Abstract
Curvature is a fundamental lipid membrane property that influences many membrane-mediated biological processes and dynamic soft materials. One of the key parameters that determines the energetics of curvature change is the membrane bending rigidity. Understanding the intrinsic effect of pressure on membrane bending is critical to understanding the adaptation and structural behavior of biomembranes in deep-sea organisms as well as soft material processing. However, it has not previously been possible to measure the influence of high hydrostatic pressure on membrane bending energetics, and this bottleneck has primarily been due to a lack of technology platforms for performing such measurements. We have developed a new high-pressure microscopy cell which, combined with vesicle fluctuation analysis, has allowed us to make the first measurements of membrane bending rigidity as a function of pressure. Our results show a significant increase in bending rigidity at pressures up to 40 MPa. Above 40 MPa, the membrane mechanics become more complex. Corresponding small and wide-angle X-ray diffraction shows an increase in density and thickness of the bilayer with increasing pressure which correlates with the micromechanical measurements. These results are consistent with recent theoretical predictions of the bending rigidity as a function of hydrocarbon chain density. This technology has the potential to transform our quantitative understanding of the role of pressure in soft material processing, the structural behavior of biomembranes, and the adaptation mechanisms employed by deep-sea organisms.
Highlights
Lipid membranes are vital in maintaining cellular integrity and play an active role in a wide range of biological functions, including cell signaling, endo- and exo-cytosis, intracellular cargo delivery and generally modulating activity of membrane associated proteins
By developing a novel high pressure microscopy system we have been able to make the first measurement of the effect of high hydrostatic pressure on the bending rigidity of model membranes
SAXS / WAXS shows that increasing pressure causes a decrease in the area per lipid chain and an increase in the bilayer thickness, which in turn leads to an increase in membrane bending rigidity
Summary
Lipid membranes are vital in maintaining cellular integrity and play an active role in a wide range of biological functions, including cell signaling, endo- and exo-cytosis, intracellular cargo delivery and generally modulating activity of membrane associated proteins. Many of these processes are facilitated by, or coupled to, changes in the curvature of lipid bilayers.[1] Over 70% of the earth is covered by oceans, and life has been found down to the bottom of the deepest ocean trenches at pressures up to 110 MPa (1100 bar). This is coupled to a microscopy system that allows high speed recording of the GUV thermal fluctuations, which are subsequently analyzed to extract the membrane bending rigidity
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