TY - JOUR
T1 - Composition, structure and properties of POPC-triolein mixtures. Evidence of triglyceride domains in phospholipid bilayers
AU - Duelund, Lars
AU - Vestergaard Jensen, Grethe
AU - Hannibal-Bach, Hans Kristian
AU - Ejsing, Christer S.
AU - Skov Pedersen, Jan
AU - Inkeri Pakkanen, Kirsi
AU - Ipsen, John Hjort
N1 - Copyright © 2013 Elsevier B.V. All rights reserved.
PY - 2013
Y1 - 2013
N2 - We have in this study investigated the composition, structure and spectroscopical properties of multilamellar vesicles composed of a phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and up to 10mol% of triolein (TO), a triglyceride. We found in agreement with previous results that the mixtures with 10mol% TO spontaneously separate into two distinct phases, heavy (HF) and light (LF), with different densities and found this also to be the case for 2 and 5mol% TO. The compositions of the two phases were investigated by quantitative lipid mass spectrometric analysis, and with this method we found that TO had a solubility maximum of about 4mol% in the HF, whereas it was markedly up-concentrated in the LF. Electron paramagnetic resonance spectroscopy indicated POPC membranes of all tested concentrations of TO in both phases to be almost unperturbed by the presence of TO and to exist as vesicular structures containing entrapped water. Bilayer structure of the membranes was supported by small angle X-ray scattering that showed the membranes to form a lamellar phase. Fluorescence spectroscopy with the polarity sensitive dye Nile red revealed, that the LF samples with more than 5mol% TO contained pure TO domains. These observations are consistent with an earlier MD simulation study by us and our co-workers suggesting triglycerides to be located in lens shaped, blister-like domains between the two lipid bilayer leaflets (Khandelia et al. (2010) [26]).
AB - We have in this study investigated the composition, structure and spectroscopical properties of multilamellar vesicles composed of a phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and up to 10mol% of triolein (TO), a triglyceride. We found in agreement with previous results that the mixtures with 10mol% TO spontaneously separate into two distinct phases, heavy (HF) and light (LF), with different densities and found this also to be the case for 2 and 5mol% TO. The compositions of the two phases were investigated by quantitative lipid mass spectrometric analysis, and with this method we found that TO had a solubility maximum of about 4mol% in the HF, whereas it was markedly up-concentrated in the LF. Electron paramagnetic resonance spectroscopy indicated POPC membranes of all tested concentrations of TO in both phases to be almost unperturbed by the presence of TO and to exist as vesicular structures containing entrapped water. Bilayer structure of the membranes was supported by small angle X-ray scattering that showed the membranes to form a lamellar phase. Fluorescence spectroscopy with the polarity sensitive dye Nile red revealed, that the LF samples with more than 5mol% TO contained pure TO domains. These observations are consistent with an earlier MD simulation study by us and our co-workers suggesting triglycerides to be located in lens shaped, blister-like domains between the two lipid bilayer leaflets (Khandelia et al. (2010) [26]).
U2 - 10.1016/j.bbamem.2013.03.020
DO - 10.1016/j.bbamem.2013.03.020
M3 - Journal article
C2 - 23567913
SN - 0304-4165
VL - 1828
SP - 1909
EP - 1917
JO - BBA General Subjects
JF - BBA General Subjects
IS - 8
ER -