membrane properties

membrane structure

Lipid bilayers are characterized with a number of different structural parameters such as thickness, lipid packing and acyl chain order. These parameters have become classical descriptors of the state of the lipid bilayer that can be used to study relevant effects of lipid composition or any physical perturbations. Many of these structural properties can be quantified from bilayer simulations and are also accessible in experiments, however individual leaflet resolution is often challenging to achieve in vitro. A central approach in our work is the identification of connections between simulations and experiments that help validate the computational trajectories while providing a window into the more detailed characterization of bilayer leaflets. Some examples include calibration of environment-sensitive probes against simulated area per lipid, the specialized analysis of cryo-EM data allowing for quantification of membrane thickness, NMR-derived order parameters of the lipid chains and modeling of small-angle scattering curves to recover bilayer parameters including lipid packing and thickness.

membrane elasticity

Biological membranes can bend and stretch in response to different stimuli including protein-membrane interactions. The respective deformations incur energetic costs that can be quantified with mechanical constants such as bending rigidity and area compressibility moduli. While these elastic properties are defined in the continuum limit and characterize the behavior of the bilayer at long length- and time-scales, relevant information can also be obtained from analysis of local lipid fluctuations. We have recently developed different methods for the calculation of apparent local moduli from simulations of lipid bilayers. One of these approaches includes the design of an improved framework for calculating relaxation rates of carbon-hydrogen bond fluctuations that can be directly compared to results from NMR spectroscopy. These and other approaches reveal a central role of the lipid dynamics at the mid-bilayer region in membrane mechanics.

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