bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence- and Structure-Specific RNA Processing by a CRISPR Endonuclease
Authors: Haurwitz Rachel E. , Jinek Martin , Wiedenheft Blake , Zhou Kaihong , Doudna Jennifer A.
Published: September 2010

CRISPR Processing

Many bacteria and archaea recognize invading viruses and plasmids. Foreign DNA is integrated into so-called clustered regularly interspaced short palindromic repeat (CRISPR) loci, and transcripts from these loci are processed into RNAs that can target the invading DNA or RNA for destruction. To investigate the molecular basis for this processing,

Haurwitz
et al.

(p.
1355
) screened CRISPR-associated (Cas) proteins in the opportunistic pathogen
Pseudomonas aeruginosa
and found they were capable of cleaving the CRISPR transcripts. The crystal structure of Cas4 with the CRISPR RNA transcript revealed how the protein specifically recognized RNA repeats, as well as the mechanism of endonucleolytic cleavage.
Electromechanical Computing at 500°C with Silicon Carbide
Authors: Lee Te-Hao , Bhunia Swarup , Mehregany Mehran
Published: September 2010

High-Temperature Electronic Switching

In electronic circuitry, the band gap of a semi-conductor helps to provide the barrier that keeps charge carriers from flowing until a voltage is applied that switches the device. As temperatures rise, the carriers acquire enough thermal energy to overcome the band gap, causing the device to leak current even when they are turned off. The higher band gap of silicon carbide (SiC) makes it an attractive candidate for higher-temperature operations compared to conventional silicon, but several performance issues occur with SiC junction field-effect transistors.

T.-H. Lee
et al.

(p.
1316
) describe the fabrication of SiC nano-electromechanical switches that formed inverter circuits with extremely low leakage currents and switched billions of times at 500°C.
Coherence Resonance in a Single-Walled Carbon Nanotube Ion Channel
Authors: Lee Chang Young , Choi Wonjoon , Han Jae-Hee , Strano Michael S.
Published: September 2010

Oscillations in Carbon Nanotube Conductivity

Theoretical studies have suggested that protons can be conducted rapidly in water trapped inside carbon nanotubes.

C. Y. Lee
et al.

(p.
1320
) connected two aqueous reservoirs with opened, single-walled carbon nanotubes, half a millimeter long but only 1.5 nanometers wide, and observed a high, stable proton current under electroosmotic conditions arising from a single nanotube. The addition of alkali cations caused random pore blocking and oscillations in ion current, resembling events seen in biological ion channels.
Arguing for the Achievable

The Idea of Justice
by Amartya Sen

Harvard University Press, Cambridge, MA, 2009. 496 pp. $29.95, £22.95, €27. ISBN 9780674036130.
Authors: Binmore Ken
Published: September 2010

In this consideration of what constitutes a just society, Sen argues for a comparative perspective that offers grounds for choosing among the alternatives people actually face.
The Blood Stem Cell Holy Grail?
Authors: Sauvageau Guy , Humphries R. Keith
Published: September 2010

A compound promotes robust expansion of human hematopoietic stem cells in culture.
Farewell to Fossil Fuels?
Authors: Hoffert Martin I.
Published: September 2010

Barring new CO2sources could curb climate change, but won't solve energy problems.
Exciting Structures
Authors: Al-Hashimi Hashim M.
Published: September 2010

High-resolution structures of folding intermediates of proteins come into view.
Oscillating Roots
Authors: Traas Jan , Vernoux Teva
Published: September 2010

Where plant roots branch may be decided by rhythmic pulses of gene expression.
Higgs or Bust? Fermilab Weighs Adding 3 Years to Tevatron Run
Authors: Cho Adrian
Published: September 2010

The director of Fermi National Accelerator Laboratory is facing a decision: whether to run the lab's 25-year-old atom smasher, the Tevatron collider, for an additional 3 years through 2014 at the cost of delaying other projects that could enhance the lab's long-term viability.
Phoenix Lander Revealing a Younger, Livelier Mars
Authors: Kerr Richard A.
Published: September 2010

Data the Phoenix lander returned in 2008 on the isotopic composition of atmospheric carbon dioxide indicate that the martian atmosphere may have been chemically interacting with liquid water recently. And where there's liquid water, of course, there could be life.
Joint Expedition Discovers Deep-Sea Biodiversity, New Volcanoes
Authors: Normile Dennis
Published: September 2010

A remotely operated vehicle surveying the shallow water reefs of the Coral Triangle has captured stunning images of massive corals, as well as unusual crustaceans and fish living at depths never before surveyed, thousands of meters below the surface.
LIFE SCIENCE TECHNOLOGIES: Biomarker Hunters Probe the Proteome
Authors: Dove Alan
Published: September 2010

The advent of sophisticated new tools has drawn many researchers into the burgeoning field of proteomic biomarker discovery, but turning their discoveries into clinical tests is still a tall order.
Muramyl Dipeptide Synergizes with
Staphylococcus aureus
Lipoteichoic Acid To Recruit Neutrophils in the Mammary Gland and To Stimulate Mammary Epithelial Cells
Authors: Bougarn Salim , Cunha Patricia , Harmache Abdallah , Fromageau Angélina , Gilbert Florence B. , Rainard Pascal
Published: September 2010

Staphylococcus aureus
, a major pathogen for the mammary gland of dairy ruminants, elicits the recruitment of neutrophils into milk during mastitis, but the mechanisms are incompletely understood. We investigated the response of the bovine mammary gland to muramyl dipeptide (MDP), an elementary constituent of the bacterial peptidoglycan, alone or in combination with lipoteichoic acid (LTA), another staphylococcal microbial-associated molecular pattern (MAMP). MDP induced a prompt and marked influx of neutrophils in milk, and its combination with LTA elicited a more intense and prolonged influx than the responses to either stimulus alone. The concentrations of several chemoattractants for neutrophils (CXCL1, CXCL2, CXCL3, CXCL8, and C5a) increased in milk after challenge, and the highest increases followed challenge with the combination of MDP and LTA. MDP and LTA were also synergistic in inducing
in vitro
chemokine production by bovine mammary epithelial cells (bMEpC). Nucleotide-binding oligomerization domain 2 (NOD2), a major sensor of MDP, was expressed (mRNA) in bovine mammary tissue and by bMEpC in culture. The production of interleukin-8 (IL-8) following the stimulation of bMEpC by LTA and MDP was dependent on the activation of NF-κB. LTA-induced IL-8 production did not depend on platelet-activating factor receptor (PAFR), as the PAFR antagonist WEB2086 was without effect. In contrast, bMEpC and mammary tissue are known to express Toll-like receptor 2 (TLR2) and to respond to TLR2 agonists. Although the levels of expression of the inflammatory cytokines tumor necrosis factor alpha (TNF-α) and IL-1β were increased by LTA and MDP at the mRNA level, no protein could be detected in the bMEpC culture supernatant. The level of induction of IL-6 was low at both the mRNA and protein levels. These results indicate that MDP and LTA exert synergistic effects to induce neutrophilic inflammation in the mammary gland. These results also show that bMEpC could contribute to the inflammatory response by recognizing LTA and MDP and secreting chemokines but not proinflammatory cytokines. Overall, this study indicates that the TLR2 and NOD2 pathways could cooperate to trigger an innate immune response to
S. aureus
mastitis.
The Th1 Immune Response toPlasmodium falciparumCircumsporozoite Protein Is Boosted by Adenovirus Vectors 35 and 26 with a Homologous Insert
Authors: Radošević Katarina , Rodriguez Ariane , Lemckert Angelique A. C. , van der Meer Marjolein , Gillissen Gert , Warnar Carolien , von Eyben Rie , Pau Maria Grazia , Goudsmit Jaap
Published: September 2010

The most advanced malaria vaccine, RTS,S, is comprised of an adjuvant portion of thePlasmodium falciparumcircumsporozoite (CS) protein fused to and admixed with the hepatitis B virus surface antigen. This vaccine confers short-term protection against malaria infection, with an efficacy of about 50%, and induces particularly B-cell and CD4+T-cell responses. In the present study, we tested by the hypothesis that the Th1 immune response to CS protein, in particular the CD8+T-cell response, which is needed for strong and lasting malaria immunity, is boosted to sustainable levels vectors adenovirus and 26 with an homologous insert 35 (Ad35.CS/Ad26.CS). In this study, we evaluated immune responses induced with vaccination regimens based on an adjuvant-containing, yeast-produced complete CS protein followed by two recombinant low-seroprevalence adenoviruses expressingP. falciparumCS antigen, Ad35.CS (subgroup B) and Ad26.CS (subgroup D). Our results show that (i) the yeast (Hansenula polymorpha)produced, adjuvanted full-length CS protein is highly potent in inducing high CS-specific humoral responses in mice but produces poor T-cell responses, (ii) the Ad35.CS vector boosts the gamma interferon-positive (IFN-γ+) CD8+T-cell response induced by the CS protein immunization and shifts the immune response toward the Th1 type, and (iii) a three-component heterologous vaccination comprised of a CS protein prime followed by boosts with Ad35.CS and Ad26.CS elicits an even more robust and sustainable IFN-γ+CD8+T-cell response than one- or two-component regimens. The Ad35.CS/Ad26.CS combination boosted particularly the IFN-γ+and tumor necrosis factor alpha-positive (TNF-α+) T cells, confirming the shift of the immune response from the Th2 type to the Th1 type. These results support the notion of first immunizations of infants with an adjuvanted CS protein vaccine, followed by a booster Ad35.CS/Ad26.CS vaccine at a later age, to induce lasting protection against malaria for which the Th1 response and immune memory is required.
Microarray for Hepatitis B Virus Genotyping and Detection of 994 Mutations along the Genome
Authors: Gauthier Marie , Bonnaud Bertrand , Arsac Maud , Lavocat Fabien , Maisetti Jérôme , Kay Alan , Simon François , Zoulim Fabien , Vernet Guy
Published: September 2010

Genome analysis of hepatitis B virus (HBV) in patient sera is helpful for monitoring treatment. We developed an improved version of a DNA microarray to identify HBV genotypes and to detect mutations of interest in the S, Pol, Core, and X genes. It includes an automated software analysis of fluorescence values for simpler, more robust data interpretation. In this version, probes were added to identify genotype H, to analyze 155 additional positions, and to detect 561 additional polymorphisms. Sequences were added to the alignments to resolve hybridization problems due to natural polymorphisms in the vicinity of important codons. The duplex PCR protocol allowed whole-genome analysis in a single tube. An alternative nested-PCR protocol allowed genotyping and mutations in S and reverse transcriptase (rt) genes in patients with low viral loads, as demonstrated in patients with less than 400 HBV genome copies/ml. Reproducibility was high, with variation coefficients lower than 3%. Only 0.57% of 20,771 codons from 253 samples could not be identified. The concordance with Sanger sequencing for the identification of codons improved from 92.8% to 95.7% with the improved version. Concordance was higher than 91% for codons associated with resistance to lamivudine, emtricitabine, telbivudine, famciclovir, entecavir, and tenofovir with vaccine escape and for pre-Core mutants. Concordance was lower for adefovir resistance mutations (68.6%) and mutations in the basal core promoter (60.3%), probably because hybridization efficiency was affected by the low GC content of the probes. A concordance of 93.7% with sequencing for genotype identification was observed in 190 specimens, lower than that obtained with the first version, possibly due to mixed virus populations.
Detection and Identification of
Mycobacterium
spp. in Clinical Specimens by Combining the Roche Cobas Amplicor
Mycobacterium tuberculosis
Assay with
Mycobacterium
Genus Detection and Nucleic Acid Sequencing
Authors: Peter-Getzlaff S. , Lüthy J. , Voit A. , Bloemberg G. V. , Böttger E. C.
Published: September 2010

We have recently developed a PCR assay for detection of
Mycobacterium
spp. at the genus level based on the Cobas Amplicor platform. The sensitivities for smear-positive and smear-negative specimens were found to be 100% and 47.9%, respectively. The specificity was 97.7%, the positive predictive value 84.6%, and the negative predictive value 93.1%. In a follow-up study, we have systematically evaluated the
Mycobacterium
genus assay in parallel with the Cobas Amplicor
Mycobacterium
tuberculosis
assay on 2,169 clinical specimens, including respiratory and nonrespiratory specimens. Based on the genus assay, nontuberculous mycobacteria were readily detected and identified to the species level by PCR-mediated sequencing. In addition, our data point to a limited specificity of the Cobas Amplicor
M. tuberculosis
assay.
Nationwide Sentinel Surveillance of Bloodstream
Candida
Infections in 40 Tertiary Care Hospitals in Spain
Authors: Cisterna R. , Ezpeleta G. , Telleria O. , Guinea J. , Regueiro B. , Garcia-Rodríguez J. , Esperalba J.
Published: September 2010

Candidemia studies have documented geographic differences in rates and epidemiology, underscoring the need for surveillance to monitor trends. We conducted prospective candidemia surveillance in Spain to assess the incidence, species distribution, frequency of antifungal resistance, and risk factors for acquiring a
Candida
infection. Prospective laboratory-based surveillance was conducted from June 2008 to June 2009 in 40 medical centers located around the country. A case of candidemia was defined as the isolation of a
Candida
species from a blood culture. Incidence rates were calculated per 1,000 admissions. Antifungal susceptibility tests were performed by using broth microdilution assay according to the guidelines of the Clinical and Laboratory Standards Institute. We detected 984 cases, for an overall incidence of 1.09 cases per 1,000 admissions. The crude mortality was 20.20%.
Candida
albicans
was the most common species (49.08%), followed by
C
.
parapsilosis
(20.73%),
C. glabrata
(13.61%), and
C. tropicalis
(10.77%). Overall, decreased susceptibility to fluconazole occurred in 69 (7.01%) incident isolates. Antifungal resistance was rare, and a moderate linear correlation between fluconazole and voriconazole MICs was observed. This is the largest multicenter candidemia study conducted to date and shows the substantial morbidity and mortality of candidemia in Spain.
Interlaboratory Evaluation of Different Extraction and Real-Time PCR Methods for Detection ofCoxiella burnetiiDNA in Serum
Authors: Tilburg Jeroen J. H. C. , Melchers Willem J. G. , Pettersson Annika M. , Rossen John W. A. , Hermans Mirjam H. A. , van Hannen Erik J. , Nabuurs-Franssen Marrigje H. , de Vries Maaike C. , Horrevorts Alphons M. , Klaassen Corné H. W.
Published: September 2010

In the Netherlands, there is an ongoing and unparalleled outbreak of Q fever. Rapid and reliable methods to identify patients infected withCoxiella burnetii, the causative agent of Q fever, are urgently needed. We evaluated the performance of different DNA extraction methods and real-time PCR assays that are in use in seven diagnostic or reference laboratories in the Netherlands. A low degree of variation in the sensitivities of most of the developed real-time PCR assays was observed. However, PCR assays amplifying short DNA fragments yielded better results than those producing large DNA fragments. With regard to DNA extraction, the automated MagNA Pure Compact system and the manual QIAamp DNA mini kit consistently yielded better results than either the MagNA Pure LC system and NucliSens EasyMag (both automated) or the High Pure viral nucleic acid kit (manual). The present study shows that multiple combinations of DNA extraction kits and real-time PCR assays offer equivalent solutions to detectC. burnetiiDNA in serum samples from patients suspected to have Q fever.
Death by Edible Mushroom: First Report of
Volvariella volvacea
as an Etiologic Agent of Invasive Disease in a Patient following Double Umbilical Cord Blood Transplantation
Authors: Salit R. B. , Shea Y. R. , Gea-Banacloche J. , Fahle G. A. , Abu-Asab M. , Sugui J. A. , Carpenter A. E. , Quezado M. M. , Bishop M. R. , Kwon-Chung K. J.
Published: September 2010

We describe a case of invasive fungal infection caused by
Volvariella volvacea
following double umbilical cord blood transplantation (UCBT). Although infections caused by several mushroom species have been documented, we believe this to be the first published report of invasive infection with
Volvariella volvacea
, an edible mushroom belonging to
Agaricales
.
Impact of ETIF Deletion on Safety and Immunogenicity of Equine Herpesvirus Type 1-Vectored Vaccines
Authors: Hofmann-Sieber Helga , Wild Jens , Fiedler Nicole , Tischer Karsten , von Einem Jens , Osterrieder Nikolaus , Hofmann Heike , Köstler Josef , Wagner Ralf
Published: September 2010

Heterologous gene transfer by viral vector systems is often limited by factors such as preexisting immunity, toxicity, low packaging capacity, or weak immunogenic potential. A novel viral vector system derived from equine herpesvirus type 1 (EHV-1) not only overcomes some of these obstacles but also promotes the robust expression of a delivered transgene and the induction of antigen-specific immune responses. Regarding an enhanced safety profile, we assessed the impact of the gene encoding the sole essential tegument protein, ETIF, on the replication and immunogenicity of recombinant EHVs. The deletion of ETIF severely attenuates replication in permissive RK13 cells and a human lung epithelial cell line but without influencing transgene expression. Whereas the intranasal administration of a recombinant luciferase EHV in BALB/c mice resulted in transgene expression in nasal cavities and lungs for 5 to 6 days, the ETIF deletion limited expression to 2 days and resulted in 30-fold-less luminescence. Attenuated replication was accompanied by a decreased capacity to induce CD8+T cells against a delivered HIV Gag transgene in BALB/c mice following repeated intranasal application. However, a single subcutaneous immunization with agagDNA vaccine primed specific T cells for substantial expansion by two subsequent intranasal booster immunizations with either thegagrecombinant ETIF mutant or the parental virus. In addition to inducing Gag-specific serum antibodies, this prime-boost strategy clearly outperformed three sequential immunizations with the parental or EHV-ΔETIF virus or repeated DNA vaccination by inducing substantial specific secretory IgA (sIgA) titers.
SUMOylation Promotes PML Degradation during Encephalomyocarditis Virus Infection
Authors: El Mchichi Bouchra , Regad Tarik , Maroui Mohamed-Ali , Rodriguez Manuel S. , Aminev Aleksey , Gerbaud Sylvie , Escriou Nicolas , Dianoux Laurent , Chelbi-Alix Mounira K.
Published: September 2010

The promyelocytic leukemia (PML) protein is expressed in the diffuse nuclear fraction of the nucleoplasm and in matrix-associated structures, known as nuclear bodies (NBs). PML NB formation requires the covalent modification of PML to SUMO. The noncovalent interactions of SUMO with PML based on the identification of a SUMO-interacting motif within PML seem to be required for further recruitment within PML NBs of SUMOylated proteins. RNA viruses whose replication takes place in the cytoplasm and is inhibited by PML have developed various strategies to counteract the antiviral defense mediated by PML NBs. We show here that primary fibroblasts derived from PML knockout mice are more sensitive to infection with encephalomyocarditis virus (EMCV), suggesting that the absence of PML results in an increase in EMCV replication. Also, we found that EMCV induces a decrease in PML protein levels both in interferon-treated cells and in PMLIII-expressing cells. Reduction of PML was carried out by the EMCV 3C protease. Indeed, at early times postinfection, EMCV induced PML transfer from the nucleoplasm to the nuclear matrix and PML conjugation to SUMO-1, SUMO-2, and SUMO-3, leading to an increase in PML body size where the viral protease 3C and the proteasome component were found colocalizing with PML within the NBs. This process was followed by PML degradation occurring in a proteasome- and SUMO-dependent manner and did not involve the SUMO-interacting motif of PML. Together, these findings reveal a new mechanism evolved by EMCV to antagonize the PML pathway in the interferon-induced antiviral defense.
A 27-Amino-Acid Deletion in the Neuraminidase Stalk Supports Replication of an Avian H2N2 Influenza A Virus in the Respiratory Tract of Chickens
Authors: Sorrell Erin M. , Song Haichen , Pena Lindomar , Perez Daniel R.
Published: September 2010

The events and mechanisms that lead to interspecies transmission of, and host adaptation to, influenza A virus are unknown; however, both surface and internal proteins have been implicated. Our previous report highlighted the role that Japanese quail play as an intermediate host, expanding the host range of a mallard H2N2 virus, A/mallard/Potsdam/178-4/83 (H2N2), through viral adaptation. This quail-adapted virus supported transmission in quail and increased its host range to replicate and be transmitted efficiently in chickens. Here we report that of the six amino acid changes in the quail-adapted virus, a single change in the hemagglutinin (HA) was crucial for transmission in quail, while the changes in the polymerase genes favored replication at lower temperatures than those for the wild-type mallard virus. Reverse genetic analysis indicated that all adaptive mutations were necessary for transmission in chickens, further implicating quail in extending this virus to terrestrial poultry. Adaptation of the quail-adapted virus in chickens resulted in the alteration of viral tropism from intestinal shedding to shedding and transmission via the respiratory tract. Sequence analysis indicated that this chicken-adapted virus maintained all quail-adaptive mutations, as well as an additional change in the HA and, most notably, a 27-amino-acid deletion in the stalk region of neuraminidase (NA), a genotypic marker of influenza virus adaptation to chickens. This stalk deletion was shown to be responsible for the change in virus tropism from the intestine to the respiratory tract.
Fluidity of HIV-1-Specific T-Cell Responses during Acute and Early Subtype C HIV-1 Infection and Associations with Early Disease Progression
Authors: Mlotshwa Mandla , Riou Catherine , Chopera Denis , de Assis Rosa Debra , Ntale Roman , Treunicht Florette , Woodman Zenda , Werner Lise , van Loggerenberg Francois , Mlisana Koleka , Abdool Karim Salim , Williamson Carolyn , Gray Clive M.
Published: September 2010

Deciphering immune events during early stages of human immunodeficiency virus type 1 (HIV-1) infection is critical for understanding the course of disease. We characterized the hierarchy of HIV-1-specific T-cell gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) assay responses during acute subtype C infection in 53 individuals and associated temporal patterns of responses with disease progression in the first 12 months. There was a diverse pattern of T-cell recognition across the proteome, with the recognition of Nef being immunodominant as early as 3 weeks postinfection. Over the first 6 months, we found that there was a 23% chance of an increased response to Nef for every week postinfection (
P
= 0.0024), followed by a nonsignificant increase to Pol (4.6%) and Gag (3.2%). Responses to Env and regulatory proteins appeared to remain stable. Three temporal patterns of HIV-specific T-cell responses could be distinguished: persistent, lost, or new. The proportion of persistent T-cell responses was significantly lower (
P
= 0.0037) in individuals defined as rapid progressors than in those progressing slowly and who controlled viremia. Almost 90% of lost T-cell responses were coincidental with autologous viral epitope escape. Regression analysis between the time to fixed viral escape and lost T-cell responses (
r
= 0.61;
P
= 0.019) showed a mean delay of 14 weeks after viral escape. Collectively, T-cell epitope recognition is not a static event, and temporal patterns of IFN-γ-based responses exist. This is due partly to viral sequence variation but also to the recognition of invariant viral epitopes that leads to waves of persistent T-cell immunity, which appears to associate with slower disease progression in the first year of infection.
Altered Receptor Specificity and Cell Tropism of D222G Hemagglutinin Mutants Isolated from Fatal Cases of Pandemic A(H1N1) 2009 Influenza Virus
Authors: Liu Yan , Childs Robert A. , Matrosovich Tatyana , Wharton Stephen , Palma Angelina S. , Chai Wengang , Daniels Rodney , Gregory Victoria , Uhlendorff Jennifer , Kiso Makoto , Klenk Hans-Dieter , Hay Alan , Feizi Ten , Matrosovich Mikhail
Published: September 2010

Mutations in the receptor-binding site of the hemagglutinin of pandemic influenza A(H1N1) 2009 viruses have been detected sporadically. An Asp222Gly (D222G) substitution has been associated with severe or fatal disease. Here we show that 222G variants infected a higher proportion of ciliated cells in cultures of human airway epithelium than did viruses with 222D or 222E, which targeted mainly nonciliated cells. Carbohydrate microarray analyses showed that 222G variants bind a broader range of α2-3-linked sialyl receptor sequences of a type expressed on ciliated bronchial epithelial cells and on epithelia within the lung. These features of 222G mutants may contribute to exacerbation of disease.
Electrolytic reduction of o-nitrobenzyl thiocyanate in buffered solutions on mercury
Authors: Hlavatý Jaromír
Published: September 2010

The o-nitrobenzyl thiocyanate (I) behaves differently on the DME and on a large mercury pool electrode. Polarography did not give a sufficiently clear explanation of the reaction mechanism, only the preparative experiments yielded useful results. Whereas polarographic curves in solutions of Britton-Robinson buffer system with 50% by vol. ethanol exhibit two cathodic waves within the pH region 1-12, corresponding according to their height ratio to an uptake of 4 e and 2 e respectively, the controlled potential preparation electrolysis (CPE) and coulometry results indicate a more complicated reaction path. In the CPE carried out at the concentration of I 1 . 10 -2 mol/l the electroreductive splitting of CH2-SCN occurs as the first step. Nitrobenzyl radicals so formed react in the follow-up dimerization resulting in dibenzyl or toluene structures. Simultaneously or at a later stage the completion of the electrolytic reduction of the nitro group proceeds to the hydroxylamino group. In solution of 9 > pH > 1 the CPE of nitro compound I takes place by an ECEC mechanism yielding dibenzodiazocine III, its N-oxide IV and 2,2'-dimethylazoxybenzene (V). In course of preparative electrolysis in strongly acidic medium 2-amino-benzo(l,3)-thiazine-l-oxide (II) is formed by an EC mechanism.
Gas holdup and kLa in perforated-plate bubble columns in the presence of solid particles
Authors: Kratochvíl Jan , Winkler Kurt , Zahradník Jindřich
Published: September 2010

The effect of solid particles on values of volumetric liquid-side mass transfer coefficient, kLa, and gas holdup, εG, was determined in a bubble column 0.14 m in diameter within the range of solid phase concentration cS = 0-10% (mass). Experiments were carried out in air-water system at zero liquid flow rate, glass spheres of average diameters 24, 36, 50, 102, 142, 190, and 280 μm and fine Zn0 powder (average particle size 2.3 μm) were used as a solid phase. Perforated plate with holes diameter 1.6 mm and free plate area 0.2% was used for gas distribution, superficial gas velocities ranged between 0.036 and 0.215 m/s. Only negative effect of the gas holdup and kLa was observed in the whole range of experimental conditions, this effect being most pronounced in the region of small particle sizes (dS ⪬ 36 μm).
Conformation of branched polypeptides based on poly(L-lysine): The effect of terminal amino acids in the branches
Authors: Votavová Hana , Hudecz Ferenc , Kajtár Judit , Šponar Jaroslav , Bláha Karel , Szekerke Mária
Published: September 2010

CD Spectra of branched polypeptides based on poly(L-lysine) and containing three DL-alanine residues and one to three other L- or D-amino acid residues in the branches were measured in water, water-methanol and water-trifluoroethanol mixtures. In aqueous solutions dependence of the CD spectra on pH and ionic strength was studied. The effect of branch elongation was followed mainly with compounds containing glutamic acid. One terminal D-amino acid residue and also an extension by two L- or D-amino acid residues does not hinder the α-helix formation in the backbone but affects the conditions of its formation. In polypeptides with three L- or D-amino acids additional α-helical segments in the branches are assumed to be formed. For branches with L-amino acids the CD curves express additively the contributions of both helical components, in the case of D-amino acids the increasing population of the ordered structure in branches is manifested by compensation of dichroic contribution of the L-amino acid backbone leading even to enantiomorphous curves.
Assignment techniques for 29Si NMR chemical shifts in pertrimethylsilylated products. Tests of empirical assignment rules by a modified 29Si indor
Authors: Schraml Jan , Larin Michail Fedorovich , Pestunovich Vadim Aleksandrovich
Published: September 2010

A modification of the 29Si INDOR technique is described that monitors instead of the usual Si(CH3)3 proton line the line of CHnXSi (n = 1, 2; X = O, S, NH) protons while the 29Si NMR spectrum is being scanned. Though less sensitive and accurate than the routine INDOR, the modified method permits assignment of 29Si chemical shifts providing that the CHn proton lines in 1H NMR spectrum are well separated and assigned. The modified INDOR is used here to assign the 29Si chemical shifts in pertrimethylsilylated 1,6-anhydro-β-D-glucopyranose (1) and methyl β-D-xylopyranoside (2). The values of chemical shifts determined by this technique agree with those determined by standard 29Si NMR methods but the assignment suggested for 1 on empirical grounds previously must be partially revised, the empirical assignment in the spectrum of 2 (based on additivity rule) is fully confirmed.
Sodium salt, sulfonates and carboxylates of (E)- and (Z)-3-(hydroxymethylene)-5-methyldihydro-2(3H)-furanone
Authors: Mazal Ctibor , Rothová Věra , Jonas Jaroslav
Published: September 2010

In the solid state, sodium salt of 3-(hydroxymethylene)-5-methyldihydro-2(3H)-furanone can be prepared in the form of the (Z)-isomer, (E)-isomer or as a mixture of both isomers; in solutions the salt exists exclusively as the (E)-isomer. Reaction of the corresponding isomers of this sodium salt with sulfonyl or acyl chlorides afforded sulfonates or carboxylates derived from (E)- or (Z)-3-(hydroxymethylene)-5-methyldihydro-2(3H)-furanone. Configurations of the obtained isomeric sulfonates and carboxylates were confirmed by their 1H and 13C NMR spectra. Dihedral angles, calculated from the observed coupling constants, were used in the discussion of preferred conformation of the prepared compounds.
Synthesis of the sulfonamido derivatives of arabinonucleosides
Authors: Novotný Ladislav , Hřebabecký Hubert , Beránek Jiří
Published: September 2010

Reaction of the sodium salt of 4-aminobenzenesulfonamide with cyclocytidine I and cyclouridine II led to the 2-sulfonamido derivatives V and VI while the reaction with the 5'-chloro derivatives of anhydronucleosides III and IV afforded compounds VIII and IX containing nitrogen bridge between the carbon atoms in position 2 and 5'. Kinetics of the model cyclization reaction of 5'-chloroarabinosylisocytosine (XI) was followed and the structure of prepared compounds was confirmed. Inhibition activity against L 1210 leukemia cells in the experiments in vitro was exhibited by compounds V (1.4 . 10-5 mol l-1) and VIII (3.3 . 10-6 mol l-1).
Structure of the complexes of ethylenediphosphinetetraacetic acid in solution
Authors: Podlahová Jana , Šilha Josef , Podlaha Jaroslav
Published: September 2010

Ethylenediphosphinetetraacetic acid is bonded to metal ions in aqueous solutions in four ways, depending on the type of metal ion: 1) through an ionic bond of the carboxylic groups to form weak complexes with a metal:ligand ratio of 1 : 1 (Ca(II), Mn(II), Zn(II), Pb(II), La(III)); 2) through type 1) bond with contributions from weak interaction with the phosphorus (Cd(II)); 3) through coordination of the ligand as a monodentate P-donor with the free carboxyl groups with formation of 2 : 1 and 1 : 1 complexes (Cu(I), Ag(I)); 4) through formation of square planar or, for Hg(II), tetrahedral complexes with a ratio of 1 : 2 with the ligand as a bidentate PP-donor with the free carboxyl groups (Fe(II), Co(II), Ni(II), Pd(II), Pt(II)). On acidification of the complex solution, the first two protons are bonded to the carboxyl groups. The behaviour during further protonation depends on the type of complex: in complexes of types 1) and 2) phosphorus is protonated and the complex dissociates; in complexes of types 3) and 4) the free carboxyl groups are protonated and the phosphorus-metal bond remains intact. The results are based on correlation of the stability constants, UV-visible, infrared, 1H and 31P NMR spectra and magnetic susceptibilities of the complexes in aqueous solution.
Preparation and polymerization of 3-(2-adamantyl)-3-methyl-2-azetidinone
Authors: Hauer Jan , Šebenda Jan
Published: September 2010

3-(2-Adamantyl)-3-methyl-2-azetidinone (VI) was prepared, and new compounds, namely, methyl 2-(2-adamantyl) cyanoacetate, methyl-2-(2-adamantyl)-2-cyanopropanoate and methyl-2-(2-adamantyl)-2-methyl-3-aminopropanoate, were prepared in the course of the synthesis as intermediates. The anionic polymerization of lactam VI gave a polymer which was characterized by intrinsic viscosity, solubility, melting temperature and its IR and 1H NMR spectra. Compared with 3-butyl-3-methyl-2-azetidinone, lactam VI polymerizes much more slowly.
Reactions of 1-(5-nitro-2-furyl)-2-nitroethylene with amino and hydroxy groups
Authors: Rosenberg Michal , Šturdík Ernest , Liptaj Tibor , Bella Juraj , Végh Daniel , Považanec František , Sitkey Vladimír
Published: September 2010

Reactions have been studied of l-(5-nitro-2-furyl)-2-nitroethylene with -NH, and -OH groups of low-molecular compounds (butylamine, aniline, glycine, taurine, glucosamine, tyramine, tryptamine, noradrenaline, histamine, ethanol, methanol, OH- ions) as well as biopolymers (ribonuclease, albumin DNA, RNA, Newcastle disease virus). With the low-molecular amines and alcohols it has been found that the reactions proceed as nucleophilic additions in aqueous medium, and the respective nucleophilic groups attack the more electrophilic C(1) atom of the exocyclic double bond of nitrofurylethylene. The modifications proved with the above-mentioned biopolymers in vitro indicate a possibility of direct interaction (without metabolic activation) between 5-nitro-2-furylethylenes and proteins or nucleic acids in vivo. These findings are significant from the point of view of recognizing mutagenic effect of nitrofurylethylenes and general biotoxicity of these compounds.
Synthesis, spectral properties, and pesticidal activity of 4-amino(alkylamino, dialkylamino)-5-chloro-2-substituted-3-oxo-2H-pyridazines and 5-amino(alkylamino, dialkylamino)-4-chloro-2-substituted-3-oxo-2H-pyridazines
Authors: Konečný Václav , Kováč Štefan , Varkonda Štefan
Published: September 2010

4-Amino(alkylamino)-5-chloro-2-substituted-3-oxo-2H-pyridazines and 5-amino(alkylamino, dialkylamino)-4-chloro-2-substituted-3-oxo-2H-pyridazines have been prepared by nucleophilic substitution reactions of 4,5-dichloro-2-substituted-3-oxo-2H-pyridazines with amines in aprotic solvent. Structure of the compounds prepared has been proved by IR and UV spectra. Fungicidal and herbicidal activity of the compounds prepared have been tested. None of the compounds prepared exceeds the standard Vitavax in the fungicidal activity tests. Compounds VIII and XII show equal or better activity on the Hill reaction as compared with the standard pyrazone.
Lipophilic-hydrophilic properties and retention of phenylhydrazonopropanedinitriles by biological systems
Authors: Šturdík Ernest , Baláž Štefan , Antalík Marián , Sulo Pavol
Published: September 2010

Apparent partition coefficients in n-octanol-buffer system, solubility in the buffers, and retention by mitochondria from rat liver, by Mycobacterium phlei and by Saccharomyces cerevisiae (after 10 min incubation) have been characterized for 13 arylsubstituted phenylhydrazonopropanedinitrile derivatives. Regression analysis has shown linear dependence of logarithms of the apparent partition coefficients on the published π parameters characterizing lipophilicity of the substituents. The apparent partition coefficients are inversely proportional to the solubility of the phenylhydrazonopropanedinitriles. The retention by the biosystems studied increases linearly with increasing lipophilicity, being independent of reactivity of the phenylhydrazonopropanedinitriles. The non-linear dependence of concentration of the phenylhydrazonopropanedinitriles remaining in the medium on the lipophilicity indicates that a lipophilic-hydrophilic equilibrium is established in the given time. The retained amount of the derivatives tested decreases with increasing pH values. The dependences are Z-shaped and have been described by the equations derived from the model presented by application of non-linear regression analysis.
Topological aspects of chemical reactivity. Photochemical and free radical reactions
Authors: Ponec Robert
Published: September 2010

Recently proposed method of the so called overlap determinant is extended in thus study to free radical and photochemical reactions. In comparison with existing alternative procedures the advantage of this generalised formalisms consists not only in its simplicity but above all in its universality allowing to analyse in a unified manner all types of chemical reactions.
Topological aspects of chemical reactivity. Theoretical justification of overlap determinant method
Authors: Ponec Robert
Published: September 2010

The mutual relation of overlap determinant method and the selection rules in chemical reactivity has been analysed in terms of the technique of the configuration analysis. Such approach allows to prove the generality and the universality of the originally introduced criterion not only for thermal but also for photochemical reactions.
Coulometric determination of hydroquinone, 4-aminophenol and methol with trivalent manganese fluoride complex
Authors: Barek Jiří , Berka Antonín , Divoká Dagmar
Published: September 2010

The possibility of the coulometric generation of trivalent manganese in fluoride solutions was examined and the current efficiency was measured in dependence on the solution composition and current density. Direct coulometric titrations of reversibly oxidizable organic compounds were tested on hydroquinone, 4-aminophenol, and methol in milligram and microgram quantities. As a more convenient approach, a method of coulometric retitration of trivalent manganese fluoride complex with divalent iron was worked out and its limits were established. The applicability of the trivalent manganese-divalent iron dual system to the indirect determination of the above model organic substances was verified.
A system for testing mass-transfer models with a chemical reaction in liquid -dispersions: Iodine, n-heptane/potassium iodide, potassium hexacyanoferrate(II), water
Authors: Hudec Petr , Rod Vladimír , Lukešová Svatava
Published: September 2010

Mass transfer of iodine from n-heptane into the aqueous phase containing potassium iodide and potassium hexacyanoferrate(II) was investigated in a diffusion cell with vibrational agitation. The data obtained were employed to evaluate parameters of the model describing the transfer of iodine accompanied by the formation of triiodide and by oxidation of the hexacyanoferrate(II). The system described is suitable for testing mass-transfer models with a chemical reaction in the liquid-liquid dispersions, since, by a proper choice of concentrations of its reaction components, mass-transfer resistances in individual phases can be varied in a wide range and high sensitivity of parameters of the model can be achieved.
Approximate relations for determining the activity coefficient at very low concentration by the method of variation of solute concentration
Authors: Doležal Bohuslav , Holub Robert
Published: September 2010

The calculation of activity coefficients at very low concentration is described from the experimental data obtained by the method of the variation of solute concentration for a way of saturation with ensured sufficiently long contact time of the liquid and gas phases and intensive stirring of both phases when the amount of the observed component in the vapour phase above the solution is negligible with regard to its content in the liquid phase. Two variants of experimental procedure were considered: stripping by a pure inert gas and by a gas saturated with solvent vapours. The relations derived can be used either directly for computer calculations or on introducing some simplifying assumptions for a rapid manual calculation with a good agreement of the results.
The effect of two-phase flow regime on hydrodynamics and mass transfer in a horizontal-tube gas-liquid reactor
Authors: Zahn Andreas , Ebner Lothar , Winkler Kurt , Kratochvíl Jan , Zahradník Jindřich
Published: September 2010

The effect of two-phase flow regime on decisive hydrodynamic and mass transfer characteristics of horizontal-tube gas-liquid reactors (pressure drop, liquid holdup, kLaL) was determined in a cocurrent-flow experimental unit of the length 4.15 m and diameter 0.05 m with air-water system. An adjustable-height weir was installed in the separation chamber at the reactor outlet to simulate the effect of internal baffles on reactor hydrodynamics.

Flow regime maps were developed in the whole range of experimental gas and liquid flow rates both for the weirless arrangement and for the weir height 0.05 m, the former being in good agreement with flow-pattern boundaries presented by Mandhane. In the whole range of experi-mental conditions pressure drop data could be well correlated as a function of gas and liquid flow rates by an empirical exponential-type relation with specific sets of coefficients obtained for individual flow regimes from experimental data. Good agreement was observed between values of pressure drop obtained for weirless arrangement and data calculated from the Lockhart-Martinelli correlation while the contribution of weir to the overall pressure drop was well described by a relation proposed for the pressure loss in closed-end tubes. In the region of negligible weir influence values of liquid holdup were again succesfully correlated by the Lockhart-Martinelli relation while the dependence of liquid holdup data on gas and liquid flow rates obtained under conditions of significant weir effect (i.e. at low flow rates of both phases) could be well described by an empirical exponential-type relation. Results of preliminary kLaL measurements confirmed the decisive effect of the rate of energy dissipation on the intensity of interfacial mass transfer in gas-liquid dispersions.
A note on detection of gross errors in chemical engineering measurements
Authors: Madron František
Published: September 2010

Detection of gross errors in chemical engineering measurements is studied, based on statistical analysis of redundant data. A method of simple evaluation of the gross error detection efficiency is presented. The construction of the power characteristics is illustrated by an example. The study complements the previous authors work on this subject, where the same problem was studied by stochastic simulation.
Bromine and period of Belousov-Zhabotinskii type oscillation reaction
Authors: Ševčík Peter , Adamčíková Ľubica
Published: September 2010

Belousov-Zhabotinskii type oscillation reaction with oxalic acid proceeds in a closed system, in a flow-through open system, as well as under intermediate conditions. Oscillations are started in either of the following three ways: 1) Increasing the removal of bromine from solution by bubbling inert gases, 2) chemically, and 3) in a flow-through reactor. The oscillation period is largely dependent on the removal rate of bromine, other reactant concentrations being constant.
The equilibrium acidity of cyclic and linear amides and its effect on the anionic polymerization of lactams
Authors: Valter Bohumír , Terekhova M. I. , Petrov E. S. , Stehlíček Jaroslav , Šebenda Jan
Published: September 2010

The equilibrium acidity of lactams with rings of various size and of linear N-substituted amides was measured in dimethyl sulfoxide by the spectrophotometric method. The pK values of these NH-acids thus determined varied in the range 22-27. The data are used to characterize the acidobasic equilibrium between the amide groups of the monomer, polymer and their N-anions during the anionic polymerization of lactams. The effect of acidity on the anionic copolymerization of lactams is also discussed.
The equilibrium acidity of substituted N-(phenylcarbamoyl)-6-hexanelactams and disubstituted ureas and their effect on the anionic polymerization of lactams
Authors: Valter Bohumír , Terekhova M. I. , Petrov E. S. , Stehlíček Jaroslav , Šebenda Jan
Published: September 2010

The equilibrium acidity of substituted N-(phenylcarbamoyl)-6-hexanelactams, N-butyl-N'-phenylurea and N,N'-diethylurea was determined spectrophotometrically in dimethyl sulfoxide. Using the determined pK values, the effect of activator acidity of the N-(phenylcarbamoyl)-lactam type on the anionic polymerization of lactams was estimated, and the possible effect of the individual types of urea on the concentration of lactam anions was predicted.
Quaternary alkaloids from Glaucium oxylobum BOISS. et BUSHE
Authors: Slavíková Leonora , Slavík Jiří , Dolejš Ladislav
Published: September 2010

From the fraction of quaternary alkaloids of the aerial part of Glaucium oxylobum BOISS. et BUSHE (-)-trans-N-rnethylcanadinium iodide was isolated as the main alkaloid after conversion to iodides, and, in a smaller amount, (+)-N-methylcorydinium iodide, detected for the first time in Papaveraceae, further (-)-trans-N-methylstylopinium iodide, magnoflorine iodide and a new quaternary alkaloid, N-methyldomesticinium iodide, isolated for the first time as a natural substance. In the roots, magnoflorine iodide accompanied by (+)-N-methylcorydinium iodide represented the main component of the quaternary fraction. From both plant parts corytuberine was also isolated for the first time. In the tertiary fraction of alkaloids (+)-corydine, protopine and allocryptopine were the major components, accompanied by smaller amounts of sanguinarine, chelerythrine, chelirubine, domesticine, isoboldine and scoulerine. In the fraction of quaternary protoberberines coptisine, berberine and traces of corysamine were detected.
Activity and physical properties of Ni/SiO2 hydrogenation catalysts
Authors: Kinza Horst , Paseka Ivo , Popova N. M.
Published: September 2010

The influence of the reduction temperature of Ni/SiO2 catalyst on the amount of adsorbed hydrogen and on the hydrogenation rate of o-nitrophenol and sunflower oil has been followed. The total amount and two forms of adsorbed hydrogen have been determined by TPD and electrochemical cyclic galvanostatic charging methods. The properties of catalysts were further studied by the measurement of polarization curves of electrochemical oxidation and evolution of hydrogen.The correlation between the hydrogenation rates of o-nitrophenol and weakly adsorbed hydrogen on the one hand and that of sunflower oil and total amount of adsorbed hydrogen on the other hand has been found.