title: Reversible Lifting of Surface Supported Lipid Bilayers with a Membrane-Spanning Nonionic Triblock Copolymer.
abstract: Neutron reflectometry was used to monitor structural variations in surface-supported dimyristoylphosphatidycholine (DMPC) bilayers induced by the addition of Triton X-100, a surfactant commonly used to aid solubilization of membrane proteins, and the coaddition of a membrane spanning nonionic amphiphilic triblock copolymer, (PEO117-PPO47-PEO117, Pluronic F98). Surfactant addition causes slight compression of the bilayer thickness and the creation of a distinct EO layer that increases the hydrophilic layer proximal to the supporting substrate (i.e., a water and EO gap between the lipid bilayer and quartz) to 6.8 ± 0.4 Å. Addition of the triblock copolymer into the DMPC:Triton X-100 bilayer increases the complexity of (broadens) the lipid phase transition, further compresses the bilayer, and continues to expand the proximal hydrophilic layer thickness. The observed structural changes are temperature dependent with transmembrane polymer insertion achieved at 37 °C, leading to a compressed membrane thickness of 39.2 ± 0.2 Å and proximal gap of 45.0 ± 0.2 Å. Temperature-driven exclusion of the polymer at 15 °C causes partitioning of the polymer into the proximal space generating a large hydrogel cushion 162 ± 16 Å thick. An intermediate gap width (10-27 Å) is achieved at room temperature (22-25 °C). The temperature-driven changes in the proximal hydrophilic gap dimensions are shown to be reversible, but thermal history causes variation in magnitude. Temperature-driven changes in polymer association with a supported lipid bilayer offer a facile means to reversibly control both the membrane characteristics as well as the separation between membrane and solid substrate.
authors.affiliation: Materials Physics & Applications, Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory , Mail Stop K771, Los Alamos, New Mexico 87545, United States.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hayden
authors.affiliation: Lujan Neutron Scattering Center, Los Alamos Neutron Science Center (LANSCE), Los Alamos National Laboratory , Mail Stop H805, Los Alamos, New Mexico 87545, United States.|Materials Science & Engineering (MST-7), Los Alamos National Laboratory , Mail Stop H805, Los Alamos, New Mexico 87545, United States.
authors.forename: Ann
authors.initials: A
authors.lastname: Junghans
authors.affiliation: Materials Physics & Applications, Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory , Mail Stop K771, Los Alamos, New Mexico 87545, United States.|Lujan Neutron Scattering Center, Los Alamos Neutron Science Center (LANSCE), Los Alamos National Laboratory , Mail Stop H805, Los Alamos, New Mexico 87545, United States.|Department of Chemical Engineering, University of California Davis , Davis, California 95616, United States.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Majewski
authors.affiliation: Materials Physics & Applications, Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory , Mail Stop K771, Los Alamos, New Mexico 87545, United States.
authors.forename: Millicent A
authors.identifier: 0000-0002-8671-1502
authors.initials: MA
authors.lastname: Firestone
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D009502:Neutrons; D017830:Octoxynol / Q000737:chemistry; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D011108:Polymers; D013501:Surface-Active Agents; D017830:Octoxynol; D004134:Dimyristoylphosphatidylcholine