Effect of the barometric phase transition of a DMPA bilayer on the lipid/water interface. An atomistic description by molecular dynamics simulation.
Understanding the structure and dynamics of phospholipid bilayers is of fundamental relevance in biophysics, biochemistry, and chemical physics. Lipid Langmuir monolayers are used as a model of lipid bilayers, because they are much more easily studied experimentally, although some authors question the validity of this model. With the aim of throwing light on this debate, we used molecular dynamics simulations to obtain an atomistic description of a membrane of dimyristoylphosphatidic acid under different surface pressures. Our results show that at low surface pressure the interdigitation between opposite lipids (that is, back-to-back interactions) controls the system structure. In this setting and due to the absence of this effect in the Langmuir monolayers, the behavior between these two systems differs considerably. However, when the surface pressure increases the lipid interdigitation diminishes and so monolayer and bilayer behavior converges. In this work, four computer simulations were carried out, subjecting the phospholipids to lateral pressures ranging from 0.17 to 40 mN/m. The phospholipids were studied in their charged state because this approach is closer to the experimental situation. Special attention was paid to validating our simulation results by comparison with available experimental data, therebeing in general excellent agreement between experimental and simulation data. In addition, the properties of the lipid/solution interface associated with the lipid barometric phase transition were studied.
Casares
J J Giner
JJ
Departmento Química Física y TermodinAmica Aplicada, Ed. Marie Curie, Campus de Rabanales, Universidad de Córdoba, 14014 Córdoba, Spain.
Camacho
L
L
Romero
M T Martín
MT
Cascales
J J López
JJ
D000814:Aniline Compounds / Q000737:chemistry*; D008051:Lipid Bilayers; D008962:Models, Theoretical; D014867:Water / Q000737:chemistry
D000814:Aniline Compounds; D008051:Lipid Bilayers; D014867:Water; C050795:N,N-dimethyl-4-anisidine