Direct carbamation of cellulose fiber sheets

The paper is on introducing carbamate groups in sheets of cellulose fiber assemblies by pad-dry-cure treatments with aqueous solutions of polyethylene glycol, amide and salt. The effects of process variables—on carbamation levels and on mechanical properties of the substrate—are reported. Depending on treatment conditions, the nitrogen contents in substrates are in the range 0.668–2.252 wt%, corresponding to nominal degrees of carbamate group substitution of 0.08–0.28. The carbamation is initiated at 140 °C curing, and the levels rise with temperature up to 220 °C, but decrease at higher temperatures. The duration of curing also exerts an influence. There is a catalytic effect of sodium acetate on the carbamation, but the salt also induces a brown coloration in samples, which is likely a result of Maillard-type reactions. The treatments cause hydrolytic degradation in substrates, but there are options to adjust treatment conditions and minimize damage. Pad-dry-cure treatments are a common operation in the textile and paper industries, and the process may be adopted in commercial-scale operations to create derivatized paper or fabrics (woven, knitted or non-woven) for utilization in applications such as adsorbents for heavy metals from waste water, in hygiene products, in the creation of flame retardant products, or in creating all-cellulose composites by further treatment with alkali.     

Solvatochromic Effect in the Optical Spectra of Calcofluor and its Relation to Fluorescent Staining of Yeast Cell Walls

Fluorescence spectral properties of calcofluor (a popular stain used to visualize cell walls of bacteria, yeast and fungi) has been studied. The analysis of calcofluor fluorescence emission spectra measured in a wide range of solvents (including media containing chitin), and in yeast cell suspensions has revealed that the solvatochromic properties of calcofluor ensue essentially from the by solvent-solute hydrogen bonding, or from the hydrogen bonding to cell wall polysaccharides with an eventual contribution of calcofluor aggregation at the cell surface. Preliminary data suggest that calcofluor emission spectra can be employed as a practical marker of variations in the quality of yeast cell wall.     

Characterization of metabolites of sibutramine in primary cultures of rat hepatocytes by liquid chromatography–ion trap mass spectrometry

Liquid chromatography–ion trap mass spectrometry was used for the detection and structural characterization of metabolites of the anti-obesity drug sibutramine. Metabolites were profiled from incubations of sibutramine in primary cultures of rat hepatocytes. In addition, enantioselectivity of sibutramine metabolism was investigated by carrying out separate incubations with (R)- and (S)-sibutramine. As a result, biotransformation profile for sibutramine with rat hepatocytes is proposed. Nineteen metabolites and several of their isomers formed via demethylation, hydroxylation, dehydrogenation, acetylation, attachment of CO₂, and glucuronidation were identified in MS² and MS³ experiments, though the exact position of the functionality, mostly hydroxylation, could not always be determined from the mass spectrometric information. However, clear enantioselective formation was observed for two hydroxyl derivatives and two glucuronide conjugates, indicating that the hydroxyl/glucuronic acid moiety in those structures is close to the chiral center. Most of the metabolites found in this study are new metabolites of sibutramine, which were not previously reported.     

Biomimetic surface modifications based on the cyanobacterial iron chelator anachelin

Siderophores are natural iron chelators that have been evolutionarily selected to bind to Fe ions with very high binding constants. We utilize these unique properties to bind to metal oxide surfaces using a fragment of the cyanobacterial siderophore anachelin. The resulting poly(ethylene glycol) conjugate forms stable adlayers on TiO2 as has been shown by variable angle spectroscopic ellipsometry and X-ray photoelectron spectroscopy. Moreover, these coated surfaces are highly protein-resistant against the adsorption of full human serum.     

Utilisation of separation methods in the analysis of chemical warfare agents

Chemical warfare agents and their degradation products represent a broad group of compounds with different chemical properties (polarity, volatility, thermostability, etc.). These chemicals often have to be detected and determined in complex matrices and therefore highly efficient separation techniques hyphenated to selective and sensitive detectors play an indispensable role. This review offers an overview of selected papers devoted to the title subject. It cannot be considered as a comprehensive literature compilation but should allow the reader to obtain an insight into the application of separation techniques in the important area of human protection and control of chemical weapons.     

Investigation of the metabolism of monepantel in ovine hepatocytes by UHPLC/MS/MS

Monepantel (MOP) belongs to a new class of anthelmintic drugs known as aminoacetonitrile derivatives. It was approved for use in veterinary practice in Czech Republic in 2011. So far, biotransformation and transport of MOP in target animals have been studied insufficiently, although the study of metabolic pathways of anthelmintics is very important for the efficacy of safety of therapy and evaluation of the risk of drug–drug interactions. The aim of this study was to identify MOP metabolites and to suggest the metabolic pathways of MOP in sheep. For this purpose, primary culture of ovine hepatocytes was used as a model in vitro system. After incubation, medium samples and homogenates of hepatocytes were extracted separately using solid-phase extraction. Analysis was performed using a hybrid quadrupole-time-of-flight analyzer with respect to high mass accuracy measurements in full scan and tandem mass spectra for the confirmation of an elemental composition. The obtained results revealed S-oxidation to sulfoxide and sulfone and arene hydroxylation as MOP phase I biotransformations. From phase II metabolites, MOP glucuronides, sulfates, and acetylcysteine conjugates were found. Based on the obtained results, a scheme of the metabolic pathway of MOP in sheep has been proposed.     

Behavior of cadmium(II) in irradiated aqueous solutions

Behavior of cadmium(II) in aqueous solutions irradiated by accelerated electrons was studied. A concentration of 8.8 × 10⁻⁴ mol L⁻¹ of cadmium dissolved from Cd(NO₃)₂ requires dose of 15 kGy to be effectively removed from the system containing 1 × 10⁻² mol L⁻¹ of HCOOK as a scavenger of OH radicals. The positive effect of deaeration with N₂O or N₂ was observed in the range of lower doses. The addition of solid modifiers (bentonite, active carbon, zeolite, Cu₂O, NiO, TiO₂ and CuO) reduced the effectivity of radiation removal of cadmium. Product of irradiation is CdCO₃. On the contrary, in the system with cadmium dissolved from CdCl₂ radiation reduction takes place. Systems contained organic complexants (ethylene diamine tetraacetic acid–EDTA, citric acid) were also studied. The solutions of Cd(NO₃)₂ containing initial concentration 2.37 × 10⁻⁴ mol L⁻¹ of Cd^II were mixed with 3 × 10⁻⁴ mol L⁻¹ EDTA. In this system the efficient degradation proceeds up to 90% at a dose of 45 kGy with addition of 5 × 10⁻³ mol L⁻¹ carbonate (pH 10.5). The product of irradiation is CdCO₃. The presence of 1 × 10⁻² mol L⁻¹ of HCOOK in the solution is necessary for radiation removal of cadmium complexed with citric acid (1 × 10⁻³ mol L⁻¹) at pH 8. With increasing concentration of HCOOK (up to 5 × 10⁻² mol L⁻¹) decreases the pH value necessary for the radiation induced precipitation of cadmium. The best result was obtained in the system containing zeolite as a solid modifier.     

Gas chromatography/mass spectrometry of oils and oil binders in paintings

A GC/MS procedure has been developed, optimized, and applied to characterization of oil binders in paintings. The procedure involves hydrolysis of lipids to fatty acids (FAs) and derivatization of FAs to fatty acid methyl esters (FAMEs) by a solution of sodium methanolate in methanol at an elevated temperature. FAMEs are analyzed by temperature-programed GC followed by full-scan MS. Old and dried samples are subjected to extraction of nonpolymerized FAMEs into dichloromethane prior to hydrolysis. The method provides a good repeatability of results and has been applied to the characterization of common plant oils used in paintings, to commercial oil and tempera paints, to model painting samples, and to samples taken from real paintings. The fresh oils and binders can readily be identified and characterized. The ratio of the methyl esters of palmitic and stearic acids can be used to characterize oil binders in old works of art.     

C,N‐chelated organotin(IV) compounds as catalysts for transesterification and derivatization of dialkyl carbonates

The potential catalytic activity of selected C,N‐chelated organotin(IV) compounds (e.g. halides and trifluoroacetates) for derivatization of both dimethyl carbonate (DMC) and diethyl carbonate (DEC) was investigated. Some tri‐, di‐ and monoorganotin(IV) species (L^CN(n‐Bu)₂SnCl (1), L^CN(n‐Bu)₂SnCl.HCl (1a), L^CN(n‐Bu)₂SnI (2), L^CNPh₂SnCl (3), L^CNPh₂SnI (4), L^CN(n‐Bu)SnCl₂ (5), L^CNSnBr₃ (6) and [L^CNSn(OC(O)CF₃)]₂(μ‐O)(μ‐OC(O)CF₃)₂ (7)) bearing the L^CN moiety (L^CN = 2‐(N,N‐dimethylaminomethyl)phenyl‐) were assessed as catalysts for reactions of both DMC and DEC with various substituted anilines. The catalytic activities of 4 and 7 for derivatization of DMC with p‐substituted phenols were studied for comparison with the standard base K₂CO₃/Silcarbon K835 catalyst (catalyst 8). The composition of resulting reaction mixtures was monitored by multinuclear NMR spectroscopy, GC and GC‐MS techniques. In general, catalysts 1, 3 and 7 exhibited the highest catalytic activity for all reactions studied, while some of them yielded selectively carbonates, carbamates, lactam or substituted urea. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of the Flow of Magnetoelastic Materials

We consider evolutionary models for magnetoelastic materials. The PDEs modeling the flow of the material were derived from variational principles in a continuum mechanical setting. In this article, we discuss the existence of weak solutions for two models, one with gradient flow type dynamics on the magnetic variable and in the other the dynamics of the magnetization is described by the Landau-Lifshitz-Gilbert equation. We highlight the main differences of the proofs in the two cases. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)