A thermodynamic and NMR investigation of 1-lyso-palmitoyllecithin/1,2-dipalmitoylphosphatidylethanol-amine/water system
cholesterol; Crystallography; fusion; liposomal membranes; lysolecithin; temperature; vesicle
The effect of incorporation of 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC) on the bilayer structures occurring in aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) has been studied by phosphorus 31 nuclear magnetic resonance and calorimetric methods. The polymorphism of the system as a function of PLPC concentration has been defined. Experimental data allowed us to determine phase boundaries. Changes of molecular packing of the PLPC molecules in DPPE bilayers in the phase diagram are invoked to explain the experimental findings.
Nicoletta F P; Checchetti A; Grasso D; Imbardelli D; LaRosa C; Westerman P; Chidichimo G
Molecular Crystals and Liquid Crystals Science and Technology Section a-Molecular Crystals and Liquid Crystals
1996
1996
Journal Article
<a href="http://doi.org/10.1080/10587259608031892" target="_blank" rel="noreferrer noopener">10.1080/10587259608031892</a>
Anomalous Phase Transition In Dipalmitoylphosphatidylethanolamine/palmitoylphosphatidylcholine/water System
bilayer; Biochemistry & Molecular Biology; Biophysics; Chemistry; compressibility; DSC; lysolecithin; lysophosphatidylcholine; membrane; NMR; permeability; phase transition; phosphatidylcholine vesicles; phosphatidylethanolamine; phospholipid; phospholipid-vesicles; translocation; volumetric
An anomalous phase transition with a marked rise in specific heat, the isobaric thermal expansion coefficient, and the compressibility coefficient at 62.5 degrees C for an equimolar mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC), in water (34 wt.%) has been shown by differential scanning calorimetry, scanning dilatometry and isothermal compressibility measurements. This transition occurs 15 degrees C above a first-order transition observed in the same system, P-31 and H-2 nuclear magnetic resonance results are consistent with the occurrence of 'defects' in the bilayer in the temperature range between the first and the anomalous phase transitions, It is proposed that conically, PLPC molecules prefer regions with high curvature in the defective bilayer, while DPPE molecules are mostly confined to the flat regions of the bilayers. (C) 1998 Elsevier Science B.V.
La Rosa C; Grasso D; Checchetti A; Golemme A; Chidichimo G; Westerman P
Biophysical Chemistry
1998
1998-01
Journal Article or Conference Abstract Publication
n/a
Effect of 1-palmitoyl lysophosphatidylcholine on phase properties of 1,2-dipalmitoyl phosphatidylethanolamine: A thermodynamic and NMR study
Biophysics; Biochemistry & Molecular Biology; cholesterol; fusion; lysolecithin; lipid; membranes; bilayer; H-2-NMR; transition; nuclear-magnetic-resonance; phosphatidylcholine vesicles; lecithin; bilayers; DSC; mixtures; P-31-NMR; phosphatidylethanolamine
The effect of 1-palmitoyl lysophosphatidylcholine (PLPC) on the phase behaviour of 1,2-dipalmitoyl phosphatidylethanolamine (DPPE) in excess water (34 wt%) has been examined by differential scanning calorimetry, scanning dilatometry and isothermal compressibility measurements. Mole percentages of PLPC in DPPE between 14 and 62% have been studied over the temperature range 30-75 degrees C. The temperature dependence of orientational ordering at selected sites in H-2-labelled PLPC and 2H(2)O has been determined from measurement of time-averaged chemical shift anisotropies and quadrupole splittings in the P-31- and H-2-NMR spectra. These data have been used to further characterize phase behaviour. At less than equimolar contents of PLPC, when a single phase transition with a reduced transition temperature is observed, spectral and calorimetric data indicate complete miscibility of the two lipid components. An equimolar mixture of PLPC and DPPE shows a sharp first order transition at 47.3 degrees C and a second order transition at 62.5 degrees C. NMR data are consistent with the existence of a defective bilayer at intermediary temperatures. In this range it is proposed that PLPC molecules prefer regions with high curvature in the vicinity of the defects, while DPPE molecules are mostly confined to flatter regions of the bilayer. A possible molecular model is described, At temperatures above 62.5 degrees C, PLPC and DPPE are completely miscible and exist as lamellae. At higher PLPC content (> 50 mol%), thermodynamic and spectral data are indicative of phase separation of the two components over the temperature range examined.
Checchetti A; Golemme A; Chidichimo G; LaRosa C; Grasso D; Westerman P W
Chemistry and Physics of Lipids
1996
1996-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1016/0009-3084(96)02574-1" target="_blank" rel="noreferrer noopener">10.1016/0009-3084(96)02574-1</a>
On the stability of the ripple phase in the DPPC/PLPC/water ternary system
Biophysics; Biochemistry & Molecular Biology; gel; cholesterol; lysolecithin; membranes; nuclear-magnetic-resonance; water; transition; lipid bilayers; phospholipid-bilayers; Lipids; differential scanning calorimetry (DSC); lecithin; phosphatidylcholine; phosphatidylcholine bilayers; pretransition; scanning dilatometry (SD)
The effect of incorporation of 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC) on the structure of the P-beta' ripple mesophase in aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been studied by differential scanning calorimetry (DSC) and scanning dilatometry (SD). For samples containing 34 wt. % (H2O)-H-2 and 0-15 wt. % PLPC, a pretransition was observed by DSC. The pretransition disappears at 15 wt. % PLPC. The behavior of thermodynamic functions at the pretransition and main transition gives new insights on the structural changes produced by PLPC on bilayers of DPPC. (C) 1997 Elsevier Science Ireland Ltd.
Checchetti A; Chidichimo G; Golemme A; Grasso D; Imbardelli D; LaRosa C; Nicoletta F P; Westerman P W
Chemistry and Physics of Lipids
1997
1997-11
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1016/s0009-3084(97)00086-8" target="_blank" rel="noreferrer noopener">10.1016/s0009-3084(97)00086-8</a>