title: Unusual penetration of phospholipid mono- and bilayers by Quillaja bark saponin biosurfactant.
abstract: The interactions between a model phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and a biosurfactant Quillaja Bark Saponin (QBS) obtained from the bark of Quillaja saponaria Molina were studied using simple models of biological membranes. QBS is known to interact strongly with the latter, exerting a number of haemolytic, cytotoxic and anti-microbial actions. The interaction of QBS dissolved in the subphase with DPPC monolayers and silicon-supported bilayers was studied above the cmc (10(-3)M). Surface pressure relaxation and surface dilatational rheology combined with quartz crystal microbalance (QCM) and neutron reflectivity (NR) were employed for this purpose. The DPPC-penetrating abilities of QBS are compared with those of typical synthetic surfactants (SDS, CTAB and Triton X-100). We show that the penetration studies using high surface activity (bio)surfactants should be performed by a subphase exchange, not by spreading onto the surfactant solution. In contrast to the synthetic surfactants of similar surface activity, QBS does not collapse DPPC mono- and bilayers, but penetrates them, improving their surface dilatational elastic properties even in the highly compressed solid state. The dilatational viscoelasticity modulus increases from 204 mN/m for pure DPPC up to 310 mN/m for the QBS-penetrated layers, while it drops to near zero values in the case of the synthetic surfactants. The estimated maximum insertion pressure of QBS into DPPC monolayers exceeds the maximum surface pressure achievable in our setup, in agreement with the surface rheological response of the penetrated layers.
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. Electronic address: kamil.wojciechowski@ch.pw.edu.pl.
authors.forename: Kamil
authors.initials: K
authors.lastname: Wojciechowski
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Orczyk
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutberlet
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Trapp
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
authors.forename: Kuba
authors.initials: K
authors.lastname: Marcinkowski
authors.affiliation: Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kobiela
authors.affiliation: Laboratory for Neutron Scattering, Paul Scherrer Institute, WHGA/110, 5232 Villigen - PSI, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Geue
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000031:analogs & derivatives / Q000378:metabolism; D001692:Biological Transport; D008051:Lipid Bilayers / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D031990:Quillaja / Q000378:metabolism*; D012503:Saponins / Q000378:metabolism*; D013499:Surface Properties; D013500:Surface Tension; D013501:Surface-Active Agents / Q000378:metabolism*; D014867:Water / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D010743:Phospholipids; D012503:Saponins; D013501:Surface-Active Agents; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C081581:colfosceril palmitate
keywords: DPPC; Neutron reflectivity; QBS; QCM; Surface rheology