Browsing by Author "Vernier, P. Thomas"
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artículo de publicación periódica.listelement.badge Asymmetric patterns of small molecule transport after nanosecond and microsecond electropermeabilization(2018) Sözer, Esin B.; Pocetti, Florencia; Vernier, P. Thomas"Imaging of fluorescent small molecule transport into electropermeabilized cells reveals polarized patterns of entry, which must reflect in some way the mechanisms of the migration of these molecules across the compromised membrane barrier. In some reports, transport occurs primarily across the areas of the membrane nearest the positive electrode (anode), but in others cathode-facing entry dominates. Here we compare YO-PRO-1, propidium, and calcein uptake into U-937 cells after nanosecond (6 ns) and microsecond (220 ls) electric pulse exposures. Each of the three dyes exhibits a different pattern. Calcein shows no preference for anode- or cathode-facing entry that is detectable with our measurement system. Immediately after a microsecond pulse, YO-PRO-1 and propidium enter the cell roughly equally from the positive and negative poles, but transport through the cathode-facing side dominates in less than 1 s. After nanosecond pulse permeabilization, YO-PRO-1 and propidium enter primarily on the anode-facing side of the cell."artículo de publicación periódica.listelement.badge Electropore formation in mechanically constrained phospholipid bilayers(2018-04) Fernández, María Laura; Risk, Marcelo; Vernier, P. Thomas"Molecular dynamics simulations of lipid bilayers in aqueous systems reveal how an applied electric field stabilizes the reorganization of the water–membrane interface into water-filled, membrane-spanning, conductive pores with a symmetric, toroidal geometry. The pore formation process and the resulting symmetric structures are consistent with other mathematical approaches such as continuum models formulated to describe the electroporation process. Some experimental data suggest, however, that the shape of lipid electropores in living cell membranes may be asymmetric. We describe here the axially asym-metric pores that form when mechanical constraints are applied to selected phospholipid atoms. Electropore formation pro-ceeds even with severe constraints in place, but pore shape and pore formation time are affected. Since lateral and transverse movement of phospholipids may be restricted in cell membranes by covalent attachments to or non-covalent associations with other components of the membrane or to membrane-proximate intracellular or extracellular biomolecular assemblies, these lipid-constrained molecular models point the way to more realistic representations of cell membranes in electric fields."artículo de publicación periódica.listelement.badge Transport of charged small molecules after electropermeabilization — drift and diffusion(2018-03) Sözer, Esin B.; Pocetti, Florencia; Vernier, P. Thomas"We provide a direct quantitative comparison of molecular transport of three similarly sized but chemically different fluorescent indicators of membrane permeabilization — two cationic molecules (YO-PRO-1 and propidium), and one anionic molecule (calcein). Our results show that the influx of YO-PRO-1 and propidium (both cations) into electropermeabilized cells is an order of magnitude greater than that of calcein (an anion) after the same pulse exposure. Calcein efflux from cells loaded before permeabilization, however, is similar in magnitude to YO-PRO-1 and propidium influx."