Role of the solvent on the stability of cycloserine under ESI‐MS conditions

The effects of methanol (M) and acetonitrile (A) on the stability of cycloserine (1) have been studied. InfraRed Multiphoton PhotoDissociation (IRMPD) spectroscopy of the ionic species from electrospray ionization tandem mass spectrometry (ESI‐MS) of 1/M and 1/A solutions points to extensive dimerization of 1 to cis‐3,6‐bis(aminooxymethyl)‐2,5‐piperidinedione (2), while the same process is not observed in the ESI‐MS of 1/M solutions. 1D and 2D nuclear magnetic resonance experiments confirmed these findings by showing that partial dimerization of 1 actually takes place at room temperature in acetonitrile even before ESI‐MS analysis. Comparison of nuclear magnetic resonance and IRMPD spectroscopic data from the same 1/A solution suggests that dimerization of cycloserine is enhanced in the ESI source. Copyright © 2014 John Wiley & Sons, Ltd.     

THE USE OF INTERNALIZABLE DERIVATIVES OF CHLORIN E6 FOR INCREASING ITS PHOTOSENSITIZING ACTIVITY

Experiments with human hepatoma PLC/PRF/5 cells and human embryo skin fibroblasts involving the use of three different tests (colony formation, Trypan blue exclusion, labeled thymidine incorporation) have demonstrated a significantly higher photosensitizing activity of chlorin e₆ conjugates with internalizable ligands as compared to that of chlorin e₆ itself. Receptor-mediated internalization of chlorin e₆ conjugates ensures a greater photosensitization of cells than binding of those conjugates to cell surface receptors. The suitability of such conjugates that permit the delivery of a photosensitizer to sensitive intracellular targets is discussed.     

Cyclophosphorylation of β-cyclodextrin silyl derivatives with trivalent phosphorus acids dichlorides

A study of cyclophosphorylation with trivalent phosphorus acids dichlorides showed that the reaction, in contrast to a similar phosphorylation with phosphorous acid di- and triamides is less effective, and in the case of phenylphosphonous dichloride is accompanied by a noticeable desilylation.     

Effect of the solvent nature on the course of quaternization of 3,5-diethoxycarbonyl-2,6-dimethyl-4-(3-pyridyl)-1,4-dihydropyridine

The effect of the solvent nature and temperature on the quaternization of 3,5-diethoxycarbonyl-2,6-di- methyl-4-(3-pyridyl)-1,4-dihydropyridine by lipophilic alkyl bromides has been investigated. By comparison of the solvent effect (acetone, acetonitrile, and 2-butanone) on the alkylation of the pyridine fragment of 3,5-diethoxycarbonyl-2,6-dimethyl-4-(3-pyridyl)-1,4-dihydropyridine it was established that conducting the reaction in acetonitrile at 81 °C is the most optimal.     

Solvent and hydrogen confinement in molecular capsules-Hirshfeld surface and molecular simulation analysis

Hirshfeld surface analysis of the 'ordered' inner phase of the molecular capsule complex, [(chloroform)(6)@C-n-butylpyrogallol[4]arene)(6)], provides insight into the intermolecular contacts and orientation of the solvent molecules. Molecular simulations show that adding two or three hydrogen molecules to the six solvent molecules is energetically favoured, and this correlates with NMR studies.     

Hydrodynamic thickness and deformational properties of adsorption layers of poly(ethyleneoxides)

From the measurements of surface potentials of quartz capillaries before and after adsorption of poly(ethylene oxides) (PEO) of various molecular mass, an assessment of the equilibrium hydrodynamic thickness of the adsorption layers has been obtained. The results have been compared with those of independent measurements of . The flow of the polymer solution under increasing pressure drops at the ends of a capillary, which causes the corresponding shear stress () on the surface of adsorbed PEO layers, results in the deformation of the latter, which manifests itself in decreasing 5. The values decrease by several times when the shear stress rises to 2×10₂ N m^–2. Such values of have been obtained using thin capillaries (r = 5÷6 mm) and by application of the capillary electrokinetic method with pressure drops up to 5÷6 MPa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 31–37, January, 1994.     

Anionic high-temperature conduction in single crystals of nonstoichiometric phases R1 ? y M y F3 ? y (R = La-Lu, M = Ca, Sr, Ba) with the tysonite (LaF3) structure

Electrophysical properties of single crystals of nonstoichiometric phases R_{1 − y} M _y F_{3 − y} , where R = La-Lu, M = Ca, Sr, or Ba, with the tysonite (LaF₃) structure, which are present in a metastable state after being grown and cooled, are measured in the temperature interval extending from 300 to 1073 K. It is discovered that, during a sufficiently long high-temperature investigation, solid solutions R_{1 − y} Ca _y F_{3 − y} , where R = Tb, Dy, or Ho, undergo irreversible variations in the phase composition in the temperature region 723 to 823 K. This level of temperatures, which correspond to partial decomposition of phases R_{1 − y} Ca _y F_{3 − y} with the rare-earth elements of the end of the period, lies above the temperatures to which the fluoride solid electrolytes are usually heated when used in solid-state electrochemical devices. The temperature and concentration dependences of the phases’ electroconduction are explained in the framework of the vacancy mechanism of anionic transport. Original Russian Text ? N.I. Sorokin, B.P. Sobolev, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 4, pp. 420–431. The paper is dedicated to the memory of Prof. M.W. Breiter, formerly of the Vienna Technical University, Austria.