bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning and molecular characterization of a novel acyl‐CoA:diacylglycerol acyltransferase 1‐like gene (PtDGAT1) from the diatom Phaeodactylum tricornutum
Authors: Guihéneuf Freddy , Leu Stefan , Zarka Aliza , Khozin‐Goldberg Inna , Khalilov Ilkhom , Boussiba Sammy
Published: August 2011

We have identified and isolated a cDNA encoding a novel acyl‐CoA:diacylglycerol acyltransferase (DGAT)1‐like protein, from the diatom microalga Phaeodactylum tricornutum (PtDGAT1). The full‐length cDNA sequences of PtDGAT1 transcripts revealed that two types of mRNA, PtDGAT1short and PtDGAT1long, were transcribed from the single PtDGAT1 gene. PtDGAT1short encodes a 565 amino acid sequence that is homologous to several functionally characterized higher plant DGAT1 proteins, and 55% identical to the putative DGAT1 of the diatom Thalassiosira pseudonana, but shows little homology with other available putative and cloned algal DGAT sequences. PtDGAT1long lacks several catalytic domains, owing to a 63‐bp nucleotide insertion in the mRNA containing a stop codon. Alternative splicing consisting of intron retention appears to regulate the amount of active DGAT1 produced, providing a possible molecular mechanism for increased triacylglycerol (TAG) biosynthesis in P. tricornutum under nitrogen starvation. DGAT mediates the last committed step in TAG biosynthesis, so we investigated the changes in expression levels of the two types of mRNA following nitrogen starvation inducing TAG accumulation. The abundance of both transcripts was markedly increased under nitrogen starvation, but much less so for PtDGAT1short. PtDGAT1 activity of PtDGAT1short was confirmed in a heterologous yeast transformation system by restoring DGAT activity in a Saccharomyces cerevisiae neutral lipid‐deficient quadruple mutant strain (H1246), resulting in lipid body formation. Lipid body formation was only restored upon the expression of PtDGAT1short, and not of PtDGAT1long. The recombinant yeast appeared to display a preference for incorporating saturated C16 and C18 fatty acids into TAG.

Database

Nucleotide sequence data are available in the GenBank/EMBL/DDBJ databases under accession number HQ589265, sequence to be released November 15 2011.
INFLUENCE OF DIFFERENT PROCESSING PARAMETERS ON THE ISOLATION OF LUPIN (LUPINUS ANGUSTIFOLIUS L.) PROTEIN ISOLATES: A PRELIMINARY STUDY
Authors: SUSSMANN DANIELA , PICKARDT CLAUDIA , SCHWEIGGERT UTE , EISNER PETER
Published: August 2011

Protein isolates were prepared from full‐fat flakes of Lupinus angustifolius L. (cv Vitabor) by salt‐induced extraction followed by precipitation with cold demineralized water. Different process parameters were screened to evaluate their significant influences on the extracted or overall protein yields in lab scale. During the extraction, the factors NaCl concentration, pH value and the ratio of flakes to solvent significantly influenced the protein yields, whereas the extraction time can be neglected in a specific range. During precipitation, the salt concentration, the initial protein concentration, the ratio between extract and water, and finally the sedimentation time had significant effect on the overall protein yield. However, the temperature difference between extract and water as well as the order and speed of addition had no considerable impact on the final protein yield. This study gathered important processing parameters for an efficient protein isolation and their suitable ranges for a subsequent optimization.

PRACTICAL APPLICATIONS

In search of viable ways to create more sustainable diets, the application of dietary proteins from plant‐based sources would be an appropriate possibility. Plant proteins, in particular protein isolates, will find an introduction into the world's food system as extenders, supplements and replacements of animal proteins. Currently, the major drawback of protein isolate production is its insufficient economical efficiency including cost‐efficient processing and low recovery yields. Although some important parameters on protein isolation are well established, systematic studies on overall yield including all relevant processing parameters are still scarce. This study identified significant process parameters on the overall protein yield using lupin seed as an example. These findings are a prerequisite for further optimization to obtain plant protein isolates in an efficient and systematic way. This knowledge will facilitate the implementation of plant protein processing on industrial scale and will ensure appropriate amounts of protein isolates with superior quality.
Explained variance for blood gases in a population with COPD
Authors: Saure Eirunn Waatevik , Eagan Tomas Mikal Lind , Jensen Robert Leroy , Voll‐Aanerud Marianne , Aukrust Pål , Bakke Per Sigvald , Hardie Jon Andrew
Published: August 2011

Introduction:  Variation of blood gas levels in chronic obstructive pulmonary disease (COPD) patients has not been extensively reported and there is limited knowledge about predictors of chronic respiratory failure in COPD patients.

Objectives:  The aim of this study was to identify predictors of hypoxemia, hypercapnia and increased alveolar‐arterial oxygen difference in COPD patients. We hypothesized that prediction of arterial blood gases will be improved in multivariate models including measurements of lung function, anthropometry and systemic inflammation.

Methods:  A cross‐sectional sample of 382 Norwegian COPD patients, age 40–76, Global Initiative for Chronic Obstructive Lung Disease stage II–IV, with a smoking history of at least 10 pack‐years, underwent extensive measurements, including medical examination, arterial blood gases, systemic inflammatory markers, spirometry, plethysmography, respiratory impedance and bioelectrical impedance. Possible predictors of arterial oxygen (PaO2), arterial carbon dioxide (PaCO2) and alveolar‐arterial oxygen difference (AaO2) were analyzed with both bivariate and multiple regression methods.

Results:  We found that various lung function measurements were significantly associated with PaO2, PaCO2 and AaO2. In addition, heart rate and Fat Mass Index were predictors of PaO2 and AaO2, while heart failure and current smoking status were associated with PaCO2. The explained variance (R2) in the final multivariate regression models was 0.14–0.20.

Conclusions:  With a wide assortment of possible clinical predictors, we could explain 14–20% of the variation in blood gas measurements in COPD patients.

Please cite this paper as: Saure EW, Eagan TML, Jensen RL, Voll‐Aanerud M, Aukrust P, Bakke PS and Hardie JA. Explained variance for blood gases in a population with COPD. Clin Respir J 2012; 6: 72–80.
Acute Effects of Nicardipine and Esmolol on The Cardiac Cycle, Intracardiac Hemodynamic and Endothelial Shear Stress in Patients With Unstable Angina Pectoris and Moderate Coronary Stenosis: Results From Single Center, Randomized Study
Authors: Chen Shao‐Liang , Hu Zuo‐Ying , Zhang Jun‐Jie , Ye Fei , Kan Jing , Xu Tian , Liu Zhi‐Zhong , Zhang Yao‐Jun , Zhang Jun‐Xia , Chen Mengxuan
Published: August 2011

Objective: This study aimed to compare the acute effects of nicardipine and esmolol on hemodynamic and endothelial shear stress (ESS) in patients with unstable angina (UA) and moderate coronary stenosis (MCS). Background: Nicardipine and esmolol exhibit cardioprotection via different mechanisms. However, their acute effects on hemodynamic and ESS are still unknown. Methods: One‐hundred sixteen patients with UA and MSC were randomly divided into nicardipine (n = 59) and esmolol (n = 57) groups. Drugs were injected as a bolus followed by continuous infusion to achieve the steady states defined as the mean blood pressure (MBP) reduced by ≥10% or a heart‐rate change by ≥15 bpm, lasting for at least 10 min. The aortic pressure (AP), EKG, blood velocity, right atrial pressure, distal coronary pressure (DCP), systolic time (ST), isovolumetric diastolic time (IVDT), speed filling time (SFT), and ESS were simultaneously calculated at baseline and steady states. Results: Both drugs significantly reduced blood pressure and rate‐pressure load. Infusion of nicardipine was associated with negative remodeling of the distal segment (P= 0.005). Esmolol, rather than nicardipine, increased minimal lumen diameter (P= 0.040), prolonged SFT (0.34 ± 0.03 s vs. 0.41 ± 0.03 s, P < 0.001), reduced DCP (P < 0.001) and increased blood velocity (33.65 ± 1.07 cm/s vs. 43.36 ± 1.25 cm/s, P < 0.001) at SFT stages, with increased blood‐flow (P < 0.001). Both drugs increased downstream ESS. Esmolol significantly reversed abnormally increased ESS (P < 0.001) and increased upstream ESS compared with nicardipine (P < 0.001). Conclusion: Beyond a similar reduction of AP, patients with UA and MCS could benefit more from the reduction of heart rate induced by esmolol (ChiCTR‐TRC‐10000964).
Lipopolysaccharide (LPS) Inner-Core Phosphates Are Required for Complete LPS Synthesis and Transport to the Outer Membrane in Pseudomonas aeruginosa PAO1
Authors: DeLucia Angela M. , Six David A. , Caughlan Ruth E. , Gee Patricia , Hunt Ian , Lam Joseph S. , Dean Charles R.
Published: August 2011

Gram-negative outer membrane (OM) integrity is maintained in part by Mg
2+
cross-links between phosphates on lipid A and on core sugars of adjacent lipopolysaccharide (LPS) molecules. In contrast to other Gram-negative bacteria,
waaP
, encoding an inner-core kinase, could not be inactivated in
Pseudomonas aeruginosa
. To examine this further, expression of the kinases WaaP or WapP/WapQ
/
PA5006 was placed under the control of the arabinose-regulated pBAD promoter. Growth of these strains was arabinose dependent, confirming that core phosphorylation is essential in
P. aeruginosa
. Transmission electron micrographs of kinase-depleted cells revealed marked invaginations of the inner membrane. SDS-PAGE of total LPS from WaaP-depleted cells showed accumulation of a fast-migrating band. Mass spectrometry (MS) analysis revealed that LPS from these cells exhibits a unique truncated core consisting of two 3-deoxy-
d
-manno-octulosonic acids (Kdo), two
l
-glycero-
d
-manno-heptoses (Hep), and one hexose but completely devoid of phosphates, indicating that phosphorylation by WaaP is necessary for subsequent core phosphorylations. MS analysis of lipid A from WaaP-depleted cells revealed extensive 4-amino-4-deoxy-
l
-arabinose modification. OM prepared from these cells by Sarkosyl extraction of total membranes or by sucrose density gradient centrifugation lacked truncated LPS. Instead, truncated LPS was detected in the inner membrane fractions, consistent with impaired transport/assembly of this species into the OM.

IMPORTANCE
Gram-negative bacteria have an outer membrane (OM) comprised of a phospholipid inner leaflet and a lipopolysaccharide (LPS) outer leaflet. The OM protects cells from toxic molecules and is important for survival during infection. The LPS core kinase gene
waaP
can be deleted in several Gram-negative bacteria but not in
Pseudomonas aeruginosa
. We used a controlled-expression system to deplete WaaP directly in
P. aeruginosa
cells, which halted growth. WaaP depletion also caused gross changes in cell morphology and led to the accumulation of an aberrant LPS lacking several core sugars and all core phosphates. The aberrant LPS failed to reach the OM, suggesting that WaaP is essential in
P. aeruginosa
because it is required to produce the full-length LPS that is recognized by the OM transport/assembly machinery in this organism. Therefore, WaaP may constitute a good target for the development of novel antipseudomonal agents.
Dipole moments induced in larger molecule. Long-chain aliphatic esters
Authors: Exner Otto , Bapçum Ayfer
Published: August 2011

Dipole moments of straight-chain aliphatic esters Ia-Ic and IIa-IIf were measured in benzene solution. The observed trends are poorly reproduced by the classical Smith-Eyring theory; the reason may be partly the unknown conformation, partly even donor-acceptor complexes with the solvent. No deviations were observed with the highest members of the series, attributable to violation of some basic assumptions of the theory of dielectrics.
Synthesis and properties of benzoannelated 6-(1,3-dithiolan-2-yliden)-2,4-cyclohexadien-1-ones
Authors: Koutek Bohumír , Pavlíčková Libuše , Buděšínský Miloš , Souček Milan
Published: August 2011

A general route to push-pull stabilized quinone methides starting from the corresponding phenols and proceeding viaalkylation of aromatic hydroxy dithiocarboxylates has been used to synthesize the 1-oxo-2-(1,3-dithiolan-2-yliden)-1,2-dihydronaphthalene (V) and 9-oxo-10-(1,3-dithiolan-2-ylide)-9,10-dihydrophenanthrene (VI). In the case of α-naphthole, the reaction leads to a mixture of isomers with little preference shown for para vs ortho. The structures of the compounds are elucidated by their 1H-NMR spectra.
Antidepressant fluorinated prothiadene derivatives: 9-Fluoro and 2,9-difluoro derivative of 11-(3-dimethylaminopropylidene)-6,11-dihydrodibenzo[b,e]thiepin
Authors: Rajšner Miroslav , Svátek Emil , Metyš Jan , Protiva Miroslav
Published: August 2011

6-Fluorophthalide (IV), obtained from 6-aminophthalide by the Schiemann method, was transformed by reactions with potassium salts of thiophenol and 4-fluorothiophenol and 4-fluorothiophenol to the acid V and VI. Cyclization with polyphosphoric acid gave 9-fluoro- and 2,9-difluorodibenzo[b,e] thiepin-11(6H)-one (VII, VIII) which were treated with 3-dimethylaminopropylmagnesium chloride and afforded the tertiary alcohols IX and X. Dehydration by heating with dilute hydrochloric acid resulted in the title compounds II and III whose IR spectra indicated the E-configuration. Both compounds showed properties of tricyclic antidepressants being, however, less active than prothiadene (I) in the tests for the antireserpine activity.
Mechanism of acid cleavage of some steroid epoxides. Competition between neighboring group participation and external nucleophile attack
Authors: Kočovský Pavel , Tureček František , Černý Václav
Published: August 2011

The mechanism of perchloric acid cleavage of epoxides I and II was established on the basis of experiments using H2 18O. The 2α,3α-epoxide I gave two products: the cyclic ether V (60%) arising by 5(O)n participation of the 19-acetoxyl and the diol VI (40%). The latter compound is formed by two mechanisms: 1) By direct cleavage of the oxirane ring with H2 18O as external nucleophile and 2) by 7(O)π,n participation via the ion III. Under the same conditions the 5α,6α-epoxide II yielded two diols: The diequatorial diol VIII (96%) arising by 6(O)π,n participation and the diaxial diol IX which is again formed by both direct cleavage of the oxirane ring with H2 18O and by 7(O)π,n participation via the intermediate ion X. The competition of several mechanisms is discussed.
[9-Aminoacetone]oxytocin and [8-p-aminobenzamide, 9-des-glycinamide]oxytocin: Chemical synthesis and properties
Authors: Hlaváček Jan , Frič Ivo , Barth Tomislav , Jošt Karel
Published: August 2011

[9-Aminoacetone]oxytocin and [8-p-aminobenzamide, 9-des-glycinamide]oxytocin were prepared by condensation of amino-terminal linear hexapeptide with peptides simulating the carboxy-terminal tripeptide chain of oxytocin, according to the 6 + 3 scheme. Both the analogues had significantly lower biological activities than oxytocin. CD spectra of the analogues were compared with those of oxytocin and [9-des-glycine]oxytocin in order to study the effect of structural changes in the carboxy-terminal part of the analogues on the conformation of their cyclic part.
Glutamate kinases from winter-wheat leaves and some properties of the proline-inhibitable glutamate kinase
Authors: Vašáková Ludmila , Štefl Miroslav
Published: August 2011

Three glutamate kinases (GK 1, GK 2 and GK 3) have been found in the leaves of winter wheat (Triticum aestivum L). They were separated by salting out with ammonium sulphate and by chromatography on DEAE-cellulose in a concentration gradient of KCl and on Sephadex G-100. GK 1 belongs to the biosynthesis of L-proline, which inhibits it according to the principle of feedback, GK 2 to the biosynthesis of glutamine; the function of GK 3 has not been found. The partically purified oligomer GK 1 had a molecular weight of 254 000 and dissociated to subunits of molecular weights 84 000 and 42 000. In a K+-phosphate buffer, 50 mmol/l, it was active in a pH range of 6.3 to 8.0, with an optimum of 7.2. An amine buffer inhibited it completely. The reaction required Mg2+ ions as activators and L-glutamate and ATP as substrates. ATP in a concentration above 70 mmol/l inhibited it. The steady-state kinetics at the optimum pH have shown that GK 1 produces a complex co-operativity of the substrates and belongs to the slowly dissociating hysteretic enzymes of the type Np P.
Oxidation of (1-hydroxyethyl)ferrocene with bis(triphenylsilyl) chromate
Authors: Holeček Jaroslav , Handlíř Karel , Nádvorník Milan
Published: August 2011

Stoichiometry and kinetics have been studied of the oxidation of (1-hydroxyethyl)ferrocene with bis(triphenylsilyl) chromate in benzene solutions at 20-45°C. The two compounds react at a molar ratio 1 : 1 to give acetylferrocene, a compound of Cr(IV) and mixture of triphenylsilanol with hexaphenyldisiloxane. A reaction mechanism is suggested and discussed.
Study of a new type of active carbon CF-1 as an adsorbent in gas chromatography
Authors: Feltl Ladislav , Hronková Jana , Smolková Eva
Published: August 2011

A new type of active carbon, CF-1, was used as the stationary phase in gas chromatography. The adsorption of n-alkanes C2-C5, 1-alkenes C2-C4, acetylene, alcohols, ethyl ethers, CO2, H2S and SO2 was studied. The measurements were carried out with the original adsorbent and after its reduction with hydrogen at a temperature of 1 000°C. The original and pretreated active carbon were evaluated on the basis of the determined retention data and calculated value of the differential heats of adsorption.
Kinetics of the anionic coordination dimerization of isoprene
Authors: Bartoň Jan , Kašpar Miroslav , Růžička Vlastimil
Published: August 2011

The kinetics of the anionic coordination dimerization of isoprene (i.e., 2-methyl-1,3-butadiene) to β-myrcene (i.e., 7-methyl-3-methylene-1,6-octadiene) was investigated. The reaction was initiated with sodium in the presence of dicyclohexyl amine in tetrahydrofuran. Kinetic measurements showed that ionic pairs of isoprenyl sodium were additionally solvated by two molecules of tetrahydrofuran. A kinetic model of the reaction enabled the time dependence of the isoprene concentration to be expressed in terms of a two-parameter equation.
Synthesis of several 1-(aminoacyl)-4-cinnamylpiperazines as potential analgetics
Authors: Protiva Miroslav , Kopicová Zdeňka , Grimová Jaroslava
Published: August 2011

A reaction of 1-cinnamylpiperazine (III) with chloroacetyl gave the chloroacetyl derivative IV which was subjected to substitution reactions with aniline, 4-phenylpiperidin-4-ol (XIa),4-(4-fluorophenyl)piperidin-4-ol (XIb) and 4-(4-chloro-3-trifluoromethyl)piperidin-4-ol and afforded the title compounds V and VII-IX. Acylation reactions of compounds V and VII with propionyl chloride gave the propionanilide derivative VI and the 4-phenyl-4-propanoyloxypiperidine derivative X. With the exception of compound VIII, the new substances are analgetically less active than 1-butyryl-4-cinnamylpiperazine (I) and as antiinflammatory agents they are little active or inactive.
The structure of yatein. Determination of the positions, and configurations of benzyl groups in lignans of the 2,3-dibenzylbutyrolactone type
Authors: Harmatha Juraj , Buděšínský Miloš , Trka Antonín
Published: August 2011

The structure of yatein isolated from Libocedrus yateensis has been determined as (2R, 3R)-2-(3,4,5-trimethoxybenzyl)3-(3,4-methylenedioxybenzyl)butyrolactone (Ia). The assignment of individual signals of the 1H NMR spectrum of yatein and further lignans of the 2,3-dibenzyl-butyrolactone type is discussed and supported by the use of a lanthanide shift reagent and by mass spectrometry of deuterated derivatives IIa, IIb. A method of determination of absolute configuration of the centres C(2) and C(3) of these 2,3-dibenzylbutyrolactone lignans on the basis of a combination of information obtained from 1H NMR spectra and optical rotation is proposed. The erroneous interpretation of the ORD and CD spectra used in some instances for the determination of absolute configuration of these substances, as well as the often repeated error in the assignment of benzyl and C(2)-H, C(3)-H protons in 1H NMR spectra of trans-lignans is also discussed. A complete analysis of the 1H NMR spectra permitted the proposition of the preferred conformation for trans and cis isomer Ia and Ib.
Absolute configuration of xerantholide, a sesquiterpenic lactone from Anthemis austriaca JACQ.
Authors: Holub Miroslav , Buděšínský Miloš , Samek Zdeněk , Drożdż Bohdan , Grabarczyk Halina , Ulubelen Ayhan , Öksüz Sevil , Rychłewska Urszula
Published: August 2011

The isolation of the sequiterpenic lactone xerantholide (I) from Anthemis austriaca JACQ. of Polish and Turkish origin is described and its structure confirmed. Absolute configuration is also derived.
Synthesis of methyl 3-(N'-alkylureido)-2-methyl-2-propenoates and their cyclization to 3-alkyl-5-methyluracils
Authors: Ledvina Miroslav , Farkaš Jiří
Published: August 2011

Stereoisomeric methyl 3-(N' -alkylureido)-2-methyl-2-propenoates (Ia-Id) were prepared by acid-catalyzed reaction of N-alkylureas (R = methyl, benzyl, isopropyl and tert-butyl) with methyl 3-methoxy-2-methyl-2-propenoate (III). Reaction of the ester III with N-tert-butyl-thiourea afforded the thioureides (E)-Ie and (Z)-Ie. On treatment with sodium methoxide in methanol, compounds Ia-Ic cyclized to the corresponding 3-alkyl-5-methyluracils IIa-IIc whereas compounds Id and Ie underwent only a base-catalyzed E/Z isomerization with (E)-isomers predominating.
First reaction steps and intermediates of the oxidation of ascorbic acid by dioxygen. Catalysis by cobalt(II) tetrasulphophthalocyanine
Authors: Wagnerová Dana M. , Blanck Jürgen , Vepřek-Šiška Josef
Published: August 2011

The oxidation of ascorbic acid by dioxygen catalyzed by cobalt(II) tetrasulphophthalocyanine (CoTSP) has been studied by the stopped-flow method. Two reactive intermediates, [O2.CoTSP. ascorbic acid] and [O2.CoTSP], characterized by separate absorption bands at 570 nm and 634 nm, respectively, have been proved to form in the reaction. The individual steps of the reaction have been elucidated, and their rate constants have been determined or estimated.
Simultaneous heat and mass transfer during evaporation from a film of liquid into the turbulent gas
Authors: Kolář Václav , Červenka Jan
Published: August 2011

The paper presents results obtained by processing a series of published experimental data on heat and mass transfer during evaporation of pure liquids from the free board of a liquid film into the turbulent gas phone. The data has been processed on the basis of the earlier theory of mechanism of heat and mass transfer. In spite of the fact that this process exhibits a strong Stefan's flow, the results indicate that with a proper definition of the driving forces the agreement between theory and experiment is very good.
The effect of substitution on the reactivity of the monomer in the copolymerization of styrene with 2,3-unsatured aldehydes and ketones
Authors: Seyček Otakar , Bednář Bohumil , Houska Milan , Kálal Jaroslav
Published: August 2011

The monomer reactivity ratios of the copolymerization of styrene with propenal, 2-methylpropenal, 2-ethylpropenal, methylvinyl ketone and methylisopropenyl ketone were determined and their reliability was checked. For copolymerization conducted to low conversions, a simple procedure was proposed in order to rule out the effect of the conversion heterogeneity of copolymers on the determination of r1, r2 by calculation using a differential copolymerization equation. When comparing aldehydes and ketones with reference monomers having a similar skeleton of the molecule, the effect of substitution on the monomer reactivity in the copolymerization was examined, and a new correlation, e~σn, was suggested, interpreting the influence of polar effects of substituents on the monomer reactivity. It was proved that the copolymerization kinetics of 2-ethylpropenal is affected by the steric hindrance from the part of the too bulky substituent.
29Si, 13C and 31P NMR spectra of silicon-substituted ω-diphenylphosphinoalkyl silanes, (CH3)3-n(OC2H5)nSi(CH2)mP(C6H5)2
Authors: Schraml Jan , Čapka Martin , Jancke Harald
Published: August 2011

29Si, 13C, and 31P NMR spectra of a series of compounds of the structure (CH3)3-n(C2H5O)n.Si(CH2)mP(C6H5)2 (m = 1-6, n = )-3) are reported and assigned. Using monodeutero derivative of the compound with m = 3 and n = 0 an earlier assignment of 13C NMR spectrum is confirmed, but the assignment in the compounds with m = 4 is reversed. Introduction of ethoxy groups leads to violation of additivity rule for the 13C chemical shifts in the derivatives with m = 1. In all derivatives presence of one ethoxy group in the molecule has a profound effect on 31P chemical shift which is not changed by any further increase in the number of ethoxy groups in the molecule. The changes in 29Si chemical shifts follow the pattern known from other series of compounds. The observed trends in NMR parameters with changing n and m values can be explained by an interaction between phosphorus and oxygen atoms. Possible connections between the spectral parameters and catalysis employing the studied compounds are discussed.
Thermal desorption: Chemisorption of carbon monoxide on polycrystalline tungsten
Authors: Hrbek Jan , Pavlíček Jan
Published: August 2011

The adsorption isotherm was constructed from thermal desorption spectra of carbon monoxide on tungsten. Comparison of the experimental results with model isotherms supports a concept of the dissociative adsorption of carbon monoxide on tungsten.
Formation of sulfur compounds in the hydrodenitrogenation of piperidine, pyridine, 1-pentylamine and 1-pent-4-enylamine on a nickel-tungsten catalyst in the presence of hydrogen sulfide
Authors: Černý Mirko
Published: August 2011

Hydrogenations of piperidine, pyridine, 1-pentylamine, and 1-pent-4-enylamine were carried out in an autoclave at 300°C on a sulfidized nickel-tungsten catalyst using either pure hydrogen or a mixture of hydrogen with hydrogen sulfide. Hydrogen sulfide was found to raise the degree of conversion of the starting substances and accelerate the hydrodenitrogenation by formation of sulfur compounds; 1-pentanethiol, di(1-pentyl)sulfide, 2-methylthiacyclopentane, thiacyclohexane and other sulfur compounds were detected in the reaction mixtures in the presence of hydrogensulfide. A reaction pathway is suggested of the hydrodenitrogenation of piperidine in the presence of hydrogen sulfide, accounting for the favourable effect of the latter on the hydrodenitrogenation of nitrogen compounds.
Synthesis and absolute configuration of 1,7-diazaspiro[4,4]nonane-2,6-dione
Authors: Majer Zsuzsanna , Kajtár Márton , Tichý Miloš , Bláha Karel
Published: August 2011

Synthesis and determination of absolute configuration of the title compound are described and its CD spectrum is presented.
Biosynthesis of mucidin, an antifungal antibiotic from basidiomycete Oudemansiella mucida 2H-, 13C-, and 14C-labelling study
Authors: Nerud František , Sedmera Petr , Zouchová Zdeňka , Musílek Vladimír , Vondráček Miloslav
Published: August 2011

Incorporation of 2H-, 13C- and 14C-labelled precursors into mucidin (I) was studied by mass and 13C NMR spectroscopy and chemical degradations. Biosynthesis of I is connected with shiki-mate and acetate-malonate pathways. Methionine participates on the C- and O-methylation.
The stability constants of ethylenediphosphinetetraacetate complexes
Authors: Podlahová Jana , Podlaha Jaroslav
Published: August 2011

The stability constants of complexes formed by the anions of ethylenediphosphinetetraacetic acid and the metal ions Cu(I), Ag(I), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II) and La(III) were determined by various methods (mainly potentiometry and UV-VIS spectrophotometry), followed by data treatment using standard computer programs. The type and stability of the complexes formed depend mostly on the relative affinity of the particular metal ion for the two donor groups of the ligand. Unlike EDTA, the ligand is highly selective for soft metal ions, whose complexes are very stable even in strongly acidic aqueous solutions.
Carbon-13 and nitrogen-15 NMR spectra of cis- and trans-azobenzene, 4-monosubstituted and 4,4'-disubstituted trans-azobenzenes
Authors: Lyčka Antonín
Published: August 2011

13C and 15N NMR spectra of cis- and trans-azobenzene, 4-substituted trans-azobenzenes (N(CH3)2; NH2; OH; OCH3; CH3; Br; NO2) and 4,4'-disubstituted trans-azobenzenes (OH; NO2; NH2; OH; N(CH3)2, CH3; N(CH3)2, NO2) were measured. In comparison with trans-azobenzene, cis-azobenzene exhibits a downfield shift of nitrogen and C(1) signals and an upfield one of the C(2) and C(4) signals. The individual coupling constants nJ(15N13C) in 4-substituted and 4,4'-disubstituted trans-azobenzenes, respectively, have characteristic values and can be used for carbon signal assignment. With 4-substituted trans-azobenzenes, the 15N substitution chemical shifts of the nitrogen of the azo-bond were determined and their additivity in series of 4,4'-disubstituted trans-azobenzenes was proved.
The metastable zone width of ammonium aluminium sulphate and mechanisms of secondary nucleation
Authors: Nývlt Jaroslav
Published: August 2011

The metastable zone width of aqueous solution of ammonium aluminium sulphate was measured as a function of the cooling rate. The measurements were carried out a) in the absence of seed crystal, b) with one seed crystal at a fixed position in the flowing solution, and c) with one seed crystal moving freely on the bottom of the measuring vessel. The results obtained distinctly differ for the three measurements, providing evidence that primary nucleation took place in the first case, secondary nucleation induced by the surface-layer mechanism combined with fluid shear occurred in the second case, and the contact mechanism of secondary nucleation operated in the third case.
Scale-up of agitated crystallizers; Cooling batch crystallization of potassium aluminium sulphate
Authors: Nývlt Jaroslav , Karpiński Piotr , Žáček Stanislav , Karel Miloslav , Budz Jerzy , Naruć Zbigniew
Published: August 2011

The crystallization of potassium aluminium sulphate was conducted by cooling a solution saturated at 70°C to a temperature of 25°C at three various cooling rates. The measurements were performed on a small scale (160 cm3) and a large laboratory scale (0.021 m3). The mean size of product crystals was determined by sieve analysis, and the system constant, BN, was calculated using previously derived relations. The BN value is the same, within experimental error, for all the experiments and scales, indicating that agitated-vessel cooling crystallizers can be modelled successfully even on a very small laboratory scale.
2-Formyl derivatives of 6-methylergoline-I
Authors: Beneš Jan , Semonský Miroslav
Published: August 2011

Reaction of ergoline derivatives I, III - VI with 2-alkoxy-1,3-dithiolan, generated in situ, gave the 2-(1,3-dithiolan-2-yl) derivatives VII, XI - XIV.Hydrolysis of the thioacetal group in these compounds produced 2-formylergoline derivatives, XV-XIX, which proved to have only a weak inhibitory effect on the secretion of prolactin.
Quantum chemical study of physical characteristics of Co- and Ni-faujasites
Authors: Beran Stanislav
Published: August 2011

The CNDO/2 method was used for a physico-chemical characterization of faujasite zeolites, modelled by T6O6(OH)12 clusters containing Ni+, Ni2+, Ni(OH)+, Co2+, Co3+, Co(OH)+ cations localized in the SII and SI' cationic positions. It is shown that the cations are bound preferentially to the oxygen atoms of the zeolite skeleton by a strong electron donor-acceptor bond. As the consequence of the bond formation, the electron charge is significantly shifted from a skeleton to the cation. The charge densities calculated on the cations (Ni+ ~ 0.3, Ni2+ ~ 0.35, Co2+ ~ 0.4, Co3+ ~ 1.1 respectively) show that with uni- and bivalent cations the positive charge is in main part compensated by donation of electrons from the skeleton, while with trivalent cations the compensation is only partial. The Ni+ cation possesses significant electron donor properties whereas the Co3+ cation has a strong electron acceptor character. For both cations bivalency appears to be the most stable valent state. Both studied cations show great affinity to hydratation, however, their corresponding hydroxyl adducts - the Ni(OH)+ and Co(OH)+ cations exhibit substantially less acid properties, compared with the hydroxyl groups of the skeleton.
Possible application of approximate models for calculation of selectivity of consecutive reactions under the effect of mass transfer
Authors: Kaštánek František , Fialová Marie
Published: August 2011

The possibility of use of approximate models for calculation of selectivity of consecutive reactions is critically analysed. Simple empirical criteria are proposed which enable safer application of approximate analytical reactions. A more universal modification has been formulated by use of which the difference of selectivity calculated by the exact numerical method and by the approximate analytical method is at maximum 12%.
The dissociation constants of eriochromcyanine R and bromopyrogallol red in the presence of carbethoxypentadecyltrimethylammonium bromide (Septonex)
Authors: Škarydová Vlasta , Čermáková Ludmila
Published: August 2011

The values of the mixed dissociation constants pKa of triphenylmethane dyes (eriochromcyanine R and bromopyrogallol red) in dependence on the concentration of cation-active tenside (1-carbethoxypentadecyltrimethylammonium bromide - Septonex) were found from spectrophotometric data and the effect of formation of micelle tenside aggregates was evaluated.
Unsaturated analogues of 1-triacontanol
Authors: Kocián Oldřich , Stránský Karel , Závada Jiří
Published: August 2011

A simple regio- and stereoselective synthesis of unsaturated analogues of the plant growth stimulator 1-triacontanol from ω-alkyn-1-ols is reported. Starting from the easily accessible 10-undecyn-1-ol, eight n-C30 alcohols containing -C ≡ C-, (E) -C=C- or (Z) -C=C- group in the position 21 and/or 10 have been prepared. Spectral and gas-chromatographic properties (Kováts retention indices) of the novel compounds are described.
On definition of electronegativity within the framework of MO methods
Authors: Ponec Robert
Published: August 2011

The possibility of generalization of the electronegativity concept to valence states of atom in molecule has been studied by semiempirical CNDO and INDO approximations. It is shown that the concept of electronegativity as the property of a given atom in molecule can be defined only on the basis of the simplest CNDO approximation.
Substituent effects in 1,3-indanediones
Authors: Perjéssy Alexander
Published: August 2011

The carbonyl stretching frequencies correlate well with substituent constants in a series of 166 1,3-indanediones using improved and extended Seth-Paul-Van Duyse equation. Transmissive factors and group electronegativities have been used to find empirical equations for calculation of substituent constants of more complex structural fragments.
Oxidation of polysubstituted pyridinium salts
Authors: Nesvadba Petr , Kuthan Josef
Published: August 2011

Oxidation of 1-substituted 2,4,6-triphenylpyridinium salts Ia-Ij with potassium ferricyanide in an alkaline medium was accompanied by contraction of the pyridine ring and formation of 1,2,3,5-tetrasubstituted pyrroles II. The derivative IIf underwent facile electrophilic substitution in the position 4. Contrary to compounds Ia-Ij, the 1-substituted-2,6-diphenylpyridinium salts IIIa,b were oxidized to give a complex reaction mixture containing 4-pyridones IVa,b.
Synthesis of two isomeric 16,17-cyclopropano derivatives of 5-pregnene
Authors: Kohout Ladislav , Šanda Vlastimil , Fajkoš Jan
Published: August 2011

Simmons-Smith methylenation of the epimeric 5,16-pregnadien-3β,20-diols, as well as some reactions of these compounds carrying the cyclopropane ring in position 16,17 have been studied.
Acid-base equilibria of some 7-dimethylamino-3-phenoxazone derivatives
Authors: Dostál Vladimír , Kotouček Milan , Kalašová Hana , Bryndová Vladimíra , Šimek Jiří
Published: August 2011

The acid-base equilibria of some phenoxazine dyes in aqueous-ethanolic solutions were studied spectrophotometrically. The compounds examined were prepared in reagent grade purity, their main spectral characteristics in UV and VIS reagion were found and their dissociation constants were determined in 41% (m/m) ethanol. For the analytically most interesting derivative, gallocyanine methyl ester (IV), the pK values were measured also in solutions with different proportions of ethanol. The colour changes accompanying the protolytic reactions and the factors governing the phenomena are discussed.
Study of the photosenzitive surface compounds
Authors: Gorochovskii V. M.
Published: August 2011

Abstract in Russian
Chemiluminescence determination of chromium(VI), molybdenum(VI), and vanadium(V) with bis-(2,4,6-trichlorophenyl) oxalate and perylene
Authors: Holzbecher Záviš , Kábrt Lubomír , Janšta Lubomír
Published: August 2011

The effect of the experimental conditions (pH, ionic strength, hydrogen peroxide concentration) and of various metal salts on the chemiluminescence occurring during oxidation of bis-(2,4,6-trichlorophenyl) oxalate (TCPO) with hydrogen peroxide in the presence of perylene was studied in water-methyl acetate solutions. The spectrum of the emitted radiation was found practically identical with the fluorescence spectrum of perylene. The observed catalytic effect of Cr(IV), Mo(VI), and V(V) on the chemiluminescence reaction in question can be explained so that these elements form peroxo acids with hydrogen peroxide, thereby facilitating the oxygen transfer from the latter to TCPO. Based on this phenomenon, a method is suggested for the determination of the above elements in concentrations about 10-3 to 10-4 mol l-1; its precision, represented by the relative standard deviation, is about 3-4%, the limits of determination of Cr(VI), Mo(VI), and V(V) are approximately 5-10 μg.
Cross-reactivity of anti-oxytocin sera
Authors: Slaninová Jiřina , Robinson Iain C. A. F. , Hrbas Pavel , Barth Tomislav
Published: August 2011

Two anti-oxytocin sera, raised using thyroglobulin-oxytocin conjugates as immunogens in a rabbit and a pig, have been compared. Differences in assay conditions gave rise to large differences in the apparent titre of the antisera, and altered the specificity of the resulting assays.
Electrochemical behaviour of molybdenum-nitrosyl complexes of the type Mo(NO)2Cl2L2 and Mo(NO)Cl3L2
Authors: Mašek Jiří , Fiedler Jan , Klíma Jiří , Seyferth Karl , Taube Rudolph
Published: August 2011

Electrochemical behaviour of 22 molybdenum-nitrosyl complexes of the title types serving as catalyst precursors of olefin metathesis reactions was investigated and the odd-electron localization in the 1-electron reduction products was determined by ESR spectroscopy. It was found that the mononitrosyl complexes containing the fragment {Mo(NO)}4 are reduced in a potential region more positive and distinctly separated from that of the dinitrosyl complexes containing the fragment {Mo(NO)2}6. In the reduction of the former complexes the electrons are accepted into a MO having prevailingly metal d-character while with the latter class of complexes the electrons accepted in the reduction are accommodated in a π-NO based MO. The comparison of the electrochemical results with the catalytic activity of the corresponding systems shows that the ability of the precursor complexes to form the catalytically active species depends on their substitution lability rather than on their redox properties.
Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst
Authors: Kudláček Rostislav , Lokoč Jan
Published: August 2011

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.
Gas chromatographic analysis of metabolites of trees damaged by exhalations
Authors: Kusý Vladimír , Kusý Jaroslav
Published: August 2011

The composition of volatile organic compounds expired by the plant was investigated in dependence on the environment. Using two-step adsorption-concentration, hydrocarbons were preseparated from oxygen-containing compounds present in metabolites. In addition to gaseous samples water excreted by the plant was also analysed for the content of volatile organic compounds. Using gas chromatography differences were found in the content of unsaturated hydrocarbons, aldehydes and other substances in the metabolites of sick and healthy trees. The greatest differences in the composition of metabolites in dependence on the environment were found in Norway spruce (Picea excelsa), and the lowest for birch (Betula verrucosa).
Photochemical reactions of substituted 2(3H)-oxazolones with carbonyl compounds
Authors: Sekretár Stanislav , Kopecký Jan , Martvoň Augustin
Published: August 2011

Photocycloaddition of carbonyl compounds of various triplet energy to 3-acetyl-2(3H)-oxazolone (V) and 3-acetyl-4,5-dimethyl-2(3H)-oxazolone (VI) afforded oxetanes XIII-XX. Other investigated 2(3H)-oxazolones VII-IX gave no oxetanes. The photoreactivity of 2(3H)-oxazolones and the regioselectivity of the photocycloaddition were correlated with the HMO reactivity indices.
Synthesis and conformational investigation of β-turn forming tetra- and hexapeptides
Authors: Rahman A. N. Abdel , Rahman S. Abdel
Published: August 2011

Tetra- and hexapeptides containing Pro-Gly or Gly-Pro or Aib-Pro in their sequences were synthesized using the liquid-phase method. The high solubility of the poly(ethylene glycol) bound peptides in water and in organic solvents enables the application of the singlet-singlet energy transfer method for conformational investigation of these peptides. The conformational study in solid state by IR and in solution by CD were carried out in parallel to the energy transfer method. The qualitative results generated by IR and CD were found to be in good agreement with the quantitative end-to-end distances given by the energy transfer method.
Quantum-chemical study of energy surface and the minimum-energy reaction path of the proton transfer along O-H...N hydrogen bond in acetic acid-imidazole x 2 H2O system
Authors: Remko Milan
Published: August 2011

The semi-empirical quantum-chemical PCILO method has been used for calculation of the energy surface of the proton transfer along the O-H...N hydrogen bond in acetic acid-imidazole . 2 H2O system. The PCILO calculations gave the energy surface with two minima. The most stable minimum corresponds to the O-H...N hydrogen bond and has been found at the distances RH...N = 0.149 nm and RO...N = 0.107 nm. According to the PCILO calculations the proton transfer is accompanied by significant changes in the O...N distance. The second energy minimum corresponding to the proton transfer O-...NH+ complex has been found at RH...N = 0.10 nm and RO...N = 0.30 nm. The approximative minimum energy reaction path for the proton transfer has been calculated by the procedure developed by Muller and Brown. The calculated energy barrier represents a value 376.15 kJ/mol. The second energy minimum lies higher by 246 kJ/mol.
Spectrophotometric determination of uranium(VI) by extraction of its thiocyanate anion with cationogenic tensides
Authors: Blažys Irvis , Malát Miroslav
Published: August 2011

The method is described of a spectrophotometric determination of U(VI) based on the extraction of its complex thiocyanate anion with a chloroform solution of 1-ethoxycarbonylpentadecyltrimethylammonium. The method is rapid and affords reliable results; 0.2 to 5 μg of uranium can be determined in 1 ml of organic phase. Combination with a preliminary separation treatment is feasible.
Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent
Authors: Karhan Jiří , Ksandr Zbyněk , Vlková Jiřina , Špatná Věra
Published: August 2011

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.
Kinetics of ammonia oxidation on cobalt catalyst II application of tubular reactor with catalytically active wall
Authors: Bernauer Bohumil , Šimeček Antonín , Vosolsobě Jan
Published: August 2011

The kinetics of ammonia oxidation on cobalt catalyst is described on basis of experimental data measured in the tubular reactor with catalytically active wall. In the temperature range up to 623 K, where the products of ammonia oxidation are nitrogen monoxide and elementary nitrogen, it is possible to describe the rate of formation of these components by empirical equations (5) and (6), at the temperature above 900 K, where the products are nitrogen dioxide and elementary nitrogen, by equations (7) and (8).
Some 1-β-D-ribofuranosyl-5-phenylcytosines and -5-(2-chlorophenyl)-2-thiocytosine
Authors: Buděšínský Zdeněk , Šmejkal František , Buděšínský Miloš
Published: August 2011

5-Phenylcytidine (XI), 5-(4-nitrophenyl)cytidine (XII) and 5-(2-chlorophenyl)-2-thiocytidine (XIII) were prepared from corresponding trimethylsilyl derivatives V-VII. Nitro derivative XII was converted to amino derivative XIV by catalytic reduction. Cytidines XI-XIV and the starting cytosines I-IV do not display any in vitro inhibitory effect against the influenza virus AWS, virus NDV, vaccinia, herpes simplex and WEE, or in vivo effect on mice infected with the herpes simplex virus type 2 (HSV-2) either.
3'-O-Formyl-(N-acyl)-2'-deoxyribonucleosides as building units in the synthesis of oligodeoxyribonucleotides
Authors: Smrt Jiří
Published: August 2011

5'-O-Dimethoxytrityl-(N-acyl)-2'-deoxyribonucleosides afford 3'-O-formyl-(N-acyl)-2'-deoxyribonucleosides Ia-Id by the action of formic acetic anhydride followed by the action of 80% aqueous acetic acid. The formyl group is removed from Ia-Id by treatment with 1 mol l-1 triethylamine 3'-O-Formyl-2'-deoxythymidine (Ia) gives 3'-O-dimethoxytrityl-2'-deoxythymidine (V) by subsequent treatment with acetic anhydride, triethylamine, dimethoxytrityl chloride and methanolic ammonia. The use of compounds I for the synthesis of d-GGAGG (XIX) and d-T16 (XXXII) is described. Systems for thin-layer chromatography of 5'-O-dimethyltrityl-oligodeoxyribonucleotides on silica gel are described.