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Biomedical subjects

Paul Dommersnes

Publications and source records attributed to Paul Dommersnes.

6 recordsLinked to original sources
PubMed2006

Zipper dynamics of surfactant nanotube Y junctions.

We investigate the formation of Y junctions in surfactant nanotubes connecting vesicles. Based on experimental observations of the surfactant flow on the nanotubes, we conclude that a Y junction propagates with a zipperlike mechanism. The surfactants from two nanotube branches undergo 1:1 mixing at the junction, and spontaneously form the extension of the third nanotube branch. Taking into account the tension driven surfactant flow, we develop a model for the Y junction dynamics that is in quantitative agreement with the experimental data.

Lipids↗
PubMed2006

Osmotically driven shape transformations in axons.

We report a cylindrical-peristaltic shape transformation in axons exposed to a controlled osmotic perturbation. The peristaltic shape relaxes and the axon recovers its original geometry within minutes. We show that the shape instability depends critically on the swelling rate and that volume and membrane area regulation are responsible for the shape relaxation. We propose that volume regulation occurs via leakage of ions driven by elastic pressure, and analyze the peristaltic shape dynamics taking into account the internal structure of the axon. The results obtained provide a framework for understanding peristaltic shape dynamics in nerve fibers occurring in vivo.

Animals↗
PubMed2005

Single-file electrophoretic transport and counting of individual DNA molecules in surfactant nanotubes.

We demonstrate a complete nanotube electrophoresis system (nanotube radii in the range of 50 to 150 nm) based on lipid membranes, comprising DNA injection, single-molecule transport, and single-molecule detection. Using gel-capped electrodes, electrophoretic single-file transport of fluorescently labeled dsDNA molecules is observed inside nanotubes. The strong confinement to a channel of molecular dimensions ensures a detection efficiency close to unity and identification of DNA size from its linear relation to the integrated peak intensity. In addition to constituting a nanotechnological device for identification and quantification of single macromolecules or biopolymers, this system provides a method to study their conformational dynamics, reaction kinetics, and transport in cell-like environments.

Bacteriophage phi X 174↗
PubMed2005

Fluid mixing in growing microscale vesicles conjugated by surfactant nanotubes.

This work addresses novel means for controlled mixing and reaction initiation in biomimetic confined compartments having volume elements in the range of 10(-12) to 10(-15) L. The method is based on mixing fluids using a two-site injection scheme into growing surfactant vesicles. A solid-state injection needle is inserted into a micrometer-sized vesicle (radius 5-25 microm), and by pulling on the needle, we create a nanoscale surfactant channel connecting injection needle and the vesicle. Injection of a solvent A from the needle into the nanotube results in the formation of a growing daughter vesicle at the tip of the needle in which mixing takes place. The growth of the daughter vesicle requires a flow of surfactants in the nanotube that generates a flow of solvent B inside the nanotube which is counterdirectional to the pressure-injected solvent. The volume ratio psi between solvent A and B inside the mixing vesicle was analyzed and found to depend only on geometrical quantities. The majority of fluid injected to the growing daughter vesicle comes from the pressure-based injection, and for a micrometer-sized vesicle it dominates. For the formation of one daughter vesicle (conjugated with a 100-nm radius tube) expanded from 1 to 200 microm in radius, the mixing ratios cover almost 3 orders of magnitude. We show that the system can be expanded to linear strings of nanotube-conjugated vesicles that display exponential dilution. Mixing ratios spanning 6 orders of magnitude were obtained in strings of three nanotube-conjugated micrometer-sized daughter vesicles.

Fluorescent Dyes↗
PubMed2004

Mechanical tweezer action by self-tightening knots in surfactant nanotubes.

Entanglements and trefoil knots on surfactant nanotubes in the liquid phase were produced by a combination of network self-organization and micromanipulation. The resulting knots are self-tightening, and the tightening is driven by minimization of surface free energy of the surfactant membrane material. The formation of the knot and the steady-state knot at quasi-equilibrium can be directly followed and localized by using fluorescence microscopy. Knots on nanotubes can be used as nanoscale mechanical tweezers for trapping and manipulation of single nano- and micrometer-sized high-aspect ratio objects. Furthermore, we demonstrate that by controlling the surface tension, objects captured by a knot can be transported along given trajectories defined by the nanotube axes.

Fluorescence↗