Ricerc@Sapienza

The project will develop full size, integrated, dynamical models of lipid membranes. Lipid bilayers are found in the cytosolic membrane of cells and in the barriers that isolate their internal organelles. They are highly dynamic systems able to rearrange their topology in response to mechanical and chemical stimuli. In addition to the biological interest, the dynamic compartmentalization they feature can be exploited for biomimetic systems for, e.g., enzyme synthesis, membrane based sensors, desalination and water purification and personalized medicine. Based on their multiscale nature - nanometer thickness and micrometer lateral extension - lipid bilayers are considered continuous surfaces endowed with curvature elasticity. This approach cannot handle topological modifications like vesicles fusion or detachment with/from the bilayer, see, e.g., endo- and exocytosis. On the other hand, molecular modeling is limited to portions of the membrane of tens of nanometers which cannot capture the global dynamics. The present project overcomes these limitations exploiting phase-field methods and leveraging the interdisciplinary PI's expertise in developing innovative mesoscale models able to capture topological transitions. The proposal is structured into complementary parts: 1) mesoscale lipid bilayer dynamics, implemented in the context of phase field models with an original approach that includes thermal fluctuations in the spirit of fluctuating hydrodynamics and accounts for actin and membrane proteins; 2) molecular dynamics simulations aimed at extracting information from the microscopic dynamics; 3) experiments on artificial bilayers for direct measure of the membrane parameters and validation. An innovative proposal to quantify the elusive Gaussian contribution to the bending rigidity, crucial in establishing the free energy barrier for topology rearrangement, will require an additional personnel resource to be hired on the project.