Orientational behavior of phosphatidylcholine bilayers in the presence of aromatic amphiphiles and a magnetic field

Abstract

A number of aromatic-containing additives which can influence the orientation of fragments of lipid bilayer membranes by a magnetic field have been investigated. Two properties of these additives prove important: (1) sufficient detergency to facilitate reorganization of bilayer components and (2), sufficient anisotropy in magnetic susceptibility the preferred direction of fragment orientation. Triton X-100 is identified as effective in terms of facilitating magnetic field ordering of bilayer fragments but does not alter the preferred direction of orientation. A combination of the detergent CHAPSO (3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate) and the aromatic alcohol 1-naphthol facilitates both ordering and alters the preferred direction of bilayer orientation. As mixtures of dimyristoylphosphatidylcholine (DMPC) and CHAPSO, which orient with bilayer normals perpendicular to the magnetic field, were titrated with 1-naphthol, the assemblies underwent transitions, first to random orientation, and then to an orientation with bilayer normals parallel to the field. Based on temperature-induced phase transitions and the extent of motional averaging of the 31P shielding tensor of the DMPC headgroup, the DMPC in these oriented samples appears to maintain a bilayer morphology during transitions. The insight provided in this study regarding factors which influence fragment stability and orientation lays the groundwork for the design of improved field-oriented media for spectroscopic investigation of membrane components.

Bicelles as model membranes for solid‐ and solution‐state NMR studies of membrane peptides and proteins

“…This was first observed when an aromatic amphiphile, 1-naphtol, was added to DMPC/CHAPSO bicelles (53). High concentration of the ion channel gramicidin A was also found to flip the bicelle alignment (62,63).…”

“…This method allows the assignment of the 13 C resonances by following peaks to their isotropic position, and the calculation of the CSA (11,53).…”

Liposome Solubilization and Membrane Protein Reconstitution Using Chaps and Chapso

“…H'-transporting ATP synthase (EC 3.6.1.34). new approach to produce magnetically orientable phospholipid bilayers useful for NMR experiments (Sanders et al, 1993;Sanders and Prestegard, 1990). Both Chaps and Chapso have been used in reconstitution studies and some reports appeared in the literature dealing with the formation of active proteoliposomes (Yoda et al, 1984;Helmke and Howard, 1987).…”

Lanthanide Chelates as Bilayer Alignment Tools in NMR Studies of Membrane-Associated Peptides

“…It is consequently desirable to use a bilayered model system that spontaneously aligns with the bilayer normal parallel to the applied magnetic field. Parallel alignment of phospholipid bilayers has been shown to be feasible by altering the magnetic susceptibility anisotropy of the membrane through the addition of either large amounts of aromatic molecules (9) or small amounts of the trivalent lanthanide ions Eu 3ϩ , Er 3ϩ , Tm 3ϩ , and Yb 3ϩ (10,11). In particular, it has been recently shown that less than 1 mol% Tm 3ϩ or Yb 3ϩ , relative to DMPC, is needed to induce parallel alignment (12).…”