Supported Lipid Bilayers on Mica and Silicon Oxide: Comparison of the Main Phase Transition Behavior

Abstract

The usual biophysical approach to the study of biological membranes is that of turning to model systems. From these models, general physical principles ruling the lateral membrane structure can be obtained. A promising model system is the supported lipid bilayer (SLB) which could foresee the simultaneous investigation of the structure and physical properties of lipid bilayers reconstituted with membrane proteins. A complete exploitation of the model system to retrieve biologically relevant information requires an in-depth knowledge of the possible effect that experimental parameters could have on the behavior of the SLB. Here we used atomic force microscopy (AFM) to study the effect of different types of substrates on the behavior of SLBs as far as their main phase transition is concerned. We found that different substrates (mica and silicon oxide) can affect in dissimilar ways the interleaflet coupling of the bilayer, which might represent a sort of lipid signaling allowing communication between receptors on the extracellular leaflet and cytoplasmic components. By decreasing the interaction between the SLB and the substrate the interleaflet coupling is preserved independently of the bilayer preparation strategy. Moreover, we investigated by time-lapse AFM an isothermal phase transition induced by a pH change on a SLB. We established that the presence of a pH gradient across the bilayer can weaken the strength of the interleaflet coupling which is present in symmetrical pH conditions.

Lipid tail protrusions mediate the insertion of nanoparticles into model cell membranes

“…While future work will be needed to establish that such factors affect AuNP insertion, there is some evidence in existing experimental results that supports the idea that enhanced lipid fluctuations reduce the barrier for AuNP insertion. In this study, hard substrates were used to support the planar lipid bilayers that may reduce lipid mobility by stabilizing the contacting lipid head groups 57,58 . This effect likely reduced the probability of tail protrusions, further limiting the insertion of AuNPs into the defect-free bilayers.…”

Unraveling lipid/protein interaction in model lipid bilayers by Atomic Force Microscopy

“…In the latter case a strong coupling between the two leaflets could be the reason for the same lateral mobility. We recently demonstrated that the interleaflet coupling is strongly related to the experimental details of the sample preparation, including preparation temperature and the type of support (Seeger et al, 2009b;Seeger et al, 2010). So, it is not always possible to compare the obtained results even if related to the same system.…”

Comparison of Actin- and Glass-Supported Phospholipid Bilayer Diffusion Coefficients

“…It is noted that the change of the diffusion mode occurred at approximately the main-phase transition temperature determined from the diffusion coefficients measured via z-scan FCS. Examination of the data for the glass-supported bilayers suggests similar results, with the change in the diffusion mode potentially occurring near the measured main-phase transition temperature of 24.3 C. However, the uncertainty of the data in the temperature range of [20][21][22][23][24] C prohibits any absolute statements about the diffusion behavior. Regardless, it is clear that there is a substrate-dependent difference in behavior in the [20][21][22][23][24] C temperature range when comparing the actin-supported and glass-supported bilayers.…”

“…The diffusion coefficients for the glass-supported membranes (Fig. 3, triangles) also increased with temperature, but over a more narrow range (22)(23)(24)(25)(26)(27)(28)(29)(30) C). The main-phase transition temperature for each model membrane was determined via …”