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Interlamellar forces and the thermodynamic characterization of lamellar phospholipid systems

Sparr, Emma LU and Wennerström, Håkan LU (2011) In Current Opinion in Colloid & Interface Science 16(6). p.561-567
Abstract
In this review, we summarize a series of experimental studies of the swelling of zwitterionic lamellar phospholipid and phospholipid-cholesterol systems using a novel double twin calorimeter. With this method, one can obtain simultaneous measures of the partial molar free energy and the partial molar enthalpy, and the experimental studies thus provide a complete thermodynamic characterization of the isothermal swelling process. A major finding is that the swelling of lamellar zwitterionic phospholipid systems at higher water contents (>4 water molecules per lipid) is endothermic. The enthalpy has the opposite sign relative to the free energy, thus demonstrating that the swelling process is entropy driven. The water uptake also triggers... (More)
In this review, we summarize a series of experimental studies of the swelling of zwitterionic lamellar phospholipid and phospholipid-cholesterol systems using a novel double twin calorimeter. With this method, one can obtain simultaneous measures of the partial molar free energy and the partial molar enthalpy, and the experimental studies thus provide a complete thermodynamic characterization of the isothermal swelling process. A major finding is that the swelling of lamellar zwitterionic phospholipid systems at higher water contents (>4 water molecules per lipid) is endothermic. The enthalpy has the opposite sign relative to the free energy, thus demonstrating that the swelling process is entropy driven. The water uptake also triggers a transition from a gel to a liquid crystalline state showing that, at given water content, the swelling pressure is much higher in the liquid crystal than in the gel. When cholesterol is added to the system the liquid ordered phase is formed at all available water contents. In this phase the swelling pressure varies smoothly and takes relatively low values at water contents below two per phospholipid, while it is substantially higher than in the gel phase at higher water contents. Together, these data demonstrate that the swelling pressure is sensitive to the phase state of the lipids. We also describe a series of studies that demonstrate that the addition of a second polar solute to the phospholipid-water system has a remarkably small effect on the swelling behavior when analyzed with respect to solvent volume. The reviewed experimental studies provide a thermodynamic characterization of the swelling of lamellar zwitterionic phospholipid systems that should be encompassed in the mechanistic molecular interpretation of the "hydration force." (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Phase diagrams, Isothermal sorption microcalorimeter, molar enthalpy, Partial, Water chemical potential, Phospholipid-water-cosolvent systems, Cholesterol-DMPC interaction, Phospholipid hydration, Lamellar phases
in
Current Opinion in Colloid & Interface Science
volume
16
issue
6
pages
561 - 567
publisher
Elsevier
external identifiers
  • wos:000298523900016
  • scopus:84855902703
ISSN
1359-0294
DOI
10.1016/j.cocis.2011.05.003
language
English
LU publication?
yes
id
92583dfe-2f22-4dbc-8302-55b43ce77a15 (old id 2799356)
date added to LUP
2012-06-19 14:54:37
date last changed
2017-03-26 04:03:46
@article{92583dfe-2f22-4dbc-8302-55b43ce77a15,
  abstract     = {In this review, we summarize a series of experimental studies of the swelling of zwitterionic lamellar phospholipid and phospholipid-cholesterol systems using a novel double twin calorimeter. With this method, one can obtain simultaneous measures of the partial molar free energy and the partial molar enthalpy, and the experimental studies thus provide a complete thermodynamic characterization of the isothermal swelling process. A major finding is that the swelling of lamellar zwitterionic phospholipid systems at higher water contents (>4 water molecules per lipid) is endothermic. The enthalpy has the opposite sign relative to the free energy, thus demonstrating that the swelling process is entropy driven. The water uptake also triggers a transition from a gel to a liquid crystalline state showing that, at given water content, the swelling pressure is much higher in the liquid crystal than in the gel. When cholesterol is added to the system the liquid ordered phase is formed at all available water contents. In this phase the swelling pressure varies smoothly and takes relatively low values at water contents below two per phospholipid, while it is substantially higher than in the gel phase at higher water contents. Together, these data demonstrate that the swelling pressure is sensitive to the phase state of the lipids. We also describe a series of studies that demonstrate that the addition of a second polar solute to the phospholipid-water system has a remarkably small effect on the swelling behavior when analyzed with respect to solvent volume. The reviewed experimental studies provide a thermodynamic characterization of the swelling of lamellar zwitterionic phospholipid systems that should be encompassed in the mechanistic molecular interpretation of the "hydration force."},
  author       = {Sparr, Emma and Wennerström, Håkan},
  issn         = {1359-0294},
  keyword      = {Phase diagrams,Isothermal sorption microcalorimeter,molar enthalpy,Partial,Water chemical potential,Phospholipid-water-cosolvent systems,Cholesterol-DMPC interaction,Phospholipid hydration,Lamellar phases},
  language     = {eng},
  number       = {6},
  pages        = {561--567},
  publisher    = {Elsevier},
  series       = {Current Opinion in Colloid & Interface Science},
  title        = {Interlamellar forces and the thermodynamic characterization of lamellar phospholipid systems},
  url          = {http://dx.doi.org/10.1016/j.cocis.2011.05.003},
  volume       = {16},
  year         = {2011},
}