Preparation of Large Monodisperse Vesicles

Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (∼100 nm in diameter) results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-µm-diameter pores eliminates vesicles larger than 5 µm in diameter. Dialysis of extruded vesicles against 3-µm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 µm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of ∼4 µm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery

Filamentation and Pulse Self-compression in the Anomalous Dispersion Region of Glasses

International audienceThe propagation of near-infrared ultra-short laser pulses in the regime of anomalous dispersion of transparent solids is associated with a host of self-induced effects including a significant spectral broadening extending from the ultraviolet into the infrared region, pulse self-compression down to few-cycle pulse durations, free and driven third harmonic generation, conical emission and the formation of stable filaments over several cm showing the emergence of conical light bullets. We review measurements performed in different experimental conditions and results of numerical simulations of unidirectional propagation models showing that the interpretation of all these phenomena proceed from the formation of non-spreading conical light bullets during filamentation

Self-referenced spectral interferometry for ultra-short infrared pulse characterization

Self-Referenced Spectral Interferometry is used for single shot pulse characterization over the 0.9-2.5 µm spectral range with a single spectrometer and an optimized optical setup. We characterize sub-55 fs pulses from 1.4 µm to 2 µm and broadband 2.5-cycle pulses at 1.65 µm (13 fs FWHM)

Self-referenced spectral interferometry for ultra-short infrared pulse characterization

Self-Referenced Spectral Interferometry is used for single shot pulse characterization over the 0.9-2.5 µm spectral range with a single spectrometer and an optimized optical setup. We characterize sub-55 fs pulses from 1.4 µm to 2 µm and broadband 2.5-cycle pulses at 1.65 µm (13 fs FWHM)

Self-referenced spectral interferometry for ultrashort infrared pulse characterization

Self-Referenced Spectral Interferometry is used for single shot pulse characterization over the 0.9-2.5 µm spectral range with a single spectrometer and an optimized optical setup. We characterize sub-55 fs pulses from 1.4 µm to 2 µm and broadband 2.5-cycle pulses at 1.65 µm (13 fs FWHM)

Partition coefficient of a surfactant between aggregates and solution: application to the micelle-vesicle transition of egg phosphatidylcholine and octyl beta-D-glucopyranoside.

The mechanism of the solubilization of egg phosphatidylcholine containing 10% (M/M) of egg phosphatidic acid unilamellar vesicles by the nonionic detergent, octyl beta-D-glucopyranoside, has been investigated at both molecular and supramolecular levels by using fluorescence and turbidity measurements. In the lamellar region of the transition, the solubilization process has been shown to be first a function of the initial size before reaching an equilibrium aggregation state at the end of this region (the onset of the micellization process). The analysis during the solubilization process of the evolution of both the fluorescence energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-phosphatidylethanolamine (NBD-PE) and N-(lissamine rhodamine B sulfonyl)-phosphatidylethanolamine (Rho-PE) and the fluorescence of 6-dodecanoyl-2-dimethylaminoaphtalene (Laurdan) has allowed us to determine the evolution of the detergent partitioning between the aqueous and the lipidic phases, i.e., the evolution of the molar fraction of OG in the aggregates (XOG/Lip) with its monomeric detergent concentration in equilibrium ([OG]H2O), throughout the vesicle-to-micelle transition without isolating the aqueous medium from the aggregates. The curve described by XOG/Lip versus [OG]H2O shows that the partition coefficient of OG is changing throughout the solubilization process. From this curve, which tends to a value of 1/(critical micellar concentration), five different domains have been delimited: two in the lamellar part of the transition (for 0 < [OG]H2O < 15.6 mM), one in the micellization part, and finally two in the pure micellar region (for 16.5 < [OG]H2O < 21 mM). The first domain in the lamellar part of the transition is characterized by a continuous variation of the partition coefficient. In the second domain, a linear relation relates XOG/Lip and [OG]H2O, indicating the existence of a biphasic domain for which the detergent presents a constant partition coefficient of 18.2 M-1. From the onset to the end of the solubilization process (domain 3), the evolution of (XOG/Lip) with [OG]H2O can be fitted by a model corresponding to the coexistence of detergent-saturated lamellar phase with lipid-saturated mixed micelles, both in equilibrium with an aqueous phase, i.e., a three-phase domain. The micellar region is characterized first by a small two-phase domain (domain 4) with a constant partition coefficient of 21 M-1, followed by a one-phase mixed-micellar domain for which XOG/Lip no longer linearly depends on [OG]H2O. The results are discussed in terms of a phase diagram