Single isolated droplets with net charge as a source of ions

A levitation device for charged particles has been used to position a single isolated droplet at a time at atmospheric pressure near the sampling orifice of a vacuum chamber. Following a brief desolvation period (550 ms), a series of coluomb fission events were initiated. Several atmospheric pressure electrode designs were evaluated with respect to guiding the progeny droplets/ions, to the sampling orifice. The best design tested consisted of a series of four annular electrodes of decreasing radius positioned above the levitation ring electrodes, and, on average, 40 ions were counted per single isolated droplet. The ion utilization (charge detected versus charge in the original droplet) with this electrode design has been estimated to be 5 x 10(-6), a substantial improvement over the current utilization measured to be < or = 1 x 10(-9) with a conventional electrospray ion source using the same vacuum apparatus.     

Drug effect prediction by polypharmacology-based interaction profiling

Most drugs exert their effects via multitarget interactions, as hypothesized by polypharmacology. While these multitarget interactions are responsible for the clinical effect profiles of drugs, current methods have failed to uncover the complex relationships between them. Here, we introduce an approach which is able to relate complex drug-protein interaction profiles with effect profiles. Structural data and registered effect profiles of all small-molecule drugs were collected, and interactions to a series of nontarget protein binding sites of each drug were calculated. Statistical analyses confirmed a close relationship between the studied 177 major effect categories and interaction profiles of ca. 1200 FDA-approved small-molecule drugs. On the basis of this relationship, the effect profiles of drugs were revealed in their entirety, and hitherto uncovered effects could be predicted in a systematic manner. Our results show that the prediction power is independent of the composition of the protein set used for interaction profile generation.     

Using ionic liquids to formulate microemulsions: Current state of affairs

Microemulsions are stable mixtures of a polar solvent, surfactant and an unpolar solvent. Ionic liquids (ILs, i.e. salts with melting points below 100 °C) are a huge class of potentially promising solvents. We discuss here published structural or thermodynamic investigations concerning microemulsions in which one or more of the three classical components are ILs.In microemulsions IL can replace respectively the “oil”, the “surfactant” and the “water” phase. Experimental proofs of the existence and stability of microemulsions are given as well as hints at their microstructure. While the four regimes initially defined by Winsor are all accessible, most of the examples of microemulsions containing ionic liquids belong to the class of “rigid” microemulsions. Since additional solutes have characteristic distribution coefficients for each pseudo phase, IL based microemulsions may provide a useful tool for solubilization (reaction medium) and separation, thus allowing the recovery of a large variety of reaction products, but also waste. Further to a discussion of phase diagrams and thermodynamics, we will show some application examples and propose challenges for future studies, in this vast but only emerging domain.     

Application of mixed mode resins for the purification of antibodies

The downstream processing of monoclonal antibodies from cell culture supernatant is usually done by a number of chromatographic and non-chromatographic steps. Efforts are taken to reduce the costs associated to those steps, while maintaining a high product purity. A possibility to reach this goal is the reduction of the number of chromatographic steps using mixed mode resins that offer more than one functionality in one chromatographic step. In this work, a commercially available mixed mode resin was evaluated systematically with respect to the adsorption of proteins. The Henry coefficient, which quantifies the adsorption strength, was measured for the full working range of the stationary phase as a function of the salt concentration and the pH. The results were compared to a conventional anion exchange and a hydrophobic interaction resin. Furthermore, the resin was applied for the polishing step of an antibody from an industrial clarified cell culture supernatant.     

Ring-opening metathesis polymerization for the preparation of norbornene-based weak cation-exchange monolithic capillary columns

Functionalized monolithic columns were prepared via ring-opening metathesis polymerization (ROMP) within silanized fused silica capillaries with an internal diameter of 200 μm by in situ grafting. This procedure is conducted in two steps, the first of which is the formation of the basic monolithic structure by polymerization of norborn-2-ene (NBE) and 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene (DMN-H6) in a porogenic system (toluene and 2-propanol) using RuCl₂(PCy₃)₂(CHPh) as ROMP initiator. In the second step the still active initiator sites located on the surface of the structure-forming microglobules were used as receptor groups for the attachment (“grafting”) of functional groups onto the monolithic backbone by flushing the monolith with 7-oxanorborn-2-ene-5,6-carboxylic anhydride (ONDCA). Functionalization conditions were first defined that did not damage the backbone of low polymer content (20%) monoliths allowing high-throughput chromatographic separations. Variation of the functionalization conditions was then shown to provide a means of controlling the degree of functionalization and resulting ion-exchange capacity. The maximum level of in situ ONDCA grafting was obtained by a 3 h polymerization in toluene at 40 °C. The weak cation-exchange monoliths obtained provided good separation of a standard peptide mixture comprising four synthetic peptides designed specifically for the evaluation of cation-exchange columns. An equivalent separation was also achieved using the lowest capacity column studied, indicative of a high degree of robustness of the functionalization procedure. As well as demonstrably bearing ionic functional groups enabling analyte separation in the cation-exchange mode, the columns exhibited additional hydrophobic characteristics which influenced the separation process. The functionalized monoliths thus represent useful tools for mixed-mode separations.     

Detection of negative ions in glow discharge mass spectrometry for analysis of solid specimens

A new method is presented for elemental and molecular analysis of halogen-containing samples by glow discharge time-of-flight mass spectrometry, consisting of detection of negative ions from a pulsed RF glow discharge in argon. Analyte signals are mainly extracted from the afterglow regime of the discharge, where the cross section for electron attachment increases. The formation of negative ions from sputtering of metals and metal oxides is compared with that for positive ions. It is shown that the negative ion signals of F^? and TaO₂F^? are enhanced relative to positive ion signals and can be used to study the distribution of a tantalum fluoride layer within the anodized tantala layer. Further, comparison is made with data obtained using glow-discharge optical emission spectroscopy, where elemental fluorine can only be detected using a neon plasma. The ionization mechanisms responsible for the formation of negative ions in glow discharge time-of-flight mass spectrometry are briefly discussed.     

Recent progress in nickel oxide-based electrodes for high-performance supercapacitors

In recent years, interest in nanostructured electrode materials for use in supercapacitors has been on the rise. Nickel oxide has been reported as a good candidate for supercapacitor applications due to its high theoretical capacitance and low cost. However, its poor electrical conductivity has resulted in actual poor specific capacitance and cycling ability. Over the years, researchers have studied various techniques to modify the structure and composition of NiO with the aim of improving its electrochemical performance. In this review, we opine that NiO-based electrodes can be fabricated using different approaches and different composite forms in order to obtain cells of high efficiency and specific capacitances. We discuss the recent advances in NiO-based electrodes fabricated using different approaches.     

Inclusion complexes of sulfanilamide with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin

Sulfanilamide belongs to the group of drugs that have a bacteriostatic effect on different pathogenic microorganisms. This activity originates from the competitive antagonism with p-aminobenzoic acid, which is an integral part of folic acid. The safe use of sulfanilamide is limited due to poor solubility in the aqueous medium. Therefore, the aim of this paper is the synthesis of sulfanilamide, as well as preparing and structural characterization of its inclusion complexes with cyclodextrins. The crude sulfanilamide was obtained in the synthesis between acetanilide and chlorosulfonic acid according to the standard procedure. The synthesized sulfanilamide was recrystallized from water in order to obtain the satisfactory purity of the substance. Sufanilamide was complexed with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin by the co-precipitation method. A molecular encapsulation of sulfanilamide was confirmed by using FTIR, ¹H-NMR, XRD and DSC methods. Phase-solubility techniques were used to assess the formation of the inclusion complex between sulfanilamide and cyclodextrins. The photostability of sulfanilamide and its inclusion complexes was estimated by UVB irradiation in a photochemical reactor by applying the UV–Vis method. Based on the UV–Vis analysis, sulfanilamide:2-hydroxypropyl-β-cyclodextrin complex was presented as more photostable than sulfanilamide:β-cyclodextrin complex and sulfanilamide. The obtained results enable the potential use of these inclusion complexes for the preparation of oral formulations due to the enhanced solubility of sulfanilamide.     

Reaction of O,O-dialkyl alkylphosphonates with thionyl chloride. A remarkable effect of the O-(2-dialkylamino)ethyl substituent

Reaction of dialkyl alkylphosphonates with SOCl₂ in the presence of DMF, reported by Maier, can serve as a convenient route to simple monoalkyl alkylphosphonochloridates. However, when a substrate contains a (2-dialkylamino)ethyl group as one of the ester functions, the course of the reaction is determined by the nature of the N-alkyl groups. With the NMe₂ group present, reaction with SOCl₂ occurs at nitrogen, and no exchange of groups at phosphorus takes place. The NEt₂ group, on the other hand, directs the reaction to phosphorus, and the Maier reaction of the exchange of one ester group OR for Cl proceeds in high yields. © 1996 John Wiley & Sons, Inc.