title: Structural evaluation of phospholipid bicelles for solution-state studies of membrane-associated biomolecules.
abstract: Several complementary physical techniques have been used to characterize the aggregate structures formed in solutions containing dimyristoylphosphatidylcholine (DMPC)/dihexanoylphosphatidylcholine (DHPC) at ratios of < or =0.5 and to establish their morphology and lipid organization as that of bicelles. (31)P NMR studies showed that the DMPC and DHPC components were highly segregated over a wide range of DMPC/DHPC ratios (q = 0.05-0.5) and temperatures (15 degrees C and 37 degrees C). Only at phospholipid concentrations below 130 mM did the bicelles appear to undergo a change in morphology. These results were corroborated by fluorescence data, which demonstrated the inverse dependence of bicelle size on phospholipid concentration as well as a distinctive change in phospholipid arrangement at low concentrations. In addition, dynamic light scattering and electron microscopy studies supported the hypothesis that the bicellar phospholipid aggregates are disk-shaped. The radius of the planar domain of the disk was found to be directly proportional to the ratio of DMPC/DHPC and inversely proportional to the total phospholipid concentration when the DMPC/DHPC ratio was held constant at 0.5. Taken together, these results suggest that bicelles with low q retain the morphology and bilayer organization typical of their liquid-crystalline counterparts, making them useful membrane mimetics.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0359, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Glover
authors.forename: J A
authors.initials: JA
authors.lastname: Whiles
authors.forename: G
authors.initials: G
authors.lastname: Wu
authors.forename: N
authors.initials: N
authors.lastname: Yu
authors.forename: R
authors.initials: R
authors.lastname: Deems
authors.forename: J O
authors.initials: JO
authors.lastname: Struppe
authors.forename: R E
authors.initials: RE
authors.lastname: Stark
authors.forename: E A
authors.initials: EA
authors.lastname: Komives
authors.forename: R R
authors.initials: RR
authors.lastname: Vold
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D018716:Molecular Mimicry; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010743:Phospholipids; D012996:Solutions; C032166:1,2-hexanoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine