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Not just a fluidifying effect : omega-3 phospholipids induce formation of non-lamellar structures in biomembranes

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Scoppola,  Ernesto
Emanuel Schneck, Biomaterialien, Max Planck Institute of Colloids and Interfaces, Max Planck Society;

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Citation

de Santis, A., Vitiello, G., Appavou, M.-S., Scoppola, E., Fragneto, G., Barnsley, L. C., et al. (2020). Not just a fluidifying effect: omega-3 phospholipids induce formation of non-lamellar structures in biomembranes. Soft Matter, 16(46), 10425-10438. doi:10.1039/D0SM01549K.


Cite as: http://hdl.handle.net/21.11116/0000-0007-63EC-0
Abstract
Polyunsaturated omega-3 fatty acid docosahexaenoic acid (DHA) is found in very high concentrations in a few peculiar tissues, suggesting that it must have a specialized role. DHA was proposed to affect the function of the cell membrane and related proteins through an indirect mechanism of action, based on the DHA-phospholipid effects on the lipid bilayer structure. In this respect, most studies have focused on its influence on lipid-rafts, somehow neglecting the analysis of effects on liquid disordered phases that constitute most of the cell membranes, by reporting in these cases only a general fluidifying effect. In this study, by combining neutron reflectivity, cryo-transmission electron microscopy, small angle neutron scattering, dynamic light scattering and electron paramagnetic resonance spectroscopy, we characterize liquid disordered bilayers formed by the naturally abundant 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and different contents of a di-DHA glycero-phosphocholine, 22:6-22:6PC, from both a molecular/microscopic and supramolecular/mesoscopic viewpoint. We show that, below a threshold concentration of about 40% molar percent, incorporation of 22:6-22:6PC in the membrane increases the lipid dynamics slightly but sufficiently to promote the membrane deformation and increase of multilamellarity. Notably, beyond this threshold, 22:6-22:6PC disfavours the formation of lamellar phases, leading to a phase separation consisting mostly of small spherical particles that coexist with a minority portion of a lipid blob with water-filled cavities. Concurrently, from a molecular viewpoint, the polyunsaturated acyl chains tend to fold and expose the termini to the aqueous medium. We propose that this peculiar tendency is a key feature of the DHA-phospholipids making them able to modulate the local morphology of biomembranes.