Osmotic permeability in a molecular dynamics simulation of water transport through a single-occupancy pore

Determination of cells' water membrane permeability: unexpected high osmotic permeability of Saccharomyces cerevisiae

Water permeability (Lp), calculated from the volume variations of cells subjected to an osmotic shock, is classically used to characterize cell membrane properties. In this work, we have shown the importance of the kind of mixing reactor used to measure the Lp parameter. A mathematical model including the mixing time constant has been proposed allowing an accurate Lp estimation even though the mixing time constant is higher than the cell time constant obtained in response to a perfect shock. The estimated Lp values of human leukemia K562 cells were found to be the same whatever the mixing time constant. The Lp value of Saccharomyces cerevisiae could not be exactly estimated. However, S. cerevisiae has unexpectedly high water permeability, implying that this yeast may contain water channels in the membrane.

Statistical thermodynamics of biomembranes

An overview of the major issues involved in the statistical thermodynamic treatment of phospholipid membranes at the atomistic level is summarized: thermodynamic ensembles, initial configuration (or the physical system being modeled), force field representation as well as the representation of long-range interactions. This is followed by a description of the various ways that the simulated ensembles can be analyzed: area of the lipid, mass density profiles, radial distribution functions (RDFs), water orientation profile, deuterium order parameter, free energy profiles and void (pore) formation; with particular focus on the results obtained from our recent molecular dynamic (MD) simulations of phospholipids interacting with dimethylsulfoxide (Me(2)SO), a commonly used cryoprotective agent (CPA).