title: On the Interaction between Digitonin and Cholesterol in Langmuir Monolayers.
abstract: In this article, we describe the effect of a highly hemolytic saponin, digitonin, on model lipids cholesterol and dipalmitoylphosphatidylcholine (DPPC) using a combination of tensiometric (surface pressure and dilatational surface elasticity), spectroscopic (infrared reflection absorption spectroscopy, IRRAS), microscopic (fluorescence microscopy), and scattering techniques (neutron reflectivity, NR, and grazing incidence X-ray diffraction, GIXD). The monolayers of individual lipids and their 10:9 (mol/mol) mixture were exposed to an aqueous solution of digitonin (10(-4) M) by subphase exchange using a setup developed recently in our laboratory. The results confirm that digitonin can adsorb onto both bare and lipid-covered water-air interfaces. In the case of DPPC, a relatively weak interaction can be observed, but the presence of cholesterol drastically enhances the effect of digitonin. The latter is shown to dissociate the weak cholesterol-DPPC complexes and to bind cholesterol in an additional layer attached to the original lipid monolayer.
authors: Faculty of Chemistry, Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw, Poland.
authors: Kamil
authors: K
authors: Wojciechowski
authors: Faculty of Chemistry, Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw, Poland.
authors: Marta
authors: M
authors: Orczyk
authors: Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany.
authors: Thomas
authors: T
authors: Gutberlet
authors: Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, Potsdam, Germany.
authors: Gerald
authors: G
authors: Brezesinski
authors: Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute , WHGA/110, 5232 Villigen - PSI, Switzerland.
authors: Thomas
authors: T
authors: Geue
authors: Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin BP48, Gif-sur-Yvette Cedex, France.
authors: Philippe
authors: P
authors: Fontaine
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000327:Adsorption; D000388:Air / Q000032:analysis; D002784:Cholesterol / Q000737:chemistry*; D004072:Digitonin / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D053835:Unilamellar Liposomes; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol; D004072:Digitonin