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Monatshefte Für Chemie

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https://www.readbyqxmd.com/read/29887646/effect-of-surface-vacancies-on-the-adsorption-of-pd-and-pb-on-mgo-100
#1
Piotr Matczak
Theoretical quantum mechanical calculations have been carried out to establish the effect of surface vacancies on the adsorption of Pd and Pb atoms on the defective MgO(100) surface. The investigated defects included neutral, singly and doubly charged O and Mg vacancies on the (100) surface of MgO. These vacancies played the role of Fs n + and Vs n - ( n  = 0, 1, 2) adsorption centers for a single Pd or Pb atom. From the results of calculations, it is clear that the Pd- and Pb-atom adsorption at the Fs n + and Vs n - centers shows different characteristics than at the regular O2- and Mg2+ centers...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29887645/identification-of-a-biliverdin-geometric-isomer-by-means-of-hplc-esi-ms-and-nmr-spectroscopy-differentiation-of-the-isomers-by-using-fragmentation-in-source
#2
Rafał Frański, Błażej Gierczyk, Łukasz Popenda, Małgorzata Kasperkowiak, Tomasz Pędzinski
A commercially available biliverdin sample was analyzed by means of HPLC/ESI-MS and NMR spectroscopy. It was been found that beside the main IXα 5 Z ,10 Z ,15 Z isomer, the sample contains also the geometric isomer IXα 5 Z ,10 Z ,15 E. It was also found the isomers behave differentially upon "in-source" fragmentation in negative ion mode (in contrast to the their behavior upon "in-source" fragmentation in positive ion mode and to their behavior upon MS/MS fragmentation in both modes): the relative abundances of deprotonated molecules and fragment ions are significantly different for both isomers, which can be used as an analytical tool to differentiate between the isomers...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29720770/application-of-x-ray-powder-diffraction-and-differential-scanning-calorimetry-for-identification-of-counterfeit-drugs
#3
Izabela Jendrzejewska, Paweł Zajdel, Ewa Pietrasik, Zoja Barsova, Tomasz Goryczka
X-ray analysis confirmed that in all investigated samples, the active API (acetylsalicylic acid and ascorbic acid) was present. The values of the interplanar distance d hkl for the studied samples are in good accordance with those presented in the ICDD database. The intensities of the diffraction lines depend on the content of the component in the tested preparation. Therefore, different intensities of lines for the APIs were observed in the obtained diffraction patterns. Thermal analysis of the studied substances showed that during the thermal analysis, the following phenomena might occur: dehydration and (or) melting, crystalline transformation...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29720769/the-influence-of-physical-division-of-tablets-on-the-variability-of-release-kinetics-of-gliclazide
#4
Dorota Wójcik-Pastuszka, Anna M Biedrawa, Dorota Haznar-Garbacz, Witold S Musiał
Tablets are often used in splitting process when the appropriated, registered dose is not available on the market or patients exhibit swallowing difficulties caused by the size of the tablet. The aim of the work was to assess the impact of physical division of tablets on the kinetics of in vitro gliclazide release from the intact and divided tablets. Gliclazide was released from prolonged release tablets containing 30 or 60 mg of the drug into a phosphate buffer, pH 7.4 and the amount of the drug in acceptor fluid was determined by UV-Vis spectrophotometry...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29720768/the-evaluation-of-alternative-method-of-ferrous-ions-assessment-in-pharmaceutical-preparations
#5
Anna Lisik, Anna Prescha, Levent E Cavlaz, Halina Grajeta, Witold Musiał
The atomic absorption spectrometry (AAS) method is one of the most accessible procedures for ferrous ions testing in various compositions including pharmaceutical preparations. The aim of the study was to develop and partially validate analytical method which could be an excellent alternative to the routine procedure performed within dissolution studies. Electric conductivity is simple, fast, and hassle-free method. The samples during dissolution process were measured using conductivity probe in entire dissolution assessment protocol...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681660/synthesis-of-novel-ligands-targeting-phenazine-biosynthesis-proteins-as-a-strategy-for-antibiotic-intervention
#6
Nikolaus Guttenberger, Thomas Schlatzer, Mario Leypold, Sebastian Tassoti, Rolf Breinbauer
In this contribution, we report synthetic strategies towards potential ligands for the study of binding differences between PhzE, the first enzyme in the biosynthesis of phenazines, and the related enzyme anthranilate synthase. The ligands were designed with the overriding goal to develop new antibiotics via downregulation of phenazine biosynthesis.
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681659/a-computational-model-to-predict-the-diels-alder-reactivity-of-aryl-alkyl-substituted-tetrazines
#7
Dennis Svatunek, Christoph Denk, Hannes Mikula
The tetrazine ligation is one of the fastest bioorthogonal ligations and plays a pivotal role in time-critical in vitro and in vivo applications. However, prediction of the reactivity of tetrazines in inverse electron demand Diels-Alder-initiated ligation reactions is not straight-forward. Commonly used tools such as frontier molecular orbital theory only give qualitative and often even wrong results. Applying density functional theory, we have been able to develop a simple computational method for the prediction of the reactivity of aryl/alkyl-substituted tetrazines in inverse electron demand Diels-Alder reactions...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681658/palladium-complexes-containing-imino-phenoxide-ligands-synthesis-luminescence-and-their-use-as-catalysts-for-the-ring-opening-polymerization-of-rac-lactide
#8
Mrinmay Mandal, Manuela List, Ian Teasdale, Günther Redhammer, Debashis Chakraborty, Uwe Monkowius
The preparation, structural characterization, luminescence, and catalytic activity of three palladium(II) complexes bearing imino phenoxide ligands are reported. The X-ray studies revealed that the complexes are mononuclear with palladium centres coordinated in a square-planar coordination environment. Two of the complexes are emissive in solution at room temperature. The catalytic activities towards the ring-opening polymerization of rac -lactide ( rac -LA) were tested. Polymers with moderate molecular weights and relatively broad dispersity ( Ð ) were obtained...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681657/synthesis-and-characterization-of-meso-substituted-a-2-b-corroles-with-extended-%C3%AF-electronic-structure
#9
Michael Haas, Sabrina Gonglach, Stefan Müllegger, Wolfgang Schöfberger
We report the chemical synthesis and characterization of the stable 5,15-bis(pentafluorophenyl)-10-(trimethylsilylethynyl)corrole which serves as a precursor for the subsequent in situ sila-Sonogashira-cross-coupling reaction and metalation with copper(II) acetate. Under ambient conditions and a common catalyst system the reaction with 1-iodopyrene occurred within five hours. Due to the direct conjugation of the 18π-electronic system of the corrole macrocycle over the alkynyl group to the pyrene moiety the optical transitions in the Soret (B-) band Q-band region are significantly altered...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681656/novel-naphthylpyridines-from-cobalt-catalyzed-cyclotrimerization-of-a-chiral-diyne
#10
Volkmar Trommer, Fabian Fischer, Marko Hapke
The concise synthesis of a novel chiral diyne substrate for the assembly of chiral naphthylpyridines was described and different conditions for the cobalt-catalyzed co-cyclotrimerization with nitriles investigated. The products are novel naphthylpyridines possessing configurationally stable biaryl axes.
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681655/regioselective-synthesis-of-pyridines-by-redox-alkylation-of-pyridine-n-oxides-with-malonates
#11
Miran Lemmerer, Christopher J Teskey, Daniel Kaiser, Nuno Maulide
A regioselective synthesis of pyridines by the addition of malonate anions to pyridine N -oxide derivatives, which have been activated by trifluoromethanesulfonic anhydride, is reported. The reaction selectively affords either 2- or 4-substituted pyridines in good yields.
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29681654/progress-in-the-synthesis-of-%C3%AE-sultones
#12
REVIEW
Christina Gaunersdorfer, Mario Waser
Sultones, the cyclic esters of hydroxyl sulfonic acids, are a fascinating class of heterocycles and the recent years have witnessed an increasing interest in these molecules, especially in six-ring δ-sultones. The importance of these compounds is either because of their biological properties themselves or due to their versatility as intermediates in more complex target syntheses. Accordingly, the development of new synthesis methods to access δ-sultones is an important and rewarding task which we wish to highlight in this review...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29576659/benzil-triethylamine-a-photo-reducing-system-for-cu-2
#13
Max Schmallegger, Georg Gescheidt
We have investigated the photo-induced reduction of Cu2+ -Cu0 using benzil/triethylamine mixtures. The formation of elemental Cu is indicated by the appearance of its characteristic plasmon absorption peaks at 515 nm and 620 nm. Importantly, the nature of the counterion of the Cu2+ salt affects the reduction process. In the presence of Cl- , the reduction proceeds faster than with SO4 2- . Photo-induced electron transfer between excited benzil and triethylamine leads to the benzil radical anion, which acts as the reducing agent for Cu2+ and generates Cu0 ...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29576658/insights-in-the-determination-of-saxitoxin-with-fluorogenic-crown-ethers-in-water
#14
Bernhard J Müller, Günter Mistlberger, Ingo Klimant
In this contribution, we present new insights and a critical discussion in the optical detection of saxitoxin using fluorophores with crown ethers. Fluorescence enhancement is caused by the reduction of photoinduced electron transfer upon complexation with the analyte. Our attempts to improve this detection method neither did yield a functioning sensor nor were the attempts to reproduce published data in this area successful. Due to the fact that only low concentrations of saxitoxin are available, multiple surrogates were investigated at high concentrations...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29497214/syntheses-characterization-and-biological-activity-of-novel-mono-and-binuclear-transition-metal-complexes-with-a-hydrazone-schiff-base-derived-from-a-coumarin-derivative-and-oxalyldihydrazine
#15
Esther Theresa Knittl, Azza A Abou-Hussein, Wolfgang Linert
A hydrazone Schiff base ligand was synthesized by the condensation of 3-formyl-4-hydroxycoumarin and oxalyldihydrazide in the molar ratio 2:1. The Schiff base ligand acts as a mono-, bi-, tri- or even tetradentate ligand with metal cations in the molar ratios 1:1 or 2:1 ( M : L ) to yield either mono- or binuclear complexes as keto or enol isomers, where M  = Co(II), Ni(II), Cu(II), VO(IV), and Fe(III). The ligand and its metal complexes were characterized by elemental analyses, IR, 1 H NMR, mass, and UV-Vis spectroscopy...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29497213/low-temperature-heat-capacities-and-thermodynamic-functions-described-by-debye-einstein-integrals
#16
Ernst Gamsjäger, Manfred Wiessner
Thermodynamic data of various crystalline solids are assessed from low temperature heat capacity measurements, i.e., from almost absolute zero to 300 K by means of semi-empirical models. Previous studies frequently present fit functions with a large amount of coefficients resulting in almost perfect agreement with experimental data. It is, however, pointed out in this work that special care is required to avoid overfitting. Apart from anomalies like phase transformations, it is likely that data from calorimetric measurements can be fitted by a relatively simple Debye-Einstein integral with sufficient precision...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29290635/on-the-rearrangement-of-n-aryl-n-boc-phosphoramidates-to-n-boc-protected-o-aminoarylphosphonates
#17
Edyta Kuliszewska, Friedrich Hammerschmidt
Various arylamines were converted in two steps to N -Boc- N -arylphosphoramidates. LiTMP and LDA induced directed ortho -metalation at temperatures from -78 to 0 °C. The ensuing [1,3]-migration of the phosphorus atom with its substituents from the nitrogen to the ortho -carbanionic carbon atom gave N -Boc-protected o -aminoarylphosphonates. The nature of the substituent of 3-substituted phenylphosphoramidates strongly influenced the regioselectivity of phosphonate formation. A crossover experiment with a deuterated phosphoramidate proved the intramolecular course of the rearrangement...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29290634/stepwise-photosensitized-thymine-dimerization-mediated-by-an-exciton-intermediate
#18
Clemens Rauer, Juan J Nogueira, Philipp Marquetand, Leticia González
Cyclobutane thymine dimerization is the most prominent DNA photoinduced damage. While the ultrafast mechanism that proceeds in the singlet manifold is nowadays well established, the triplet-state pathway is not completely understood. Here we report the underlying mechanism of the photosensitized dimerization process in the triplet state. Quantum chemical calculations, combined with wavefunction analysis, and nonadiabatic molecular dynamics simulations demonstrate that this is a stepwise reaction, traversing a long-lived triplet biradical intermediate, which is characterized as a Frenkel exciton with very small charge-transfer character...
2018: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29187762/formation-of-potentially-toxic-carbonyls-during-oxidation-of-triolein-in-the-presence-of-alimentary-antioxidants
#19
Marini Damanik, Michael Murkovic
A relation between oil uptake and cancer as well as induction of hepatic inflammation was shown earlier. It is discussed that the main oil oxidation products-hydroperoxides and carbonyls-might be the reason for the mentioned diseases. In this manuscript quantitative determination of aldehydes which are formed during oxidation of triolein-as a model substance-using the Rancimat 679 is described. The oxidation of 11 g of triolein is carried out at 120 °C sparging air with a flow of 20 dm3 /h for 10 h. A series of aliphatic aldehydes starting from hexanal to decanal as well as decenal was identified by LC-MS/MS and quantified as DNPH derivatives...
2017: Monatshefte Für Chemie
https://www.readbyqxmd.com/read/29104319/cytochrome-b-5-plays-a-dual-role-in-the-reaction-cycle-of-cytochrome-p450-3a4-during-oxidation-of-the-anticancer-drug-ellipticine
#20
Marie Stiborová, Radek Indra, Eva Frei, Kateřina Kopečková, Heinz H Schmeiser, Tomáš Eckschlager, Vojtěch Adam, Zbyněk Heger, Volker M Arlt, Václav Martínek
Ellipticine is an anticancer agent that forms covalent DNA adducts after enzymatic activation by cytochrome P450 (CYP) enzymes, mainly by CYP3A4. This process is one of the most important ellipticine DNA-damaging mechanisms for its antitumor action. Here, we investigated the efficiencies of human hepatic microsomes and human recombinant CYP3A4 expressed with its reductase, NADPH:CYP oxidoreductase (POR), NADH:cytochrome b 5 reductase and/or cytochrome b 5 in Supersomes™ to oxidize this drug. We also evaluated the effectiveness of coenzymes of two of the microsomal reductases, NADPH as a coenzyme of POR, and NADH as a coenzyme of NADH:cytochrome b 5 reductase, to mediate ellipticine oxidation in these enzyme systems...
2017: Monatshefte Für Chemie
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