Semi-Continuous Desalination and Concentration of Small-Volume Samples.

Electrodialysis is an electric-field-mediated process separating ions exploiting selective properties of ion-exchange membranes. The ion-exchange membranes create an ion-depleted zone in an electrolyte solution adjacent to the membrane under DC polarization. We constructed a microfluidic system that uses the ion-depleted zone to separate ions from the processed water solution. We tested the separation performance by desalting a model KCl solution spiked with fluorescein for direct observation. We showed both visually and by measuring the conductivity of the output solutions that the system can work in three modes of operation referred to as continuous desalination, desalination by accumulation, and unsuccessful desalination. The mode of operation can easily be set by changing the control parameters. The desalination factors for the model KCl solution reached values from 80 to 100%, depending on the mode of operation. The concentration factor, given as a ratio of concentrate-to-feed concentrations, reached zero for desalination by accumulation when only diluate was produced. The water recovery, therefore, was infinite at these conditions. Independent control of the diluate and concentrate flow rates and the DC voltage turned our system into a versatile platform, enabling us to set proper conditions to process various samples.

Preparation of 1-Azido-2-Bromo-1,1,2,2-Tetrafluoroethane and Its Use in the Synthesis of N-Fluoroalkylated Nitrogen Heterocycles.

A straightforward synthesis of 1-azido-2-bromo-1,1,2,2-tetrafluoroethane on a multigram scale from 1,2-dibromotetrafluoroethane and sodium azide in a novel process initiated by organomagnesium compounds (i-PrMgCl·LiCl, turbo Grignard) is reported. Synthetic utility of the title azide in the preparation of N-tetrafluoroethylated and N-difluoromethylated five-membered nitrogen heterocycles was demonstrated with azide-alkyne cycloaddition to N-bromotetrafluoroethyl 1,2,3-triazoles, subsequent reduction to N-tetrafluoroethyl triazoles, rhodium-catalyzed transannulation with nitriles to N-tetrafluoroethylated imidazoles and rhodium-catalyzed ring-opening, and cyclization to N-difluoromethylated oxazoles and thiazoles.

ccNetViz: a WebGL-based JavaScript library for visualization of large networks.

SUMMARY: Visualizing a network provides a concise and practical understanding of the information it represents. Open-source web-based libraries help accelerate the creation of biologically based networks and their use. ccNetViz is an open-source, high speed and lightweight JavaScript library for visualization of large and complex networks. It implements customization and analytical features for easy network interpretation. These features include edge and node animations, which illustrate the flow of information through a network as well as node statistics. Properties can be defined a priori or dynamically imported from models and simulations. ccNetViz is thus a network visualization library particularly suited for systems biology. AVAILABILITY AND IMPLEMENTATION: The ccNetViz library, demos and documentation are freely available at http://helikarlab.github.io/ccNetViz/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Effect of channel geometry on ion-concentration polarization-based preconcentration and desalination.

Polarization of the ion-selective systems results in the formation of ion-depleted and ion-concentrated zones in the electrolyte layers adjacent to the system. One can employ ion-concentration polarization for the removal of charged large molecules and small ions from the flowing liquid. Removal of large molecules from the flowing solution and their local accumulation is often referred to as preconcentration, removal of small ions as desalination. Here, we study the effect of the channel geometry on the removal of charged species from their water solutions experimentally. Straight, converging, and diverging channels equipped with a pair of heterogeneous cation-exchange membranes are compared in terms of their effect on preconcentration of an observable fluorescein dye and on desalination of water solution of potassium chloride. Our results show that preconcentration of the dye is not significantly affected by the channel geometry. The distance of the preconcentration band from one of the membranes was approximately the same in all tested channel geometries. The major difference was in the location of the band within the channel, when the conical channels localized the band at one of the channel walls. The straight channel showed a slightly broader range of applicable flow rates. The semibatch desalination of 0.01M KCl solution turned out to be more efficient in conical channels, which was associated with a larger volume of the channel available for the accumulation of the concentrated solution. Our results suggest that conical channels can be advantageously used in transforming the ion-concentration-polarization-based semibatch desalination into a fully continuous one.

Stereoselective Synthesis of (Z)-ß-Enamido Triflates and Fluorosulfonates from N-Fluoroalkylated Triazoles.

N-Fluoroalkylated 1,2,3-triazoles in the presence of triflic acid or fluorosulfonic acid underwent a cascade reaction consisting of triazole protonation, ring opening, nitrogen elimination, sulfonate addition, HF elimination, and hydrolysis to furnish novel trifluoromethanesulfonyloxy- or fluorosulfonyloxy-substituted enamides, respectively, in a highly stereoselective fashion. The vinyl triflates underwent cross-coupling reactions to a variety of substituted enamides and serve as sources of the aminovinyl cations. In reactions with triflic acid, electron-rich triazoles afforded 2-fluoroalkylated oxazoles.