investigating-single-molecule-adhesion-by-atomic-force-spectroscopy

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Atomic force spectroscopy is an ideal tool to study molecules at surfaces and interfaces. An experimental protocol to couple a large variety of single ...

Technische Universität München

Ethanol has a profound impact on biological systems and is moreover used in various medical and nonmedical applications. Its interaction with the lipid part of biological membranes has been the subject of intensive studies, but surprisingly, to our knowledge, no study has examined the influence of ethanol on lipid bilayer nanomechanics. We performed atomic force microscopy-based measurements to assess the influence of ethanol on the nanomechanical properties of fluid supported lipid bilayers. Ethanol significantly reduces membrane stability, bilayer thickness, Young's modulus, area stretch modulus, and bending stiffness. Altogether, our data suggest that ethanol addition to supported lipid bilayers supports both the hydrophobic and the hydrophilic permeation pathways by a decrease of bilayer thickness and reduced stability, respectively.

The nanomechanical properties of lipid membranes are significantly influenced by the presence of ethanol.

Cholesterol is important for the formation of microdomains in supported lipid bilayers and is enriched in the liquid-ordered phase. To understand the interactions leading to this enrichment, we developed an AFM-based single-lipid-extraction (SLX) approach that enables us to determine the anchoring strength of cholesterol in the two phases of a phase-separated lipid membrane. As expected, the forces necessary for extracting a single cholesterol molecule from liquid-ordered phases are significantly higher than for extracting it from the liquid-disordered phases. Interestingly, application of the Bell model shows two energy barriers that correlate with the head and full length of the cholesterol molecule. The resulting lifetimes for complete extraction are 90 s and 11 s in the liquid-ordered and liquid-disordered phases, respectively. Molecular dynamics simulations of the very same experiment show similar force profiles and indicate that the stabilization of cholesterol in the liquid-ordered phase is mainly due to nonpolar contacts.

Article	Year
The nanomechanical properties of lipid membranes are significantly influenced by the presence of ethanol. Biophysical journal\| PubMed ID: 23473487	2013
Single lipid extraction: the anchoring strength of cholesterol in liquid-ordered and liquid-disordered phases. Biophysical journal\| PubMed ID: 25185552	2014

Frank W. S. Stetter

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