bluuebunny/crossref_metadata_2025 huggingface dataset:
Discovery of Potent Small-Molecule Inhibitors of Multidrug-Resistant
Plasmodium falciparum
Using a Novel Miniaturized High-Throughput Luciferase-Based Assay
Authors: Lucumi Edinson , Darling Claire , Jo Hyunil , Napper Andrew D. , Chandramohanadas Rajesh , Fisher Nicholas , Shone Alison E. , Jing Huiyan , Ward Stephen A. , Biagini Giancarlo A. , DeGrado William F. , Diamond Scott L. , Greenbaum Doron C.
Published: June 2010

Malaria is a global health problem that causes significant mortality and morbidity, with more than 1 million deaths per year caused by
Plasmodium falciparum
. Most antimalarial drugs face decreased efficacy due to the emergence of resistant parasites, which necessitates the discovery of new drugs. To identify new antimalarials, we developed an automated 384-well plate screening assay using
P. falciparum
parasites that stably express cytoplasmic firefly luciferase. After initial optimization, we tested two different types of compound libraries: known bioactive collections (Library of Pharmacologically Active Compounds [LOPAC] and the library from the National Institute of Neurological Disorders and Stroke [NINDS]) and a library of uncharacterized compounds (ChemBridge). A total of 12,320 compounds were screened at 5.5 μM. Selecting only compounds that reduced parasite growth by 85% resulted in 33 hits from the combined bioactive collection and 130 hits from the ChemBridge library. Fifteen novel drug-like compounds from the bioactive collection were found to be active against
P. falciparum
. Twelve new chemical scaffolds were found from the ChemBridge hits, the most potent of which was a series based on the 1,4-naphthoquinone scaffold, which is structurally similar to the FDA-approved antimalarial atovaquone. However, in contrast to atovaquone, which acts to inhibit the
bc
1
complex and block the electron transport chain in parasite mitochondria, we have determined that our new 1,4-napthoquinones act in a novel, non-
bc
1
-dependent mechanism and remain potent against atovaquone- and chloroquine-resistant parasites. Ultimately, this study may provide new probes to understand the molecular details of the malaria life cycle and to identify new antimalarials.
Daptomycin-Oxacillin Combinations in Treatment of Experimental Endocarditis Caused by Daptomycin-Nonsusceptible Strains of Methicillin-Resistant
Staphylococcus aureus
with Evolving Oxacillin Susceptibility (the “Seesaw Effect”)
Authors: Yang Soo-Jin , Xiong Yan Q. , Boyle-Vavra Susan , Daum Robert , Jones Tiffanny , Bayer Arnold S.
Published: June 2010

In vivo
development of daptomycin resistance (DAP
r
) among
Staphylococcus aureus
strains, especially methicillin-resistant
S. aureus
(MRSA) strains, in conjunction with clinical treatment failures, has emerged as a major problem. This has raised the question of DAP-based combination regimens to enhance efficacy against such strains. We studied five recent DAP-susceptible (DAP
s
)/DAP
r
clinical MRSA strain pairs obtained from patients who failed DAP monotherapy regimens, as well as one DAP
s
/DAP
r
MRSA strain pair in which the resistant strain was generated by
in vitro
passage in DAP. Of note, we identified a DAP-oxacillin (OX) “seesaw” phenomenon
in vitro
in which development of DAP
r
was accompanied by a concomitant fall in OX resistance, as demonstrated by 3- to 4-fold decreases in the OX MIC, a susceptibility shift by population analyses, and enhanced early killing by OX in time-kill assays. In addition, the combination of DAP and OX exerted modest improvement in
in vitro
bactericidal effects. Using an experimental model of infective endocarditis and two DAP
s
/DAP
r
strain pairs, we demonstrated that (i) OX monotherapy was ineffective at clearing DAP
r
strains from any target tissue in this model (heart valve, kidneys, or spleen) and (ii) DAP-OX combination therapy was highly effective in DAP
r
strain clearances from these organs. The mechanism(s) of the seesaw effect remains to be defined but does not appear to involve excision of the staphylococcal cassette chromosome
mec
(SCC
mec
) that carries
mecA
.
New Fixed-Dose Artesunate-Mefloquine Formulation against Multidrug-Resistant
Plasmodium falciparum
in Adults: a Comparative Phase IIb Safety and Pharmacokinetic Study with Standard-Dose Nonfixed Artesunate plus Mefloquine
Authors: Krudsood S. , Looareesuwan S. , Tangpukdee N. , Wilairatana P. , Phumratanaprapin W. , Leowattana W. , Chalermrut K. , Ramanathan S. , Navaratnam V. , Olliaro P. , Vaillant M. , Kiechel J. R. , Taylor W. R. J.
Published: June 2010

A new fixed-dose artesunate (AS)-mefloquine (MQ) was assessed in adults hospitalized for 28 days with uncomplicated drug-resistant falciparum malaria. The patients (
n
= 25/arm) were treated with (i) two fixed-dose tablets (AS-MQ arm; 100 mg AS-200 mg MQ/tablet) daily for 3 days (days 0, 1, and 2) or (ii) nonfixed AS (AS-plus-MQ arm; 4 mg/kg of body weight/day for 3 days) plus MQ (15 mg/kg on day 1 and 10 mg/kg on day 2), dosed by weight. Clinical laboratory electrocardiogram (ECG), adverse events (AEs), efficacy, and pharmacokinetic parameters were assessed over 28 days. Both regimens were well tolerated. No AEs were drug related. Two serious AEs of malaria-induced hypotension occurring in the AS-MQ arm necessitated rescue treatment. There were no significant changes in hematology, biochemistry, or PR and QRS intervals. For all patients, mean Fridericia-corrected QT intervals were significantly (
P
≤ 0.0027) prolonged on day 3 (407 ms) and day 7 (399 ms) versus day 0 (389 ms), in parallel with significant (
P
≤ 0.0003) falls in heart rates (67 [day 3], 73 [day 7], and 83 [day 0] beats/minute). Fixed-nonfixed formulations were bioequivalent for MQ, but not for AS and dihydroartemisinin (DHA). One AS-MQ patient developed a new infection on day 28; his day 28 plasma MQ concentration was 503.8 ng/ml. Fixed-dose AS-MQ was well tolerated, had pharmacokinetic (PK) profiles broadly similar to those of nonfixed AS plus MQ, and is a suitable replacement.
Evaluation of a DNA Microarray, the Check-Points ESBL/KPC Array, for Rapid Detection of TEM, SHV, and CTX-M Extended-Spectrum β-Lactamases and KPC Carbapenemases
Authors: Naas T. , Cuzon G. , Truong H. , Bernabeu S. , Nordmann P.
Published: June 2010

Extended-spectrum ß-lactamases (ESBLs) and
Klebsiella pneumoniae
carbapenemases (KPC carbepenemases) have rapidly emerged worldwide and require rapid identification. The Check-Points ESBL/KPC array, a new commercial system based on genetic profiling for the direct identification of ESBL producers (SHV, TEM, and CTX-M) and of KPC producers, was evaluated. Well-characterized Gram-negative rods (
Enterobacteriaceae
,
Pseudomonas aeruginosa
,
Acinetobacter baumannii
) expressing various ß-lactamases (KPC-2, SHV, TEM, and CTX-M types) were used as well as wild-type reference strains and isolates harboring ß-lactamase genes not detected by the assay. In addition, phenotypically confirmed ESBL producers isolated in clinical samples over a 3-month period at the Bicetre hospital were analyzed using the Check-Points ESBL/KPC array and by standard PCR. The Check-Points ESBL/KPC array allowed fast detection of all TEM, SHV, and CTX-M ESBL genes and of the KPC-2 gene. The assay allowed easy differentiation between non-ESBL TEM and SHV and their ESBL derivatives. None of the other tested ß-lactamase genes were detected, underlining its high specificity. The technique is suited for
Enterobacteriaceae
but also for
P. aeruginosa
and
A. baumannii
. However, for nonfermenters, especially
P. aeruginosa
, a 1:10 dilution of the total DNA was necessary to detect KPC-2 and SHV-2a genes reliably. The Check-Points ESBL/KPC array is a powerful high-throughput tool for rapid identification of ESBLs and KPC producers in cultures. It provided definitive results within the same working day, allowing rapid implementation of isolation measures and appropriate antibiotic treatment. It showed an interesting potential for routine laboratory testing.
Microbial Growth Inhibition by Alternating Electric Fields in Mice withPseudomonas aeruginosaLung Infection
Authors: Giladi Moshe , Porat Yaara , Blatt Alexandra , Shmueli Esther , Wasserman Yoram , Kirson Eilon D. , Palti Yoram
Published: June 2010

High-frequency, low-intensity electric fields generated by insulated electrodes have previously been shown to inhibit bacterial growthin vitro. In the present study, we tested the effect of these antimicrobial fields (AMFields) on the development of lung infection caused byPseudomonas aeruginosain mice. We demonstrate that AMFields (10 MHz) significantly inhibit bacterial growthin vivo, both as a stand-alone treatment and in combination with ceftazidime. In addition, we show that peripheral (skin) heating of about 2°C can contribute to bacterial growth inhibition in the lungs of mice. We suggest that the combination of alternating electric fields, together with the heat produced during their application, may serve as a novel antibacterial treatment modality.
Distribution and Phylogeny of Immunoglobulin-Binding Protein G in Shiga Toxin-Producing
Escherichia coli
and Its Association with Adherence Phenotypes
Authors: Merkel Viktor , Ohder Barbara , Bielaszewska Martina , Zhang Wenlan , Fruth Angelika , Menge Christian , Borrmann Erika , Middendorf Barbara , Müthing Johannes , Karch Helge , Mellmann Alexander
Published: June 2010

eibG
in Shiga toxin-producing
Escherichia coli
(STEC) O91 encodes a protein (EibG) which binds human immunoglobulins G and A and contributes to bacterial chain-like adherence to human epithelial cells. We investigated the prevalence of
eibG
among STEC, the phylogeny of
eibG
, and
eibG
allelic variations and their impact on the adherence phenotype.
eibG
was found in 15.0% of 240
eae
-negative STEC strains but in none of 157
eae
-positive STEC strains. The 36
eibG
-positive STEC strains belonged to 14 serotypes and to eight multilocus sequence types (STs), with serotype O91:H14/H
−
and ST33 being the most common. Sequences of the complete
eibG
gene (1,527 bp in size) from
eibG
-positive STEC resulted in 21 different alleles with 88.11% to 100% identity to the previously reported
eibG
sequence; they clustered into three
eibG
subtypes (
eibG
-α,
eibG
-β, and
eibG
-γ). Strains expressing EibG-α and EibG-β displayed a mostly typical chain-like adherence pattern (CLAP), with formation of long chains on both human and bovine intestinal epithelial cells, whereas strains with EibG-γ adhered in short chains, a pattern we termed atypical CLAP. The same adherence phenotypes were displayed by
E. coli
BL21(DE3) clones containing the respective
eibG
-α,
eibG
-β, and
eibG-
γ subtypes. We propose two possible evolutionary scenarios for
eibG
in STEC: a clonal development of
eibG
in strains with the same phylogenetic background or horizontal transfer of
eibG
between phylogenetically unrelated STEC strains.
Photoinduced energy and electron transfer in micellar solutions of methylene blue
Authors: Řehák Viktor , Rybová Yvona
Published: June 2010

In the micellar medium of sodium dodecyl sulphate the monomer-dimer equilibrium of methylene blue is shifted markedly in favour of the monomer. Methylene blue quenches the fluorescence of pyrene solvated in micelles, which is explained in terms of resonance energy transfer. Based on the theoretical model, the pyrene fluorescence quenching constant in the micelles was determined (kqm = 1.8 106 s-1) and the average pyrene-methylene blue interaction distance for the singlet-singlet energy transfer estimated. The T1 → Tn absorption of methylene blue is quenched by pyrene and tetrasodium salt of ethylenediaminetetraacetic acid (EDTA); the quenching rate constants corresponding to the electron transfer are 5 106 and 2.05 108 1 mol-1 s-1, respectively.
Random errors in equilibrium composition of ternary liquid-liquid systems and their effect on the calculated number of theoretical stages of countercurrent extraction
Authors: Dojčanský Ján , Bafrncová Soňa , Surový Július
Published: June 2010

The influence of size of random errors in the determination of ternary liquid-liquid equilibrium concentrations on the accuracy of the calculated number of theoretical stages of a countercurrent extractor is evaluated by using five hypothetical systems differing in the extent of mutual solubility of components, tie-line slope, and type of binodal curve.
Modelling of fixed bed catalytic reactors with catalyst deactivation under constant-pattern travelling wave assumption
Authors: Markoš Jozef , Brunovská Alena
Published: June 2010

The models of fixed bed catalytic reactors in which catalyst deactivation takes place can be significantly simplified by introducing quasi-steady state and constant-pattern travelling wave assumption. This results in faster algorithms. In the present paper the plug-flow, radial dispersion, and well-mixed regions in the series pseudohomogenous models under the above assumptions are discussed. The obtained results are compared with experimental ones in the case of hydrogenation of benzene on a nickel catalyst with thiophene as a poison (irreversible deactivation).
ESR study of the structure and bonding situation in thiocyanatocopper(II) complexes with imidazole derivatives
Authors: Mašlejová Anna , Kirmse Reinhard
Published: June 2010

ESR spectra of thianatocopper(II) complexes with imidazole derivatives were studied in ethanolic solutions at 295 and 123 K. Axialsymmetric spectra, attributed to the monomeric complex units, were obtained for the frozen solutions. The bonding parameters were interpreted by using calculated g, Cu-hyperfine, and 14N-ligand hyperfine splitting values. The Cu-N bond parameters indicate a considerable delocalization of the unpaired electron. The values of the isotropic Cu-hyperfine splitting suggest that the deviations from the planar symmetry of the CuN4 units are due to tetrahedral perturbation of the ligand field.
Lithium - Heavier alkali metal exchange in organolithium compounds induced by alkoxides of heavier alkali metals and reactions occurring in this system
Authors: Lochmann Lubomír , Trekoval Jiří
Published: June 2010

Organolithium compounds of various types undergo an exchange reaction lithium-heavier alkali metal when treated with heavier alkali metal alkoxides. In the presence of a third reactive compound the exchange reaction gives rise to a compound of the third component substituted with the heavier alkali metal. Using this exchange reaction, organic derivatives of heavier alkali metals in the individual state can be easily prepared. The mechanism of such reactions is discussed, and the formation of lithium alkoxide is assumed to contribute significantly to the driving force of the reaction. Organic compounds of heavier alkali metals possess a considerably higher reactivity than organolithium compounds, and are therefore used as reactive intermediates in preparative chemistry, or as polymerization initiators in macromolecular chemistry. This review provides information about the scope and possibilities of this exchange reaction, which has been increasingly widely used in the recent years.
On the mechanism of rifampicin inhibition of DNA dependent RNA polymerase from Escherichia coli: A new hypothesis of the drug action
Authors: Cvekl Aleš , Horská Květa , Šebesta Karel
Published: June 2010

The influence of rifampicin on the temperature dependent synthesis of trinucleotides ApUpA and UpApU was studied. Whereas the elongation of dinucleotide ApU is stimulated to a great extent, the elongation of UpA is inhibited to about 50%. These results cannot be explained in terms of different models proposed for the mechanism of inhibition of RNA synthesis caused by rifampicin. According to our hypothesis rifampicin inhibits internal rearrangement of the RNA polymerase which occurs during the transition of the initiation complex to the stable elongation complex.
Membrane proton transport mediated by phenylhydrazonopropanedinitriles
Authors: Kluka Ľubomír , Šturdík Ernest , Baláž Štefan , Kordík Dušan , Rosenberg Michal , Antalík Marián , Augustín Jozef
Published: June 2010

Some fundamental physicochemical characteristics as stability in solutions, solubility in various solvents and association constants describing equilibria with protons and potassium ions in aqueous solutions were determined for phenylhydrazonopropanedinitriles (PHPD). The effect of pH and sodium, potassium, calcium, and magnesium cations on the distribution of PHPD were examined in a two-compartment system 1-octanol-water. The transmembrane transfer of protons by PHPD causing a disturbance of the pH-gradient was verified in vitro using a model three-compartment system water-octanol-water, imitating the in vivo intracristal space-inner mitochondrial membrane – matrix system. Transfer of H+ ions mediated by PHPD in the system under study was found to be considerably faster when an exchange with K+ ions (ion-exchanging antiport H+/K+) was possible. A model was described indicating the reality of ion-exchanging antiport H+/Me+ mediated by PHPD on biomembranes which is in line with the chemiosmotic theory.
Study of the azo-hydrazone tautomeric equilibrium by electronic spectroscopy and quantum chemistry. II. HMO calculations
Authors: Titz Miloš , Nepraš Miloš , Nečas Miroslav , Hrdina Radim , Luňák Stanislav , Lyčka Antonín
Published: June 2010

Experimental data obtained in Part I of this work for p-hydroxy and p-amino derivatives of four arylazo compounds with different fused ring systems were correlated with some indices calculated by the simple HMO quantum chemical method in relation to the π-electron structure of the azo and hydrazone tautomers of the compounds studied. Mental fragmentation and the related stability of the systems expressed by Julg’s aromaticity indices of the hydrocarbon fragments appeared to be basically different for the two tautomers.
Titrimetric and gravimetric determination of the specific pore volume of microparticulate silica gels
Authors: Šimek Zdeněk , Vespalec Radim , Neča Jiří
Published: June 2010

The titrimetric and gravimetric methods of determination of the specific pore volume were studied unmodified and modified chromatographic silica gels of mean particle size above 5 μm. The apparatus and titrimetric procedure suggested elsewhere were adapted so that the relative standard deviation of measurement did not exceed 2%. Water, n-octane, and methanol were used as titrants, and methanol was found to suit best from the point of view of accuracy and rapidity of analysis and versatility of use. This solvent is also suitable for the gravimetric measurements, which can be carried out without thermostatting and at barometric pressure. The titrimetric procedure is less time consuming than the gravimetric procedure which, on the other hand, is less tedious and less instrumentation-demanding.
1,3-Dipolar cycloaddition reactions of 7-alkenyl- or 7-alkynyl-8-azidomethyltheophyllines
Authors: Hesek Dušan , Rybár Alfonz , Považanec František , Martvoň Augustin , Kováč Jaroslav
Published: June 2010

8-Azidomethyltheophillines XI-XIV, containing dipolarophilic alkenyl or alkynyl (i.e. allyl, 2-butenyl, cinnamyl, and 2-propynyl) groups in position 7, undergo thermally induced 1,3-dipolar intramolecular cycloaddition under formation of 7-substituted 1,3-dimethyl-2,4-dioxo-1,2,3,4,6,6a,7,11-octahydro(1,2,3)triazolo[1’,5’:1,2]pyrazino[5,4-f]purines XV-XVII and 1,3-dimethyl-2,4-dioxo-1,2,3,4,6,11-hexahydro(1,2,3)triazolo[1’,5’:1,2]pyrazino[5,4-f]purine (XVIII), respectively. The compounds were synthesized starting from 8-hydroxymethyltheophilline (I) which was alkylated to give 7-alkenyl- and 7-alkynyl-8-hydroxymethyltheophillines III-VI and these were converted into the corresponding 8-halogenomethyl derivatives VII-X by treatment with thionyl chloride or phosphorus tribromide. Reaction of VII-X with sodium azide afforded the 8-azidomethyl derivatives XI-XIV.
Reactions of 4-chloro-1-nitrobenzene with (3-chloro-4-methoxyphenyl)acetonitrile and (3,4-dimethoxyphenyl)acetonitrile; Synthesis of 8-chloro-1-methyl (and methylthiomethyl-6-(3,4-disubstituted phenyl)-4H-s-triazolo[4,3-a]-1,4-benzodiazepines
Authors: Vejdělek Zdeněk , Holubek Jiří , Buděšínský Miloš , Ryska Miroslav , Svátek Emil , Protiva Miroslav
Published: June 2010

Reactions of 4-chloro-1-nitrobenzene with (3-chloro-4-methoxyphenyl)acetonitrile and (3,4-dimethoxyphenyl)acetonitrile in methanolic potassium hydroxide gave the corresponding 3-aryl-5-chloro-2,1-benzisoxazoles Ia and Ib in good yields; compounds Va, Vb, VI-VIII and X were isolated as by-products and identified by means of spectra. Compounds Ia and Ib were transformed in five steps to the title compounds XVab and XVIab which were found inactive in tests for central depressant and anticonvulsant activity.
Mechanism of denaturation of human serum albumin by urea
Authors: Chmelík Josef , Anzenbacher Pavel , Chmelíková Jitka , Matějčková Milada , Kalous Vítěz
Published: June 2010

The mechanism of denaturation of human serum albumin by urea was examined by polarography, polarimetry, circular dichroism, UV-spectrophotometry, gel chromatography, and polyacrylamide gel electrophoresis. Comparison of the results obtained by these methods shows that this reaction is a complex process which cannot be described by a two-state denaturation model. It has been demonstrated that the different states which denaturation produces arise under different denaturation conditions. The different behavior of various species of human serum albumin (monomer, mercaptalbumin and nonmercaptalbumin) during denaturation by urea was examined. As a result the following probable denaturation scheme was proposed: The denaturation of human serum albumin by urea is regarded as a stepwise process involving one stable intermediary product at least ( demonstrated electrophoretically). After the rapid initial change of the ordered helical structure extensive hydrophobic domains of the molecule remain folded. Cystine residues are gradually liberated from these domains. Denaturated mercaptalbumin has the conformation of a random coil in which the pairing of native disulfide bonds has been altered because of SH-S-S interchange reactions; in contrast native disulfide bonds are retained in nonmercaptalbumin.
On theory of ionic volumes in dilute aqueous solutions of electrolytes
Authors: Čeleda Jiří
Published: June 2010

For purposes of calculation of densities of aqueous solutions of strong electrolytes and of their mixtures, theoretical substantiation of the formerly outlined empirical model of apparent molar ionic volumes φ in solution is presented. According to the model, the hydration sheaths of ions consisting of radially close-packed H2O molecules having effective molar volume V’w the same for all ions, are on their contact with the adjacent structure of liquid water surrounded by a layer of excess voids. This layer can bee substituted in the model by continuous gap of which d0, which again is common to all the ions and is temperature-independent. Using experimental φ values of twenty-seven strong electrolytes together with the data on electrolytic transport of water on ions, V’w = 12 cm3 mol-1 and d0 = (40 ± 2) pm were found for mono- and divalent ions in 1 mol dm-3 solutions, independently of ionic charges and crystallographic radii. The exception are small ions Li+ and Na+, the volumes of which – if interpreted on the basis of the model – correspond to hydration sheaths formed by a cluster of voluminous ice-like structure. An anomaly in this respect has been encountered also in the case of NH+4 ion.
IR study of dynamic bahaviour of 2-propanol on alumina
Authors: Morávek Vladimír , Kraus Miloš , Malysheva L. V. , Paukshtis E. A. , Yurchenko E. N.
Published: June 2010

Dynamic behavior of surface complexes of 2-propanol on aluminia during adsorption and dehydration was studied using IR spectroscopy. Good agreement was found between the first-order rate constants of alkene formation in pulse-flow experiments and that of disapearance of a reactive surface complex. It was shown that the simple surface alkoxide 2-Pr-O-Al remains on the surface constant temperature, but it can be completely removed by hydrolysis, or by heating up to 200 °C. The surface carboxylates are formed very slowly and are stable even in the presence of water vapour at 300 °C.
The effect of migration in laminar diffusion layers
Authors: Wein Ondřej
Published: June 2010

Newman's similarity model of convective diffusion of ions through multi-ionic concentration boundary layer in the presence of electric field is generalized for non-linear velocity profiles in the diffusion layer, and put into a form that can be integrated by the Runge-Kutta method. The results of a numerical solution are compared with voltammetric data from the literature.
Determination of trace quantities of freon by laser optoacoustic detection and classical infrared spectroscopy
Authors: Zelinger Zdeněk , Papoušková Zlata , Jakoubková Marie , Engst Pavel
Published: June 2010

The sensitivity threshold was determined for a homebuilt apparatus with laser optoacoustic detection, enabling gases absorbing in the range of emission by the CO2 laser used to be detected selectively in trace concentrations. Gravimetrically calibrated homemade permeation tubes containing Freon 11 (CCl3F) were used, and a sensitivity threshold of 20 ppb was established. The dependence of the optoacoustic signal on the concentration of Freon 11 was measured in the dynamic mode; this concentration is given by the permeation standard type, carrier gas flow rate, and temperature. Classical IR spectroscopic measurements in the static mode were also performed.
Tricyclic analogues of the antiallergic agent oxatomide: 1-(3-(4-(10,11-Dihydro-5H-dibenzo[a,d]cycloheptene-5-yl)-1-piperazinyl)propyl)-1,3-dihydro-2H-benzimidazol-2-one and the related 6,11-dihydrodibenzo[b,e]thiepin, 4,9-dihydrothieno[2,3-c]-2-benzothiepin, and 10,11-dihydrodibenzo[b,f]thiepin derivatives
Authors: Jílek Jiří , Holubek Jiří , Svátek Emil , Metyš Jan , Frycová Hana , Pomykáček Josef , Protiva Miroslav
Published: June 2010

11-Chloro-6,11-dihydrodibenzo[b,e]thiepin and its 2-methyl derivative VI were transformed via the 11-(4-ethoxycarbonyl)-1-piperazinyl) compounds IVc and Vc to 11-(1-piperazinyl)compounds IVb and Vb. Their reactions with 1-(3-chloropropyl)-1,3-dihydro-2H-benzimidazol-2-one (II) afforded the title compounds IVa and IVb. Similar reactions and sequences in the series of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene, 4,9-dihydrothieno[2,3-c]-2-benzothiepin, and 10,11-dihydrodibenzo[b,f]thiepin led to further oxatomide (Ia) analogues IIIa and VIIa-XIa. In the test of passive cutaneous anaphylaxis in rats, compound VIIIa was more active than Ia, and IVa had similar activity like Ia.
Turbulent flow chracteristics for pitched blade turbine
Authors: Jaworski Zdzisław , Fořt Ivan , Stręk Fryderyk
Published: June 2010

Measurements of the velocity of a stirred liquid in turbulent flow were performed for the area surrounding a pitched blade turbine. A cylindrical tank equipped with four standard baffles and the stirrer was used in the study. A number of traces of tracer particles were photographed and used to determine instantaneous values of the radial and axial components of the liquid local velocity. Those values were employed to estimate local values of the radial and axial components of the mean and fluctuating velocities. Analysis of the radial distribution of the fluctuating velocity components revealed the existence of the local isotropy of those components for the entire investigated area upstream and downstream the stirrer. Moreover, the homogeneity of turbulence in the stream entering the stirrer and in the induced stream can be assumed. The discharge stream showed an approximate homogeneous turbulence of intensity over 2 times higher than that for the other streams.
Kinetics and mechanism of the reaction of iron(III) and 2,2,6,6-tetramethyl-3,5-heptanedione in aqueous solution
Authors: Hernando José M. , Blanco Carlos , Mateo Manuel
Published: June 2010

In this work the kinetic of formation of (2,2,6,6-tetramethyl-3,5-heptanedione)iron(III) complex (stoichiometry 1 : 1) has been studied in aqueous solution. It was found that the reaction is of first order with respect to diketone. The influence of several factors such as reagent concentrations, pH, ionic strength and temperature was systematically examined. A mechanism SN1 is proposed for the complexation process that accounts successfully for the experimental results.
The preparation and characterization of 2-propylphosphinediacetic acid
Authors: Podlahová Jana , Podlaha Jaroslav
Published: June 2010

Phosphineacetic acids of the RP(CH2COOH)2 type, where R is a large substituent with a +I-effect, cannot be prepared by the reaction of chlorophosphine with an organozinc compound because of the lability of the P-CH2COO bonds. The bis(ethyl ester) of 2-propylphosphinediacetic acid as the simplest substance of this kind was prepared by the reaction of chlorophosphine with ethylacetate enolate, which is universal for these substituents. 2-Propylphosphinediacetic acid, obtained from the ester by the usual procedure, was characterized with respect to its use as a hydrophilic phosphine ligand.
Calculation of the differential rate constants of quaternization reactions of polymer amines
Authors: Přádný Martin , Ševčík Stanislav , Dragan Stela
Published: June 2010

A method is described for the calculation of differential rate constants using an empirical description of the time dependence of the product of integral rate constant and time or of conversion. The method has been verified for quaternization reactions of poly(2-dimethylaminoethyl methacrylate), poly(4-dimethylaminomethylstyrene), poly[N-(3-dimethylaminopropyl)acrylamide], poly(4-vinylpyridine), poly(iminoethylene), and [4-bis(2-hydroxyethyl)aminomethylstyrene] as a function of conversion of the reaction. The calculations were carried out using reported data on the dependence of conversion on time.
Reactions of methyl esters of N-(2,4-dinitrophenyl)glycine and N-methyl-N-(2,4-dinitrophenyl)glycine with sodium methoxide
Authors: Macháček Vladimír , Štěrba Vojeslav , Kolb Ivan , Lyčka Antonín
Published: June 2010

The reaction of methyl ester of N-(2,4-dinitrophenyl)glycine (I) with sodium methoxide produces 5-nitro-2(3H)benzimidazolone (III). The product identity has been proved by its isolation from the reaction mixture under conditions similar to those of kinetic experiments and by independent synthesis. The reaction of methyl ester of N-methyl-N-(2,4-dinitrophenyl)glycine with methoxide proceeds in two steps, the second one being substantially slower. The first step produces N-methyl-2-nitroso-4-nitroaniline (IV), which can be prepared by this reaction in good yield and purity. N-Methyl-2-nitroso-4-nitroaniline undergoes subsequent reactions in the methoxide solutions. Products of the subsequent reactions have not been identified at the starting ester II concentrations of about 10-4 mol l-1, whereas at higher concentrations of the starting substance the reaction produces 2-amino-2'-methylamino-5,5'-dinitro-ONN-azoxybenzene (V) and 2,2'-bis(methylamino)-5,5'-dinitroazoxybenzene (VI).
Electrophilic ipso substitutions of furan vinamidinium salts
Authors: Gracza Tibor , Arnold Zdeněk , Kováč Jaroslav
Published: June 2010

5-(N,N-Dialkylamino)-2-furfurylidene-N,N-dialkylimminium salts I (the vinamidinium salts of furan) react with arenediazonium salts to give products of ipso substitution in position 2 of the furan ring, i.e. 5-(N,N-dialkylamino)-2-azoarenefuran salts II. The structure of these products was evidenced by 1H NMR and UV spectral data.
Cycloaddition of arylnitrile oxides to 2H,5H-1,6-benzodioxocine and related compounds
Authors: Fišera Lubor , Jarošková Libuše , Schroth Werner , Gäbler Michael , Oravec Peter
Published: June 2010

3-Aryl-3a,4,11,11a-tetrahydroisoxazolo[5,4c]-1,6-benzodioxocines VIII were formed by a 1,3-dipolar cycloaddition of arylnitrile oxides to 2H,5H-1,6-benzodioxocine (III). The heterocycle VII afforded monoadducts IX, whereas dipolarophiles IV-VI do not yield cycloaddition products with nitrile oxides under the same reaction conditions. Irradiation of isoxazolines VIII, IX with UV light led to tarry products.
Subcellular and cellular studies on relationship between structure and uncoupling effect of phenylhydrazonopropanedinitriles on oxidative phosphorylation
Authors: Šturdík Ernest , Baláž Štefan , Ďurčová Edita , Antalík Marián , Sulo Pavol , Šturdíková Maria , Mikeš Vladimír
Published: June 2010

The characterization of relations between the assumed activity-determining physico-chemical parameters (partition coefficients, dissociation constants, reactivity to thiol compounds) of o-, m-, and p-substituted phenylhydrazonopropanedinitriles and their uncoupling effect on oxidative phosphorylation in mitochondria isolated from rat liver, Paracoccus denitrificans bacteria and animal leukemia P 388 cells have shown that from the viewpoint of action mechanism the concept of proton-translocating (pH-gradient disturbing) effect is more plausible than the modification of the corresponding membrane proteins. The dependence of the activity of the compounds studied on their physicochemical characteristics is represented by a saturation curve with a plateau starting at log P 5-6 when the uncoupling effect is plotted versus lipophilicity and by a bell-shaped curve having a maximum at pKa 4·5-5·5 with respect to basicity.
Electrochemical reactor systems for pollution control and the removal of toxic metals from industrial wastewaters
Authors: Fleet Bernard
Published: June 2010

A review of electrochemical reactor systems for the recovery of metals and for pollution control applications is presented. The major engineering factors which influence the design of reactors are evaluated and the key features of two-dimensional and three-dimensional reactor designs are discussed. Some examples of the application of electrochemical reactors to the recovery of metals from dilute solutions are given in the form of case studies, covering both pollution control and resource recovery processes. Finally a comparison is made of the relative technical and economic merits of electrochemical recovery pollution control systems and conventional chemical waste treatment routes.
Certain problems with the application of stochastic diffusion processes for description of chemical engineering phenomena; Kolmogorov and classic diffusion equations
Authors: Kudrna Vladimír
Published: June 2010

The paper presents alternative forms of partial differential equations of the parabolic type used in chemical engineering for description of heat and mass transfer. It points at the substantial difference between the classic form of the equations, following from the differential balances of mass and enthalpy, and the form following from the concept of stochastic motion of particles of mass or energy component. Examples are presented of the processes that may be described by the latter method. The paper also reviews the cases when the two approaches become identical.
The synthesis of highly pure octachlorocyclotetraphosphazene (PNCl2)4+
Authors: Kouřil Milan , Mezník Lubomír , Dlabaja Ladislav
Published: June 2010

On the basis of literature data we prepared linear chlorophosphazenes (PCl3NPCl3)+Cl- and (PCl3NPCl2NPCl2PCl3)+PCl6-, and followed the course of their amonolysis. The amonolysis of these compounds leads to the formation of cyclic chlorophosphazenes (PNCl2)n n = 3,4. We found conditions for the preparation of the tetramer (PNCl2)4 - octachlorocyclotetraphosphazene in a pure state and in a larger amount. In principle the tetramer is formed according to the reaction PCl3 + Cl2 + NH3, leading to a mixture of chlorophosphazenes (PNCl2)n n = 3-8, from which it must be isolated using various separation methods.
Cooligomerization of propadiene with propyne catalysed by nickel(0) complexes
Authors: Čermák Jan , Blechta Vratislav , Chvalovský Václav
Published: June 2010

Cooligomerization of propadiene with propyne catalysed by bis(1,5-cyclooctadiene)nickel and tetrakis(triphenylphosphine)nickel gives a variety of products, including besides the cooligomers also the homooligomers of both monomers. The type of catalyst affects partially the product distribution due to changes in the degree of oligomerization. Cooligomerization of propadiene with 3-deuteriopropyne provided information about relative proportion of propadiene and propyne units in the oligomers.
Spectrophotometric study of analytical reactions of triphenylmethane dyes with uranyl in the presence of cationic surfactants
Authors: Jančář Luděk , Havel Josef , Sommer Lumír
Published: June 2010

Numerical analysis of absorbance data for the analytically significant UO22+ - Chromazurol B, UO22+ - Chromazurol S, and UO22+ - Eriochromcyanine R systems in the presence of the cationic surfactant SeptonexR revealed that also in micellar medium, complex equilibria establish and several complexes are formed in dependence on pH and concentration of uranyl ions, reagent, and surfactant. Based on the results, optimum conditions are found for the spectrophotometric determination of low concentration of uranium.
Naive models as active expert system in bioengineering and chemical engineering
Authors: Dohnal Mirko
Published: June 2010

A possibility of qualitative variable utilization for description and evaluation of phenomena and processes from non-formal human thinking point of view is presented. Paper gives methods of naïve modelling and realistically assesses results that can be awaited. The method is demonstrated on two case studies that are given in full details, namely continuous fermentation (fermentor, two separators) and anaerobic fermentation.
Nitriles in heterocyclic synthesis: Novel syntheses of benzo[b]pyrans, naphtho[1,2-b]pyrans, naphtho[2,1-b]pyrans, pyrano[3,2-h]quinolines and pyrano[3,2-c]quinolines
Authors: Elagamey Abdel Ghani A. , Sawllim Salah Z. , El-Taweel Fathy M. A. , Elnagdi Mohamed H.
Published: June 2010

Benzo[b]pyrans, naphtho[1,2-b]pyrans, naphtho[2,1-b]pyrans, pyrano[3,2-h]quinolines, and pyrano[3,2-c]quinolines were synthesized by the reaction of cinnamonitriles with phenols, naphthols, 8-hydroxyquinoline, and 1-methyl-4-hydroxy-2-quinoline.
Synthesis of 2-methyl-3-(5-phenyl or 1,5-diphenyl-2-pyrazolin-3-yl)-1,8-naphthyridines
Authors: Chary Maringanti Thirumala , Mogilaiah Kaleru , Sreenivasulu Bathula
Published: June 2010

3-Cinnamoyl-2-methyl-1,8-naphthyridines II have been synthesized utilizing Claisen-Schmidt condensation of 3-acetyl-2-methyl-1,8-naphthyridine I with aromatic aldehydes. The cinnamoyl naphthyridines react with hydrazine hydrate and phenylhydrazine to create the corresponding pyrazolinyl 1,8-naphthyridine derivatives (III and IV). The structures II-IV have been confirmed by their elemental analyses and spectral data. Some of the compounds have been screened for their fungicidal activity.
A contribution to peroxy acid oxidation of α,β-unsaturated ketones and linearly conjugated dienones: Reactions in the cholestane series
Authors: Černý Václav , Buděšínský Miloš , Ryba Miloš , Tureček František
Published: June 2010

Oxidation with 3-chloroperoxybenzoic acid of s-cis α,β-unsaturated ketones IX, XI and s-trans types X, XII was compared. The s-cis ketones show higher reactivity and furnish a higher yield of the corresponding α,β-epoxy ketones than the s-trans ketones. Products of the Baeyer-Villiger reaction are formed only in low yield. The dienone VI is oxidized predominantly to VII thus violating the rule that linear conjugated dienones are epoxidized at the double bond more distant from the carbonyl group; this result is in accord with the behaviour of s-cis α,β-unsaturated ketones. 1H NMR and 13C NMR data of the starting compounds and of the products are reported.
Theory of moments, Hückel rule and stability
Authors: Pick Štěpán
Published: June 2010

The connection between moments of the electronic Hamiltonian and topology of a quantum mechanical system is studied. Based on simplifications similar to those usually employed in simple chemical and physical theories, criteria resembling the Hückel rule for cyclic conjugated systems are suggested. Several examples of interest in chemistry and solid physics are discussed. No information on the wave function is necessary in the present approach.
The stereochemistry of the bis[N-(2-carbamoylethyl)iminodiacetate] cobalt(III) complex
Authors: Pavelčík František , Novomeský Pavol , Soldánová Jiřina , Polynova Tamara N.
Published: June 2010

A complex with the composition K[Co(ceida)2].2 H2O was isolated from solution after reaction of N-(2-carbamoylethyl)iminodiacetic acid, H2ceida, with CoCl2 in an aqueous solution of CH3COOK after oxidation with H2O2. Its structure was studied in D2O solution using 1H and 13C NMR spectroscopy and by X-ray diffraction of the crystalline substance. Both methods indicate that the complex anion is centrosymmetric in the octahedral complex. The ligand is coordinated by two oxygen atoms of the carboxylic groups and the nitrogen atom of the imino group. The amide group is not coordinated. Of the three possible isomers, only the trans-facial isomer was isolated. The uncoordinated ceida chain can assume two different conformations in the crystal. The K+ cations and molecules of water of crystallization are disordered.
Synthesis and biological activity of some basic-substituted 4,9-dihydro-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinolines
Authors: Rádl Stanislav , Zikán Viktor
Published: June 2010

Compounds Ia, Ib were obtained by an alkylation of 4,9-dihydro-6-hydroxy-1,3,9-trimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline (VIIb) with the respective dialkylaminoalkyl chloride. The same alkylation of 4,9-dihydro-6-hydroxy-2,3,9-trimethyl-4-oxo-2H-pyrazolo[3,4-b]quinoline (VIIIb) yielded compounds IIa and IIb. Similar alkylation of 4,9-dihydro-6-hydroxy-3,9-dimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline (IXa) and its 6-methoxy derivative (IXb) afforded IIIa-IIId. Compound IV was prepared from 4-chloro-3-methyl-1H-pyrazolo[3,4-b]quinoline (Xa) via its 1-(3-dimethylaminopropyl)derivative (Xb). Compounds VIa, VIb were prepared from 4,9-dihydro-6-hydroxy-3,9-dimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline (IXc) and the respective dialkylaminoalkyl chloride. The compounds prepared were tested for antiviral activity in vivo in mice against influenza virus A2-Hongkong and encephalomyocarditis virus.
A new variational expression for the scattering matrix
Authors: Miller William H.
Published: June 2010

The S-matrix version of the Kohn variational method is used to obtain a new, more concise expression for the scattering matrix, one that has both esthetic and practical advantages over earlier ones that have been used.
Electronic structures of electrically conductive fragment models in pyrolyzed polymers
Authors: Yamabe Tokio , Yamashita Shoji , Yamabe Hiroko , Fukui Kenichi , Tanaka Kazuyoshi
Published: June 2010

The electronic structures of polynuclear aromatic compounds are studied as the electrically conductive fragment models in pyrolyzed polymers. It is found that the manner of the distribution of the frontier electrons, which is important in determining the path of the conduction carriers, can be broadly classified into two groups depending on the shape of each fragment.
Theory of nonradiative decay from the lowest singlet state of benzene: Excess energy dependence
Authors: Takahashi Makoto , Ikoma Tadaaki , Fujimura Yuichi , Toyota Azumao , Nakajima Takeshi
Published: June 2010

A time-independent Green function formalism is developed to study the excess energy dependence on the nonradiative decay in the S1 state of benzene. Effects of purely electronic relaxation (internal conversion, IC) and intramolecular vibrational redistribution, IVR, are taken into account at the same time. Model calculations show that the drastic increase in the nonradiative decay rate at around 3 000 cm-1 excess energy is due to the same onset of both IC and IVR rates. Our theory can explain the difference in rate constant between IVR and IC observed by Moss and Parmenter.
Coupled-pair theories and Davidson-type corrections for quasidegenerate states: The H4 model revisited
Authors: Paldus Josef , Wormer Paul E. S. , Benard Marc
Published: June 2010

The performance of various variational and non-variational approaches to the many-electron correlation problem is examined for a simple four-electron model system consisting of two stretched hydrogen molecules in trapezoidal, rectangular and linear configurations, in which the degree of quasi-degeneracy can be continuously varied from a non-degenerate to an almost degenerate situation. In contrast to an earlier work (K. Jankowski and J. Paldus, Int. J. Quantum Chem. 18, 1243 (1980)) we employ a double-zeta plus polarization basis and examine both single reference and multireference configuration interaction and coupled-cluster-type approaches. The performance of various Davidson-type corrections is also investigated.
Effects of hydration and stacking interactions on the electronic structure of DNA models
Authors: Liegener Christopher-Maria , Chen Rung Shen , Otto Peter , Ladik Janos
Published: June 2010

The energy band structures of a cytosine, adenine, and guanine stack in the presence of water have been calculated by the ab initio crystal-orbital method. The surrounding water molecules have been simulated by arrays of point charges, using for their positions the results of previous Monte-Carlo calculations of the corresponding polynucleotides. Furthermore, the effects of internucleotide interactions have been studied on the basis of calculations on base dimer stacks in comparison to the corresponding dimers and monomers.
The computation of vibrational spectra of triplet species
Authors: Hess B. Andes , Hu Jiani , Schaad Lawrence J. , Čársky Petr
Published: June 2010

Computed IR spectra of triplet vinylidenecarbene, CH2, CCO, and NCN are compared with experiment. Some triplets have much lower intensity spectra than the corresponding singlets, and for these care needs to be taken to get good computed spectra. Others are of higher intensity, and for these agreement is as good as in the usual singlet cases.
Applications of the MBPT in the localized representation the behaviour of the localization terms
Authors: Kapuy Ede , Csépes Zoltán , Bartha Ferencz , Bogár Ferencz , Kozmutza Cornelia
Published: June 2010

The behaviour of the localization corrections of the MBPT is investigated. It is shown that calculating the third and fourth order localization corrections we obtain sufficiently accurate results to the second order correlation energy both for cyclic polyenes and for saturated hydrocarbons. The evaluation of the localization diagrams does not require significant extra computer time. The extra computer time can be recovered if small non-local effects will be neglected.
A theoretical study of the disulfide/dithione valence isomerism
Authors: Fabian Jürgen , Birner Peter
Published: June 2010

According to MNDO calculations on 1,2-dithiete (IIIa), 1,2-dithiin (IVa) and 3,4-dimethylene-1,2-dithiane (Va) the closed-ring compounds are thermodynamically more stable than the open-chain compounds whereas the reverse holds for 4-methylene-1,2-dithiole (VIa). Substitution of the exocyclic CH2 group of VIa by O, S, NH, and OH+ stabilizes its cyclic mesoionic structure. The low triplet state energy of VIa and of some derivatives relative to the lowest singlet state energy signalizes the biradicaloid nature of these electronic structures. Replacement of hydrogen of the methine groups adjacent to sulfur of III, IV, and VII by CH3, CF3, C6H5, CHO or CN results more or less in stabilization of the cyclic tautomer whereas donor substituents such as NH2, OCH3 or SCH3 act less uniformly but mostly in a destabilizing way. Contrary to former assumptions, there is no indication for a species intermediate between the disulfide and dithione structure that defines the molecular ground state. A relatively low ground state barrier separates the two isomeric structures although thermal isomerization of IIIa belongs to Woodward-Hoffmann forbidden concerted reactions (calculated activation energy for the ring opening of IIIa about 36 kcal/mol). The thermal and photochemical isomerization is discussed in terms of the change of the energy along the reaction path of the closed shell ground state (S0) and lowest energy excited states (S1, T1). The energies are obtained by MNDO, MNDO/2 x 2 CI, MNDO/HE, and MNDO/HE/3 x 3 CI calculations.