Electrostatic interactions between lipid domains in membranes

WILKE, NATALIA; MANGIAROTTI, AGUSTÍN

Capital Federal

Simposio; Frontiers in Physical Sciences; 2016

ICAS, AvH Founfation, Sociedad Max Planck

Biological membranes are open and complex systems, and due to their dynamic composition, understanding the principles that rule lateral organization and the relation with its functioning constitutes a challenging task. These complexity has motivated the development of experimental models with tunable sizes, geometries and compositions that can be controlled in order to get insight into the properties of biomembranes.1 One of the most studied aspects of membranes is the formation of lipid domains as result of lipid phase segregation. The importance of these heterogeneities resides in that these kind of structures in cell membranes have been associated with protein sorting,2?4 membrane traffic,5 ion-channel regulation,6 and singaling7,8 among other cellular functions. The formation of structured domain patterns has been observed in model systems such as Langmuir monolayers at air-water interface, and this modulation has been explained as result of the competition between line tension and the inter-domain dipolar repulsion.9?12 In the case of lipid bilayers, many researchers claimed that these interactions are only important at nanoscopic scales since the membrane is immersed in an aqueous environment, and ionic screening reduces the dipolar interaction length scale. In some of the works dealing with this issue, theoretic calculations have been developed13?15 while in others, it has simply been assumed. Notwithstanding, there is a lack of experimental evidence sustaining these statements. In this study, we measured the effect of inter-domain interactions on the properties of planar lipid bilayers at a micron-scale using different approaches for neutral and charged domains. Far from being negligible, we showed that domain-domain electrostatic repulsions in bilayers appeared not only to be present but also to have a fundamental role in diffusive motion, interfacial structuring and merging of domains. These forces, very probably occurring within the membrane plane, appear to be important at a micron-ranged length scale, and at physiological conditions. Therefore, electrostatic interactions between the species inserted in the cell membranes may account to a manner for regulating the membrane properties, and of communication of the molecules within the membrane. In addition to biological membranes, it is important to remark that these results may be relevant to other kinds of thin films with a mesoscopic structuration of dipolar or charged species.References 1-Y.-H. M. Chan and S. G. Boxer, Curr. Opin. Chem. Biol., 2007, 11, 581?7.2-D. Lingwood and K. Simons, Science (80-. )., 2009, 327, 46?50.3-I. Mellman and W. J. Nelson, Nat Rev Mol Cell Biol, 2008, 9, 833?845.4-M. Stöckl, J. Nikolaus and A. Herrmann, in Liposomes: Methods and Protocols, Volume 2: Biological Membrane Models, ed. V. Weissig, Humana Press, Totowa, NJ, 2010, pp. 115?126.5-M. F. Hanzal-Bayer and J. F. Hancock, FEBS Lett., 2007, 581, 2098?104.6-C. Dart, J. Physiol., 2010, 588, 3169?78.7-K. Simons and D. Toomre, Nat Rev Mol Cell Biol, 2000, 1, 31?39.8-A. F. G. Quest, J. L. Gutierrez-Pajares and V. A. Torres, J. Cell. Mol. Med., 2008, 12, 1130?1150.9-H. McConnell, Annu. Rev. Phys. Chem., 1991, 42, 171?195.10-T. M. Fischer and L. Mathias, 2004, 394, 383?394.11-M. Seul and D. Andelman, Science, 1995, 267, 476?483.12-D. Andelman, MRS Proc., 1989, 177, 337?344.13-J. Liu, S. Qi, J. T. Groves and A. K. Chakraborty, J. Phys. Chem. B, 2005, 109, 19960?9.14-T. M. Konyakhina, S. L. Goh, J. Amazon, F. A. Heberle, J. Wu and G. W. Feigenson, Biophys. J., 2011, 101, L8?L10.15-J. J. Amazon, S. L. Goh and G. W. Feigenson, Phys. Rev. E - Stat. Nonlinear, Soft Matter Phys., 2013, 87, 1?10.