Anchor-lipid monolayers at the air-water interface; prearranging of model membrane systems
ABSTRACT Model membrane systems are gaining more and more interest both for basic studies of membrane-related processes as well as for biotechnological applications. Several different model systems have been reported among which the tethered bilayer lipid membranes (tBLMs) form a very attractive and powerful architecture. In all the proposed architectures, a control of the lateral organization of the structures at a molecular level is of great importance for an optimized preparation. For tBLMs, a homogeneous and not too dense monolayer is required to allow for the functional incorporation of complex membrane proteins. We present here an alternative approach to the commonly used self-assembly preparation. Lipids are spread on the air-water interface of a Langmuir film balance and form a monomolecular film. This allows for a better control of the lateral pressure and distribution for subsequent transfer to solid substrates. In this paper, we describe the properties of the surface monolayer, in terms of surface pressure, structure of the lipid molecule, content of lipid mixtures, temperature, and relaxations features. It is shown that a complete mixing of anchor-lipids and free lipids can be achieved. Furthermore, an increase of the spacer lengths and a decrease of the temperature lead to more compact films. This approach is a first step toward the fully controlled assembly of a model membrane system.
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ABSTRACT: Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) has been applied to determine the conformation, orientation, and hydration of a monolayer of 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-dl-alpha-lipoic acid ester (DPTL) self-assembled at a gold electrode surface. This Archaea analogue thiolipid has been recently employed to build tethered lipid bilayers. By synthesizing DPT(d16)L, a DPTL molecule with a deuterium substituted tetraethylene glycol spacer, it was possible to differentiate the C-H stretch vibrations of the phytanyl chains from the tetraethylene glycol spacer and acquire the characteristic IR spectra for the chains, spacer, and lipoic acid headgroup separately. Our results show that the structure of the monolayer displays remarkable stability in a broad range of electrode potentials and that the phytanyl chains remain in a liquid crystalline state. The tetraethylene glycol chains are coiled, and the IR spectrum for this region shows that it is in the disordered state. The most significant result of this study is the information that in contrast to expectations the spacer region is poorly hydrated. Our results have implications for the design of a tethered lipid membrane based on this thiolipid.Langmuir 07/2009; 25(17):10354-63. DOI:10.1021/la900907d · 4.38 Impact Factor
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ABSTRACT: Solid supported membrane systems have been established as biomimetic architectures, which allow for the systematic investigation of various membrane-related processes. Especially tethered bilayer lipid membranes have been a successful concept. They consist of a lipid bilayer that is covalently anchored to a solid substrate through a spacer group. The submembrane part, which is defined by the spacer group, is important especially for the biological activity of incorporated membrane proteins. Anchor lipids with different spacer and anchor groups have been synthesized, and the resulting membrane structures have been investigated by neutron reflectivity. The different molecular architectures had a significant effect on both the amount of water incorporated in the spacer region and the electrical properties of the bilayer. A detailed understanding of the structure-function relationship allows for an optimized design of the molecular architecture with respect to possible applications, for example an optimized protein incorporation.Langmuir 07/2010; 26(13):11035-40. DOI:10.1021/la100342k · 4.46 Impact Factor