Acrylamide polymers with covalently linked zinc(ii)tetraphenylporphyrin groups: synthesis and complexation with amino acids

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Crystal nucleation, growth, and morphology of the synthetic malaria pigment beta-hematin and the effect thereon by quinoline additives: the malaria pigment as a target of various antimalarial drugs

The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si.     

Fluorinated lithium 1,3-diketonates as reagents to modify podands and crown-ethers

Fluorinated enaminoketones, a new type of ligands, bearing two independent coordination centers (polyether's and fluorinated enaminoketones fragments) have been obtained. The crystal structure of the Cu(II) complex of 1,5-bis-[2-(4′,4′,4′-trifluoro-1′-methyl-3′-oxo-but-1′-enylamino)-phenoxy]-3-oxapentane (10) has been elucidated by X-ray crystallography. The results obtained show that the complex 10 consists of two crystallographically independent molecules C₂₆H₂₄CuF₆N₂O₅ (A and B), and the metal atom in the complex 10 has four-coordinated arrangement, as a polyhedron with a distorted square with two nitrogen and two oxygen atoms located in corners.     

Hydrogen peroxide electroreduction on composite PEDOT films with included gold nanoparticles

Composite PEDOT/Au films were obtained by chemical deposition of dispersed gold nanoparticles into PEDOT (poly-3,4-ethylenedioxythiophene) conducting polymer matrix. Morphology of the obtained gold-containing films was studied by SEM and TEM methods. To study the kinetics of the hydrogen peroxide electroreduction that proceeds on glassy carbon electrodes modified with such films, we used phosphate buffer solutions containing addenda of hydrogen peroxide species. It was observed that the electroreduction process takes place on both the gold clusters’ surface and the film surface free of metal inclusions. The rate of the process is higher in the first case and rises with increasing the gold content in modifying films, but in the limit of large gold contents it is limited only by diffusion of hydrogen peroxide species in the bathing solution. A simple theory of such parallel electroreduction is proposed, which appears to allow for quantitative treatment of the obtained results.

     

Photoluminescence of focused ion beam implanted Er3+:Y2SiO5 crystals

Erbium‐doped low symmetry Y₂SiO₅ crystals attract a lot of attention in perspective of quantum information applications. However, only doping of the samples during growth is available up to now, which yields a quite homogeneous doping density. In the present work, we deposit Er³⁺‐ions by the focused ion beam technique at yttrium sites with several fluences in one sample. With a photoluminescence study of these locally doped Er³⁺:Y₂SiO₅ crystals, we are able to evaluate the efficiency of the implantation process and develop it for the highest efficiency possible. We observe the dependence of ion activation after the post‐implantation annealing on the fluence value. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Arene Phosphorus-Containing Macrocyclic Crown Ethers: Last Studies

Abstract

The data on the synthesis, structures, and chemical properties of macrocyclic compounds containing endo-cyclic atoms of tri- and pentavalent phosphorus are summarized. Methods for the synthesis of the described macrocycles are reported. Peculiarities of structure, chemical properties, particularly formation of complexes, catalytic activity, and practical applications are analyzed. The bibliography includes 155 references.     

Redox properties of novel pyrrolidine derivatives containing sterically hindered phenol fragment

The method of cyclic voltammetry on a platinum electrode in acetonitrile is used to study the redox properties of a number of novel pyrrolidine derivatives containing a sterically hindered phenol fragment. It is found that the obtained derivatives of (3,5-di-tert-butyl-4-hydroxyphenyl)pyrrolidine-2-carboxylic acid are irreversibly oxidized in two stages with formation of a phenoxy radical. The structural analogue containing no phenyl fragment is irreversibly oxidized under similar conditions in a single stage. Formation of a stable phenoxy radical from synthesized (3,5-di-tert-butyl-4-hydroxyphenyl)pyrrolidines under PbO₂ oxidation is confirmed by ESR spectroscopy. Application of the synthesized compounds as antioxidant agents has been suggested.     

Structure and fluorescence properties of indole cyanine and merocyanine dyes with partially locked polymethine chain

The fluorescent properties of a series of symmetric cationic cyanine dyes and merocyanines with trimethylene bridge connecting N-atom of the indole residue with α-position of the polymethine chain have been explored in detail. It is shown that the constraining group influences their fluorescent properties both by steric and electronic effects. It revealed an essential decrease of the fluorescence quantum yields of the constrained symmetric cyanine dyes in comparison with those of their analogues without bridge group in their chromophore. This effect diminishes essentially at polymethine chain lengthening. In the case of merocyanines the bridge group can cause a decrease as well a substantial increase of their fluorescence quantum yields depending on their type of solvatochromism and solvent polarity. The conclusions made on the basis of the experimental data are in good agreement with the results of semiempirical quantum-chemical calculations.     

Three-dimensional optic axis determination using variable-incidence-angle polarization-optical coherence tomography

Polarization optical coherence tomography (PSOCT) is a powerful technique to nondestructively map the retardance and fast-axis orientation of birefringent biological tissues. Previous studies have concentrated on the case where the optic axis lies on the plane of the surface. We describe a method to determine the polar angle of the optic axis of a uniaxial birefringent tissue by making PSOCT measurements with a number of incident illumination directions. The method is validated on equine flexor tendon, yielding a variability of 4% for the true birefringence and 3% for the polar angle. We use the method to map the polar angle of fibers in the transitional region of equine cartilage.     

The first syntheses of 3-bromofascaplysin, 10-bromofascaplysin and 3,10-dibromofascaplysin—marine alkaloids from Fascaplysinopsis reticulata and Didemnum sp. by application of a simple and effective approach to the pyrido[1,2-a:3,4-b′]diindole system

A simple and practical approach for the synthesis of the marine sponge pigment fascaplysin was used for the total syntheses of its natural derivatives, the marine alkaloids 3-bromofascaplysin, 10-bromofascaplysin, and 3,10-dibromofascaplysin. The conditions of each step were revised, and as a result these compounds were produced by identical procedures with total yields of 40-43%.