Cytotoxicity of poly(<Emphasis Type="Italic">p</Emphasis>-phenylenediamine)

Although poly(p-phenylenediamine) is an electric non-conductor, it exhibits, analogously to conducting polymers, redox activity and could, therefore, find applications in biomedicine. In the current work, the cytotoxicity of poly(p-phenylenediamine) polymer powder produced by the chemical oxidation of p-phenylenediamine with ammonium peroxydisulfate in acidic aqueous media has been studied. Primary mouse embryonic fibroblasts were used for this purpose. Interestingly, the standard methods for the determination of polymer cytotoxicity based on international standard EN ISO 10993-5 could not be applied. The reason was the interaction of polymer extracts with MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. On the basis of the evaluation of flow cytometry and micrographs taken by fluorescence microscopy on cells treated with extracts of poly(p-phenylenediamine), it can be concluded that the powder polymer possesses severe cytotoxicity. The results suggest that practical application of the polymer within biomedicine is, at the current state of knowledge, difficult, and modification of the preparation techniques and/or subsequent purification of poly(p-phenylenediamine) is needed.     

Lanthanide(III) Complexes of 4,10‐Bis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid (trans‐H6do2a2p) in Solution and in the Solid State: Structural Studies Along the Series

Complexes of 4,10‐bis(phosphonomethyl)‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid (trans‐H₆do2a2p, H₆ L ) with transition metal and lanthanide(III) ions were investigated. The stability constant values of the divalent and trivalent metal‐ion complexes are between the corresponding values of H₄dota and H₈dotp complexes, as a consequence of the ligand basicity. The solid‐state structures of the ligand and of nine lanthanide(III) complexes were determined by X‐ray diffraction. All the complexes are present as twisted‐square‐antiprismatic isomers and their structures can be divided into two series. The first one involves nona‐coordinated complexes of the large lanthanide(III) ions (Ce, Nd, Sm) with a coordinated water molecule. In the series of Sm, Eu, Tb, Dy, Er, Yb, the complexes are octa‐coordinated only by the ligand donor atoms and their coordination cages are more irregular. The formation kinetics and the acid‐assisted dissociation of several Ln^III–H₆ L complexes were investigated at different temperatures and compared with analogous data for complexes of other dota‐like ligands. The [Ce( L )(H₂O)]^3? complex is the most kinetically inert among complexes of the investigated lanthanide(III) ions (Ce, Eu, Gd, Yb). Among mixed phosphonate–acetate dota analogues, kinetic inertness of the cerium(III) complexes is increased with a higher number of phosphonate arms in the ligand, whereas the opposite is true for europium(III) complexes. According to the ¹H NMR spectroscopic pseudo‐contact shifts for the Ce–Eu and Tb–Yb series, the solution structures of the complexes reflect the structures of the [Ce(H L )(H₂O)]^2? and [Yb(H L )]^2? anions, respectively, found in the solid state. However, these solution NMR spectroscopic studies showed that there is no unambiguous relation between ³¹P/¹H lanthanide‐induced shift (LIS) values and coordination of water in the complexes; the values rather express a relative position of the central ions between the N₄ and O₄ planes.     

Automation of static and dynamic non-dispersive liquid phase microextraction. Part 2: Approaches based on impregnated membranes and porous supports

A critical overview on automation of modern liquid phase microextraction (LPME) approaches based on the liquid impregnation of porous sorbents and membranes is presented. It is the continuation of part 1, in which non-dispersive LPME techniques based on the use of the extraction phase (EP) in the form of drop, plug, film, or microflow have been surveyed.     

A novel approach to Lab-In-Syringe Head-Space Single-Drop Microextraction and on-drop sensing of ammonia

A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, is proposed which utilizes a secondary inlet into the syringe void, used as a size-adaptable reaction chamber, via a channel passing through the syringe piston. This innovative approach allows straightforward automation of head-space single-drop microextraction, involving accurately controlled drop formation and handling, and the possibility of on-drop analyte quantification.     

The phenoxy/phenol/copper cation: a minimalistic model of bonding relations in active centers of mononuclear copper enzymes

The "bare" complex [Cu(PhOH)(PhO)](+) with a phenol (PhOH) and a phenoxy (PhO) ligand bound to copper is studied both experimentally and computationally. The binding energies and structure of this complex are probed by mass spectrometry, infrared multi-photon dissociation, and DFT calculations. Further, the monoligated complexes [Cu(PhO)](+) and [Cu(PhOH)](+) are investigated for comparison. DFT calculations on the [Cu(PhOH)(PhO)](+) complex predict that a phenolate anion interacts with copper(II) preferentially through the oxygen atom, and the bonding is associated with electron transfer to the metal center resulting in location of the unpaired electron at the aromatic moiety. Neutral phenol, on the other hand, interacts with copper preferentially through the aromatic ring. The same arrangements are also found in the monoligated complexes [Cu(PhO)](+) and [Cu(PhOH)](+). The calculations further indicate that the bond strength between the copper atom and the oxygen atom of the phenoxy radical is weakened by the presence of neutral phenol from 2.6 eV in bare [Cu(PhO)](+) to 2.1 eV in [Cu(PhOH)(PhO)](+).     

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.     

The reaction of (Sp)-2-(diphenylphosphino)ferrocenecarboxylic acid with carbodiimide reagents: Characterisation of the acid anhydride and urea products

Interaction of (S_p)-2-(diphenylphosphino)ferrocenecarboxylic acid [(S_p)-1] with N,N′-dicyclohexylcarbodiimide (DCC) and N-ethyl-N′-[3-(dimethylamino)propyl]carbodiimide (EDC) have been investigated in order to study the reacting system itself and to characterise side-products typically arising during the diimide-promoted condensation of acid (S_p)-1 with nucleophiles. The reaction between (S_p)-1 and DCC was found to give preferentially the respective urea derivative in the absence of a base, and (S_p)-2-(diphenylphosphino)ferrocenecarboxylic anhydride [(S_p,S_p)-3] when the same reaction was performed in the presence of 4-(dimethylamino)pyridine (DMAP). With EDC, the preference for a reaction pathway was less pronounced: whereas the reaction without the base afforded exclusively the corresponding urea, that in the presence of DMAP yielded a mixture of the urea and anhydride (S_p,S_p)-3.     

Solution of the generalized master equation for an externally driven and environmentally damped two-level system

Using the Generalized Master Equation (GME) we investigate the dynamics of a two-level system which is subjected both to the influence of a thermal reservoir and to an external driving field. The coupling with the phonon reservoir is represented by the usual (energy-conserving) linear-displacements interaction, which makes the model exactly solvable in the absence of the external field. The coupling with the external field is treated within the Rotating Wave Approximation (RWA). We obtain an exact formal solution of the GME and we construct a hierarchical class of weak-driving approximations avoiding usual assumption of a weak coupling to the bath. The populational difference is damped in a nontrivial manner: the relaxation is nonexponential with long-time tail behaviour in the asymptotic region. The evolution is analysed as a function of temperature, the strength of the coupling, the strength of the external field and the detuning. Our model is formally identical to the spin-boson model and our approach gives a systematic improvement of the noninteracting-blip approximation.     

Borel classes of sets of extreme and exposed points in

It is known that the sets of extreme and exposed points of a convex Borel subset of are Borel. We show that for there exist convex subsets of such that the sets of their extreme and exposed points coincide and are of arbitrarily high Borel class. On the other hand, we show that the sets of extreme and of exposed points of a convex set of additive Borel class are of ambiguous Borel class . For proving the latter-mentioned results we show that the union of the open and the union of the closed segments of are of the additive Borel class if is a convex set of additive Borel class .