Structural evaluation of phospholipid bicelles for solution-state studies of membrane-associated biomolecules.
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.
Glover
K J
KJ
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0359, USA.
Whiles
J A
JA
Wu
G
G
Yu
N
N
Deems
R
R
Struppe
J O
JO
Stark
R E
RE
Komives
E A
EA
Vold
R R
RR
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
D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010743:Phospholipids; D012996:Solutions; C032166:1,2-hexanoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine