title: A Langmuir film approach to elucidating interactions in lipid membranes: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine/cholesterol/metal cation systems.
abstract: The interactions between two membrane lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and cholesterol (CHOL), were studied in Langmuir films using surface pressure isotherms and Brewster angle microscopy. The DPPE/CHOL interactions were probed for chosen monolayer and subphase (Na(+), Ca(2+)) composition at 20, 25, and 30 degrees C. The results obtained show that DPPE and CHOL are miscible for the cholesterol mol fractions x(CHOL)=0.3-0.5. Cholesterol induces condensation of the DPPE monolayers. The most significant condensation of the DPPE/CHOL monolayers was observed in the presence of Ca(2+) ions in the subphase at x(CHOL)=0.4. The negative deviation of the molecular surface area (MMA) additivity from the ideal behavior together with negative values of excess free enthalpy of mixing in the monolayers were interpreted in terms of attractive interactions between lipid molecules.
authors.affiliation: Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, R. Ingardena 3, 30-060 Krakow, Poland. bkorch@chemia.uj.edu.pl
authors.forename: Beata
authors.initials: B
authors.lastname: Korchowiec
authors.forename: Maria
authors.initials: M
authors.lastname: Paluch
authors.forename: Yohann
authors.initials: Y
authors.lastname: Corvis
authors.forename: Ewa
authors.initials: E
authors.lastname: Rogalska
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D013696:Temperature
chemical_list: D002412:Cations; D008563:Membrane Lipids; D010714:Phosphatidylethanolamines; C007510:1,2-dipalmitoyl-3-phosphatidylethanolamine; D002784:Cholesterol; D012964:Sodium; D002118:Calcium