bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a Virus-Encoded Enzymatic Marker Reveals that a Stable Fraction of Memory B Cells Expresses Latency-Associated Nuclear Antigen throughout Chronic Gammaherpesvirus Infection
Authors: Nealy Michael S. , Coleman Carrie B. , Li Haiyan , Tibbetts Scott A.
Published: May 2010

An integral feature of gammaherpesvirus infections is the ability to establish lifelong latency in B cells. During latency, the viral genome is maintained as an extrachomosomal episome, with stable maintenance in dividing cells mediated by the viral proteins Epstein-Barr nuclear antigen 1 (EBNA-1) for Epstein-Barr virus and latency-associated nuclear antigen (LANA) for Kaposi's sarcoma-associated herpesvirus. It is believed that the expression of episome maintenance proteins is turned off in the predominant long-term latency reservoir of resting memory B cells, suggesting that chronic gammaherpesvirus infection is primarily dormant. However, the kinetics of LANA/EBNA-1 expression in individual B-cell subsets throughout a course of infection has not been examined. The infection of mice with murine gammaherpesvirus 68 (MHV68, γHV68) provides a model to determine the specific cellular and molecular events that occurin vivoduring lifelong gammaherpesvirus latency. In work described here, we make use of a heterologously expressed enzymatic marker to define the types of B cells that express the LANA homolog (mLANA) during chronic MHV68 infection. Our data demonstrate that mLANA is expressed in a stable fraction of B cells throughout chronic infection, with a prominent peak at 28 days. The expression of mLANA was detected in naïve follicular B cells, germinal-center B cells, and memory B cells throughout infection, with germinal-center and memory B cells accounting for more than 80% of the mLANA-expressing cells during the maintenance phase of latency. These findings suggest that the maintenance phase of latency is an active process that involves the ongoing proliferation or reseeding of latently infected memory B cells.
Downregulation of Robust Acute Type I Interferon Responses Distinguishes Nonpathogenic Simian Immunodeficiency Virus (SIV) Infection of Natural Hosts from Pathogenic SIV Infection of Rhesus Macaques
Authors: Harris Levelle D. , Tabb Brian , Sodora Donald L. , Paiardini Mirko , Klatt Nichole R. , Douek Daniel C. , Silvestri Guido , Müller-Trutwin Michaela , Vasile-Pandrea Ivona , Apetrei Cristian , Hirsch Vanessa , Lifson Jeffrey , Brenchley Jason M. , Estes Jacob D.
Published: May 2010

The mechanisms underlying the AIDS resistance of natural hosts for simian immunodeficiency virus (SIV) remain unknown. Recently, it was proposed that natural SIV hosts avoid disease because their plasmacytoid dendritic cells (pDCs) are intrinsically unable to produce alpha interferon (IFN-α) in response to SIV RNA stimulation. However, here we show that (i) acute SIV infections of natural hosts are associated with a rapid and robust type I IFN response
in vivo
, (ii) pDCs are the principal
in vivo
producers of IFN-α/β at peak acute infection in lymphatic tissues, and (iii) natural SIV hosts downregulate these responses in early chronic infection. In contrast, persistently high type I IFN responses are observed during pathogenic SIV infection of rhesus macaques.
An MO cavity model of enzyme catalysis: Semiempirical calculations of reaction courses of acetaldehyde reduction and ethanol oxidation by an NAD model
Authors: Krechl Jiří , Kuthan Josef
Published: May 2010

General suggestions concerning the possibility to interpret the elementary reaction steps in biocatalytic processes, as if proceeding in pseudovacuum of a protein cavity, have been presented. The approach is illustrated by MNDO investigation of the interaction of 1-methyl-1,4-dihydronicotinamide (II) with acetaldehyde or its protonated species Ia and Ib, respectively. The preactivation step Ia → Ib has been shown to accelerate the interconversion of substrate Ib into ethanol and 3-aminocarbonylpyridinium (V) more effectively than a subsequent protonation of the possible 1,6-dihydropyridine intermediate III arising from Ia and II. The opposite reaction path of V with ethanol and ethoxide is also being examined.
Vibrational spectra and thermodynamic properties of thiazole, 2-aminothiazole, 2-amino-[2H]-thiazole and 2-amino-[2H2]-thiazole
Authors: Arenas Juan F. , Perez-Peña Jesús , Gonzalez-Davila Melchor
Published: May 2010

Infrared and Raman spectra of thiazole have been reinvestigated with new assignments of overtone and combination bands being proposed. Infrared spectra in the solid phase and in different solutions for 2-aminothiazole and 2-amino-[2H2]-thiazole, as well as Raman spectrum of microcrystalline powder for 2-aminothiazole were also studied and a general assignment for all the observed bands have been proposed. The present assignment satisfies the isotopic product rule for i.r. fundamentals. On this basis thermodynamic functions have been computed.
Electroanalytical chemistry of vanadium complexes: Electrochemical oxidation of [V(IV)O(nta)(H2O)]-
Authors: Meier Roland , Werner Gerhard , Otto Matthias
Published: May 2010

Electrochemical oxidation of [V(IV)O(nta)(H2O)]- (H3nta nitrilotriacetic acid) was studied in aqueous solution by means of cyclic voltammetry, differential pulse polarography, and current sampled DC polarography on mercury as electrode material. In the pH-range under study (5.5-9.0) the corresponding V(V) complex is produced by one-electron oxidation of the parent V(IV) species. The oxidation product is stable within the time scale of cyclic voltammetry. The evaluation of the pH-dependence of the half-wave potentials leads to a pKa value for [V(IV)O(nta)(H2O)]- which is in a good agreement with previous determinations. The measured value for E1/2 is very close to the formal potential E0 calculated via the Nernst equation on the basis of known literature values for log Kox and log Kred, the complex stability constants for the oxidized and reduced form, respectively.
Effect of tensides on the optical properties of sulfophthalein dyes
Authors: Kubáň Vlastimil , Jančářová Irena , Hedbávný Josef , Vrchlabský Milan
Published: May 2010

The optical properties of bromocresol red, bromophenol blue and bromocresol green were studied spectrophotometrically in aqueous systems in the absence and in the presence of submicellar and micellar concentrations of cationic (Septonex, hexadecylpyridinium and hexadecyltrimethylammonium bromides), nonionic (Brij 35, Triton X-100) and anionic (sodium dodecylsulfate) tensides. The positions of the absorption maxima and molar absorptivities of the LH- and L2- acid-base species of the dyes depend on the kind and concentration of tenside, alkylpyridinium chain length, and kind and concentration of inert electrolyte.
Cationic modifications of polyalkenes. Polyethers as modificators of polypropylene and polyethylene
Authors: Kučera Miloslav , Kimmer Dušan , Majerová Karla
Published: May 2010

Carbocations generated on polypropylene (or polyethylene) chains are able to bond the polar polymer, e.g. poly(oxytetramethylene), poly(oxyethylene), poly(oxyphenylene) or polysiloxane onto the hydrocarbon chains. The copolymers polypropylene-block-poly(oxyethylene) and polypropylene-graft-poly(oxyethylene) have outstanding compatibilizating ability in a polypropylene-CaCO3 composite. The above named copolymer (2 mass %), mixed with polypropylene and surface non-treated CaCO3, produce a composite with 50% higher impact toughness, lower melt viscosity (better flow in) and better dispersion of the filler in the matrix in comparison with the standard composite consisting of the same polypropylene matrix and treated CaCO3 (calcium stearate and stearic treatment).
Nucleophilicity and its parametrization
Authors: Pytela Oldřich , Zima Vítězslav
Published: May 2010

The method of conjugate deviations based on the regression analysis has been suggested for construction of a new nucleophilicity scale. This method has been applied to a set of 28 nucleophiles participating in 47 physical and chemical processes described in literature. The two-parameter nucleophilicity scale obtained represents-in the parameter denoted as ND-the general tendency to form a bond to an electrophile predominantly on the basis of the orbital interaction and-in the parameter denoted as PD-the ability to interact with a centre similar to the proton (basicity). The linear correlation equation involving the ND, PD parameters and the charge appears to be distinctly better than the most significant relations used. The correlation dependences have the physico-chemical meaning. From the position of individual nucleophiles in the space of the ND and PD parameters, some general conclusions have been derived about the factors governing the reactivity of nucleophiles.
The crystal and molecular structure of 4-phosphonomethyl-2-oxo-1-piperazinylacetic acid
Authors: Pavelčík František , Havetta Karol , Páterek Jaroslav
Published: May 2010

The structure of the title compound was determined by the method of X-ray diffraction of single crystals. The substance crystallizes in the P21/c monoclinic space group. The structure was refined by the least squares method to R = 0.044 on the basis of 2 076 observed reflections. It was found that this compound is not a dicarboxylic acid but rather an intramolecularly cyclized lactam. The hydrogen phosphonato functional group participates in the betain form, while the carboxyl group is not ionized. The conformation of the six-membered oxopiperazine ring is similar to that of cyclohexane in which the peptidic group plays a similar role to the double bond.
Arctolide-revision of its stereostructure and determination of absolute configuration. Detailed 1H and 13C NMR analysis
Authors: Buděšínský Miloš , Šaman David , Pelnař Jan , Vašíčková Soňa , Drożdż Bohdan , Grabarczyk Halina , Le Viet Ngoc Phuong  , Holub Miroslav
Published: May 2010

The stereostructure of arctolide-a sesquiterpenic lactone isolated from Arctotis grandis-has been revised on the basis of detailed 1H and 13C NMR analysis and detection of intramolecular hydrogen bonding by IR spectroscopy. Its absolute configuration, represented by formula Ia, was determined from the CD spectra. The scope and limitation of modern 1D- and 2D-NMR techniques in obtaining parameters utilizable for structure determination of natural compounds have been verified.
Ferricyanide oxidation of 1-substituted pentaphenylpyridinium salts. A novel route to 1-substituted 2,3,4,5-tetraphenylpyrroles
Authors: Böhm Stanislav , Slavík Hanuš , Kuthan Josef
Published: May 2010

Oxidation of 1-substituted 2,3,4,5,6-pentaphenylpyridinium salts Ia-Ij by potassium ferricyanide in an alkaline medium yields the corresponding 1-substituted 2,3,4,5-tetraphenylpyrroles in 68 to 76% yields. The selectivity of the reaction is discussed.
Synthesis of 2-aryl-3-furancarboxylic acids by arylation of 3-furancarboxylic acid
Authors: Jurášek Adolf , Berecinová Daniela , Čakrt Miroslav , Dandárová Miloslava , Friedl Zdeněk , Štetinová Jarmila , Kováč Jaroslav
Published: May 2010

Arylation of 3-furancarboxylic acid (3-FCA) with 4-X-phenyldiazonium chlorides catalyzed by copper dichloride afforded the non-planar 2-(4-X-phenyl)-3-furancarboxylic acids (X = H, CH3, OCH3, Cl, Br, NO2). Arylation of 3-FCA with 2-X-phenyldiazonium chlorides (X = COOCH3, NO2) yielded 2-(2-methoxycarbonylphenyl)-3-furancarboxylic acid and a 3:1 mixture of 2-(2-nitrophenyl)- and 5-(2-nitrophenyl)-3-furancarboxylic acids, respectively. The pKa values of 2-(4-X-phenyl)-3-furancarboxylic acids linearly well correlate with the Hammett's σp0 constants of substituents. The IR, UV, mass, and 13C NMR spectra of the above-mentioned compounds are commented and the mechanism of arylation is discussed.
Synthesis of 2'-end lipophilized derivatives of 2'-5'-triadenylates
Authors: Pressová Martina , Smrt Jiří
Published: May 2010

Synthesis of protected derivatives of 2-5 A3 core starting from 2',3'-O-ethoxymethylene-N6-benzoyladenosine (I) by traizolidate and/or modified triester method are described. Preparation of adenylyl-(2'-5')-adenylyl-(2'-5')-2'-3'-O-(1-methoxyhexadecylidene)adenosine (X), adenylyl-(2'-5')-adenylyl-(2'-5')-2'-3'-O-palmitoyladenosine (XIII) and 5'-phosphoryladenyl-(2'-5')-adenylyl-(2'-5')-2'-3'-O-(1-methoxyhexadecylidene)adenosine (XVI) are described.
Mimicking bioactive peptides. [8-Nβ-Guanidoacetyl-α,β-diaminopropionic acid]vasopressin
Authors: Zaoral Milan , Krchňák Viktor
Published: May 2010

The title compound was prepared by solid phase methodology. It has 34.2 I.U./mg of pressor activity, 5.8 I.U./mg of uterotonic activity and by 3-4 orders of magnitude lower antidiuretic activity than DDAVP.
Estimation of the standard G-functions of substances in the ideal-gas state by the Benson method
Authors: Bureš Michal
Published: May 2010

The Benson method used to estimate thermodynamic properties of substances in the ideal-gas state is modified for calculating the standard G-functions (G0-H0298)/T. The estimation method is verified using a set of 342 organic compounds.
Liquid-liquid equilibrium in the water-ethanol-toluene system. Correlation of equilibrium data
Authors: Novák Josef P. , Matouš Jaroslav , Říčná Květuše , Kubíček Vladimír
Published: May 2010

Liquid-liquid equilibrium data in the water-ethanol-toluene system were correlated by the superposition of the Wilson and Redlich-Kister equations with a ternary term. The correlation of both homogeneous binary systems was taken from the literature. The ternary liquid-liquid equilibrium data were at all temperatures satisfactorily described on using only three ternary parameters determined from the equilibrium data at 50 °C. The parameters obtained by the correlation yield also a good estimate of boiling point and composition of homogeneous azeotropic mixture.
The fluorimetric determination of cerium and terbium
Authors: Holzbecher Záviš
Published: May 2010

It has been found that phosphoric acid decreases the first excitation maximum of Ce(III) at 256 nm, increases the second excitation maximum at 297 nm and shifts the fluorescence maximum from 350 to 346 nm. Under optimum conditions, with λexc = 297 nm and λem = 346 nm, Ce(III) can be determined fluorimetrically with a detection limit of 1.2 ng ml-1 in 12M-H3PO4 medium. No interference was observed from a 20-200 fold excess of HCl, H2SO4, Na, K, NH4+, Al and the rare earth elements. HNO3 interferes and Ce(IV) and Fe(III) interfere strongly. It follows from the stereofluorograms of Ce and Tb that the spectra of the two elements are practically independent. The detection limit for Tb(III) in 0.02-2.5M-H2SO4 medium for λexc = 222 nm and λem = 494 nm is 33 ng ml-1. No interference was observed from a 5-20 fold excess of Al3+ and the other rare earth elements. The determination is slightly less sensitive in H3PO4 or HCl medium. The relative standard deviation of the measurement for 10 ng ml-1 Ce(III) or 50 ng ml-1 Tb(III) is about 3%.
Spectrophotometric investigation of interactions of sulfophthalein dyes with surfactants
Authors: Kubáň Vlastimil , Hedbávný Josef , Jančářová Irena , Vrchlabský Milan
Published: May 2010

The effect of cationic (hexadecylpyridinium bromide, hexadecyltrimethylammonium bromide, Septonex), anionic (sodium dodecyl sulfate) and nonionic (Brij 35, Triton X-100) surfactants on the deprotonation of the phenolic oxygen in bromophenol red, bromophenol blue and bromocresol green is studied. The conditional dissociation constants Kai* depend on the surfactant concentration and, in the alkylpyridinium surfactant series, on the alkyl chain length at a constant concentration of inert electrolyte, and on the concentration of the inert electrolyte (Cl-, Br-, NO3-, SO42-, H2PO4-, CH3COO-, HCOO-, ClO4-) or of the sulfophthalein dye at a constant concentration of a cationic surfactant. In acid and alkaline solutions, cationic surfactants (tensides, T) and the dyes (H2L) form ionic associates with the stoichiometric composition {T+, LH-} and {T2+, L2-}, respectively, exhibiting absorption maxima at 400-430 nm (ε = 1.3-2.0 m2 mmol-1) and at 570-630 nm (ε = 3.5-4.5 m2 mmol-1), respectively, formation of these associates was confirmed for chloroform extracts by the continuous variations and molar ratios methods.
Distribution of the circulation times in a batch mixed by two impellers on a common shaft
Authors: Kudrna Vladimír , Koza Václav , Hájek Jiří
Published: May 2010

The paper has been devoted to the study of the circulation times in a batch mixed by several impellers on a common shaft. A simple method has been used to carry out the measurements based on visual observation of the motion of a tracer particle in the mixed batch. Individual passages of the tracer particle through the check surface have been signalized to a computer performing the primary processing of data, calculation of the basic statistical characteristics (expected value and variance) and the frequency function of the circulation times of the tracer particle. A model developed earlier for a vessel mixed by a single impeller has been used to interpret the data. This theoretical model has been compared with experimental results.
The structure of the compounds Na24As2Z22O83 and its relationship to the structure of Na2Z2O7 (Z = Mo, W)
Authors: Drátovský Milan , Novák Ctirad , Petříček Václav , Štengl Václav
Published: May 2010

X-ray study of the structure of the compounds Na24As2Z22O83 (Z = Mo, W) indicated that these compounds and the compounds Na2Z2O7 are all isomorphic. They crystallize in the orthorhombic system with a space group of Cmca. The compound Na24As2Z22O83 is formed by replacing part of the Mo atoms by As in the centres of the oxygen tetrahedra in the structure of Na2Mo2O7. This substitution As ##c Mo results in loss of one oxygen atom for every two arsenic atoms in the Na2Mo2O7 structure so that two AsO4 tetrahedra are joined through an oxygen apex to form a As-O-As bond. The exact atomic ratio As:Mo = 1:11 in the studied compounds was also sufficiently confirmed by study of the phase diagrams NaAsO3-Na2Z2O7.
Alkylated benzimidazole and benzotriazole derivatives of 3-amino-2-propenoic acid
Authors: Milata Viktor , Ilavský Dušan , Goljer Igor
Published: May 2010

The alkylation of unsubstituted 3-(5-benzimidazolyl- and 5-benzotriazolyl)amino derivatives of 2-propenoic acid (I) results in the replacement of hydrogen atom at the nitrogen of YZC=CH-NH- substituent (II-IV). The model compounds with a methyl group in the azole nucleus (V-VII) have been prepared by an independent synthesis. The structure of all products has been confirmed and confronted with their IR, UV, 1H and 13C NMR spectra.
Biosynthesis of water-soluble metabolites of UDP-D-galactose containing D-galactose by an enzymic preparation isolated from tissue culture of poplar (Populus alba L., var. pyramidalis)
Authors: Bilisics Ladislav , Kubačková Marta
Published: May 2010

Biosynthesis of constituents of pectic polysaccharides containing D-galactose was investigated in poplar tissue culture in vitro. The particulate enzymic preparation isolated from the tissue culture of poplar catalyzed the transfer of D-[U-14C]-galactose unit form UDP-D-[U-14C]-galactose into various endogenous acceptors to form galactolipides, water-soluble metabolites and membrane-bound galactoproteins. The initial rate of formation of water-soluble metabolites depends on the substrate concentration and is time and amount of the enzymic protein directly proportional. Optimal formation of these metabolites proceeds at pH 7·6 and 40 °C in the presence of 0.1 mM ATP and 10 mM MgCl2. Long-term incubations afforded a mixture of three radioactive water-soluble metabolites: a neutral oligomer of Mr ~ 620 consisting at least of two β-D-[U-14C]-galactose units linked by (1 → 6) bonds and two oligomers of Mr ~ 1 400 and ≥ 2 950, respectively, containing (1 → 6) and (1 → 4)-linked D-[U-14C]-galactose units. Their relative proportion in the mixture changed in relation to incubation time and the substrate concentration. Structural features of these metabolites resembled those of D-galactans or L-rhamnogalacturonan side chains previously found in primary cell walls of some higher plants.
On the electroreduction mechanism of halobenzenes: Detection of intermediates in reduction of monohalobenzenes
Authors: Casado Juan , Gallardo Iluminada
Published: May 2010

Experimental results from electrochemical behaviour of halobenzenes in DMF at a mercury cathode are used to discuss alternative mechanisms of reduction. Intermediates of these mechanisms, such as phenyl anion, phenylmercury radical and phenylmercury cation have been detected at the electrode by using cyclic voltammetry and a rotating ring-disk electrode.
On-line HPLC analysis of PTH-amino acids derived from Edman degradation of proteins and peptides: Optical sensor controlled sample injection
Authors: Pavlík Manfred , Jehnička Jiří , Kostka Vladimír
Published: May 2010

A new principle in the system of identification and quantitation of amino acid phenylthiohydantoins derived from automated Edman degradation of proteins and peptides is described. The beginning of the on-line HPLC analysis of PTH's, the actuation of the valve and the sample injection are controlled by an optoelectronic sensor placed at the sample loop outlet. At the moment the loop has been loaded the sensor actuates the injection valve thus starting the chromatography run. This arrangement eliminates the possibility of incomplete (irreproducible) loading of the loop or of void injection. The chromatographic separation of the PTH's is carried out by isocratic elution.
Determination of the dead volume of columns in reversed phase liquid chromatography
Authors: Vít Ivan , Fähnrich Jan , Popl Milan
Published: May 2010

The method for the determination of the dead volume of RPLC columns by measuring the retention volume of phloroglucinol is compared with the method based on the retention data of homologous series of organic solutes and that based on the use of isotopically labelled components of the mobile phase. The use of homologous series is tedious and moreover, satisfactory results are not always obtained. The phloroglucinol method is found well suited to replacing the method based on the use of isotopically labelled components of the mobile phase; poorer results with phloroglucinol are only obtained when the mobile phase contains more than 40% (v/v) water, for the Separon SE polymeric sorbent, and in alkaline medium.
On the convective diffusion under partial slip at wall
Authors: Wein Ondřej , Kučera Petr
Published: May 2010

Extended Leveque problem is studied for linear velocity profiles, vx(z) = u + qz. The existing analytic solution is reconsidered and shown to be inapplicable for the accurate calculation of mean mass-transfer coefficients. A numerical solution is reported and its accuracy is checked in detail. Simple but fairly accurate empirical formulas are suggested for the calculating of local and mean mass-transfer coefficients.
Brassinolide analogues without side chain
Authors: Kohout Ladislav , Strnad Miroslav
Published: May 2010

New brassinolide analogues, characterized by a modified androstane structure without substituent in position 17, were prepared. In the second internode assay, 2α,3α-dihydroxy-B-homo-6-oxa-5α-androstan-7-one (XVII) had the highest brassinoid activity.
Use of 5-deoxy-ribo-hexofuranose derivatives for the preparation of 5'-nucleotide phosphonates and homoribonucleosides
Authors: Mikhailov Sergei N. , Padyukova Nelly Sh. , Karpeiskii Marat Ya. , Kolobushkina Lidiya I. , Beigelman Leon N.
Published: May 2010

A convenient and general method is proposed for the synthesis of 5'-nucleotide phosphonate analogs starting from 5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose which can easily be produced in preparative quantities from D-glucose. Phosphonate IIIe was synthesized by means of the Arbuzov reaction between 3-O-benzoyl-6-bromo-5,6-dideoxy-1,2-O-isopropylidene-α-D-ribo-hexofuranose and triethyl phosphite. The consecutive acetolysis, condensation with uracil and N6-benzoyladenine bis-trimethylsilyl derivatives and deblocking possessed phosphonate analogs of 5'-nucleotides in good yields. The intermediate 5-deoxy-1,2-O-isopropylidene-α-D-ribo-hexofuranose derivatives were used for the preparation of homonucleosides.
Studies on condensed pyrazoles: Synthesis of new methyl and amino pyrazolo[1,5-a]pyrimidines and of pyrazolo[5,1-c][1,2,4]triazines
Authors: Elnagdi Mohamed Hilmy , Taha Nadia Hassen , Abd El All Fatma Abdel Maksoud , Abdel-Motaleb Ramadan Maawad , Mahmoud Fivian Farouk
Published: May 2010

A variety of 3-arylazo 5-amino and 7-aminopyrazolo[1,5-a]pyrimidines were obtained via reacting Ia-Id with cinnamonitriles. The structure of products was confirmed via 1H NMR. Both 5-amino- and 7-amino-3-arylazo pyrazolo[1,5-a]pyrimidines reacted, with protons in acetic acid-sulphuric acid mixture to yield the corresponding 3-unsubstituted acetylaminopyrazolo[1,5-a]pyrimidines. Diazotized Ia and Ib coupled with a variety of active methylene reagents to yield pyrazolo[5,1-c][1,2,4]triazines.
Facile synthesis and biological activity of sulfonate ester-containing imidazolylpyridine, imidazo(4,5-b)pyridine and imidazo(5',1':2,3)imidazo(4,5-b)pyridine derivatives
Authors: Girges Margret Mansour , El-Zahab Mohamed Mahmoud Abou , Hanna Mokhtar Ayad
Published: May 2010

Different ring systems containing imidazole and/or pyridine moieties and accomodating sulfonate ester moiety in their structure were prepared via ring opening of 2-oxazolin-5-one derivatives under various reaction conditions. The assigned structures for the prepared compounds were established through elemental analysis, spectral data and if possible by alternative synthetic routes. The antimicrobial activity of the synthesized compounds was also investigated.
Alkaloids from Papaver rhoeas var. chelidonioides O. KUNTZE, P. confine JORD., and P. dubium L.
Authors: Slavík Jiří , Slavíková Leonora , Bochořáková Jitka
Published: May 2010

Papaver rhoeas var. chelidonioides O. KUNTZE (diploid, 2n = 14) contains rhoeadine (0.027%) and coptisine (0.004%) as the dominant alkaloids, the latter being the yellow principle of the latex. As minor constituents were isolated protopine, papaverrubine A, rhoeagenine, (-)-stylopine, an unidentified alkaloid PCH 1 (m.p. 205 °C), 2-methyl-1,2,3,4-tetrahydro-β-carboline and (-)-trans-N-methylstylopinium hydroxide. Chromatographic analysis detected isorhoeadine, allocryptopine, cryptopine, papaverrubine C, D and E, scoulerine, isoboldine, berberine, corysamine, magnoflorine and corytuberine. P. confine JORD. (tetraploid, 2n = 28) was found to display a very low alkaloid content (0.003%) and afforded corytuberine and berberine as principal alkaloids, along with minor amounts of protopine rhoeadine, scoulerine and cryptopine. Chromatography identified isocorydine, corydine, allocryptopine, aporheine, stylopine, sinactine, thebaine, mecambrine, papaverrubines A, E, C and D, coptisine and corysamine. The tertiary alkaloid fraction from ripe capsules of P. dubium L. (hexaploid, 2n = 42; 0.24% of alkaloids) of domestic origin afforded (+)-roemerine (aporheine) as the main constituent (87% of total bases); mecambrine, protopine, rhoeadine and papaverrubines D and C (traces of A and E) were detected. From strongly polar bases N-methylaporheinium hydroxide (as iodide) was isolated and corytuberine detected.
Structure of hard body fluids. A critical compilation of selected computer simulation data
Authors: Nezbeda Ivo , Labík Stanislav , Malijevský Anatol
Published: May 2010

Computer simulation data on structural properties [spherical harmonic expansion coefficients of the full pair correlation function g(1,2), radial slices through g(1,2), the background correlation function y(1,2), and the triplet correlation function (for hard spheres), various angle averages of g(1,2) and, for hard spheres, also the direct correlation and bridge functions] of pure hard body fluids known to date have been critically assessed and tables of selected data are presented. In addition to the tables, parametrizations of the data are also given whenever they have been available. The molecular models considered include both convex body models (spheres and prolate spherocylinders) and interaction -site models (homo- and heteronuclear diatomics, linear and nonlinear symmetric triatomics, and tetrahedral penta-atomics).
The potential energy surface for the C3 molecule determined from experimental data. Evidence for a bent equilibrium structure
Authors: Jensen Per
Published: May 2010

The Morse oscillator-rigid bender internal dynamics (MORBID) Hamiltonian for triatomic molecules (Jensen P.: J. Mol. Spectrosc. 128, 478 (1988)) has been used to refine the potential energy function for the X1*Sg+ electronic ground state of C3 by fitting to experimental data. In accordance with previous ab initio calculations by Kraemer W. P., Bunker P. R., and Yoshimine M. (J. Mol. Spectrosc. 107, 191 (1984)), C3 is found to have a bent equilibrium structure. The MORBID calculation reported here yields a barrier to linearity of 16.5(3.6) cm-1 and an equilibrium bond angle of 162.5° (1.0°) with one standard error given in parentheses.
Pulse polarographic study of the behaviour of some o,o'-dihydroxyazo-compounds
Authors: Casassas Enric , Esteban Miquel , Alier Santiago
Published: May 2010

The reduction of several o,o'-dihydroxyazo-compounds is studied by means of pulse polarographic techniques (DPP, NPP and RPP). The compounds studied are the following: 2-(2'-hydroxyphenylazo)-phenol (o,o'-dihydroxyazobenzene), 1-(2'-hydroxy-1'-naphthylazo)-2-naphthol-4-sulphonic acid (calcon or Eriochrome Blue Black R), 1-(2'-hydroxy-4'-sulpho-1'-naphthylazo)-2-hydroxy-3-naphthoic acid (calcon carboxylic acid), and 1-(1'-hydroxy-2'-naphthylazo)-6-nitro-2-naphthol-4-sulphonic acid (Eriochrome Black T). Correlations between Ip and Epand experimental variables (pH, T, conc.) and instrumental parameters (dropping time, t, and pulse magnitude, ΔE) are established. Reaction mechanisms formerly proposed are discussed on the basis of the new obtained results, and the ranges are defined where adsorption and/or acid-base catalysis are operative.
Degrees of dissociation and hydration numbers of six tetra alkyl ammonium halides and nineteen 2:1 strong electrolytes in aqueous solutions at 25 °C
Authors: Heyrovská Rajalakshmi
Published: May 2010

The actual ionic concentrations and hydration numbers of some tetra alkyl ammonium halides and 2:1 strong electrolytes in aqueous solutions at 25 °C have been evaluated for the first time from the existing osmotic coefficient data.
Dipole moments and conformation of some olefinic and ortho-substituted aromatic methoxy derivatives
Authors: Hnyk Drahomír , Fajgar Radek , Všetečka Václav , Exner Otto
Published: May 2010

Dipole moments of stereoisomeric 3-methoxypropenenitriles (I,II), substituted 2-methoxybenzonitriles (III-VI) and substituted 2-chlorophenyl methyl ethers (VII-X) were measured in benzene solution and analyzed in terms of group moments. Aromatic derivatives III-X exist in the prevailing conformation ap (CH3 trans to Cl or to CN). Any minor conformation was not detected; small differences between experimental and calculated dipole moments were explained by induction of the two adjacent dipoles. Conformations of 3-methoxypropenenitriles were estimated to prevailing sp for I and practically only ap for II. Irrespective of the conformations, dipole moments revealed a strong conjugation of the CN and OCH3 groups in I and II. The intensity of this conjugation in various derivatives thus decreases steeply in the series: olefinic E > olefinic Z > aromatic para > aromatic ortho.
Electrochemical oxidation of pyrrole derivatives in alcoholic medium
Authors: Tedjar Farouk , Ymmel Salah , Janda Miroslav , Duchek Petr , Holý Petr , Stibor Ivan
Published: May 2010

Electrochemical oxidation of pyrrole (I), 1-methylpyrrole (II), 1,2,5-trimethylpyrrole (III), methyl 1-methyl-2-pyrrolecarboxylate (IV) and diethyl 3,5-dimethyl-2,4-pyrroledicarboxylate (V) has been studied. An advantageous method of preparation of polypyrroles (PP) and conductive PVC-PP composites has been elaborated, permitting a 20 fold starting concentration of the monomer. Electrooxidation of II in methanol leads either to 5,5-dimethoxy-1-methyl-3-pyrrolin-2-one (VII) or 1-methyl-2,2,5,5-tetramethoxy-3-pyrroline (VI), their ratio depending on water content in the alcohol used. Oxidation of IV affords the analogous 5-carbomethoxy-5-methoxy-1-methyl-3-pyrrolin-2-one (X), oxidation of III and V leads to products of substitution at the methyl groups.
Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride
Authors: Magura Miroslav , Vojtko Ján , Ilavský Ján
Published: May 2010

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.
Spontaneous transannular reaction in Δ9-unsaturated A-homo-B,19-dinorsteroids
Authors: Kasal Alexander , Zajíček Jaroslav
Published: May 2010

The epoxidation of 3β-hydroxy derivatives of Δ9-unsaturated A-homo-B,19-dinorsteroids (type I-IV) proceeds with spontaneous participation of the 3β-hydroxyl under formation of transannular 9α-hydroxy-3β,10β-oxides IX, X, XV and XVII. Epoxidation of the corresponding esters V-VIII affords predominantly 9α,10α-epoxides XIV, XVI, XVIII and XIX which, after hydrolysis of the ester groups are also converted into the transannular 3β,10β-oxides of the type IX.
Potential neurotropic and antiinflammatory agents: 2-Chloro-10,11-dihydrodibenzo[b,f]thiepin-10-yl sulfides
Authors: Valenta Vladimír , Vlková Marie , Protiva Miroslav
Published: May 2010

2-Chloro-10,11-dihydrodibenzo[b,f]thiepin-10-thiol (VII) was synthesized from 2,10-dichloro-10,11-dihydrodibenzo[b,f]thiepin (IV) and was alkylated with a series of aminoalkyl chlorides which led to amino sulfides IX, XII, XIII, and XVI-XX. The primary amine IXa was transformed by treatment with ethyl chloroformate to the carbamate Xa which was reduced to the methylamino compound XIa. The carbamate XX was similarly reduced to compound XXI. Alkylation of VII with 2-bromoethanol gave the alcohol XIVa which was transformed to the crude tosylate XVa. Its reactions with the corresponding piperazines gave compounds XXII to XXIV. The alcohol XXII was esterified to the decanoate XXV. Reactions of the sodium salt of VII with ethyl chloroacetate, ethyl 2-chloropropionate and ethyl 4-chlorobutyrate gave the corresponding esters which were saponified to acids XXVIb-XXVIIIb. Their amides XXVId to XXVIIId and XXVIe were prepared either via the acid chlorides or via the esters. Out of the compounds prepared only XIa showed a clear profile of a potential antidepressant. The other compounds showed indications of thymoleptic, antiinflammatory and antimicrobial activities.
The power input of screw rotors and agitators: The power input of screw agitator with a draught tube
Authors: Rieger František
Published: May 2010

The power input has been measured of 52 various geometries of the screw agitator with a draught tube. The obtained results have been correlated by a relation derived for the power input of screw rotors in the previous paper.
Preparation and electron transfer-induced cis-trans isomerization reactions of 1-(5-nitro-2-furyl)-, 1-(5-nitro-2-thienyl)-, and 1-(4-nitrophenyl)-2-R ethylenes
Authors: Prousek Josef , Hayden Viktor
Published: May 2010

Mixtures of E- and Z-isomers of 1,2-bis(5-nitro-2-furyl)ethylene (I), 1-(5-nitro-2-furyl)-2-(4-nitrophenyl)ethylene (II), 1,2-bis(4-nitrophenyl)ethylene (III), 1-(5-methoxycarbonyl-2-furyl)-2-(4-nitrophenyl)ethylene (IV), 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-furyl)ethylene (V) and 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-thienyl)ethylene (VI) were prepared by the Wittig reaction. These derivatives were isomerized by electron transfer-induced reactions via the radical anion in the CT-complex using aniline as electron donor at 25 °C in the light or at 80 °C in the dark. The starting as well as the final E:Z ratio was determined by 1H NMR spectroscopy. In all cases only the cis → trans isomerization was observed.
Synthesis of 2-(4-aryl-2-pyrazolin-3-yl)-1,8-naphthyridines by 1,3-dipolar cycloaddition
Authors: Rama Rao Gurram , Mogilaiah Kaleru , Sreenivasulu Bathula
Published: May 2010

2-(4-Aryl-2-pyrazolin-3-yl)-1,8-naphthyridines III have been prepared by the cycloaddition of diazomethane to 2-styryl-1,8-naphthyridines II. The structures of the compounds have been confirmed by elemental analyses and spectral data. All these compounds have been screened for fungicidal activity.
Separation of analytes as a source of information
Authors: Eckschlager Karel
Published: May 2010

It is shown how the amount of information gained by separation and detection or determination of several components depends on the selectivity of the analytical procedure in question. The selectivity is characterized in terms of the information entropy. Rules useful in the optimization of multicomponent analysis are derived from the results of information field mapping.
Fluorimetric determination of beryllium with 3-hydroxy-2-naphthoic acid by flow injection analysis after preconcentration on a silica gel microcolumn
Authors: Kubáň Vlastimil , Havel Josef , Patočková Bronislava
Published: May 2010

A method was worked out for the selective determination of trace concentrations of beryllium by flow injection analysis (FIA) with fluorimetric detection using 3-hydroxy-2-naphthoic acid (λex = 375 nm, λem = 455 nm) at cL = 50 μmol l-1 in 0.1M ammonium acetate, pH 7·1. In injected sample volumes of 80 μl, Be can be determined in concentrations of 10 to 156 μg l-1 with relative standard deviations not exceeding 5%, after its selective sorption on a microcolumn (2 x 40 or 3 x 30 mm) of silica gel from a medium of 0.05M-EDTA and 0.1M tartaric acid followed by elution with 0.1M-HCl. After preconcentration from 5 to 15 ml volumes, Be can be determined under the same conditions in samples at concentrations of ρBe = 0.5 to 4.6 or 0.1 to 0.8 μg l-1, respectively, with sr from 6 to 12%, the enrichment factor being as high as 200. The method was applied to beryllium bronzes and to dust from the atmosphere of the beryllium bronze foundry. The relative deviations of the beryllium content did not exceed 8% for the bronzes as compared to certified values, and 5% for the dust as compared to results obtained by ETA AAS.
Determination of trace concentrations of copper by FIA-FAAS after preconcentration on chelating sorbents
Authors: Kubáň Vlastimil , Komárek Josef , Zdráhal Zbyněk
Published: May 2010

A FIA-FAAS apparatus containing a six-channel sorption equipment with five 3 x 26 mm microcolumns packed with Spheron Oxin 1 000, Ostsorb Oxin and Ostsorb DTTA was set up. Combined with sorption from 0.002M acetate buffer at pH 4.2 and desorption with 2M-HCl, copper can be determined at concentrations up to 100, 150 and 200 μg l-1, respectively. For sample and eluent flow rates of 5.0 and 4.0 ml min-1, respectively, and a sample injection time of 5 min, the limit of copper determination is LQ = 0.3 μg l-1, repeatability sr is better than 2% and recovery is R = 100 ± 2%. The enrichment factor is on the order of 102 and is a linear function of time (volume) of sample injection up to 5 min and of the sample injection flow rate up to 11 ml min-1 for Spheron Oxin 1 000 and Ostsorb DTTA. For times of sorption of 60 and 300 s, the sampling frequency is 70 and 35 samples/h, respectively. The parameters of the FIA-FAAS determination (acetylene-air flame) are comparable to or better than those achieved by ETA AAS. The method was applied to the determination of traces of copper in high-purity water.
NMR spectroscopic investigation of p-substituted 2,4,4,6-tetraphenyl-1,4-dihydropyridines and their oxa and thia analogues
Authors: Schwarz Marián , Trška Petr , Kuthan Josef
Published: May 2010

The 1H, 13C and 19F NMR spectra of photochromic p-substituted 2,4,4,6-tetraphenyl-1,4-dihydropyridines IIa-IIg, 1-methyl-2,4,4,6-tetraphenyl-1,4-dihydropyridines IIIa-IIIg, 2,4,4,6-tetraphenyl-4H-pyrans IVa-IVh, and 2,4,4,6-tetraphenyl-4H-thiopyran V were inspected; it was found that compounds IIa-IIg occur in a dynamic equilibrium with their dihydro tautomer VIa-VIg. Also deuteriodeprotonation of IIa and IIIa and their reaction with trifluoroacetic acid were investigated by NMR spectroscopy.
Potential antidepressants: 6-(Aminoalkoxy)dibenzo[b,f]thiepin-10(11H)-ones and 6-(aminoalkoxy)-10,11-dihydrodibenzo[b,f]thiepin-10-ols
Authors: Červená Irena , Holubek Jiří , Svátek Emil , Ryska Miroslav , Protiva Miroslav
Published: May 2010

Sodium salts of 6-hydroxydibenzo[b,f]thiepin-10(11H)-one and its 2-chloro derivative were reacted with hydrochlorides of 2-dimethylaminoethyl chloride, 2-(piperidino)ethyl chloride, 3-dimethylaminopropyl chloride, and 3-(piperidino)propyl chloride in ethanol in the presence of sodium ethoxide which resulted in the title compounds IIa, IIb, IVa, Va, Vb, and VIIa. The tertiary amines IIa, IIb, and Va were partially demethylated via the carbamates VIIIa, VIIIb, and IXa to the secondary amines IIIa, IIIb, and VIa. The amino ketones IIa and Va were reduced to the amino alcohols XII and XIII. With the exception of compound Va (hydrochloride VÚFB-15 515), the products lacked completely the expected pharmacological profile of potential antidepressants.
Potential antidepressants: 2-(Aminoalkoxy)biphenyls and some related ω-substituted 2-alkoxybiphenyls
Authors: Červená Irena , Holubek Jiří , Svátek Emil , Metyš Jan , Protiva Miroslav
Published: May 2010

Reactions of 2-hydroxybiphenyl with α,ω-dibromoalkanes gave the 2-(bromoalkoxy)biphenyls IIIa-IIId. The 2-(dimethylaminoalkoxy)biphenyls VIa and VIb were transformed via carbamates VIIa and VIIb to the secondary amines Va and Vb. Their homologues Vc and Vd were obtained from the bromo compounds IIIc and IIId by treatment with methylamine. Bromo compounds IIIa and IIIb were reacted with 1-methylpiperazine, 2-(1-piperazinyl)ethanol, 3-(1-piperazinyl)propanol, and 4-amino-1-benzylpiperidine and gave the diamines VIIIa, VIIIb, IXa, Xa, Xb, and XIa. Addition of 2-hydroxybiphenyl to acrylonitrile afforded the nitrile XIIa. The homologous nitrile XIIb was obtained from the bromo compound IIIb and sodium cyanide in dimethyl sulfoxide. Nitriles XIIa and XIIb were reduced with aluminium hydride to diamines IVb and IVc. The nitriles were also transformed to hydrochlorides of the corresponding ethyl imidates XIVa and XIVb. Their hydrolysis resulted in the esters XVa and XVb. The acid XIIIa was obtained by acid hydrolysis of the nitrile XIIa; the acid XIIIb resulted from the acid hydrolysis of the ester XVb. The imidate XIVb was transformed to the amidine XVIb and to the dihydroimidazole XVIIb. Only the amine Vc showed properties indicative of potential antidepressant.
Liquid chromatography of carbamate, urea, triazine, phenoxycarboxylic and organochlorine pesticides
Authors: Svoboda Ladislav , Jandera Pavel , Churáček Jaroslav
Published: May 2010

The applicability of high performance liquid chromatography to the analysis of pesticide substances was tested using the Silasorb C 18 octadecyl silica gel stationary phase. The basic retention data were determined for 43 compounds of the title type and the optimum conditions for their chromatographic analysis were established. The results can be used in the determination of these substances in various environmental samples or in the quality control of commercial pesticide agents.
Contribution to the research and development of radiation chambers in steam reforming
Authors: Stehlík Petr , Šika Jan , Bébar Ladislav , Raus Luboš
Published: May 2010

The mathematical model for investigation of combined heat transfer in the steam reforming radiation chamber with the application of zonal method, its development and final feature is discussed. The calculation results of the steam reforming radiation chamber unit generating syngas for the production of ammonia with the capacity of 1 000 t/day are confronted with the values measured on this unit. Also described is the effect of flue gas mixing on the characteristics of steam reforming process and application of the calculation method for the determination of life of reactor tubes in the field of creep.
Chemometrical analysis of substituent effects on 13C and 15N NMR chemical shifts in 1-aroyl-3-substituted thioureas
Authors: Pytela Oldřich , Jirman Josef , Lyčka Antonín
Published: May 2010

The methods of conjugated deviations and regression analysis have been used to study the substituent effects on 13C and 15N NMR chemical shifts of 12 derivatives of 1-aroyl-3-phenylthiourea and 1-aroyl-3-methylthiourea. The 13C NMR chemical shifts can be described by two latent variables, one univocally correlated with the Hammett substituent constants (r = 0.993) and the other reflecting the increased shielding of the nuclei due to overlap of the adjacent bond electrons as a consequence of electron-donor or electron-acceptor character of the substituents.This effect is less pronounced with the 15N nuclei. Application of dual substituent constants σR, σF with the additional constant σα describing the polarization has failed in giving sufficiently close correlations and explanation of the substituent effect found.