Biology subjects

Aleksanyan, M.

Publications and source records attributed to Aleksanyan, M..

3 recordsLinked to original sources

bioRxiv2023

Modulating membrane shape and mechanics of minimal cells by light: area increase, softening and interleaflet coupling of membrane models doped with azobenzene-lipid photoswitches

Light can effectively interrogate biological systems in a reversible and physiologically compatible manner with high spatiotemporal precision. Understanding the biophysics of photo-induced processes in bio-systems is crucial for achieving relevant clinical applications. Employing membranes doped with the photolipid azobenzene-phosphatidylcholine (azo-PC), we provide a holistic picture of light-triggered changes in membrane kinetics, morphology and material properties obtained from correlative studies on cell-sized vesicles, Langmuir monolayers, supported lipid bilayers and molecular dynamics simulations. Light-induced membrane area increase as high as [~]25% and a 10-fold decrease in the membrane bending rigidity is observed upon trans-to-cis azo-PC isomerization associated with membrane leaflet coupling and molecular curvature changes. Vesicle electrodeformation measurements and atomic force microscopy reveal that trans azo-PC bilayers are thicker than POPC bilayer but have higher specific membrane capacitance and dielectric constant suggesting an increased ability to store electric charges across the membrane. Lastly, incubating POPC vesicles with azo-PC solutions resulted in the insertion of azo-PC in the membrane enabling them to become photoresponsive. All these results demonstrate that light can be used to finely manipulate the shape, mechanical and electric properties of photolipid-doped minimal cell models and liposomal drug carriers, thus, presenting a promising therapeutic alternative for the repair of cellular disorders.

biophysics↗

bioRxiv2022

Kinetic relaxation of giant vesicles validates diffusional softening in a binary lipid mixture

The stiffness of biological membranes determines the work required by cellular machinery to form and dismantle vesicles and other lipidic shapes. Model membrane stiffness can be determined from the equilibrium distribution of giant unilamellar vesicle surface undulations observable by phase contrast microscopy. With two or more components, lateral fluctuations of composition will couple to surface undulations depending on the curvature sensitivity of the constituent lipids. The result is a broader distribution of undulations whose complete relaxation is partially determined by lipid diffusion. In this work, kinetic anaysis of the undulations of giant unilamellar vesicles made of phospatidylcholine-phosphatidylethanolamine mixtures validates the molecular mechanism by which the membrane is made 25% softer than a single-component one. The mechanism is relevant to biological membranes, which have diverse and curvature-sensitive lipids.

biophysics↗

bioRxiv2022

GM1 asymmetry in the membrane stabilizes pores

Cell membranes are highly asymmetric and their stability against poration is crucial for survival. We investigated the influence of membrane asymmetry on electroporation of giant unilamellar vesicles with membranes doped with GM1, a ganglioside asymmetrically enriched in the outer leaflet of neuronal cell membranes. Compared to symmetric membranes, the lifetimes of micronsized pores are about an order of magnitude longer suggesting that pores are stabilized by GM1. Internal membrane nanotubes caused by the GM1 asymmetry, obstruct and additionally slow down pore closure, effectively reducing pore edge tension and leading to leaky membranes. Our results point to the drastic effects this ganglioside can have on pore resealing in biotechnology applications based on poration as well as on membrane repair processes. SIGNIFICANCEMembrane pore closure is crucial for cell survival and is important for biotechnological and medicine applications based on transfer of material, e.g. drugs, genes, through pores. Electroporation is widely used as means to perforate the membrane but factors governing membrane resealing are still a matter of debate, in particular the large variations of pore lifetimes. Here, we probed the effect of bilayer asymmetry on pore dynamics employing cell-sized giant unilamellar vesicles doped with the ganglioside GM1 (asymmetrically enriched in neurons). We find that the presence of GM1 and its asymmetric distribution in the bilayer dramatically slows down pore resealing, not only by mere molecular stabilization of the pore rim, but also by generating membrane nanotubes.

biophysics↗