NMR spectroscopy of lipid bilayers.

Knowledge of lipid structure and dynamics in a membranous environment is of first importance for deciphering cellular function. Sterols and sphingolipids are key molecules in maintaining membrane integrity and are the building blocks of membrane domains, such as "rafts". Phosphatidyl inositols are crucial in signalling pathways as they are recognition sites at the membrane surface.

Biphenyl phosphatidylcholine: a promoter of liposome deformation and bicelle collective orientation by magnetic fields.

Membrane lipids with long saturated or unsaturated acyl chains are usually not sensitive to magnetic fields. We report in this review a few exceptions with potential use in structural biology or drug delivery. Mixtures of short and long chain phospholipids called bicelles can form discs-shaped nanoobjects (40nm) that can indeed be oriented in magnetic fields.

Bicelles: A natural 'molecular goniometer' for structural, dynamical and topological studies of molecules in membranes.

Major biological processes occur at the biological membrane. One of the great challenges is to understand the function of chemical or biological molecules inside the membrane; as well of those involved in membrane trafficking. This requires obtaining a complete picture of the in situ structure and dynamics as well as the topology and orientation of these molecules in the membrane lipid bilayer.

Solution and solid-state NMR of lipids.

Lipid structure and dynamics are of first importance for cellular function. Lipids such as phosphatidyl inositol (PtdIns) are essential in signaling pathways, as they are recognition sites at the membrane surface. Their headgroup or chain structure appears to be crucial for such a signaling role.

Solid-state NMR spectroscopy of a membrane protein in biphenyl phospholipid bicelles with the bilayer normal parallel to the magnetic field.

Bicelles composed of the long-chain biphenyl phospholipid TBBPC (1-tetradecanoyl-2-(4-(4-biphenyl)butanoyl)-sn-glycero-3-PC) and the short-chain phospholipid DHPC align with their bilayer normals parallel to the direction of the magnetic field. In contrast, in typical bicelles the long-chain phospholipid is DMPC or DPPC, and the bilayers align with their normals perpendicular to the field. Samples of the membrane-bound form of the major coat protein of Pf1 bacteriophage in TBBPC bicelles are stable for several months, align magnetically over a wide range of temperatures, and yield well-resolved solid-state NMR spectra similar to those obtained from samples aligned mechanically on glass plates or in DMPC bicelle samples "flipped" with lanthanide ions so that their bilayer normals are parallel to the field.

Probing the dynamics of intact cells and nuclear envelope precursor membrane vesicles by deuterium solid state NMR spectroscopy.

Membrane dynamics is an essential part of many cellular mechanisms such as intracellular trafficking, membrane fusion/fission and mitotic organelle reconstitution. The dynamics of membranes is dependent primarily on their phospholipid and cholesterol composition and how these molecules are ordered in relation to one another. To determine the physical status of membranes in whole cells or purified membranes of subcellular compartments we have developed a novel application exploiting solid-state (2)H-NMR spectroscopy.

Plant sterols in "rafts": a better way to regulate membrane thermal shocks.

Specialized lipid domains (rafts) that are generally enriched in sterols and sphingolipids, are most likely present in cell membranes of animals, plants and fungi. While cholesterol and ergosterol are predominant in vertebrates and fungi, plants possess complex sterol profiles, dominated by sitosterol and stigmasterol in Arabidopsis thaliana. Fully hydrated model membranes of composition approaching those found in rafts of mammals, fungi and plants were investigated by means of solid-state 2H-NMR, using deuterated dipalmitoylphosphatidylcholine (2H(62)-DPPC).

Biphenyl bicelle disks align perpendicular to magnetic fields on large temperature scales: a study combining synthesis, solid-state NMR, TEM, and SAXS.

A phosphatidylcholine lipid (PC) containing a biphenyl group in one of its acyl chains (1-tetradecanoyl-2-(4-(4-biphenyl)butanoyl)-sn-glycero-3-PC, TBBPC) was successfully synthesized with high yield. Water mixtures of TBBPC with a short-chain C(6) lipid, dicaproyl-PC (DCPC), lead to bicelle systems formation. Freeze-fracture electron microscopy evidenced the presence of flat bilayered disks of 800 A diameter for adequate composition, hydration, and temperature conditions.

Pro-apoptotic bax-alpha1 synthesis and evidence for beta-sheet to alpha-helix conformational change as triggered by negatively charged lipid membranes.

Solid phase synthesis of Bax-alpha1, the 25 amino acids domain (14TSSEQIMKTGALLLQGFIQDRAGRM38) of the pro-apoptotic Bax protein has been accomplished using Fmoc chemistry. A new fast and harmless protocol is described for complete TFA removal from the purified peptide powder leading to a final purity greater than 98% as controlled by 19F-NMR, UV and MALDI-TOF mass spectrometry. Secondary structure was determined in various solution and membrane media using UV Circular Dichroism.

Bicelle membranes and their use for hydrophobic peptide studies by circular dichroism and solid state NMR.

Mixtures of dicaproyl- (DC), dimyristoyl- (DM) and 1-tetradecanoyl-2-biphenylbutanoyl-(TBB) phosphatidylcholine (PC) in water produce bicelle membranes that are oriented by magnetic fields. DMPC/DCPC systems orient such that their membrane plane is parallel to the magnetic field, whereas for TBBPC/DCPC, the plane is perpendicular to the field. Partial temperature-composition-hydration diagrams are established using solid-state 31P-NMR.