Methylene blue adsorption on a DMPA lipid langmuir monolayer.
Adsorption of methylene blue (MB) onto a dimyristoylphosphatidic acid (DMPA) Langmuir air/water monolayer is studied by molecular dynamics (MD) simulations, UV reflection spectroscopy and surface potential measurements. The free-energy profile associated with MB transfer from water to the lipid monolayer shows two minima of -66 and -60 kJ mol(-1) for its solid and gas phase, respectively, corresponding to a spontaneous thermodynamic process. From the position of the free-energy minima, it is possible to predict the precise location of MB in the interior of the DMPA monolayer. Thus, MB is accommodated in the phosphoryl or carbonyl region of the DMPA Langmuir air/water interface, depending on the isomorphic state (solid or gas phase, respectively). Reorientation of MB, measured from the bulk solution to the interior of the lipid monolayer, passes from a random orientation in bulk solution to an orientation parallel to the surface of the lipid monolayer when MB is absorbed.
Giner Casares
Juan José
JJ
Universidad de Córdoba, Departamento de Química Física y Termodinámica Aplicada, Ed. Marie Curie, Campus de Rabanales, 14014. Córdoba. Spain.
Camacho
Luis
L
Martín-Romero
Maria Teresa
MT
López Cascales
José Javier
JJ
D000327:Adsorption; D000388:Air; D020404:Glycerophospholipids / Q000737:chemistry*; D008751:Methylene Blue / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry
D020404:Glycerophospholipids; D014867:Water; C025602:dimyristoylphosphatidic acid; D008751:Methylene Blue