Morphological characterization of DMPC/CHAPSO bicellar mixtures: a combined SANS and NMR study.
Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), (31)P NMR, and stimulated echo (STE) pulsed field gradient (PFG) (1)H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (= 3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were also found at low temperature and lower lipid concentration mixtures. At high temperature, perforated lamellae were observed in high-concentration mixtures (≥7.5 wt %) whereas uniform unilamellar vesicles and bicelles formed in low-concentration mixtures (≤2.5 wt %), respectively, when the mixtures were moderately and highly charged. From the results, spontaneous structural diagrams of the zwitterionic and charged systems were constructed.
Polymer Program, Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States.
Ming
M
Li
Hannah H
HH
Morales
John
J
Katsaras
Norbert
N
Kučerka
Yongkun
Y
Yang
Peter M
PM
Macdonald
Mu-Ping
MP
Nieh
D002793:Cholic Acids / Q000737:chemistry*; D004058:Diffusion; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D033363:Neutron Diffraction; D010715:Phosphatidylglycerols / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D053838:Scattering, Small Angle; D013696:Temperature; D014867:Water / Q000737:chemistry
D002793:Cholic Acids; D008823:Micelles; D010715:Phosphatidylglycerols; D014867:Water; D011092:Polyethylene Glycols; C048531:chapso; C002773:dimyristoylphosphatidylglycerol; D004134:Dimyristoylphosphatidylcholine