title: Impact of two different saponins on the organization of model lipid membranes.
abstract: Saponins, naturally occurring plant compounds are known for their biological and pharmacological activity. This activity is strongly related to the amphiphilic character of saponins that allows them to aggregate in aqueous solution and interact with membrane components. In this work, Langmuir monolayer techniques combined with polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and Brewster angle microscopy were used to study the interaction of selected saponins with lipid model membranes. Two structurally different saponins were used: digitonin and a commercial Merck Saponin. Membranes of different composition, namely, cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) were formed at the air/water and air/saponin solution interfaces. The saponin-lipid interaction was characterized by changes in surface pressure, surface potential, surface morphology and PM-IRRAS signal. Both saponins interact with model membranes and change the physical state of membranes by perturbing the lipid acyl chain orientation. The changes in membrane fluidity were more significant upon the interaction with Merck Saponin. A higher affinity of saponins for cholesterol than phosphatidylglycerols was observed. Moreover, our results indicate that digitonin interacts strongly with cholesterol and solubilize the cholesterol monolayer at higher surface pressures. It was shown, that digitonin easily penetrate to the cholesterol monolayer and forms a hydrogen bond with the hydroxyl groups. These findings might be useful in further understanding of the saponin action at the membrane interface and of the mechanism of membrane lysis.
authors.affiliation: Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland. Electronic address: bkorch@chemia.uj.edu.pl.
authors.forename: Beata
authors.initials: B
authors.lastname: Korchowiec
authors.affiliation: Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland.
authors.forename: Marcelina
authors.initials: M
authors.lastname: Gorczyca
authors.affiliation: Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland; Structure et Réactivité des Systèmes Moléculaires Complexes, BP 239, CNRS/Université de Lorraine, 54506 Vandoeuvre-lès-Nancy cedex, France.
authors.forename: Kamila
authors.initials: K
authors.lastname: Wojszko
authors.affiliation: Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, ul. R. Ingardena 3, 30-060 Krakow, Poland; Faculty of Physics, Astronomy, and Applied Computer Science, Jagiellonian University, ul. S. Lojasiewicza 11, 30-348 Krakow, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Janikowska
authors.affiliation: Structure et Réactivité des Systèmes Moléculaires Complexes, BP 239, CNRS/Université de Lorraine, 54506 Vandoeuvre-lès-Nancy cedex, France.
authors.forename: Max
authors.initials: M
authors.lastname: Henry
authors.affiliation: Structure et Réactivité des Systèmes Moléculaires Complexes, BP 239, CNRS/Université de Lorraine, 54506 Vandoeuvre-lès-Nancy cedex, France. Electronic address: ewa.rogalska@univ-lorraine.fr.
authors.forename: Ewa
authors.initials: E
authors.lastname: Rogalska
mesh_terms: D004072:Digitonin / Q000737:chemistry*; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D008422:Materials Testing; D008560:Membrane Fluidity; D008968:Molecular Conformation; D012503:Saponins / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D012503:Saponins; D004072:Digitonin
keywords: Digitonin; Langmuir films; Lipid monolayers; Saponin–membrane interactions