higher activation energy, consequently yielding compressed interbilayer distances in multilamellar vesicles at equilibrium with unaltered bilayer thicknesses. At XDMSO >0.1, DMSO enters the lipid interface and restricts the lipid headgroup motion. We postulate that DMSO acts as an efficient cryoprotectant even at low concentrations by exclusively disrupting the water network near the lipid membrane surface, weakening the cohesion between water and adhesion of water to the lipid headgroups, and so mitigating the stress induced by the volume change of water during freeze-thaw.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Diffusion; Dimethyl Sulfoxide; Fatty Acids, Monounsaturated; Magnetic Resonance Spectroscopy; Membranes, Artificial; Phosphatidylcholines; Phosphatidylglycerols; Quaternary Ammonium Compounds; Scattering, Small Angle; Water; X-Ray Diffraction

Two decapeptide fragments of the non-structural hepatitis G NS3 protein (GBV-C/HGV), 513-522 (RGRTGRGRSG) and 505-514 (SAELSMQRRG), as well as their palmitoylated derivatives were synthesized. The physico-chemical properties of the peptides were analyzed in both the absence and presence of the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), the negative 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG) and the positive 1,2-dioeloyl-3-trimethylammonium-propane (DOTAP) lipid monolayers. Based on their high hydrophilic properties, neither parent peptide presented surface activity and their incorporation into lipid monolayers was low. In contrast, their palmitoylated derivatives showed concentration-dependent surface activity and could be inserted into lipid monolayers to varying degrees depending on their sequence. Compression isotherms showed that the presence of palmitoylated peptides in the subphase resulted in a molecular arrangement less condensed than that corresponding to the pure phospholipid. In concordance with the monolayer results, differential scanning calorimetry (DSC) demonstrated that the parent peptides did not have any effect on the thermograms, while the palmitoylated derivatives affected the thermotropic properties of DPPC bilayers.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Algorithms; Calorimetry, Differential Scanning; Fatty Acids, Monounsaturated; Lipid Bilayers; Lipids; Peptides; Phosphatidylglycerols; Pressure; Quaternary Ammonium Compounds; Surface Properties; Thermodynamics; Viral Nonstructural Proteins