Mass-selected reagent ion chemical ionization and multiple tandem mass spectrometry techniques in an ion trap mass spectrometer for structural analysis

Mass-selected reagent ion chemical ionization (CI) performed in an ion trap instrument is an efficient tool to investigate gas-phase ion reactivities and therefore to find out new and/or optimized applications for structural analysis. For instance, it was shown that the C₃H₆O^{+ .} (58 mass units) molecular ion originated from vinyl methyl ether (VME) should necessarily be used alone (i.e. unit-mass selected) to produce significant diagnostic-ions for double bond location in aliphatic alkenes. Regarding the assignment of epoxides, the previous NO⁺/CI method was adapted for an optimal use in the trap through isolation of NO⁺ cation from N₂O (instead of NO) plasma and production of the acylium diagnostic-ions via CID of [M − H]⁺ formed by NO⁺-induced hydride abstraction. New alkylation ion-products, e.g. RCH = O⁺-al , were also found to characterize isomeric epoxides as a result of either an initial electrophilic addition of the C₂H₅⁺ cation (with saturated epoxides) or a methyl-transfer from [VME]^{+ .} (with α,β-unsaturated epoxides). The multiple tandem mass spectrometry (MSⁿ) capabilities of the ion trap were essential to achieve reagent ion mass-selection, structural assignment of the diagnostic-ions, or to provide further selectivity. © 1997 John Wiley & Sons, Ltd.     

A simple constraint qualification in convex programming

We introduce and characterize a class of differentiable convex functions for which the Karush—Kuhn—Tucker condition is necessary for optimality. If some constraints do not belong to this class, then the characterization of optimality generally assumes an asymptotic form.We also show that for the functions that belong to this class in multi-objective optimization, Pareto solutions coincide with strong Pareto solutions,. This extends a result, well known for the linear case.Research partly supported by the National Research Council of Canada.     

Novel and chemoselective dehydrogenation of 2-substituted imidazolines with potassium permanganate supported on silica gel

Various types of 2-imidazolines are efficiently oxidized to the corresponding imidazoles using potassium permanganate supported on silica gel under mild conditions at room temperature. 2-Alkylimidazolines are selectively converted to their corresponding imidazoles in the presence of 2-arylimidazolines. Chemoselective oxidation of 2-imidazolines in the presence of other oxidizable functional groups such as sulfide, ether, aldehyde, acetal, and THP ether was also achieved by this reagent system.     

Self-action effects in ionization and fragmentation of toluene by femtosecond laser pulses

Occurrence and influence of several self-action effects, induced in the entrance window of a time-of-flight interaction chamber, on the ion and fragment yields of the toluene molecule in the focus of a Ti:sapphire laser pulse are analyzed. Experimental data are obtained using different focusing geometries and are compared with results from numerical simulations using a nonlinear pulse propagation model as well as those from the strong-field S-matrix theory. It is shown that (a) self-focusing leads to a displacement of the focus while amplified small perturbations of the input beam result in hot spots in the spatial distribution and in an energy-dependent focus area, (b) small self-phase modulation changes the form of the spectrum and broadens it slightly. A strong increase of the toluene fragmentation appears to correlate to linear and nonlinear changes in the focal spot area, while the scenario of excitation of Raman modes proposed in an earlier publication is ruled out as the dominant effect.This revised version was published online in March 2005. In the previous version, the published online date was missing     

Antimicrobial activity of nanocellulose conjugated with allicin and lysozyme

In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC₅₀ and MIC₉₀ was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials.     

Selective adsorption of metoprolol enantiomers using 2‐hydroxypropyl‐β‐cyclodextrin cross‐linked multiwalled carbon nanotube

This study investigates the ability of functionalized multiwalled carbon nanotubes (MWCNTs) for enantio‐separation of metoprolol chiral forms. 2Hydroxypropyl‐β‐cyclodextrin (2HP‐β‐CD) was applied as a chiral selector to functionalize carbon nanotubes (CNTs). The modified multiwalled CNT samples were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. The results of analyses showed that CNTs were successfully cross‐linked with 2HP‐β‐CD. To evaluate the enantio‐separation property of the products, the separation of metoprolol chiral forms on the initial and final products was examined. Further, UV–visible spectroscopy and polarimeter analyses were used for characterization. The results indicate that MWCNT does not have any intrinsic enantio‐separation ability, although its selectivity for enantio‐separation can be enhanced by cross‐linking it to 2HP‐β‐CD. Moreover, the optimal mass of adsorbent as well as optimal mass of functional groups is estimated to achieve maximum enantio‐separation efficiency. The results indicate that applying large amounts of 2HP‐β‐CD to CNTs functionalization decreases the cross‐linking efficiency, which consequently reduces enantio‐separation efficiency. Copyright © 2014 John Wiley & Sons, Ltd.     

A new and facile access to the 2-(indol-3-yl)-3-nitriloquinolines based on Friedländer annulations

Preparation of 2-(indol-3-yl)-3-nitriloquinolines via Friedländer quinoline synthesis using 3-cyanoacetylindoles possessing an α-methylene group and ortho-amino arylketones have been described. This reaction took place in PEG-400 as a green solvent and it is catalyzed with polyphosphoric acid (PPA) to give novel types of quinolines containing both indoles and cyano functions in one step under thermal and microwave conditions.     

Silica Chloride/NaNO 2 as a Novel Heterogeneous System for the Oxidation of 1,4-Dihydropyridines Under Mild Conditions via In Situ Generation of NOCl

A combination of silica chloride and sodium nitrite in the presence of wet SiO 2 were used as an effective oxidizing agent for the oxidation of dihydropyridines to their corresponding pyridine derivatives under mild and heterogeneous conditions in moderate to excellent yields.     

A biocompatible composite based on poly(ε‐caprolactone fumarate) and hydroxyapatite

Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and ¹H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd.