title: Phospholipid bicelles that align with their normals parallel to the magnetic field.
abstract: We have recently reported phospholipid bicelles (bilayered micelles) that have positive anisotropy of the magnetic susceptibility and align with their normals parallel to an external magnetic field [J. Am. Chem. Soc. 2001, 123, 1537]. Improvements have been made via the synthesis of a new phospholipid, 1-dodecanoyl-2-(4-(4-biphenyl)butanoyl)-sn-glycero-3-phosphocholine (DBBPC). Bicelles can be formed by mixing DBBPC with a short-chain phospholipid, 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in a ratio between 5.1:1 and 6.5:1 in an aqueous medium. The (31)P NMR spectra clearly show that these bicelles align with their principal axes parallel to the magnetic field within a wide temperature range. The (31)P chemical shifts indicate that the conformation of the polar headgroup in these bicelles may be different from that in common bicelles. The phase behavior of a mixture of DBBPC/DHPC with 6:1 mole ratio was investigated in the temperature range of 10-75 degrees C using (31)P, (2)H, and (23)Na NMR. At lower temperatures (10-54 degrees C), the system is dominated by the bicellar phase. At higher temperatures (54-75 degrees C), isotropic micelles are formed and coexist with the bicelles. The partial alignment of maltotriose in the DBBPC/DHPC system was studied at three temperatures, and the (1)H-(13)C dipolar coupling constants are compared with those obtained for two other bicelle solutions.
authors.affiliation: Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019-3051, USA.
authors.forename: Chibing
authors.initials: C
authors.lastname: Tan
authors.forename: B M
authors.initials: BM
authors.lastname: Fung
authors.forename: Gyoujin
authors.initials: G
authors.lastname: Cho
mesh_terms: D003903:Deuterium; D008051:Lipid Bilayers / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010758:Phosphorus; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000737:chemistry*; D012975:Sodium Isotopes
chemical_list: D008051:Lipid Bilayers; D012975:Sodium Isotopes; D010767:Phosphorylcholine; D010758:Phosphorus; D003903:Deuterium