bluuebunny/crossref_metadata_2025 huggingface dataset:
Subpopulation-Specific Transcriptome Analysis of Competence-Stimulating-Peptide-Induced Streptococcus mutans
Authors: Lemme André , Gröbe Lothar , Reck Michael , Tomasch Jürgen , Wagner-Döbler Irene
Published: February 2011

Competence-stimulating-peptide (CSP)-mediated competence development in
Streptococcus mutans
is a transient and biphasic process, since only a subpopulation induces the expression of ComX in the presence of CSP, and the activation of the DNA uptake machinery in this fraction shuts down ∼3 to 4 h postinduction. Here, we combine for the first time, to our knowledge, the bacterial flow-cytometric sorting of cells and subpopulation-specific transcriptome analysis of both the competent and noncompetent fraction of CSP-treated
S. mutans
cells. Sorting was guided by a ComX-green fluorescent protein (ComX-GFP) reporter, and the transcriptome analysis demonstrated the successful combination of both methods, because a strong enrichment of transcripts for
comX
and its downstream genes was achieved. Three two-component systems were expressed in the competent fraction, and among them was ComDE. Moreover, the recently identified regulator system ComR/S was expressed exclusively in the competent fraction. In contrast, the expression of bacteriocin-related genes was at the same level in all cells. GFP reporter strains for ComE and CipB (mutacin V) confirmed this expression pattern on the single-cell level. Fluorescence microscopy revealed that some ComX-expressing cells committed autolysis in an early stage of competence initiation. In viable ComX-expressing cells, the uptake of DNA could be shown on the single-cell level. This study demonstrates that all cells in the population respond to CSP through the activation of bacteriocin-related genes. Some of these cells start to activate ComX expression but then segregate into two subpopulations, one becoming competent and another one that lyses, resulting in intrapopulation diversity.
Decomposition of hydrogen peroxide on nickel oxide-vanadium pentoxide catalysts and the effect of ionizing radiation on them
Authors: Múčka Viliam
Published: February 2011

Some physico-chemical and catalytic properties of nickel oxide-vanadium pentoxide two-component catalysts were studied over the entire concentration region of the components, using the decomposition of hydrogen peroxide in aqueous solution as the test reaction. The two oxides were found to affect each other, which appeared in the dependences of the specific surface area, the V4+ ion concentration, and the catalyst activity on the system composition. At low vanadium pentoxide concentrations (up to 15 mol%) the reaction takes place on nickel oxide modified with vanadium pentoxide, whereas in the region of higher vanadium pentoxide concentrations the decomposition of the peroxide is catalyzed primarily in the homogenous phase by vanadium (V) peroxide ions; in sample with 30 mol% V2O5, trivalent vanadium also plays a part. With catalysts obtained by a mere mechanical mixing of the two oxides, a modified activity was observed in the region of high excess of nickel oxide. The activity of catalyst, particularly pure nickel oxide, is increased by its partial reduction and decreased by its exposition to gamma radiation if the dose is higher than 105 Gy. The effects observed are interpreted in terms of the concept of bivalent catalytic centres.
Photochemical reactions of 2-substituted furans with some carbonyl compounds
Authors: Sekretár Stanislav , Rudá Jana , Štibrányi Ladislav
Published: February 2011

Photochemical reactions of 2-substituted furans I, IV and V with benzaldehyde, benzophenone and 4-methylbenzophenone gave substitued 2,7-dioxabicyclo[3,2,0]-3-heptenes, which can be used for syntheses of 2,3- or 2,4-disubstituted furans. Regioisomeric (2:1)-cycloadducts XV and XVI were distinguished on the basis of their 1H and 13C NMR spectra.
Noncataleptic neuroleptic agents: 2-Halogeno-8-isopropyl-10-piperazino-10,11-dihydrodibenzo[b,f,]thiepins
Authors: Polívka Zdeněk , Jílek Jiří , Holubek Jiří , Svátek Emil , Dlabač Antonín , Valchář Martin , Protiva Miroslav
Published: February 2011

Reactions of 5-fluoro, 5-chloro- and 5-bromo-2-iodobenzoic acid with 4-isopropylthiophenol in solutions of potassium hydroxide in the presence of copper gave the acids VIIabc which were transformed via the intermediates VIIIabc-Xabc to 2-[5-halogeno-2-(4-isopropylphenylthio)-phenyl]acetic acids XIabc. Their cyclization with polyphosphoric acid resulted in 2-halogeno-8-isopropyldibenzo[b,f]thiepin-10(11H)-ones XIIabc.The 2-iodo ketone XIId was obtained from 2-(2-chloro-5-nitrophenyl)acetic acid by treatment with 4-isopropylthiophenol, by the following reduction of the resulting nitro acid XIe with hydrazine to the amino acid XIf, by its cyclization to the amino ketone XIIf and finally by its diazotization and reaction with potassium iodide. The ketones XIIa-d were reduced to the alcohols XIIIa-d giving by treatment with hydrogen chloride the chloro compounds XIVa-d. Substitution reactions with 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine afforded the title compounds Vabc and VIa-d. Only the fluoro derivatives Va and VIa showed a clear cataleptic activity in rats. The other compounds are very little active in this line and the iodo derivative VId was found to be completely inactive in a high oral dose, but it revealed an intensive antidopaminergic action in biochemical tests. By its pharmacological profile it resembles the known noncataleptic neuroleptic agent clozapine.
A quantum-chemical study of pesticidal activity of phenylurea derivatives. The equilibrium geometries
Authors: Mocko Vladimír , Fiedler Karol , Leška Jaroslav
Published: February 2011

Quantum-chemical methods have been used to study geometry of 13 phenylurea derivatives with respect to their herbicidal activity. From energy hypersurfaces of the equilibrium geometries it was possible to determine the shape and evaluate the flexibility of the molecules. An interdependence is observed between space arrangement and herbicidal activity of some derivatives. However, the exception found indicate that conformational geometry of the molecules studied does not represent a sufficient condition for their herbicidal activity.
A comparison of supports for quantitative gas chromatographic analysis of nickel and zinc dithiocarbamates
Authors: Chovancová Jana , Krupčík Ján , Garaj Ján
Published: February 2011

The gas chromatographic behaviour of nickel and zinc diethyldithiocarbamates was examined on various supports, mainly of the Chromaton and Chromosorb families, coated with polydimethylsiloxane nonpolar stationary phase. The coefficients of asymmetry, retention ratios and relative molar responses with respect to C28H58, and numbers of theoretical plates were determined. While poor results were obtained with Chromosorb G, Chromaton N Super appears to suit well to thedetermination.
cw CO2 laser photosensitited decomposition of cyclohexane
Authors: Pola Josef
Published: February 2011

The cw CO2 laser photosensitized (SF6) decomposition of cyclohexane affords high yields of ethylene and butadiene along with minor amounts of propene, methane and ethane. The products distribution is very slightly altered with the reaction progress. The process is shown to have practical importance, and its course different from conventional pyrolysis is inferred to come from the absence of surface effects.
Conformational study of blocked pentofuranoses and their 1,5-anhydro derivatives by 1H NMR spectroscopy
Authors: Zajíček Jaroslav , Buděšínský Miloš , Farkaš Jiří
Published: February 2011

Preferred conformations of the furanose ring and conformer population about the C(5)-C(4) bond in a series of benzoylated pentofuranosyl cyanides have been determined from their 1H NMR spectra. For the 1,5-anhydropentofuranose derivatives the results of the 1H NMR spectral analysis have been compared with the quantum chemical calculations.
The side reactions in the esterification of phthalic anhydride with 2-ethylhexane-1-ol in the presence of organotitanates
Authors: Novrocík Jan , Novrocíková Marta , Norek Jiří , Koruna Ivan , Ryska Miroslav
Published: February 2011

Using synthetic, chromatographic and spectral methods, we studied the side reactions accompanying the preparation of di-2-ethylhexyl phthalate from phthalic anhydride and 2-ethyl-hexane-1-ol in the presence of catalytic amounts of tetra-n-butyl titanate.The catalyst proper was titanium(IV) mono-2-ethylhexyl phthalate. The possibility of a simultaneous gas-chromatographic quantitative determination of mono-2-ethylhexyl phthalate, di-2-ethylhexyl phthalate, 2-ethylhexane-1-ol and tetra-n-butyl titanate, reported in the literature, has been refuted. In the esterification catalysed by hydrated titanium dioxide homogeneous catalysis by the formed organotitanate was dominating. The dissolving of hydrated titanium dioxide in the esterification of phthalic anhydride with 2-ethylhexane-1-ol was studied polarographically.
4-Deoxy-4-fluoro-D-fructose: Preparation and structure
Authors: Buděšínský Miloš , Černý Miloslav , Doležalová Jitka , Kulhánek Miloš , Pacák Josef , Tadra Milan
Published: February 2011

4-Deoxy-4-fluoro-D-fructose (II) was prepared by specific hydrogenation of 3-deoxy-3-fluoro-D-mannitol (I), using the enzymatic system of Gluconobacter oxydans. Using 1H, 13C and 19F NMR spectra its structure and its existence in the pyranose conformation 2C5(D) in aqueous solution was demonstrated.
Substituted 5- and 6-quinoxalinecarboxylic acids and their tuberculostatic activity
Authors: Roubínek František , Bydžovský Viktor , Buděšínský Zdeněk
Published: February 2011

Condensation of aliphatic and aliphatic-aromatic α-diketones, and of substituted benzils with 2,3- and 3,4-diaminobenzoic acids and with 4,5-diamino-2-hydroxybenzoic acid gave 74 5- and 6-quinoxalinecarboxylic acids, with the same or different alkyls and aryls as substituents at position 2 and 3. The compounds with different substituents at positions 2 and 3 were resolved into positional isomers. Their structures were determined by means of the dipole moments. The compounds were tested for tuberculostatic activity. Some exhibited it in vitro (LI, LVII), but failed in vivo.
Lead tetraacetate oxidation of 3β-acetoxy-B-homo-5α-cholestan-7aβ-ol
Authors: Kohout Ladislav , Zajíček Jaroslav
Published: February 2011

Oxidation of the alcohol I with lead tetraacetate afforded low yields of the 7aβ,19-epoxide IIand an aldehyde which represented the main product. The structure of this aldehyde as th-3β-acetoxy-7a,8-seco-B-homo-5α-cholest-9(11)-en-7a-one (III) has now been established by chemical and spectral means.
Contribution to the theory of parachor
Authors: Čeleda Jiří
Published: February 2011

Deriving theoretically the dependence of the surface tension of a liquid substance, σ, on its density ρ1, the author has arrived by means of a simplified molecular-statistical model, to a temperature-independent product ρ1-1σ1/y, with denominatory in the exponent equal to n/2 + 2/3 (where n is the power of decrease of intermolecular potential energy of attractive forces, with increasing distance). Taking into account the finite gradient of the repulsive forces (exponent n'), we obtain an additional relatively small correction in a positive sense. The value resulting hence for γ, in the case of the individual real compounds, is in average close to 4 - in agreement with the empirical formula of the Sugden parachor representing a temperature-invariant quantity. This quantity is subjected to the theoretical analysis from the point of view of its applicability to investigation of the chemical constitution of substances in solutions, in terms of the additivity principle assumed by Sugden. As a result of this analysis, a concept is intriduced of the apparent parachor of a solute, IIi, (as a quantity experimentally accessible) - in analogy to its apparent volume φi.
Determination of molybdenum in rocks by atomic absorption spectrometry with electrothermal atomization after its separation with α-benzoinoxime
Authors: Kolčava Dalibor , Janáček Jan
Published: February 2011

A method has been worked out for a sensitive and accurate determination of molybdenum in rocks in contents of the order of 10-1 g/t. The sample is decomposed with acids and molybdenum is separated from practically all other elements by extraction with α-benzoinoxime from solution of 1.5 M hydrochloric acid and 0.13 M tartaric acid into chloroform, and determined in the extract by AAS with electrothermal atomization. The quantitativeness of the extraction has been examined and the optimum conditions for the determination in a graphite furnace have been established. The effects of chloroform and of the graphite atomizer on the signal of molybdenum have been investigated, and the accuracy of the method has been tested on GXR geochemical standards.
Characterization of the surface of hydrodesulphurization catalysts by adsorption of hydrocarbons
Authors: Hillerová Eva , Zdražil Miroslav
Published: February 2011

Reversible adsorption of heptane and benzene on model and industrial hydrodesulphurization molybdena catalysts has been studied by elution chromatographic method at 150 °C. An increase in the adsorption of heptane on sulphidation of adsorbents was small for Al2O3 and great for MoO3. Supported catalysts behaved as mixture of Al2O3 and MoO3.The portion of surface which can be transformed by sulphidation into MoS2 ranged from 0 to 65% for individual commercial catalysts, as determined from the change in heptane adsorption after sulphidation of a given sample. The polarity of catalysts, including their acidity, was estimated from the difference between adsorption of benzene and heptane. The polarity of model and industrial catalysts in oxidic form was similar to that of alumina in most cases. The decrease in the polarity after sulphidation of the adsorbents was small for Al2O3 and great for MoO3. The decrease in polarity resulting from sulphidation of supported catalysts was relatively small, since the reaction of MoO3 monolayer with hydrogen sulphide leads to partial reformation of the alumina surface. The acidity of supported sulphided hydrodesulphurization catalysts has been shown by this method to be comparable with the acidity of the support itself.
Isomeric oxatricyclodecanones with non-planar lactone groups: Synthesis, absolute configuration, NMR and X-ray study
Authors: Tichý Miloš , Farag Ahmed , Buděšínský Miloš , Otroshchenko Ludmila P. , Shibanova Tatjana A. , Bláha Karel
Published: February 2011

Several rigid polycyclic lactones, potentially suitable as models for investigation of the lactone grouping geometry, were synthesized. (3S)-4-Oxatricyclo[4.3.1.03,7]decan-5-one ((+)-I), (3R)-5-oxatricyclo[4.3.1.03,8]decan-4-one ((+)-III) and (4S)-5-oxatricyclo[5.2.1.04,8]decan-6-one ((-)-VIII) were prepared by acid-catalyzed lactonization of (2R)-endo-bicyclo[2.2.2]oct-5-ene-2-carboxylic acid. (1S)-4-Oxatricyclo[4.4.0.03,8]decan-5-one ((-)-II) was synthesized from (2S, 5S)-endo,endo-bicyclo[2.2.2]-octane-2,5-dicarbolyxic acid. The structure of VIII was unequivocally proved by its NMR, spectra and the geometry of III was determined by X-ray analysis. The absolute configuration of (+)-III was assigned by correlation with (1R)-bicyclo[3.2.1]nonan-6-one. The acid-induced interconversion of I, II, III and VIII was studied. Lactones II and III represent suitable rigid models for investigations of non-planar lactone groups of known chirality and geometry.
Effect of thermal history of aqueous solutions of KCl on the metastable zone width
Authors: Nývlt Jaroslav
Published: February 2011

The metastable zone width of an aqueous solution of KCI was measured as a function of the time and temperature of overheating above the equilibrium solubility temperature. It has been found that when the experiments follow close upon one another, the parameters of the preceding experiment affect the results of the experiment to follow.The results are interpreted in terms of hypotheses advanced in the literature to account for the effect of thermal history of solution. The plausibility and applicability of these hypotheses are assessed for the given cause of aqueous solution of a well soluble electrolyte.
1,2,3-Dithiazolyle, eine neue Klasse persistenter Radikale
Authors: Mayer Roland , Domschke Gunter , Bleisch Siegfried , Fabian Jürgen , Bartl Anton , Staško Andrej
Published: February 2011

Die persistenten 1,2,3-Dithiazolyle bilden sich aus den verschiedenartigsten Ausgangsverbindungen, zum Teil in sehr einfacher Weise. Es wurde eine größere Anzahl unterschiedlich substitüierter 1,2,3-Dithiazolyle hergestellt und ESR- bzw. UV-spektroskopisch characteristiert. Die Struktur der Radikale konnte durch Rückoxidation in die u. a. als Ausgangsstoffe dienenden 1,2,3-Dithiazoliumsalze, durch 33S-ESR-Spektren und durch Vergleich der Hyperfeinaufspaltungskonstanten aN bzw. der Spindichten mit quantenchemisch berechneten Werten gesichert werden.
Nonideal mixer as a source of random fluctuations
Authors: Kudrna Vladimír , Hasal Pavel , Vyhlídková Jitka
Published: February 2011

An attempt is made here to describe distribution of residence times of a fluid in a nonideal flow mixer for turbulent flow of the charge, i.e. for the case when the flow velocity exhibits random fluctuations. The analysis is based on the assumption that the flow of fluid in mixer may be considered as a stationary Markov's process and is aimed at application of the mixer as a linear filter.
The preparation of O-(formylmethyl)cellulose
Authors: Petruš Ladislav , Gemeiner Peter , Némethy Tomáš
Published: February 2011

A new aldehyde derivative of cellulose, O-(formylmethyl)cellulose was prepared by three methods. The first one is based on the base-catalysed elimination of nitromethane from O-(3-nitro-2-hydroxypropyl)cellulose obtained by the reaction of sodium nitrite in dimethylformamide with O-(3-iodo-2-hydroxypropyl)cellulose. The second process is a mild acid hydrolysis of O-(2,2-diethoxylethyl)cellulose formed through the alkylation of dry alkali cellulose by bromoacetaldehyde diethyl acetal. The principle of the third procedure is a periodate oxidation of O-(2,3-dihydroxypropyl)cellulose, prepared from an O-(3-chloro-2-hydroxypropyl) derivative in an aqueous alkali solution. The procedure yields a mixed aldehydic derivative - O-(formylmethyl)-2,3-dialdehydocellulose. The application of these reactions to bead cellulose preserves its porosity as well as the spheric particle-shape even at the degree of substitution by formylmethyl groups up to 0.2.
Chiroptical and conformational properties of ketohexoses
Authors: Bystrický Slavomír , Sticzay Tibor , Kučár Štefan
Published: February 2011

Circular dichroism of acyclic forms of D-fructose, L-sorbose, D-tagatose, and four deoxy derivatives of D-fructose has been interpreted from the point of view of the equilibrium of rotamers around the bond of the chromophore and chiral residue of the molecule. The conformational equilibrium manifested by the double-sign dichroic curve changes with constitutional, solvation, and temperature conditions. It can be characterized as a syn ⇌ anti equilibrium according to mutual orientation of the carbonyl and vicinal hydroxyl groups.
Components of the extract from the underground parts of Laserpitium siler L. of slovenian origin, mainly sesquiterpenic lactones
Authors: Smítalová Zdenka , Buděšínský Miloš , Šaman David , Vašíčková Soňa , Holub Miroslav
Published: February 2011

In the analysis of the underground parts of Laserpitium siler L. of Slovenia origin the authors succeeded in isolating the phenylpropane derivatives 1-(3,4-methylenedioxy-5-methoxyphenyl)-propan-1-one (IV) and 1-(3,4-methylenedioxy-5-hydroxyphenyl)propan-1-one (XXI), three current phytosterols and thirteen sesquiterpenic lactones. Of these eleven are newly described, while eight have not yet been mentioned in literature at all. The structures of the following four undescribed lactones, including relative and absolute configuration, are determined: 8α-(2'-methylbutyroyloxy)-10β-hydroxy-11α-acetoxyslov-3-enolide (XIV), 8α-isobutyroyloxy-10β-hydroxy-11α-acetoxyslov-3-enolide (XIX), 8α-hydroxy-10β,11α-diacetoxyslov-3-enolide (XXIX) and 8α,10β-dihydroxy-11α-acetoxyslov-3-enolide (XXXII). For the lactones derived from 1βH,5βH,6αH,7αH-guaian-6,12-olide (slovanolide) a semisystematic nomenclature is proposed.
Preparation of 21,26,27-trinor-5α-cholest-23-en-25→20-olide from a propargyl synthone
Authors: Pouzar Vladimír , Drašar Pavel , Černý Ivan , Havel Miroslav
Published: February 2011

Reaction of 21-nor-5α-pregnan-20-al (I) with propargylmagnesium bromide afforded two isomeric 21-nor-5α-chol-23-yn-20-ols (II and IV) whose absolute configuration at C(20) was determined by chemical correlation with the known 21-nor-5α-cholan-20-ols (VI and VII). Extension of the side-chain in the compound by one carbon atom gave (20R)-21,26,27-trinor-5α-cholest-23-yne-20,25-diol (XIV). The isomeric (20S)-diol XX was obtained by the same procedure from the alcohol IV. Alternative synthesis of the diols XIV and XX by reaction of the lithium salt of 1-methoxymethoxy-2-propyne with (20S)-20,21-epoxy-5α-pregnane (XV) and the (20R)-isomer XXI, respectively, gave only low yields. The diols XIV and XX were converted into the respective unsaturated lactones, i.e. (20R)-21,26,27-trinor-5α-cholest-23-en-25→20-olide (XVII) and (20S)-21,26,27-trinor-5α-cholest-23-en-25→20-olide (XXIII).
Kinetic analysis of oxalic and citric acids mixtures with manganese(III) sulphate
Authors: Barek Jiří , Berka Antonín , Civišová Dagmar
Published: February 2011

Model mixtures of oxalic and citric acids were used to verify the applicability of the logarithmic extrapolation method for 2nd order reactions to the analysis of mixtures of pairs of substances reacting with the oxidant employed with the exchange of different numbers of electrons.
13C and 15N NMR spectra of 1-(3- or 4-substituted phenyl)-3-methyl-3-phenyltriazenes
Authors: Lyčka Antonín , Vetešník Pavel
Published: February 2011

13C and 15N NMR spectra of ten 1-(3- or 4-substituted phenyl)-3-methyl-3-phenyltriazenes have been measured in deuteriochloroform. In the temperature range from 210 to 320 K the 13C NMR signals of both methyl and phenyl groups were not broadened, and no free rotation of the substituents at N(3)has been proved. From the values 2J(15N(2) 13C(5')) and 2J(15N(2)13C(1')) it was possible to determine conformation at the N(2) - N(3) bond which has partial double bond character. The value 1J(15N(1) 13C(1)) is equal to 1.0 Hz, which proves trans arrangement of the substituents at the N(1) = N(2) bond.
Competitive hydrogenation of a pair of substrates in combined two-catalyst systems
Authors: Červený Libor , Vodová Barbora , Růžička Vlastimil
Published: February 2011

A theoretical model has been set up for treating competitive hydrogenations of pairs of substrates on combined two-catalyst systems, assuming that the catalysts act in an independent manner. The hydrogenation rate constants of the two substrates and their relative adsorptitives established on the individual catalysts are used for the calculations. the model has been tested on the substrate system of 2-methyl-3-buten-2-ol and 2-phenylpropene, hydrogenated in methanol or cyclohexane on combined Pt/C, Pd/C, and Rh/C catalyst systems. The calculated and observed data are in a good agreement.
α-Benzyldopamine and some related compounds: Synthesis and pharmacological screening
Authors: Valenta Vladimír , Dlabač Antonín , Valchář Martin , Protiva Miroslav
Published: February 2011

Claisen reaction of 3,4-dimethoxyphenylacetonitrile with ethyl phenylacetate, the following stepwise hydrolysis and decarboxylation afforded the amide V 1-(3,4-dimethoxyphenyl)-3-phenylpropan-2-one (VI). Leuckart reaction resulted in the crude formamide derivative IIIb which was subjected to alkaline hydrolysis to the primary amine Ib on the one hand, and to reduction to the secondary amine IIb on the other. Demethylation with hydrobromic acid gave hydrobromides of 1-(3,4-dihydroxyphenyl)-3-phenyl-2-propylamine (title compound Ia) and its N-methyl derivative IIa. The alcohol VII, obtained by reduction of the ketone VI, was transformed by treatment with thionyl chloride to the chloro compound VIII which afforded by substitution reaction with 1-methylpiperazine the piperazine derivative IX. While the methoxylated amines Ib and IIb have mild stimulating and some antiarrhythmic effects, N-methyl-α-benzyldopamine (IIa) displayed a clear dopaminomimetic character.
The metachors of polyvalent and associated electrolytes in aqueous solutions
Authors: Čeleda Jiří , Škramovský Stanislav , Žilková Jana
Published: February 2011

The quantity metachor introduced in the preceding paper was evaluated from the experimental data on surface tension of the aqueous solutions for a set of polyvalent and weak electrolytes. The almost complete concentration independence of the metachor and its direct proportionality to the number of the free charges in a dissociated molecule (observed and theoretically substantiated in the above cited paper for strong 1,1-, 1,2- and 2,1-valent electrolytes) has been verified in the present paper also for electrolytes of the higher valency types. The metachor values of fully dissociated 1,1-, 1,2-, 1,3- and 1,4-valent electrolytes follow a ratio (5 ± 1) : (10 ± 1.5) : 15 : 22 cm3 mol-1. Association of the electrolytes decreases correspondingly the metachor value as one can see on the case of electrolytes with bulky ions (NH4SCN, KCH3COO, Na2S2O3, hexacyanoferrates(II) or with the free acids H2SO4, H2CrO4, H3PO4 etc. A weak, in the investigated concentration range neglibility dissociated oxalic acid, consisting of small hydrated hydrophilic molecules, exhibits metachor values close to zero. Dibasic organic acids with a larger number of hydrophobic CH2 groups reach very high negative metachor values, however, their salts again possess metachor values close to 10 cm3 mol-1 - in accordance with the values found for strong 1,2-valent electrolytes. The metachors of ZnCl2 and CdCl2 decrease sharply from the last mentioned value, with increasing concentration while the metachor value of zinc perchlorate remains unchanged at the level corresponding to the fully dissociated salt. This is in agreement with the well known sequence of tendency of the d10-cations to form complexes with the Cl- and ClO-4 anions. All these facts have verified that the metachor can be, in principle, applied for a diagnostic states of the electrolytes in aqueous solutions.
Determination of Hg(II) in drinking water by atomic absorption spectrometry - Cold vapour method after concentration by column extraction chromatography
Authors: Šmejkal Zdeněk , Tauferová Jitka , Madová Mária , Teplá Zlatica
Published: February 2011

The method describes concentration of mercury in samples of drinking water from water mains with Hg concentration above 1.0 . 10-7 g l-1 (5.0 . 10-10mol l-1) by means of extraction chromatography on a column packed with a carrier Synachrom E-5 wetted with saturated solution of bis(diethyldithiocarbamate)copper(II) complex in 1 : 1 mixture 1,2-dichlorobenzene + cyclohexane. After elution with 3.0 mol l-1 HCl the mercury concentration in the eluate is determined by atomic absorption spectrometry - cold vapour method. Average yield of the mercury separation from the model solutions was 95.8%.
Preparation and photochemistry of furoisoxazolines. An extraordinarily unambiguous photo-induced rearrangement
Authors: Fišera Lubor , Ľaudár Samuel , Timpe Hans-Joachim , Zálupský Peter , Štibrányi Ladislav
Published: February 2011

Preparation and photolysis of furoisoxazoline derivatives is described. The respective compounds IVa, II and VI were obtained by a 1,3-dipolar cycloaddition of benzenenitrile oxide to 5,6-dimethoxycarbonyl-7-oxabicyclo[2,2,1]-2-heptene, 2,5-dihydrofuran and furan; IVb was synthesized from benzoylnitrile oxide. The biradical primarily formed by photolysis was stabilized with respect to the arrangement of the heteroatom and the isoxazoline chromophore. The new 1,3-oxazine derivatives III and V were obtained in high yields as single products. The quantum yield of photoreaction of II, IVa and XXVII was found to be 0.04, 0.26 and 0.07, respectively. Were the stabilization of the radical by conjugation with the lone electron pair of oxygen impossible, oxazoline VII should be formed. Photolysis of the benzoyl derivative IVb had an anomalous course and yielded the β-aminochalcone Xb.
Disulfide bonds of basic acrosin inhibitor (BUSI II) from bull seminal plasma
Authors: Rzavská Alena , Meloun Bedřich , Čechová Dana
Published: February 2011

The thermolysin digest of the basic acrosin inhibitor (molecular weight 6 200) was resolved on a column of Sephadex G-15 and subsequently by electrophoretic and chromatographic techniques. Cysteine peptides, which link together half-cysteine residues 7 and 39, 17 and 36, and 25 and 57 by disulfide bonds, were isolated. The structure of the molecule of the basic acrosin inhibitor corresponds to structures of inhibitors of the Kazal type. The amino acid sequence of a few residues in the basic acrosin inhibitor has been revised.
Vapour-liquid equilibrium at low pressures from the back equation of state. II. Ternary systems
Authors: Boublík Tomáš
Published: February 2011

Ternary equilibrium diagrams in the n-hexane-cyclohexane-benzene system at temperature 298.15 K and n-hexane-benzene-toluene system at pressure 101.325 kPa were determined from the BACK equation of state. In the course of the determination of excess thermodynamic functions of mixtures the values of the BACK equation parameters for pure compounds and binary interactions parameters, ki,j, adjusted to GE and HE of the corresponding binaries were employed. The comparison of theoretical and experimental data shows very good quality of the prediction of the equilibrium behaviour of polycomponent systems from the BACK equation of state.
Valence states of atoms and their conversions
Authors: Koča Jaroslav , Kratochvíl Milan , Kunz Milan , Kvasnička Vladimír
Published: February 2011

The algebraic formalism for the description of valence states of atoms and their interconversions is elaborated. It offers a possibility to construct and trace mechanistic paths of chemical reactions, the problem of which is of great importance in computer-assisted organic syntheses. Its systematic application gives exhaustive lists of possible mechanistic paths, and furthermore, very efficient tool to classify chemical reactions and look for their common features.
Mobilities of some univalent ions in aqueous and nitrobenzene media
Authors: Makrlík Emanuel , Vanýsek Petr , Ruth Wolfgang
Published: February 2011

Limiting ionic equivalent conductivities of selected univalent ions in water, nitrobenzene, or water-saturated nitrobenzene were taken or calculated from literature data. Based on previous conductivity measurements, it was shown that the proton mobility in nitrobenzene saturated with water is comparable with that of alkali metal ions.
Some remarks concerning polarographic determination of sulphur-containing herbicides
Authors: Stará Věra , Kopanica Miloslav
Published: February 2011

The herbicide methomyl (2-methylthio-propionaldehyde-o-methylcarbamoyloxime) can be determined using fast scan differential pulse voltammetry with hanging mercury drop electrode by the measurement of the peak at -1.30 V (S.C.E.) which caused by the presence of methomyl in the ammoniacal buffer solution containing cobalt(II) salt. The peak current vs methomyl concentration dependence is linear over the concentration range 0.5 to 20.0 μg . l-1. The herbicide aldicarb (2-methyl-2(methylthio)propionaldehyde-o-methylcarbamoyloxime) is determined by its influence on the differential pulse voltammetric curve of copper(II) recorded in electrochemically enriched solution in acidic medium. The corresponding peak current at the potential + 0.08 V (S.C.E.) depends linearly on the aldicarb concentration in the range 0.07 to 5.00 μg ml-1.
Additional alkaloids from Glaucium squamigerum KAR. et KIR
Authors: Slavík Jiří , Slavíková Leonora , Dolejš Ladislav
Published: February 2011

A new quaternary alkaloid, (-)-β-N-methylisocorypalminium hydroxide, was isolated from Glaucium squamigerum KAR. et KIR. in the form of iodide. In addition to the alkaloids already known to occur in this plant, i.e. allocryptopine (the main alkaloid), protopine, chelerythrine, sanguinarine, corydine, coptisine and berberine, additional alkaloids, i.e. (-)-chelidonine, (±)-chelidonine (diphylline) and chelirubine were also isolated from the non-quaternary fraction, while from the fraction of quaternary alkaloids (-)-β-N-methylcanadinium iodide (the second main alkaloid), (-)-α-N-methylcanadinium iodide and (-)-β-N-methylstylopinium iodide were isolated after conversion of the salt to iodides. Further the presence of small amounts of stylopine, canadine, scoulerine, corysamine, corytuberine, magnoflorine, α-N-methylstylopinium hydroxide and β-N-methyltetrahydropalmatinium hydroxide were also detected.
Interpretation of heats of mixing of 1-butanol, 2-butanol and 2-methyl-2-propanol with cyclohexane in terms of some models of continuously associated solution
Authors: Veselý František , Dohnal Vladimír , Valentová Miriam , Pick Jiří
Published: February 2011

Three models of continuously associated solution complemented by an assumption of polynomial temperature dependence of corresponding interaction parameters were used for simultaneous description of the concentration and temperature dependence of heats of mixing of 1-butanol, 2-butanol and 2-methyl-2-propanol with cyclohexane. Very good results were reached for the first two systems where the Liebermann and Wilhelm model has proved to be the most suitable. With respect to the probable existence of cyclic associates in solutions of 2-methyl-2-propanol, none of the used models which assume only linear association satisfied to the extent required.
Mathematical description of nonequilibrium passive transport in biosystems
Authors: Baláž Štefan , Šturdík Ernest , Škárka Bohumil
Published: February 2011

The time course of passive transport of low-molecular mass substances in a nonequilibrium system of alternating aqueous and lipidic phases was expressed as function of physico-chemical properties of the biosystem (phase volumes, interface area, diffusion layer thickness) and of the transported compounds (diffusion coefficients, partition coefficients).
Oxidation of lignins and their components by oxygen in the presence of laccase from Polyporus versicolor. lignin detection by an enzyme electrode
Authors: Malovík Vladimír , Yaropolov A. I. , Varfolomeev S. D.
Published: February 2011

The kinetics of the laccase-catalyzed oxidation of model lignin components by oxygen has been studied. It has been shown that in natural lignis the fragments containing guaiacyl groups are enzymatically oxidized without cleavage of the ether bond in the methoxy group. The enzyme has been immobilized by entrapping in polyacrylamide gel and also by covalent attachment to the surface of alkylamine glass. Immobilized laccase was used for the construction of sensors with the Clark oxygen electrode; such sensors can be employed for the determination of the content of lignin-like and phenolic compounds in waste waters.
Quantum chemical modelling of reactions in hydrocarbon combustion. Study of the CH4 + O2 reactions
Authors: Urban Ján , Klimo Viliam , Tiňo Jozef
Published: February 2011

The rate constants of two alternative reactions, i.e CH4 + O2 → CH2 + H2O2 and CH4 + O2 → CH3 + HOO have been studied by the ab initio and MINDO/3 methods. A preliminary appreciation of the used methods has been done with a selected set of carbene reactions. The characteristics of minima as well as the saddle points on the corresponding reaction paths of both reactions have been found. The discussion of the relative probability of a pathway of the above-mentioned reactions is based on the rate constants determined by the use of transition state theory.
Estimation of parameters of the mixture of two normal distributions by nonlinear optimization
Authors: Vrba Josef , Havlíček Antonín , Čermák Jan
Published: February 2011

A method for two distributions mixture fitting is proposed. It has been proved by testing, that the method is for fitting of histograms more efficient than those using the moments of high orders.
A [8,8'-μ-I-3-Co(1,2-C2B9H10)2] metallacarborane complex with a iodonium bridge. Evidence for a bromonium analogue
Authors: Plešek Jaromír , Štíbr Bohumil , Heřmánek Stanislav
Published: February 2011

The [8,8'-μ-I-3-Co(1,2-C2B9H10)2] complex with a iodonium bridge between both dicarbollide ligands was prepared and its constitution was established by NMR methods. It behaves as a Lewis acid opening its bridge by the action of Lewis bases to form {8-I-8'-L-3-Co(1,2-C2B9H10)2] species. The less stable bromonium analogue was not isolated but its existence was confirmed by the reaction with Lewis bases affording the [8-Br-8'-L-3-Co(1,2-C2B9H10)2]derivatives.
Study of structure of bis(triphenylstannyl) chromate(VI) by infrared, Mössbauer, and 1H, 13C and 119Sn NMR spectra
Authors: Handlíř Karel , Holeček Jaroslav , Nádvorník Milan , Lyčka Antonín , Hucl Milan
Published: February 2011

The infrared, Mössbauer, and 1H, 13C and 119 Sn NMR spectra have been used to study the structure of bis(triphenylstannyl) chromate(VI) in solid state and in solvents of both noncoordinating and coordinating types. In solid state the compound forms a three-dimensional polymer: the tetrahedral CrO4 group and trans-trigonally bipyramidal (C6H5)3SnO2 grouping are connected mutually symmetrically by bridges represented by the common oxygen atoms. The three phenyl groups in the (C6H5)3SnO2 grouping are located in the equatorial plane of the trigonal bipyramide which is completed by two bridge oxygen atoms in axial positions. Solutions in noncoordinating solvents contain monomeric bis(triphenylstannyl) chromate(VI). The ester molecule contain two tetrahedral, (C6H5)3SnO groups bound by oxygen bridges to a CrO4 group which shows the C2v symmetry. In coordinating solvents the title compound forms a molecular complex having the coordination number 5 at the central tin atom.
Synthesis and reactions of furocondensed systems containing indole skeleton
Authors: Koreňová Anna , Krutošíková Alžbeta , Dandárová Miloslava , Kováč Jaroslav
Published: February 2011

The new 1,2,4-triazolo[3''', 4''':6'', 1'']-1,2,4-triazino[4'', 5'':4,5]furo[3,2-b]indoles V and 1-acetyl-9H-pyrrolo[2',3':4,5]furo[3,2-b]indole (IX) were prepared from 1,9-dihydropyrrolo[2',3':4,5]furo[3,2-b]indole-2-carboxhydrazide I and 2-(2-nitrophenyl)-4H-furo[3,2-b]pyrrole-5-carboxylic acid, respectively. Compound I gave with triethyl orthoformate or with triethyl orthoacetate 1,2-dihydro-1,2,4-triazino[4'',5'':1',5']pyrrolo[2',3':4,5]furo[3,2-b]indol-1-one or its methyl analogue II. Substances II afforded with phosphorus pentasulfide thiones III reacting with hydrazine to furnish IV. Cyclization of the latter with triethylorthoformate or orthoacetate led to V. Compounds II and III can also be obtained by a deoxygenative cyclization of VI and VII with triethyl phosphite.
S-adenosine-L-homocysteine hydrolase from Nicotiana tabacum L.: Isolation and properties
Authors: Šebestová Ladislava , Votruba Ivan , Holý Antonín
Published: February 2011

S-Adenosyl-L-homocysteine hydrolase (E.C. 3.3.1.1) (SAH hydrolase) from an explanate culture of Nicotiana tabacumL. was purified to homogeneity. The enzyme is composed of four subunits of molecular weight of 55 000. The native molecule of final molecular weight of 220 000 aggregates in solution to multimers of molecular weight of 440 000 and higher. When subjected to isoelectric focusing the enzyme yields two components of equal distribution and pI-values of 5.15 and 5.25. The enzyme is thermolabile and is readily inactivated at temperatures above 3 °C. The KM value for adenosine is 5.15 μmol l-1 and for S-adenosyl-L-homocysteine (SAH) 11 μmol l-1. The temperature optimum of both SAH synthesis and hydrolysis is 37 °C, the pH optimum of SAH hydrolysis is 8.0, of SAH synthesis 7.14. The enzyme is competitively inhibited by (S)-9-(2,3-dihydroxypropyl)adenine and inactivated by both enantiomers of eritadenine and 3-(adenin-9-yl)-2-hydroxypropionic acid.
Regio and stereospecifity of solvent photoaddition to 5-fluorouracil and 1,3-dimethyl-5-fluorouracil
Authors: Zupančič Nataša , Zupan Marko , Šket Boris
Published: February 2011

Irradiation of 1,3-dimethyl-5-fluorouracil in methanol, ethanol, water and acetic acid, and 5-fluorouracil in water at λ = 253.7 nm resulted in the formation of two addition products. Regiospecifity was in all cases the same with functionalization at position 6 while the stereochemistry of addition dependend on the solvent. In water preferential trans addition proceeded while in acetic acid cis addition was predominant. Photoconversion of starting material was also twofold increased in acetic acid, compared to that in water.
Vinamidium salts having a furan ring and their substitution electrophilic reactions
Authors: Gracza Tibor , Arnold Zdeněk , Kováč Jaroslav
Published: February 2011

5-(N,N-Dialkylamino)-2-furfuryldiene-N,N-dialkylimmonium salts I (the so called vinamidinium salts) are characteristic of their reactivity towards electrophilic reagents. A series of new furan derivatives with substituents in β-position of the furan ring were prepared via this reagent. The presented reactions involve halogenation, nitration, formylation and acylation with the Vilsmeier-type reagents.
A contribution to the electrochemiluminiscence determination of cobalt with luminol
Authors: Herejk Jiří , Holzbecher Záviš
Published: February 2011

The effect was studied of experimental conditions (pH, ionic strength, supply voltage, and type of electrodes) and of the presence of some cations and anions on the luminiscence of aqueous solutions of luminol generated by alternating current. Of the ions studied, Co2+ and Br- affected the electrochemiluminiscence (ECL) of luminol to the highest extent. Co2+ ions increase the ECL of luminol in alkaline solutions in concentrations cCo2+ = 10-3-6.10-6 mol l-1, the limit of determination of cobalt is 0.13 μg ml-1. In the presence of bromide in concentrations higher than 0.2 mol l-1, however, Co2+ lowers the ECL intensity over the concentration region of cCo2+ = 10-2-2.10-4 mol l-1. Alkali metal and alkaline earth cations as well as small amount of Pb2+, Zn2+, Cu2+, Cr3+, and Fe3+ have no appreciable effect on the ECL of luminol.
Zinc selenites: The solubility diagram and its use for the isolation of the compounds, their spectral features and thermal bahaviour and the strength of bonds in them
Authors: Ebert Miroslav , Mička Zdeněk , Uchytilová Marcela
Published: February 2011

The solubility diagrams of the ZnSeO3-SeO2-H2O system were obtained at 0 and 25 °C and utilized for the preparation of Zn(HSeO3)2.2H2O and ZnSe2O5 , respectively. The thermal stability and the infrared absorption spectra were studied for ZnSeO3, Zn(HSeO3)2.2H20, and ZnSe2O5, and the force constants of the selenium-oxygen bonds were evaluated and the hydrogen bonds present were characterized.
Beckmann rearrangement of adamantanone oxime as a route to ditopic and tritopic secondarily substituted adamantane derivatives
Authors: Tříska Jan , Vodička Luděk , Butkus Eugenijus P. , Hájek Milan
Published: February 2011

The reaction in mixtures of adamantanone with hydroxylamine hydrochloride was studied in hydrochloric, hydrobromic, and hydroiodic acid solutions. In hydrochloric and hydroiodic acids, mixtures of isomers of 4-chloroadamantan-2-one and 4-iodoadamantan-2-one, respectively, are formed, whereas in hydrobromic acid in the presence of excess hydroxylamine hydrochloride, three stereoisomers of 4,8-dibromoadamantan-2-one appear. All the stereoisomeric haloketones were isolated by elution adsorption chromatography on silica gel or by crystalization. For the pure substances, their infrared, mass, and NMR spectra were measured.
Preparation and reactions of 2-amino-3-cyano-4,5-bis(3,4-methylenedioxybenzyl)furan
Authors: Prousek Josef
Published: February 2011

Treatment of 2-hydroxy-1,4-bis(3,4-methylenedioxyphenyl)-3-butenone with propanedinitrile (I) catalyzed by diethylamine afforded 2-amino-3-cyano-4,5-bis(methylenedioxybenzyl)furan (II). The latter reacted with formamide to 4-amino-5,6-bis-(3,4-methylenedioxybenzyl)furo[2,3-b]-pyrimidine (III), and with aldehydes to the corresponding azomethines IVa-IVe. The structure of products was adduced from spectral (IR, UV, 1H NMR, and mass) data. The inhibition of incorporation of [U14C]-L-valine for DNK synthesis and proteosynthesis of leukemia P-388 cells was tested with derivatives II and III.
11-(3-[4-(2-Hydroxyethyl)piperazino]propylidene)-6,11-dihydrodibenzo[b,e]thiepin, its 2-chloro derivative and some related compounds as potential antipsychotic agents; Synthesis and pharmacology
Authors: Bártl Václav , Svátek Emil , Dlabač Antonín , Wildt Stanislav , Protiva Miroslav
Published: February 2011

Substitution reactions of (E)-11-(3-bromopropylidene)-6,11-dihydrodibenzo[b,e]thiepin (VIIIa) and its 2-chloro derivative VIIIb with 1-(2-hydroxyethyl)piperazine gave the title compounds IIIa and IIIb which afforded by treatment with acetic anhydride, decanoyl chloride and 3,4,5-trimethoxybenzoyl chloride the esters IVab-VIab. Reduction of the olefinic compounds IIIa and IIIb with hydrolytic acid resulted in the saturated amines IXa and IXb. The piperazine derivativeX was obtained by a substitution reaction of 2,11-dichloro-6,11-dihydrobenzo[b,e]thiepin with 1-(2-hydroxyethyl)piperazine. The amino alcohols IIIa and IIIb, as well as their acetates and 3,4,5-trimethoxybenzoates, are almost devoid of the CNS effects. The decanates Va and Vb have not the properties of the depot antipsychotics (neither antidepressants, nor neuroleptics). The saturated amino alcohol IXa showed some antihistamine, spasmolytic and adrenolytic effects.
Primary structure of the N-terminal region (1-95) of thermitase, a thermostable proteinase from Thermoactinomyces vulgaris
Authors: Meloun Bedřich , Baudyš Miroslav , Kostka Vladimír , Hausdorf Gert , Höhne Wolfgang Ernst
Published: February 2011

The 95-residue N-terminal amino acid sequence of thermitase, a thermostable serine proteinase from T. vulgaris, is the following: Tyr-Thr-Pro-Asn-Asp-Pro-Tyr-Phe-Ser-Ser-Arg-Gln-Tyr-Gly-Pro-Gln-Lys-Ile-Gln-Ala-Pro-Gln-Ala-Trp-Asp-Ile-Ala-Glu-Gly-Ser-Gly-Ala-Lys-Ile-Ala-Ile-Val-Asp-Thr-Gly-Val-Gln-Ser-Asn-His-Pro-Asp-Leu-Ala-Gly-Lys-Val-Val-Gly-Gly-Trp-Asp-Phe-Val-Asp-Asn-Asp-Ser-Thr-Pro-Gln-Asn-Gly-Asn-Gly-His-Gly-Thr-His-Cys-Ala-Gly-Ile-Ala-Ala-Ala-Val-Thr-Asn-Asn-Ser-Thr-Gly-Ile-Ala-Gly-Thr-Ala-Pro-Lys. The sequential data were obtained by analyses of peptides isolated from the soluble part of the tryptic digest of the N-terminal cyanogen bromide fragment of the enzyme and from the chymotryptic digest of a thermitase fragment obtained by 2-nitro-5-thiocyanobenzoate cleavage of the enzyme at its single cysteine residue.
Photometric determination of 2-oxoglutaric acid and some other 2-oxo acids by reaction with 3-methyl-2-benzothiazolinone hydrazone
Authors: Šafanda Jiří , Sobotka Pavel
Published: February 2011

2-Oxoglutaric acid reacts with 3-methyl-2-benzothiazoline hydrazone in acid solutions in the presence of FeCl3 to give a stady yellow colour. The method enables the substance to be determined in concentrations as low as 15 μmol l-1 with an accuracy of about 10%. The analysis can be performed in the presence of some additional natural or synthetic 2-oxo acids. The applicability of the method was tested in the determination of the activity of some enzymes involved in the metabolism of 2-oxoglutaric acid. Glutamic acid can be determined after its prior nonenzymatic transamination. A number of 2-oxo acids including 2-oxoglutaric acid can be determined photometrically with a high sensitivity by reaction with 3-methyl-2-benzothiazolinone hydrazone in conditions favouring the formation of blue tetra-aza-pentamethinecyanine dyes. The molar absorptivities largely lay within the region of (2-4.5) . 104 l mol-1cm-1.