bluuebunny/crossref_metadata_2025 huggingface dataset:
Target RNA–Directed Trimming and Tailing of Small Silencing RNAs
Authors: Ameres Stefan L. , Horwich Michael D. , Hung Jui-Hung , Xu Jia , Ghildiyal Megha , Weng Zhiping , Zamore Phillip D.
Published: June 2010

Close, But Not Too Close

MicroRNAs (miRNAs) in plants are generally highly complementary to their target RNAs, yet, in most animal miRNAs, only the ∼8-nucleotide “seeds” sequence bases pair fully with the target, with few base pairs between the remainder of the miRNA and target. Plant miRNAs are methylated at their 3′ ends, whereas animals' miRNAs are not.

Ameres
et al.

(p.
1534
; see the Perspective by

Pasquinelli

) noticed that, in fruit flies, miRNAs engineered to have high complementarity to target RNAs were present at reduced levels. These miRNAs were trimmed and uridylated at their 3′ ends, features involved in RNA degradation. Fly small interfering RNAs, all of which are methylated at their 3′ ends, were unaffected, unless the methylating enzyme, Hen1, was mutated. Thus, 3′-methylation may prevent complementarity-driven remodeling and degradation of small RNAs.
The Great Indo-Pacific Communicator
Authors: Oppo Delia W. , Rosenthal Yair
Published: June 2010

Warm water flowing through the Indonesian archipelago from the Pacific to the Indian Ocean influences the climate of the surrounding regions.
Reassortment of Pandemic H1N1/2009 Influenza A Virus in Swine
Authors: Vijaykrishna D. , Poon L. L. M. , Zhu H. C. , Ma S. K. , Li O. T. W. , Cheung C. L. , Smith G. J. D. , Peiris J. S. M. , Guan Y.
Published: June 2010

Surveillance of pigs is important for tracking reassortment and emergence of influenza A viruses.
Crossover from Single-Step Tunneling to Multistep Hopping for Molecular Triplet Energy Transfer
Authors: Vura-Weis Josh , Abdelwahed Sameh H. , Shukla Ruchi , Rathore Rajendra , Ratner Mark A. , Wasielewski Michael R.
Published: June 2010

Tracking Triplet-State Transfers

In devices such as organic transistors and photovoltaic cells, energy flow from donor to acceptor sites can occur via electrons that have been excited into higher electronic levels, which create a triplet state with two unpaired spins. At short distances between donor and acceptor, the transfer occurs through direct tunneling, but at longer distances, the electron “hops” in a multistep process.

Vura-Weis
et al.

(p.
1547
) used femtosecond transient absorption spectroscopy to observe this crossover in transfer mechanism directly in a series of molecules with varying bridge lengths between the donor and acceptor.
A Kantian View of Space
Authors: Palmer Linda , Lynch Gary
Published: June 2010

The animal brain is able to represent space without prior experience of exploring a location.
Arecibo to Stay Open Under New NSF Funding Plan
Authors: Bhattacharjee Yudhijit
Published: June 2010

The National Science Foundation has decided to keep the Arecibo Observatory going until at least 2016 with help from the foundation's geosciences directorate and from NASA.
A Taste for Controversy
Authors: Bohannon John
Published: June 2010

After discovering “supertasters,” Linda Bartoshuk is pushing to change how psychologists evaluate subjective experiences such as taste and pain.
Childhood's Cures Haunted by Adulthood's 'Late Effects'
Authors: Marder Jenny
Published: June 2010

As the number of cancer survivors climbs into the many millions, researchers are trying to learn why some acquire treatment-related diseases and others do not.
Resampling Approach for Determination of the Method for Reference Interval Calculation in Clinical Laboratory Practice
Authors: Pavlov Igor Y. , Wilson Andrew R. , Delgado Julio C.
Published: June 2010

Reference intervals (RI) play a key role in clinical interpretation of laboratory test results. Numerous articles are devoted to analyzing and discussing various methods of RI determination. The two most widely used approaches are the parametric method, which assumes data normality, and a nonparametric, rank-based procedure. The decision about which method to use is usually made arbitrarily. The goal of this study was to demonstrate that using a resampling approach for the comparison of RI determination techniques could help researchers select the right procedure. Three methods of RI calculation—parametric, transformed parametric, and quantile-based bootstrapping—were applied to multiple random samples drawn from 81 values of complement factor B observations and from a computer-simulated normally distributed population. It was shown that differences in RI between legitimate methods could be up to 20% and even more. The transformed parametric method was found to be the best method for the calculation of RI of non-normally distributed factor B estimations, producing an unbiased RI and the lowest confidence limits and interquartile ranges. For a simulated Gaussian population, parametric calculations, as expected, were the best; quantile-based bootstrapping produced biased results at low sample sizes, and the transformed parametric method generated heavily biased RI. The resampling approach could help compare different RI calculation methods. An algorithm showing a resampling procedure for choosing the appropriate method for RI calculations is included.
Identification of Immunologically Relevant Proteins ofChlamydophila abortusUsing Sera from Experimentally Infected Pregnant Ewes
Authors: Marques P. X. , Souda Puneet , O'Donovan J. , Gutierrez J. , Gutierrez E. J. , Worrall S. , McElroy M. , Proctor A. , Brady C. , Sammin D. , Basset H. F. , Whitelegge Julian P. , Markey B. E. , Nally J. E.
Published: June 2010

Chlamydophila abortusis an intracellular pathogen and the etiological agent of enzootic abortion of ewes (EAE).C. abortushas a biphasic development cycle; extracellular infectious elementary bodies (EB) attach and penetrate host cells, where they give rise to intracellular, metabolically active reticulate bodies (RB). RB divide by binary fission and subsequently mature to EB, which, on rupture of infected cells, are released to infect new host cells. Pregnant ewes were challenged with 2 × 106inclusion forming units (IFU) ofC. abortuscultured in yolk sac (comprising both EB and RB). Serum samples were collected at 0, 7, 14, 21, 27, 30, 35, 40, and 43 days postinfection (dpi) and used to identify antigens ofC. abortusexpressed during disease. Additionally, sera from fetal lambs were collected at 30, 35, 40, and 43 dpi. All serum samples collected from experimentally infected pregnant ewes reacted specifically with several antigens of EB as determined by one-dimensional (1-D) and 2-D gel electrophoresis; reactive antigens identified by mass spectrometry included the major outer membrane protein (MOMP), polymorphic outer membrane protein (POMP), and macrophage infectivity potentiator (MIP) lipoprotein.
Genome-Wide Single Nucleotide Polymorphism Typing Method for Identification of
Bacillus anthracis
Species and Strains among
B. cereus
Group Species
Authors: Kuroda Makoto , Serizawa Masakuni , Okutani Akiko , Sekizuka Tsuyoshi , Banno Satomi , Inoue Satoshi
Published: June 2010

As an issue of biosecurity, species-specific genetic markers have been well characterized. However,
Bacillus anthracis
strain-specific information is currently not sufficient for traceability to identify the origin of the strain. By using genome-wide screening using short read mapping, we identified strain-specific single nucleotide polymorphisms (SNPs) among
B. anthracis
strains including Japanese isolates, and we further developed a simplified 80-tag SNP typing method for the primary investigation of traceability. These 80-tag SNPs were selected from 2,965 SNPs on the chromosome and the pXO1 and pXO2 plasmids from a total of 19
B. anthracis
strains, including the available genome sequences of 17 strains in the GenBank database and 2 Japanese isolates that were sequenced in this study. Phylogenetic analysis based on 80-tag SNP typing showed a higher resolution power to discriminate 12 Japanese isolates rather than the 25 loci identified by multiple-locus variable-number tandem-repeat analysis (MLVA). In addition, the 80-tag PCR testing enabled the discrimination of
B. anthracis
from other
B. cereus
group species, helping to identify whether a suspected sample originates from the intentional release of a bioterrorism agent or environmental contamination with a virulent agent. In conclusion, 80-tag SNP typing can be a rapid and sufficient test for the primary investigation of strain origin. Subsequent whole-genome sequencing will reveal apparent strain-specific genetic markers for traceability of strains following an anthrax outbreak.
Specific Detection of Unamplified Mycobacterial DNA by Use of Fluorescent Semiconductor Quantum Dots and Magnetic Beads
Authors: Gazouli M. , Liandris E. , Andreadou M. , Sechi L. A. , Masala S. , Paccagnini D. , Ikonomopoulos J.
Published: June 2010

Here we present the development of a specific DNA detection method using fluorescent semiconductor quantum dots (QDs) and magnetic beads (MBs) for fast detection of
Mycobacterium
spp., dispensing with the need for DNA amplification. Two biotinylated oligonucleotide probes were used to recognize and detect specific complementary mycobacterial target DNA through a sandwich hybridization reaction. Cadmium selenite QDs conjugated with streptavidin and species-specific probes were used to produce a fluorescent signal. MBs conjugated with streptavidin and a genus-specific probe were used to isolate and concentrate the DNA targets. The application of the proposed method to isolated bacteria produced the expected result in all cases. The minimum detection limit of the assay was defined as 12.5 ng of DNA diluted in a sample volume of 20 μl. In order to obtain an indication of the method's performance with clinical samples, we applied the optimized assay to the detection of
Mycobacterium tuberculosis
in DNA isolated from bronchoalveolar lavage specimens from patients with tuberculosis and
Mycobacterium avium
subsp.
paratuberculosis
in DNA isolated from feces and paraffin-embedded tissues in comparison with culture, Ziehl-Neelsen staining, and real-time PCR. The concordance of these methods compared to the proposed method with regard to positive and negative samples varied between 53.84% and 87.23% and between 84.61% and 100%, respectively. The overall accuracy of the QD assay compared to real-time PCR was 70 to 90% depending on the type of clinical material. The proposed diagnostic assay offers a simple, rapid, specific, and cost-effective method for direct detection and identification of mycobacterial DNA in clinical samples.
Mitochondrial DNA Targets Increase Sensitivity of Malaria Detection Using Loop-Mediated Isothermal Amplification
Authors: Polley Spencer D. , Mori Yasuyoshi , Watson Julie , Perkins Mark D. , González Iveth J. , Notomi Tsugunori , Chiodini Peter L. , Sutherland Colin J.
Published: June 2010

Loop-mediated isothermal amplification (LAMP) of DNA offers the ability to detect very small quantities of pathogen DNA following minimal tissue sample processing and is thus an attractive methodology for point-of-care diagnostics. Previous attempts to diagnose malaria by the use of blood samples and LAMP have targeted the parasite small-subunit rRNA gene, with a resultant sensitivity for
Plasmodium falciparum
of around 100 parasites per μl. Here we describe the use of mitochondrial targets for LAMP-based detection of any
Plasmodium
genus parasite and of
P. falciparum
specifically. These new targets allow routine amplification from samples containing as few as five parasites per μl of blood. Amplification is complete within 30 to 40 min and is assessed by real-time turbidimetry, thereby offering rapid diagnosis with greater sensitivity than is achieved by the most skilled microscopist or antigen detection using lateral flow immunoassays.
Clinical Relevance and Diversity of Two Homologous Genes Encoding Glycosyltransferases inHelicobacter pylori
Authors: Oleastro Mónica , Santos Andrea , Cordeiro Rita , Nunes Baltazar , Mégraud Francis , Ménard Armelle
Published: June 2010

Helicobacter pyloriis known to be a major cause of peptic ulceration. Thejhp0562gene, encoding a glycosyltransferase involved in the synthesis of the lipopolysaccharide, was associated with peptic ulcer disease (PUD) in children. The β-(1,3)-galactosyltransferase [β-(1,3)GalT] gene (jhp0563), involved in Lewis (Le) antigen expression, is highly similar tojhp0562. The clinical significance and diversity of both genes were examined by PCR and sequencing of clinical strains (n= 117) isolated from children with PUD (n= 57) and nonulcer dyspepsia (NUD;n= 60). The prevalence of thejhp0562gene was significantly higher in strains with a more-virulent profile (strains positive for thecagpathogenicity island [PAI],vacAsl allele,babA,homB, phase-variable geneoipA“on” [i.e., functional], andhopQI allele). The distribution of genotypes according to clinical outcome showed that the presence ofjhp0562represented one of the greatest risks for the development of PUD. Moreover, the triple-positive genotype for thecagPAI,jhp0562, andhomBprovided the best discriminatory model for distinguishing PUD and NUD outcomes in children. Sequence andin vitroexpression analyses ofjhp0562showed the presence of a complete open reading frame, while the β-(1,3)GalT gene was shown to be a phase-variable gene. The regular presence ofjhp0562in strains with a truncated β-(1,3)GalT gene suggests thatjhp0562may also be implicated in the regulation of Le antigen expression. Overall, the results of this study suggest that thejhp0562gene is of great clinical relevance, being a useful comarker for severeH. pylori-related disease and contributing to host adaptation.
Comparative Study on Genotypic and Phenotypic Second-Line Drug Resistance Testing of
Mycobacterium tuberculosis
Complex Isolates
Authors: van Ingen Jakko , Simons Sami , de Zwaan Rina , van der Laan Tridia , Kamst-van Agterveld Miranda , Boeree Martin J. , van Soolingen Dick
Published: June 2010

The mycobacterium growth indicator tube (MGIT960) automated liquid medium testing method is becoming the international gold standard for second-line drug susceptibility testing of multidrug- and extensively drug-resistant
Mycobacterium tuberculosis
complex isolates. We performed a comparative study of the current gold standard in the Netherlands, the Middlebrook 7H10 agar dilution method, the MGIT960 system, and the GenoType MTBDR
sl
genotypic method for rapid screening of aminoglycoside and fluoroquinolone resistance. We selected 28 clinical multidrug- and extensively drug-resistant
M. tuberculosis
complex strains and
M. tuberculosis
H37Rv. We included amikacin, capreomycin, moxifloxacin, prothionamide, clofazimine, linezolid, and rifabutin in the phenotypic test panels. For prothionamide and moxifloxacin, the various proposed breakpoint concentrations were tested by using the MGIT960 method. The MGIT960 method yielded results 10 days faster than the agar dilution method. For amikacin, capreomycin, linezolid, and rifabutin, results obtained by all methods were fully concordant. Applying a breakpoint of 0.5 μg/ml for moxifloxacin led to results concordant with those of both the agar dilution method and the genotypic method. For prothionamide, concordance was noted only at the lowest and highest MICs. The phenotypic methods yielded largely identical results, except for those for prothionamide. Our study supports the following breakpoints for the MGIT960 method: 1 μg/ml for amikacin, linezolid, and clofazimine, 0.5 μg/ml for moxifloxacin and rifabutin, and 2.5 μg/ml for capreomycin. No breakpoint was previously proposed for clofazimine. For prothionamide, a division into susceptible, intermediate, and resistant seems warranted, although the boundaries require additional study. The genotypic assay proved a reliable and rapid method for predicting aminoglycoside and fluoroquinolone resistance.
Clostridium difficileIsolates Resistant to Fluoroquinolones in Italy: Emergence of PCR Ribotype 018
Authors: Spigaglia Patrizia , Barbanti Fabrizio , Dionisi Anna Maria , Mastrantonio Paola
Published: June 2010

Recent evidence strongly suggests an association between the use of fluoroquinolones andClostridium difficileinfection (CDI). Resistance to fluoroquinolones has been described not only in the hypervirulent strain 027, but also in other important PCR ribotypes circulating in hospital settings. In a European prospective study conducted in 2005, strains resistant to moxifloxacin represented 37.5% ofC. difficileclinical isolates. In this study, we investigated a sample of 147 toxigenicC. difficileisolates, collected in Italy from 1985 to 2008, for the presence of mutations ingyrgenes that conferred resistance to fluoroquinolones based on a LightCycler assay. Results were confirmed by the determination of MICs for moxifloxacin. Strains resistant to moxifloxacin were also investigated for resistance to three other fluoroquinolones and for a possible association between fluoroquinolone and macrolide-lincosamide-streptogramin B resistance.C. difficileisolates were typed by PCR ribotyping. In total, 50 clinical isolates showed substitutions ingyrgenes and were resistant to fluoroquinolones. Ninety-six percent of theC. difficileresistant isolates showed the substitution Thr82-to-Ile in GyrA, as already observed in the majority of resistant strains worldwide. A significant increase of resistance (P< 0.001) was observed in the period 2002 to 2008 (56% resistant) compared to the period 1985 to 2001 (10% resistant). Coresistance with erythromycin and/or clindamycin was found in 96% (48/50) of the isolates analyzed and, interestingly, 84% of resistant strains wereerm(B) negative. The majority of the fluoroquinolone-resistant isolates belonged to PCR ribotype 126 or 018. PCR ribotype 126 was the most frequently found from 2002 to 2005, whereas PCR ribotype 018 was predominant in 2007 and 2008 and still represents the majority of strains typed in our laboratory. Overall, the results demonstrate an increasing number ofC. difficilestrains resistant to fluoroquinolones in Italy and changes in the prevalence and type ofC. difficileisolates resistant to fluoroquinolones circulating over time.
Impact of Viral Dose and Major Histocompatibility Complex Class IB Haplotype on Viral Outcome in Mauritian Cynomolgus Monkeys Vaccinated with Tat upon Challenge with Simian/Human Immunodeficiency Virus SHIV89.6P
Authors: Cafaro Aurelio , Bellino Stefania , Titti Fausto , Maggiorella Maria Teresa , Sernicola Leonardo , Wiseman Roger W. , Venzon David , Karl Julie A. , O'Connor David , Monini Paolo , Robert-Guroff Marjorie , Ensoli Barbara
Published: June 2010

The effects of the challenge dose and major histocompatibility complex (MHC) class IB alleles were analyzed in 112 Mauritian cynomolgus monkeys vaccinated (n= 67) or not vaccinated (n= 45) with Tat and challenged with simian/human immunodeficiency virus (SHIV) 89.6Pcy243.In the controls, the challenge dose (10 to 20 50% monkey infectious doses [MID50]) or MHC did not affect susceptibility to infection, peak viral load, or acute CD4 T-cell loss, whereas in the chronic phase of infection, the H1 haplotype correlated with a high viral load (P= 0.0280) and CD4 loss (P= 0.0343). Vaccination reduced the rate of infection acquisition at 10 MID50(P< 0.0001), and contained acute CD4 loss at 15 MID50(P= 0.0099). Haplotypes H2 and H6 were correlated with increased susceptibility (P= 0.0199) and resistance (P= 0.0087) to infection, respectively. Vaccination also contained CD4 depletion (P= 0.0391) during chronic infection, independently of the challenge dose or haplotype.
Cellular MicroRNAs Inhibit Replication of the H1N1 Influenza A Virus in Infected Cells
Authors: Song Liping , Liu He , Gao Shijuan , Jiang Wei , Huang Wenlin
Published: June 2010

MicroRNAs (miRNAs) are a class of noncoding RNAs of lengths ranging from 18 to 23 nucleotides (nt) that play critical roles in a wide variety of biological processes. There is a growing amount of evidence that miRNAs play critical roles in intricate host-pathogen interaction networks, but the involvement of miRNAs during influenza viral infection is unknown. To determine whether the cellular miRNAs play an important role in H1N1 influenza A viral infections, 3′ untranslated region (UTR) reporter analysis was used to identify putative miRNA targets in the influenza virus genome, and virus proliferation analysis was used to detect the effect of the screened miRNAs on the replication of H1N1 influenza A virus (A/WSN/33) in MDCK cells. The results showed that miRNA 323 (miR-323), miR-491, and miR-654 inhibit replication of the H1N1 influenza A virus through binding to the PB1 gene. Moreover mutational analysis of the predicted miRNA binding sites showed that the three miRNAs bind to the same conserved region of the PB1 gene. Intriguingly, despite the fact that the miRNAs and PB1 mRNA binding sequences are not a perfect match, the miRNAs downregulate PB1 expression through mRNA degradation instead of translation repression. This is the first demonstration that cellular miRNAs regulate influenza viral replication by degradation of the viral gene. Our findings support the notion that any miRNA has antiviral potential, independent of its cellular function, and that the cellular miRNAs play an important role in the host, defending against virus infection.
Importin α3 Interacts with HIV-1 Integrase and Contributes to HIV-1 Nuclear Import and Replication
Authors: Ao Zhujun , Danappa Jayappa Kallesh , Wang Binchen , Zheng Yingfeng , Kung Sam , Rassart Eric , Depping Reinhard , Kohler Matthias , Cohen Eric A. , Yao Xiaojian
Published: June 2010

HIV-1 employs the cellular nuclear import machinery to actively transport its preintegration complex (PIC) into the nucleus for integration of the viral DNA. Several viral karyophilic proteins and cellular import factors have been suggested to contribute to HIV-1 PIC nuclear import and replication. However, how HIV interacts with different cellular machineries to ensure efficient nuclear import of its preintegration complex in dividing and nondividing cells is still not fully understood. In this study, we have investigated different importin α (Impα) family members for their impacts on HIV-1 replication, and we demonstrate that short hairpin RNA (shRNA)-mediated Impα3 knockdown (KD) significantly impaired HIV infection in HeLa cells, CD4
+
C8166 T cells, and primary macrophages. Moreover, quantitative real-time PCR analysis revealed that Impα3-KD resulted in significantly reduced levels of viral 2-long-terminal repeat (2-LTR) circles but had no effect on HIV reverse transcription. All of these data indicate an important role for Impα3 in HIV nuclear import. In an attempt to understand how Impα3 participates in HIV nuclear import and replication, we first demonstrated that the HIV-1 karyophilic protein integrase (IN) was able to interact with Impα3 both in a 293T cell expression system and in HIV-infected CD4
+
C8166 T cells. Deletion analysis suggested that a region (amino acids [aa] 250 to 270) in the C-terminal domain of IN is involved in this viral-cellular protein interaction. Overall, this study demonstrates for the first time that Impα3 is an HIV integrase-interacting cofactor that is required for efficient HIV-1 nuclear import and replication in both dividing and nondividing cells.
Pseudorabies Virus Tegument Protein Us2 Recruits the Mitogen-Activated Protein Kinase Extracellular-Regulated Kinase (ERK) to Membranes through Interaction with the ERK Common Docking Domain
Authors: Kang Ming-Hsi , Banfield Bruce W.
Published: June 2010

The pseudorabies virus (PRV) Us2 protein binds to the extracellular-regulated kinase (ERK) and inhibits the activation of ERK nuclear targets by sequestering cytoplasmic ERK on cellular membranes. Utilizing a series of Us2 truncations, we determined that the minimal portion of Us2 required for interaction with ERK is contained within its amino-terminal 214 amino acids. The loss of the ability of Us2 to bind to ERK in coimmunoprecipitation experiments was accompanied by a failure of Us2 to form oligomers, raising the possibility that higher-order Us2 structures are required for ERK interaction. To map the Us2 interaction site on ERK, we introduced mutations into the region of ERK that interacts with the ERK kinase, MEK, or into the common docking (CD) domain that mediates interactions with many ERK substrates. ERK carrying mutations within the MEK binding region maintained the ability to bind Us2, whereas ERK carrying mutations within the CD domain did not. Furthermore, the ERK CD domain was required for the Us2-mediated recruitment of ERK to membranes. Taken together, these findings suggest that Us2 regulates ERK activity by spatially restricting ERK localization and also by interfering with select ERK-substrate interactions.
Potent Lentiviral Restriction by a Synthetic Feline TRIM5 Cyclophilin A Fusion
Authors: Dietrich Isabelle , Macintyre Angela , McMonagle Elizabeth , Price Amanda J. , James Leo C. , McEwan William A. , Hosie Margaret J. , Willett Brian J.
Published: June 2010

A synthetic feline TRIM5-cyclophilin A fusion protein (feTRIMCyp) was generated and transduced into feline cells. feTRIMCyp was highly efficient at preventing infection with human (HIV) and feline (FIV) immunodeficiency virus pseudotypes, and feTRIMCyp-expressing cells resisted productive infection with either FIV-Fca or FIV-Pco. The restriction of FIV infection by feTRIMCyp was reversed by the cyclosporine (Cs) derivatives NIM811 and Debio-025 but less so by Cs itself. FeTRIMCyp and FIV infections of the cat offer a unique opportunity to evaluate TRIMCyp-based approaches to genetic therapy for HIV infection and the treatment of AIDS.
Mixing rules for the back equation of state
Authors: Boublík Tomáš , Lu Benjamin C.-Y.
Published: June 2010

Van der Waals type of mixing rule for the energy parameter us together with the mixing rules introduced previously for parameters αs and Vs0 of the BACK equation were employed in evaluating excess properties of mixing, Henry's law constant and high pressure vapour-liquid equilibria. A comparison with the experimental data reveals that the BACK equation together with the suggested mixing rules could provide good prediction of equilibrium properties of mixtures of relatively simple molecules.
Excess volumes in the methanol-tert-amyl methyl ether system at 298.15 K
Authors: Linek Jan , Bernatová Svatoslava
Published: June 2010

Excess volumes have been measured by means of a vibrating-tube densimeter in the methanol - tert-amyl methyl ether system at 298.15 K. The excess volumes are negative over the whole concentration range.
Interfacial interactions between aqueous solutions of 4,4'-bipyridyl and mercury
Authors: Heyrovský Michael , Novotný Ladislav
Published: June 2010

From analysis of electrocapillary curves obtained by drop-time measurements with spindle-type capillary and the method of controlled convection the data on reversible equilibrium adsorption of 4,4'-bipyridyl on mercury from aqueous 0·1M solutions of Na2SO4 and H2SO4 were obtained. In neutral solution 4,4'-bipyridyl is strongly adsorbed: at potential of maximum adsorption the Langmuir coefficient β = 1.4 . 102 m3 mol-1 and Γm = 1.8 . 10-6 mol m-2; in acid solution the adsorption of the doubly protonated 4,4'-bipyridylium cation is weaker and its potential dependence goes through a minimum. The increase of adsorption of the bipyridylium cation and a simultaneous increase of negative charge with increasing negative potential are explained by charge transfer in adsorbed state. The electroreduction of 4,4'-bipyridyl is preceded by formation at the electrode surface of a layer of sparingly soluble salt of the bipyridyl cation radical.
Reactions of 1,3-diacylthioureas with methoxide ion and with amines
Authors: Kaválek Jaromír , Jirman Josef , Štěrba Vojeslav
Published: June 2010

Rate constants of base-catalyzed methanolysis and dissociation constants in methanol have been determined for benzoylthiourea (II), 1,3-diacetylthiourea (III), 1,3-dibenzoylthiourea (IV), and 1-acetyl-3-benzoylthiourea (V). With the diacyl derivatives III and IV, the reaction of methoxide ion with the neutral substrate is accompanied by that of methoxide with the substrate anion (at higher alkoxide concentrations). Above 0.1 mol l-1 CH3O(-), the rate constants are also affected by medium. The rate of the reaction of neutral diacyl derivative is decreased, and that of the reaction of methoxide with the substrate anion is rapidly increased. The dissociation constant of II is higher than that of acetylthiourea (I) by about one order of magnitude, but the attack of methoxide on the carbonyl group of II is about three times slower than that in I. The benzoyl group at the N1 nitrogen exhibits a greater activating influence (in both the rate and the equilibrium constants) on the other NHCOR group than the acetyl group does. With V the ratio of methanolysis rate constants is 9 : 1 in favour of the acetyl group. The reaction of diacetyl derivative III with 1-butanamine has been followed in butanamine buffers. At the lowest butanamine concentrations, the reaction is second order in the amine, and the rate-limiting step is the proton transfer from the intermediate to the second amine molecule. At the highest butanamine concentrations the reaction becomes first order in the amine, and the rate-limiting step changes to the attack of butanamine on the carbonyl group of diacetyl derivative III.
Synthesis and reactions of furo[3,2-c]pyridine derivatives
Authors: Koreňová Anna , Krutošíková Alžbeta , Kováč Jaroslav , Celec Stanislav
Published: June 2010

The synthesis of a new type of condensed heterocycle pyrido[3',4':4,5]furo[3,2-b]indole (V) and 1,2,4-triazolo[4'',3'':1',2']pyrido[3',4':4,5]furo[3,2-b]indoles (IX) is described and the substitution nucleophilic reaction with 2-(2-nitrophenyl)-4-chlorofuro[3,2-c]pyridine (X) is presented.
Approaches to the synthesis of kainic acid. A study of the synthesis of some 4,5-dihydro-1,2,3-triazoles
Authors: Husinec Suren , Porter Alexander E. A. , Strachan Calum H.
Published: June 2010

Two strategies for the synthesis of bicyclic pyrrolidine derivatives using [3 + 2]cycloaddition reactions of azomethine ylids are described.
2α,3α-Dihydroxy-7-oxa-6-oxo-B-homo-5α-pregnan-21-oic acid and its derivatives as brassinolide analogues
Authors: Černý Václav , Zajíček Jaroslav , Strnad Miroslav
Published: June 2010

The synthesis of compounds VIIIb,c,f,h and their plant growth-promoting activity is reported. These compounds differ from the previously described substances Ia-d by the absence of the 21-methyl group, this structural change resulting in a dramatic decrease in the growth-promoting activity.
Methoxylation of substituted 1,4-benzoquinones
Authors: Kopecký Jaroslav , Šaman David , Novotný Ladislav
Published: June 2010

Methoxylation of 1,4-benzoquinones I and Ia with boron trifluoride-methanol complex afforded methyl 15-(5,6-dimethoxy-1,4-benzoquinon-2-yl)pentadecanoate (IIa) and methyl 15-(2-hydroxy-3,5-dimethoxyphenyl)pentadecanoate (IIIa). Structure of the products was established by spectroscopic methods.
Methylation of substituted 1,4-benzoquinones
Authors: Kopecký Jaroslav , Šaman David , Novotný Ladislav
Published: June 2010

Methylation of 1,4-benzoquinones I and Ia with diazomethane afforded methyl 15-(6-methoxy-3-methyl-1,4-benzoquinon-2-yl)pentadecanoate (IIa) and methyl 15-(3-methoxy-2,5-dioxobicyclo[4.1.0]hept-3-en-1-yl)pentadecanoate (IIIa), methylation of 1,4-benzoquinone IVa led to methyl 15-(5,6-dimethoxy-3-methyl-1,4-benzoquinon-2-yl)pentadecanoate (Va) and methyl 15-(3,4-dimethoxy-6-methyl-2,5-dioxobicyclo[4.1.0]hept-3-en-1-yl)pentadecanoate (VIa). Structure of the products was established by spectral methods.
Reactions in the series of substituted isoindolo[1,2-b][3]-benzazepin-5-ones
Authors: Veselý Zdeněk , Holubek Jiří , Trojánek Jan
Published: June 2010

In the reaction of 10,11-methylenedioxy-3,4,12-trimethoxy-7,8-dihydro-5H-isoindolo[1,2-b][3]-benzazepin-5-one (V) with benzyl alcohol and sodium benzyloxide nucleophilic substitution of the 4-methoxy group for benzyloxy group takes place under formation of 4-benzyloxy-3,12-dimethoxy-10,11-methylenedioxy-7,8-dihydro-5H-isoindolo[1,2-b][3]-benzazepin-5-one (VI). An analogous exchange converts compound V in the presence of corresponding alkoxides and alcohols to compounds VII-X. When reducing compound V with sodium dihydridobis(2-methoxyethoxy)aluminate the unstable base XI is formed which on reaction with trifluoroacetic acid gives the red trifluoroacetate XII. As a side product 3,12-dimethoxy-10,11-methylenedioxy-7,8-dihydroisoindolo[1,2-b][3]-benzazepin-5-one (XIII) is formed at the stage of the reduction of the nucleophilic substitution of the 4-methoxy group with the hydride anion. The reaction of compound V with various Grignard reagents always leads to the same product of phenolic character. Its structure XIV was confirmed by comparison of its mass spectra with those of the product of hydrogenolysis of compound VI. Compound VI and the product of benzylation of compound XIV were also identical.
A modified Gillespie still for measuring vapour-liquid equilibria
Authors: Graczová Elena , Huňarová Táňa , Surový Július
Published: June 2010

A modification of the Gillespie still for measuring vapour-liquid equilibrium data is described. The still was tested at different working pressures within the range of 3.7 to 86.7 kPa by measuring the isothermal L-G equilibrium data for the binary system p-xylene-dimethylformamide at the temperatures of 60, 80, 100, 120, and 130 °C. The dependence of activity coefficients of components on composition was expressed by means of the Redlich-Kister and Wilson equations. The consistency of the experimental data as well as the agreement of some measured values with the data from literature furnishes an evidence of good functioning of the apparatus.
Determination of the adsorption film characteristics of alkyltriphenylphosphonium cations from time dependent capacitance measurements
Authors: Anastopoulos Anastos , Christodoulou Anastasia
Published: June 2010

The determination of the adsorbed film characteristics at the interface between methanolic solutions of quaternary phosphonium salts and the Hg electrode is carried out by means of time dependent capacitance measurements. The maximum surface concentration, the area per adsorbed particle and the orientation of methyltriphenyl-, cyclopropyltriphenyl-, and n-butyltriphenylphosphonium cations are derived by two methods, the first of which is free of isotherm assumptions and the second involves an adsorption isotherm obeyed by the system under examination.
Separation of platinum(IV) and rhenium(VII) in the process of working-up of deactivated reforming catalysts
Authors: Kálalová Eliška , Bumbová Marcela , Mastný Libor
Published: June 2010

A procedure is suggested for the isolation of Pt(IV) and Re(VII) from solutions after the working-up of exhausted catalysts for the reforming of hydrocarbons, which in addition to the catalytically active Pt and Re contain Fe and Ti on Al2O3 as promotors. The solution is passed through a column packed with a glycidyl methacrylate chelating sorbent containing ethylenediamine functional groups; while Fe3+, Ti4+, and Al3+ cations pass freely, [PtCl6]2- and ReO4- anions are retained by the column; they are subsequently separated by gradual elution, Re(VII) first with 1-3M-H2SO4, then Pt(IV) with 2-5M-HNO3. Complexes of Pt(IV) with the polymeric ligands, forming during the separation, are identified by means of their infrared and electronic reflection spectra.
Perfluorosulphonated polymers as new materials for IR spectroscopy
Authors: Jegorov Alexandr , Ebert Miroslav , Weber Jan , Janda Pavel
Published: June 2010

Thin films of perfluorosulphonated polymer were obtained by dissolving a Nafion 117 membrane in N,N-dimethylacetamide or hexamethylphosphoric triamide and subsequent evaporation of the solution. These films can be used as a medium for IR spectroscopy in the range 4 000-1 300 cm-1, suitable for retention and identification of cations. Spectra of cations in polymer cationic forms (NH4+, MenNH3-n+, EtnNH3-n+) and of some allylammonium cations were studied.
The pumping characteristics of screw rotors. I. The theory of calculation of the pumping capacity of screw rotors
Authors: Rieger František
Published: June 2010

This paper summarizes the present state of the theory of calculation of the pumping capacity of screw rotors. The calculation starts from the equation for the volumetric flow rate of the flow between two unconfined plates modified by correction coefficients obtained from the relationships for the flow rate in simpler geometrical configurations to which the screw rotor may be, under certain circumstances, reduced.
The pumping characteristics of screw rotors. II. Measurement of pumping characteristics of screw rotors
Authors: Rieger František
Published: June 2010

The contribution has been devoted to experimental determination of the pumping characteristics of screw rotors. The paper presents the geometrical parameters of investigated screw rotors and barrels, description of experimental equipment, obtained experimental results and their evaluation.
Ultrasound-accelerated synthesis of ferrocene-containing pyrimidine derivatives
Authors: Toma Štefan , Putala Martin , Sališová Marta
Published: June 2010

The base-catalysed addition of thiourea to ferrocene analogues of chalcones is faster and more selective when the reaction mixture is sonicated than when merely heated. 4-Aryl-6-ferrocenyl- and 6-aryl-4-ferrocenyl-3,4-dihydropyrimidine-2(1H)-tyhiones were isolated in 58-79% yields.
MO study of 2,2,4-trimethyl-2H-pyran, the simplest stable 2H-pyran derivative
Authors: Böhm Stanislav , Kuthan Josef
Published: June 2010

On the basis of MNDO optimized molecular geometries of the title compound I and its acyclic valence tautomers II and III it is demonstrated that the ability to isolate heterocyclic form I can be interpreted by its relatively lowest SCF-molecular energy calculated in MNDO or 4-31G, resp., orbital bases. Quantum chemical data are discussed in connection with the more general relation between the stability of 2H-pyran cycle and structural factors causing non-planarity of the equilibrium geometries of non-cyclic tautomeric structures.
Polar effects on 13C NMR chemical shifts and rotational barriers of amides. A dual substituent parameters analysis of N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides
Authors: Friedl Zdeněk , Böhm Stanislav , Goljer Igor , Piklerová Anna , Poórová Daniela , Ríčková Anna , Kováč Jaroslav
Published: June 2010

13C NMR chemical shifts were measured for sixteen N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides in CDCl3 at 21 °C; the barriers of rotation about the C-N bond ΔGc° were determined by using the 1H NMR coalescence method, and the positions of the IR bands of the ν(C=O) stretching vibrations were measured. The dual substituent parameters (DSP) analysis of the 13C NMR chemical shifts for atoms of the vinylcarboxamide side chain -C(3)H=C(2)H-C(1)=O(-N) gives evidence that the chemical shifts for the C-1 and C-3 atoms are controlled primarily by polar effects (δ(C-3) = -3.12σI - 1.03σR0; λ = ρI/ρR = 3.0), which exert a reverse substituent effect on these atoms. Similarly, the DSP analysis of the ΔGc° and ν(C=O) data shows that the dominant factor of the total substituent effect is the polar effect (λ = 1.95 and 1.70, respectively). A confrontation of the results of the DSP analysis with the CNDO/2 calculated electron densities at the corresponding atoms demonstrates that the reactivity of the entire vinylcarboxamide side chain can be well explained in terms of a combination of the polar effect (π-electron polarization) with resonance effects.
Kinetic analysis of competitive reactions of isothiocyanates with hydroxyl and alkoxide ions
Authors: Augustín Jozef , Baláž Štefan
Published: June 2010

The reaction of isothiocyanates with hydroxyl and alkoxide ions has been followed spectrophotometrically in alkaline aqueous-alcoholic solutions. Both the nucleophiles are added to the carbon atom of isothiocyanate group in a competition reaction. The effects of concentration of the nucleophiles, temperature, and acid-base properties of the alcoholic group have been followed on the reaction course. The possibility of analogous reactions in real biological systems is discussed.
Brassino steroids with androstane and pregnane skeleton
Authors: Kohout Ladislav , Velgová Helena , Strnad Miroslav , Kamínek Miroslav
Published: June 2010

New brassino steroids XII, XXI, and XXIII were synthesized. These compounds, together with some intermediates of their synthesis, were tested for brassinolide activity. In the bean second internode bioassay, the androstane intermediate V exhibited a surprisingly high activity whereas the other tested compounds were substantially less active.
A-nor-derivatives of 19β,28-epoxy-18α-oleanane: Preparation and stereochemistry
Authors: Klinot Jiří , Rozen Jiří , Klinotová Eva , Vystrčil Alois
Published: June 2010

19β,28-Epoxy-A(1)-nor-18α-oleanan-3-one (IV) was converted into the A-nor-derivatives V-XII whose structure and configuration was confirmed by chemical reactions and spectral methods. Proton NMR and IR spectra show that the 2α- and 3β-bonds on the five-membered ring A are pseudoaxial whereas the 2β- and 3α-bonds are pseudoequatorial.
Ethylene dithioketals in ring a of 19β,28-epoxy-18α-oleanane; Mass spectra and reduction with deuterated Raney-nickel
Authors: Protiva Jiří , Očadlík Rudolf , Klinotová Eva , Klinot Jiří , Vystrčil Alois
Published: June 2010

Ethylene dithioketals in positions 1, 2 and 3 of 19β,28-epoxy-18α-oleanane were prepared and reduced with deuterated Raney-nickel. The mass spectra of dithioketals and corresponding 1,1-, 2,2- and 3,3-dideuterio derivatives were studied and discussed with the possibility of localizing the functional group in the A ring.
Endoprolylpeptidase (EC 3.4.21.26), improvement of the isolation method
Authors: Hauzer Karel , Barth Tomislav , Jošt Karel , Barthová Jana , Hauzerová Linda
Published: June 2010

The improvement of the enzyme isolation method consists in the addition of sodium sulphite (5 mmol l-1) used in the isolation procedure instead of the low-molecular thiols used previously, e.g. 2-mercaptoethanol, cystein, dithiothreitol etc. The protective effect against oxidation of the enzyme by aerial oxygen has been retained while, at the same time, autolysis of the enzyme was decreased and the final enzyme preparation exhibited higher values of specific activity.
Quasiclassical trajectory study of the CH2 + O2 reaction
Authors: Urban Ján , Klimo Viliam , Tiňo Jozef
Published: June 2010

The reaction of atomic oxygen formation from methylene and O2 reactants was studied on the LEPS surface with Sato parameters determined by fitting ab initio points of the triplet reaction hypersurface. Besides the rate constant obtained from the analysis of classical trajectories, dynamic characteristics of the reaction have been determined.
Binuclear complexes of aminoacetohydroxamic acid with copper(II) and iron(III)
Authors: Karlíček Rolf , Polášek Miroslav
Published: June 2010

Aminoacetohydroxamic acid (glycinehydroxamic acid, H2NCH2CONHOH) (HL) forms the complex species FeHL3+, Cu2H-1L2+ and CuFeH-1L3+ at cM > cL. The two binuclear complexes were proved to be formed with the elimination of two hydrogen ions from one hydroxamic functional group, the amide nitrogen atom of the hydroxamic group taking part in the coordination. The spectrophotometric characteristics of the complexes and the equilibrium constants of the reactions involved are given.
Salicylhydroxamic acid and its iron(III) complexes
Authors: Špringer Vladimír , Horňáčková Magdaléna , Karlíček Rolf , Kopecká Božena
Published: June 2010

The dissociation constants of salicylhydroxamic acid (H2L), pKa1 = 6.73 and pKa2 = 9.15 (20 °C, I = 1.0 (NaClO4)), and the stability constant of the FeHL2+ complex, logβ = 9.09, were determined by the potentiometric and spectrophotometric methods. The low-soluble Fe(OH)(HL)2.3 H2O complex was also isolated. The reagent can be conveniently used as an indicator for the chelometric determination of iron.
DC polarographic determination of surfactants
Authors: Díaz A. , González S. , Arévalo A.
Published: June 2010

The minimum on the polarographic curves for Bi(III) reduction in HCl solutions occurring when small amounts of surfactants are present can be used for their quantitative determination. The form of the polarograms was examined with respect to the concentration of the surfactant, and the range of concentrations in which the method of determination can be used is discussed.
Anodic oxidation of mercury in the presence of thioether acids: Methane-1,1-bis-mercaptoacetic acid
Authors: Casassas E. , Esteban M. , Ariño C.
Published: June 2010

The anodic oxidation of mercury in the presence of methane-1,1-bis-mercaptoacetic acid (MBMA) has been studied by DCr, DP, AC1, and AC2 polarography, cyclic voltammetry, and coulometry. The electrode process is controlled by the adsorption of the product formed according to: Hg + 2 H(2-n)Ln- → H(2-n)HgL2n- + (2-n) H+ + 2e with n = 0 at pH < pK1, n = 1 at pK1 < pH < pK2, and n = 2 at pH > pK2. No adsorption of MBMA is observed. The behaviour of MBMA at a hanging mercury drop electrode (HMDE) by cathodic stripping voltammetry (CSV) has been also studied. At MBMA concentrations above 1 10-6 mol l-1, the stripping voltammograms showed two well defined peaks, at c. -0.140 V and at c. -0.300 V. The anodic process occurring during the pre-electrolysis in CSV is described by the formation of a Hg(I) compound: 2 Hg + 2 H(2-n)Ln- → H(2-n)Hg2L2(2-2n)+ + 2e followed by its disproportionation: H(2-n)Hg2L2(2-2n)+ →c H(2-n)HgL2(2-2n)+ + Hg,

where n has the above-mentioned values.
The influence of the structure of molybdenum disulphide on its reactivity
Authors: Bartovská Lidmila , Černý Čestmír
Published: June 2010

The equilibrium in the system Mo-MoS2-H2S-H2 was studied between 569.4 and 1 276.8 K. The equilibrium gaseous mixture was analyzed by an iodometric method, the solid phase was studied by X-ray powder diffraction. The structure of MoS2 changed in the course of measurements from a “poorly crystalline” form at lower temperatures to a “well crystalline” one with a small number of stacking faults at higher temperatures. The poorly crystalline form is more reactive than the well crystalline one. For the formation of the well crystalline form of MoS2 a Gibbs-energy equation, ΔG0 (J mol-1) = -390 100 + 176.7T, was derived. It is in excellent agreement with the equation derived from the data obtained by fluorine calorimetry.
Measurement and interpretation of infrared and raman spectra of vanadyl acetylacetonate
Authors: Vlčková Blanka , Strauch Bohuslav , Horák Milan
Published: June 2010

Infrared and Raman spectra of oxobis (2,4-pentandionate) vanadium complex have been studied. A reduction of the number of spectral bands observed in the IR and Raman spectra compared to the theoretical number of normal modes expected for a complex molecule is attributed to the isolation effect of the heavy central metal atom. A simplified model involving the skeleton of the complex and one coordinated ligand has been employed for an empirical interpretation of the vibrational spectra. An exact agreement between the number of modes predicted theoretically on the basis of the simplified model and the number of bands observed experimentally has been obtained.
15N NMR study of amino-imino tautomerism in derivatives of 1,4-bis(substituted amino)-9,10-anthraquinones and 1,4-bis(substituted amino)-2,3-dihydro-9,10-anthraquinones
Authors: Lyčka Antonín , Havlíčková Libuše , Koloničný Alois , Jirman Josef
Published: June 2010

The 15N chemical shifts and 1J(15N, H) coupling constants of 1,4-bis(substituted amino)-9,10-anthraquinones and 1,4-bis(substituted amino)-2,3-dihydro-9,10-anthraquinones indicate that these derivatives exist as true aminoderivatives except for 1,4-bis(phenylamino)-2,3-dihydro-9,10-anthraquinone which forms a tautomeric mixture of the amino and imino forms in deuteriochloroform and hexadeuteriodimethyl sulphoxide.