INVESTIGADORES
PORASSO Rodolfo Daniel
congresos y reuniones científicas
Título:
Molecular Dynamics Simulation of a Model DPPC/DPPS Asymetric Membrane: Effect of Monovalent and Divalent Ions
Autor/es:
RODOLFO D. PORASSO; JOSÉ JAVIER LÓPEZ CASCALES
Lugar:
Barcelona
Reunión:
Workshop; Workshop on Electrostatic Effects in Soft Matter: Bringing Experiments, Theory and Simulation Together; 2008
Resumen:
Asymmetry in biological membranes plays a crucial role in the transport of small molecules, water and ions between the inner and outer side of the cell, and provides a proper environment to adsorb certain molecules such as membrane proteins and polysacharides , or to embed other ones such as cholesterol. In addition, the loose of phospholipid membrane asymmetry is a hallmark of the early stages of cell apoptosis processes, where the flip-flop of certain charged lipids (mainly PhosphatidylSerines PS) triggers cell clearance by phagocytosis. With the goal of providing certain daylight on this complex system, in the present work we focused our interest on how the ionic strength affects the lipid-lipid interactions and lipid/solution interface, considering the bilayer asymmetry. In this setting, with the actual enhance of the computer power and the improvement in the simulation algorithm and force fields used, the Molecular Dynamics Simulation technique is being widely used in the study of lipid bilayers, almost at the same level of confidence that other experimental techniques such as X-ray or NMR, among others. In this sense, a Molecular Dynamics Simulation study of an asymmetric membrane was carried out, where the phospholipid bilayer was modelled by DiPalmitoylPhosphatidylCholine (DPPC) and DiPalmitoylPhosphatidylSerine (DPPS-), and the ionic strength by NaCl and CaCl2 as electrolytes, in aqueous solution. Thus, the asymmetry in the lipid bilayer was generated by placing charged lipids of DPPS- in one of the two leaflets of the bilayer together with zwitterionic lipids of DPPC and in the another one, the leaflet was formed only by zwitterionic lipids of DPPC. The engine of the MD simulation was the GROMACS package. From the analysis of the simulated trajectories we investigated how the steady and dynamics properties of the system (with atomic details) changed with the ionic strength and the type of electrolyte in solution. Among other properties, the lipids head orientation, translational diffusion coefficient and lipid hydration was studied.