PMID- 15923231
OWN - NLM
STAT- MEDLINE
DCOM- 20051018
LR  - 20191210
IS  - 0006-3495 (Print)
IS  - 1542-0086 (Electronic)
IS  - 0006-3495 (Linking)
VI  - 89
IP  - 2
DP  - 2005 Aug
TI  - Interactions of cholesterol with lipid membranes and cyclodextrin characterized 
      by calorimetry.
PG  - 1109-19
AB  - Interactions of cholesterol (cho) with different lipids are commonly believed to 
      play a key role in the formation of functional domains in membranes. We introduce 
      a novel approach to characterize cho-lipid interactions by isothermal titration 
      calorimetry. Cho is solubilized in the aqueous phase by reversible complexation 
      with methyl-beta-cyclodextrin (cyd). Uptake of cho into the membrane is measured 
      upon a series of injections of lipid vesicles into a cyd/cho solution. As an 
      independent assay, cho release from membranes is measured upon titrating 
      lipid/cho mixed vesicles into a cyd solution. The most consistent fit to the data 
      is obtained with a mole fraction (rather than mole ratio) partition coefficient 
      and considering a cho/cyd stoichiometry of 1:2. The results are discussed in 
      terms of contributions from 1), the transfer of cho from cyd into a hypothetical, 
      ideally mixed membrane and 2), from nonideal interactions with POPC. The latter 
      are exothermic but opposed by a strong loss in entropy, in agreement with 
      cho-induced acyl chain ordering and membrane condensation. They are accompanied 
      by a positive heat capacity change which cannot be interpreted in terms of the 
      hydrophobic effect, suggesting that additive-induced chain ordering itself 
      increases the heat capacity. The new assays have a great potential for a better 
      understanding of sterol-lipid interactions and yield suggestions how to optimize 
      cho extraction from membranes.
FAU - Tsamaloukas, Alekos
AU  - Tsamaloukas A
AD  - Biozentrum of the University of Basel, Division of Biophysical Chemistry, 
      Switzerland.
FAU - Szadkowska, Halina
AU  - Szadkowska H
FAU - Slotte, Peter J
AU  - Slotte PJ
FAU - Heerklotz, Heiko
AU  - Heerklotz H
LA  - eng
PT  - Evaluation Study
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20050527
PL  - United States
TA  - Biophys J
JT  - Biophysical journal
JID - 0370626
RN  - 0 (Cyclodextrins)
RN  - 0 (Lipid Bilayers)
RN  - 0 (Phosphatidylcholines)
RN  - 97C5T2UQ7J (Cholesterol)
RN  - TE895536Y5 (1-palmitoyl-2-oleoylphosphatidylcholine)
SB  - IM
MH  - Calorimetry/*methods
MH  - Cholesterol/*chemistry
MH  - Computer Simulation
MH  - Cyclodextrins/*chemistry
MH  - Lipid Bilayers/*chemistry
MH  - *Membrane Fluidity
MH  - Membrane Microdomains/*chemistry
MH  - *Models, Chemical
MH  - Phase Transition
MH  - Phosphatidylcholines/*chemistry
MH  - Thermodynamics
PMC - PMC1366596
EDAT- 2005/06/01 09:00
MHDA- 2005/10/19 09:00
PMCR- 2006/08/01
CRDT- 2005/06/01 09:00
PHST- 2005/06/01 09:00 [pubmed]
PHST- 2005/10/19 09:00 [medline]
PHST- 2005/06/01 09:00 [entrez]
PHST- 2006/08/01 00:00 [pmc-release]
AID - S0006-3495(05)72759-4 [pii]
AID - 61846 [pii]
AID - 10.1529/biophysj.105.061846 [doi]
PST - ppublish
SO  - Biophys J. 2005 Aug;89(2):1109-19. doi: 10.1529/biophysj.105.061846. Epub 2005 
      May 27.