Eur. Phys. J. E 5, 259-274

A simple atomistic model for the simulation of the gel phase of lipid bilayers

G. La Penna¹, S. Letardi², V. Minicozzi³, S. Morante^{3, 4}, G.C. Rossi^{3, 5} and G. Salina<sup>5

1</sup>  Istituto di Studi Chimico-Fisici di Macromolecole Sintetiche e Naturali, CNR, Via De Marini 6, 16149 Genova, Italy
²  ENEA, Casaccia
³  Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Roma, Italy
⁴  INFM, Unità di Roma 2, Roma, Italy
⁵  INFN, Sezione di Roma 2, Roma, Italy

silvia.morante@roma2.infn.it

(Received 6 July 2000 and Received in final form 28 December 2000)

Abstract
In this paper we present the results of a large-scale numerical investigation of structural properties of a model of cell membrane, simulated as a bilayer of flexible molecules in vacuum. The study was performed by carrying out extensive Molecular Dynamics simulations, in the (NVE) micro-canonical ensemble, of two systems of different sizes ( and molecules), over a fairly large set of temperatures and densities, using parallel platforms and more standard serial computers. Depending on the dimension of the system, the dynamics was followed for physical times that go from few hundred picoseconds for the largest system to 5-10 nanoseconds for the smallest one. We find that the bilayer remains stable even in the absence of water and neglecting Coulomb interactions in the whole range of temperatures and densities we have investigated. The extension of the region of physical parameters that we have explored has allowed us to study significant points in the phase diagram of the bilayer and to expose marked structural changes as density and temperature are varied, which are interpreted as the system passing from a crystal to a gel phase.

PACS
87.15.Aa - Theory and modeling; computer simulation.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001