bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulation of HIV-1 Replication in Immature Dendritic Cells in Contact with Primary CD4 T or B Lymphocytes
Authors: Holl Vincent , Xu Ke , Peressin Maryse , Lederle Alexandre , Biedma Marina Elizabeth , Delaporte Maryse , Decoville Thomas , Schmidt Sylvie , Laumond Géraldine , Aubertin Anne-Marie , Moog Christiane
Published: February 2010

Sexual transmission is the major route of HIV-1 infection worldwide. Dendritic cells (DCs) from the mucosal layers are considered to be the initial targets of HIV-1 and probably play a crucial role in HIV-1 transmission. We investigated the role of cell-to-cell contact between HIV-1-exposed immature DCs and various lymphocyte subsets in the stimulation of HIV-1 replication. We found that HIV-1 replication and production in DCs were substantially enhanced by the coculture of DCs with primary CD4 T or nonpermissive B lymphocytes but not with primary activated CD8 T lymphocytes or human transformed CD4 T lymphocytes. Most of the new virions released by cocultures of HIV-1-exposed immature DCs and primary B lymphocytes expressed the DC-specific marker CD1a and were infectious for both immature DCs and peripheral blood mononuclear cells (PBMCs). Cocultured DCs thus produced large numbers of infectious viral particles under these experimental conditions. The soluble factors present in the supernatants of the cocultures were not sufficient to enhance HIV-1 replication in DCs, for which cell-to-cell contact was required. The neutralizing monoclonal antibody IgG1b12 and polyclonal anti-HIV-1 sera efficiently blocked HIV-1 transfer to CD4 T lymphocytes but did not prevent the increase in viral replication in DCs. Neutralizing antibodies thus proved to be more efficient at blocking HIV-1 transfer than previously thought. Our findings show that HIV-1 exploits DC-lymphocyte cross talk to upregulate replication within the DC reservoir. We provide evidence for a novel mechanism that may facilitate HIV-1 replication and transmission. This mechanism may favor HIV-1 pathogenesis, immune evasion, and persistence.
NKp46 O-Glycan Sequences That Are Involved in the Interaction with Hemagglutinin Type 1 of Influenza Virus
Authors: Mendelson Michal , Tekoah Yoram , Zilka Alon , Gershoni-Yahalom Orly , Gazit Roi , Achdout Hagit , Bovin Nicolai V. , Meningher Tal , Mandelboim Michal , Mandelboim Ofer , David Ayelet , Porgador Angel
Published: February 2010

Natural killer (NK) cells serve as a crucial first-line defense against tumors and virus-infected cells. We previously showed that lysis of influenza virus (IV)-infected cells is mediated by the interaction between the NK receptor, NKp46, and the IV hemagglutinin (HA) type 1 expressed by the infected cells. This interaction requires the presence of sialyl groups on the NKp46-T225 O-glycoforms. In the current study, we analyzed the O-glycan sequences that are imperative for the interaction between recombinant NKp46 (rNKp46) and IV H1N1 strains. We first showed that rNKp46 binding to IV H1N1 is not mediated by a glycoform unique to the Thr225 site. We then characterized the O-glycan sequences that mediate the interaction of rNKp46 and IV H1N1; we employed rNKp46s with dissimilar glycosylation patterns and IV H1N1 strains with different sialic acid α2,3 and α2,6 linkage preferences. The branched α2,3-sialylated O-glycoform Neu5NAcα2,3-Galβ1,4-GlcNAcβ1,6[Neu5NAcα2,3-Galβ1,3]GalNAc competently mediated the interaction of rNKp46 with IV H1N1, manifesting a preference for α2,3 linkage. In contrast, the linear α2,3-sialylated O-glycoform Neu5NAcα2,3-Galβ1,3-GalNAc was not correlated with enhanced interaction between rNKp46 and IV H1N1 or a preference for α2,3 linkage. The branched α2,3- and α2,6-sialylated O-glycoform Neu5NAcα2,3-Galβ1,3[Neu5NAcα2,6]GalNAc competently mediated the interaction of rNKp46 with IV H1N1, manifesting a preference for α2,6 linkage. Previous viral HA-binding-specificity studies were performed with glycopolymer conjugates, free synthetic sialyl oligosaccharides, and sialidase-treated cells. This study shed light on the O-glycan sequences involved in the interaction of glycoprotein and viral hemagglutinins and may help in the design of agents inhibitory to hemagglutinin for influenza treatment.
Polyubiquitination of APOBEC3G Is Essential for Its Degradation by HIV-1 Vif
Authors: Shao Qiujia , Wang Yudi , Hildreth James E. K. , Liu Bindong
Published: February 2010

Proteasomal degradation of APOBEC3G is a critical step for human immunodeficiency virus type 1 (HIV-1) replication. However, the necessity for polyubiquitination of APOBEC3G in this process is still controversial. In this study, we showed that although macaque simian immunodeficiency virus (SIVmac) Vif is more stable than HIV-1 Vif in human cells, SIVmac Vif induces degradation of APBOEC3G as efficiently as HIV-1 Vif. Overexpression of APOBEC3G or lysine-free APOBEC3G stabilized HIV-1 Vif, indicating that APOBEC3G degradation is independent of the degradation of Vif. Furthermore, an
in vivo
polyubiquitination assay showed that lysine-free APOBEC3G was also polyubiquitinated. These data suggest that polyubiquitination of APOBEC3G, not that of HIV-1 Vif, is crucial for APOBEC3G degradation.
Donor and Recipient Envs from Heterosexual Human Immunodeficiency Virus Subtype C Transmission Pairs Require High Receptor Levels for Entry
Authors: Alexander Melissa , Lynch Rebecca , Mulenga Joseph , Allen Susan , Derdeyn Cynthia A. , Hunter Eric
Published: February 2010

Compact, glycan-restricted envelope (Env) glycoproteins are selected during heterosexual transmission of subtype C HIV-1. Donor and recipient glycoproteins (Envs) from six transmission pairs were evaluated for entry into HeLa cells expressing different levels of CD4 and CCR5. Donor and recipient Envs demonstrated efficient entry into cells expressing high levels of CD4 and CCR5, and entry declined as CCR5 levels decreased. Infectivity for all Envs was severely impaired in cells expressing low levels of CD4, even at the highest CCR5 levels. In 5/6 pairs, there was no significant difference in efficiency of receptor utilization between the donor and recipient Envs in these HeLa-derived cell lines. Thus, HIV-1 transmission does not appear to select for viruses that can preferentially utilize low levels of entry receptors.
T Cells Engineered with a Cytomegalovirus-Specific Chimeric Immunoreceptor
Authors: Full Florian , Lehner Manfred , Thonn Veronika , Goetz Gabriel , Scholz Brigitte , Kaufmann Kerstin B. , Mach Michael , Abken Hinrich , Holter Wolfgang , Ensser Armin
Published: February 2010

Cytomegalovirus (CMV) infection in patients receiving hematopoietic stem cell transplants (HSCT) is associated with morbidity and mortality. Adoptive T cell immunotherapy has been used to treat viral reactivation but is hardly feasible in high-risk constellations of CMV-positive HSCT patients and CMV-negative stem cell donors. We endowed human effector T cells with a chimeric immunoreceptor (cIR) directed against CMV glycoprotein B. These cIR-engineered primary T cells mediated antiviral effector functions such as cytokine production and cytolysis. This first description of cIR-redirected CMV-specific T cells opens up a new perspective for HLA-independent immunotherapy of CMV infection in high-risk patients.
The Elk-1 and Serum Response Factor Binding Sites in the Major Immediate-Early Promoter of Human Cytomegalovirus Are Required for Efficient Viral Replication in Quiescent Cells and Compensate for Inactivation of the NF-κB Sites in Proliferating Cells
Authors: Caposio Patrizia , Luganini Anna , Bronzini Matteo , Landolfo Santo , Gribaudo Giorgio
Published: February 2010

The major immediate-early promoter (MIEP) region of human cytomegalovirus (HCMV) plays a critical role in the regulation of lytic and latent infections by integrating multiple signals supplied by the infecting virus, the type and physiological state of the host cell, and its extracellular surroundings. The interaction of cellular transcription factors with their cognate binding sites, which are present at high densities within the enhancer upstream from the MIEP core promoter, regulate the rate of IE gene transcription and thus affect the outcome of HCMV infection. We have shown previously that the NF-κB binding sites within the MIEP enhancer and cellular NF-κB activity induced by HCMV infection are required for efficient MIEP activity and viral replication in quiescent cells (P. Caposio, A. Luganini, G. Hahn, S. Landolfo, and G. Gribaudo, Cell. Microbiol.
9:
2040-2054, 2007). We now show that the inactivation of either the Elk-1 or serum response factor (SRF) binding site within the enhancer also reduces MIEP activation and viral replication of recombinant HCMV viruses in quiescent fibroblasts. In these cells, we show that the expression of either Elk-1 or SRF is required for optimal IE gene expression, and that the HCMV-stimulated activation of the MEK1/2-ERK1/2 signaling axis leads to Elk-1 transcriptional competency. Furthermore, the replication kinetics of recombinant viruses in which NF-κB, Elk-1, and SRF binding sites all are inactivated demonstrate that the higher levels of Elk-1 and SRF binding to MIEP in proliferating cells can compensate even for a lack of HCMV-induced NF-κB-mediated MIEP transactivation. These observations highlight the importance of the combination of different MIEP binding sites to optimize IE gene expression in cells in different physiological states.
Hepatitis B Virus Replication Induces Methylation of both Host and Viral DNA
Authors: Vivekanandan Perumal , Daniel Hubert Darius-J , Kannangai Rajesh , Martinez-Murillo Francisco , Torbenson Michael
Published: February 2010

Control of viral replication is a major therapeutic goal to reduce morbidity and mortality from chronic hepatitis B virus (HBV) infection. Recently, methylation has been identified as a novel host defense mechanism, and methylation of viral DNA leads to downregulation of HBV gene expression. To better understand the mechanisms of HBV methylation, cell lines were exposed to HBV using a model system that mimics natural infection and the expression of host DNA methyltransferase genes (DNMTs) was measured. DNMT1, DNMT2, and DNMT3 were all significantly upregulated in response to HBV. DNMT3 was further studied because of its known role in thede novomethylation of DNA. Cotransfection experiments with full-length HBV and DNMT3 led to the downregulation of viral protein and pregenomic RNA production. To investigate whether the upregulation of DNMTs could also have an effect on the methylation of host DNA, cell lines were exposed to HBV in two independent model systems, one that mimics natural infection and a second model with temporary transfection. Host DNA methylation was measured by DNA microarray analysis. Increased methylation of host CpG islands was detected in both experimental systems. Two CpG islands, corresponding to genes SUFU and TIRAP, were selected, and the downregulation of these genes in hepatocellular carcinomas was confirmed. In conclusion, hepatocytes respond to HBV infection by upregulating DNMTs. The DNMTs methylate viral DNA, leading to decreased viral gene expression and decreased viral replication. However, virus-induced overexpression of DNMTs also leads to methylation of host CpG islands.
Viral Dynamics during Primary Simian Immunodeficiency Virus Infection: Effect of Time-Dependent Virus Infectivity
Authors: Vaidya Naveen K. , Ribeiro Ruy M. , Miller Christopher J. , Perelson Alan S.
Published: February 2010

A recent experiment involving simian immunodeficiency virus (SIV) infection of macaques revealed that the infectivity of this virus decreased over the first few months of infection. Based on this observation, we introduce a viral dynamic model in which viral infectivity varies over time. The model is fit to viral load data from eight (donor) monkeys infected by intravaginal inoculation of SIVmac251, three monkeys infected by intravenous inoculation of virus isolated from the donors during the ramp-up phase of acute infection, and three monkeys infected by intravenous inoculation of virus isolated at the viral set-point. Although we only analyze data from 14 monkeys, the new model with time-dependent infectivity seems to fit the data significantly better than a widely used model with constant infectivity (P= 2.44 × 10−11). Our results indicate that plasma virus infectivity on average decays ∼8-fold (95% confidence interval [CI] = 5.1 to 10.3) over the course of acute infection, with the decay occurring exponentially with an average rate of 0.28 day−1(95% CI = 0.14 to 0.42 day−1). The decay rate in set point plasma virus recipient animals is ∼16 times slower than in ramp-up plasma virus recipient animals and ∼6 times slower than in donor animals. Throughout acute infection up to the set-point, the infection rate is higher in ramp-up plasma virus recipient animals than in set-point plasma virus recipient animals. These results show that the infectivity depends upon the source of viral infection.
Relocalization of Upstream Binding Factor to Viral Replication Compartments Is UL24 Independent and Follows the Onset of Herpes Simplex Virus 1 DNA Synthesis
Authors: Lymberopoulos Maria H. , Pearson Angela
Published: February 2010

Herpes simplex virus 1 (HSV-1) induces relocalization of several nucleolar proteins. We have found that, as for fibrillarin, the HSV-1-induced redistribution of two RNA polymerase I components, upstream binding factor (UBF) and RPA194, was independent of the viral protein UL24, which affects nucleolin localization. Nevertheless, the kinetics and sites of redistribution for fibrillarin and UBF differed. Interestingly, UBF remained associated with RPA194 during infection. Although UBF is redistributed to viral replication compartments during infection, we did not detect foci of UBF at early sites of viral DNA synthesis, suggesting that it may not be directly involved in this process at early times.
Virus-Specific CD8+T-Cell Responses Better Define HIV Disease Progression than HLA Genotype
Authors: Dinges Warren L. , Richardt Julia , Friedrich David , Jalbert Emilie , Liu Yi , Stevens Claire E. , Maenza Janine , Collier Ann C. , Geraghty Daniel E. , Smith Jeremy , Moodie Zoe , Mullins James I. , McElrath M. Juliana , Horton Helen
Published: February 2010

HLA alleles B57/58, B27, and B35 have the strongest genetic associations with HIV-1 disease progression. The mechanisms of these relationships may be host control of HIV-1 infection via CD8+T-cell responses. We examined these immune responses in subjects from the Seattle Primary Infection Cohort with these alleles. CD8+T-cell responses to conserved HIV epitopes within B57/58 alleles (TW10 and KF11) and B27 alleles (KK10 and FY10) delayed declines in CD4+T-cell counts (4 to 8 times longer), while responses to variable epitopes presented by B35 alleles (DL9 and IL9) resulted in more rapid progression. The plasma viral load was higher in B57/58+and B27+subjects lacking the conserved B57/58- and B27-restricted responses. The presence of certain B57/58-, B27-, and B35-restricted HIV-specific CD8+T-cell responses after primary HIV-1 infection better defined disease progression than the HLA genotype alone, suggesting that it is the HIV-specific CD8+T cells and not the presence of a particular HLA allele that determine disease progression. Further, the most effective host CD8+T-cell responses to HIV-1 were prevalent within an HLA allele, represented a high total allele fraction of the host CD8+T-cell response, and targeted conserved regions of HIV-1. These data suggest that vaccine immunogens should contain only conserved regions of HIV-1.
Lentiviral Nef Proteins Utilize PAK2-Mediated Deregulation of Cofilin as a General Strategy To Interfere with Actin Remodeling
Authors: Stolp Bettina , Abraham Libin , Rudolph Jochen M. , Fackler Oliver T.
Published: February 2010

Nef is an accessory protein and pathogenicity factor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) which elevates virus replication
in vivo
. We recently described for HIV type 1
SF2
(HIV-1
SF2
) the potent interference of Nef with T-lymphocyte chemotaxis via its association with the cellular kinase PAK2. Mechanistic analysis revealed that this interaction results in deregulation of the actin-severing factor cofilin and thus blocks the chemokine-mediated actin remodeling required for cell motility. However, the efficiency of PAK2 association is highly variable among Nef proteins from different lentiviruses, prompting us to evaluate the conservation of this actin-remodeling/cofilin-deregulating mechanism. Based on the analysis of a total of 17 HIV-1, HIV-2, and SIV Nef proteins, we report here that inhibition of chemokine-induced actin remodeling as well as inactivation of cofilin are strongly conserved activities of lentiviral Nef proteins. Of note, even for Nef variants that display only marginal PAK2 association
in vitro
, these activities require the integrity of a PAK2 recruitment motif and the presence of endogenous PAK2. Thus, reduced
in vitro
affinity to PAK2 does not indicate limited functionality of Nef-PAK2 complexes in intact HIV-1 host cells. These results establish hijacking of PAK2 for deregulation of cofilin and inhibition of triggered actin remodeling as a highly conserved function of lentiviral Nef proteins, supporting the notion that PAK2 association may be critical for Nef's activity
in vivo
.
Proviruses Selected for High and Stable Expression of Transduced Genes Accumulate in Broadly Transcribed Genome Areas
Authors: Plachý Jiří , Kotáb Jan , Divina Petr , Reinišová Markéta , Šenigl Filip , Hejnar Jiří
Published: February 2010

Retroviruses and retrovirus-derived vectors integrate nonrandomly into the genomes of host cells with specific preferences for transcribed genes, gene-rich regions, and CpG islands. However, the genomic features that influence the transcriptional activities of integrated retroviruses or retroviral vectors are poorly understood. We report here the cloning and characterization of avian sarcoma virus integration sites from chicken tumors. Growing progressively, dependent on high and stable expression of the transduced v-
src
oncogene, these tumors represent clonal expansions of cells bearing transcriptionally active replication-defective proviruses. Therefore, integration sites in our study distinguished genomic loci favorable for the expression of integrated retroviruses and gene transfer vectors. Analysis of integration sites from avian sarcoma virus-induced tumors showed strikingly nonrandom distribution, with proviruses found prevalently within or close to transcription units, particularly in genes broadly expressed in multiple tissues but not in tissue-specifically expressed genes. We infer that proviruses integrated in these genomic areas efficiently avoid transcriptional silencing and remain active for a long time during the growth of tumors. Defining the differences between unselected retroviral integration sites and sites selected for long-terminal-repeat-driven gene expression is relevant for retrovirus-mediated gene transfer and has ramifications for gene therapy.
Regulation of ICP0-Null Mutant Herpes Simplex Virus Type 1 Infection by ND10 Components ATRX and hDaxx
Authors: Lukashchuk Vera , Everett Roger D.
Published: February 2010

Herpes simplex virus type 1 (HSV-1) immediate-early gene product ICP0 activates lytic infection and relieves cell-mediated repression of viral gene expression. This repression is conferred by preexisting cellular proteins and is commonly referred to as intrinsic antiviral resistance or intrinsic defense. PML and Sp100, two core components of nuclear substructures known as ND10 or PML nuclear bodies, contribute to intrinsic resistance, but it is clear that other proteins must also be involved. We have tested the hypothesis that additional ND10 factors, particularly those that are involved in chromatin remodeling, may have roles in intrinsic resistance against HSV-1 infection. The two ND10 component proteins investigated in this report are ATRX and hDaxx, which are known to interact with each other and comprise components of a repressive chromatin-remodeling complex. We generated stable cell lines in which endogenous ATRX or hDaxx expression is severely suppressed by RNA interference. We found increases in both gene expression and plaque formation induced by ICP0-null mutant HSV-1 in both ATRX- and hDaxx-depleted cells. Reconstitution of wild-type hDaxx expression reversed the effects of hDaxx depletion, but reconstitution with a mutant form of hDaxx unable to interact with ATRX did not. Our results suggest that ATRX and hDaxx act as a complex that contributes to intrinsic antiviral resistance to HSV-1 infection, which is counteracted by ICP0.
The effect of the structure of the substituent in position ten on the voltammetric behaviour of phenothiazin derivatives
Authors: Zimová Naďa , Němec Ivan , Ehlová Miroslava , Waisser Karel
Published: February 2010

The electrochemical oxidation of seven derivatives of phenothiazin substituted in position 10 on the phenothiazin skeleton has been studied in acetonitrile, using a platinum disc electrode. The electron donor properties of the derivatives that depend on the substituent structure and the presence of nucleophiles in acetonitrile were followed. The diffusion coefficients for the formation of the radical cations were from 10-5 to 10-6 cm2 s-1 and depended on the concentration of the acid in acetonitrile medium. A determination of these substances has been proposed, using differential pulse voltammetry, with a detection limit of 1 . 10-7 mol l-1.
Solvent effects on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene I. Reactions in alcohols
Authors: Nevěčná Taťjana , Pytela Oldřich , Ludwig Miroslav , Kaválek Jaromír
Published: February 2010

The effect of protic solvents (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, cyclohexanol) has been studied on the kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene, using trichloroacetic acid as the acid catalyst. Both the non-dissociated acid and the proton have been found to be catalytically active. The mechanism of splitting of the triazene substrate with the non-dissociated acid involves the general acid catalysis. Comparison of the catalytic rate constants of the two acid catalysts and effect of solvents on these values indicate that the general acid catalysis probably also operates in the reaction of the substrate with proton.
The thermal dealkylation of 2-chloro-4,6-bis(bornyl- and norbornylamino)-s-triazines
Authors: Tadić Živorad D. , Jovanovic Bratislav Ž. , Antonović Dušan G.
Published: February 2010

The thermal dealkylation of 2-chloro-4,6-bis(isobornylamino)-s-triazine (I), 2-chloro-4,6-bis(bornylamino)-s-triazine (II), 2-chloro-4,6-bis(exo-norbornylamino)-s-triazine (III) and 2-chloro-4,6-bis(endo-norbornylamino)-s-triazine (IV) was performed at 250 °C. The high degree of dealkylation in the case of isobornyl derivative I was ascribed to a reaction via a seven-membered cyclic transition state, as well as to steric interaction of the dimethylmethylene group and the triazine ring. The presence of tricyclenes in the dealkylation products of this derivative also indicates that the reaction partially takes place with charge separation, i.e. by the anchimeric assistance of the C-6 atom. The lower degree of dealkylation of bornyl derivative II is in agreement with the lower reactivity of the endo-isomer and probably takes place via three different transition states yielding three products. The dealkylation of norbornyl derivatives (exo-III and endo-IV) was successful only in the case of the exo-isomer yielding the expected products, while the endo-isomer under these experimental conditions did not give any dealkylation products.
The application of FEL-EXPERT system in the interpretation of boron compounds toxicity
Authors: Štrouf Oldřich , Mařík Vladimír
Published: February 2010

The influence of substructural features on boron compounds toxicity (LD50, mice, i.p.) has been studied by FEL-EXPERT system developed at the Czech Technical University of Prague. A set of 108 compounds containing one or two boron atoms in their molecule has been arbitrarily divided into three classes: the compounds with a high toxicity (LD50 < 100 mg/kg), with a medium toxicity (100 mg/kg ⪬ LD50 < 1 000 mg/kg) and with a low toxicity (LD50 ≥ 1 000 mg/kg). The compounds have been represented by 70 substructural fragments, 27 of them being "central substructures" containing boron atom(s). The inference net consists of 118 nodes (74 of the Bayesian type), 362 production rules and 74 context links. The total classification correctness has been 98%. As a case-study, the classification of p-tolylboronic acid (LD50 = 520 mg/kg) and 4-carboxyphenylboronic acid (LD50 = 3 838 mg/kg) has been discussed.
Study of potential oscillations during reaction of an aluminium single crystal with an aqueous KOH solution
Authors: Halaša Ivan , Miadoková Milica
Published: February 2010

The authors investigated periodic potential changes measured on oriented sections of Al single crystals during spontaneous dissolution in dilute aqueous solutions of KOH, with the aim to find optimum conditions for the formation of potential oscillations. It was found that this phenomenon is related with the kinetics of the reaction investigated, whose rate also changed periodically. The mechanism of the oscillations is discussed in view of the experimental findings.
Chromatography of Mo(VI) and W(VI) chelates with 2,3-dihydroxynaphthalene
Authors: Vrchlabský Milan , Pollaková Naděžda , Hrdlička Aleš
Published: February 2010

Mo(VI) and W(VI) were separated in the form of their anionic chelates with 2,3-dihydroxynaphthalene (DHN) by reversed phase ion-pair chromatography. The effect of the organic modifier content and concentration of tetrabutylammonium cations (TBA) in the mobile phase and the effect of concentration of DHN in the injected sample on the separation were studied. The best results were attained by using a mobile phase containing DHN (0.5 mmol dm-3), TBA counter-ions (10 mmol dm-3) and phosphate buffer (50 mmol dm-3) in a medium of 30% (v/v) methanol and 30% (v/v) acetonitrile at pH 7 and by injecting Mo(VI) and W(VI) samples containing DHN in a tenfold excess. On a CGC glass column 150 . 3.3 mm i.d. packed with Separon SGX C18 (5μm), the solutes were separated at resolutions of Rij = 1.0 (DHN-Mo) and 1.6 (Mo-W). The detection limits at 240 nm were 0.5 and 0.2 nmol for Mo(VI) and W(VI), respectively.
Countercurrent pulsed and reciprocating plate extractors. Prediction of Sauter mean drop diameter
Authors: Sovová Helena
Published: February 2010

Six published correlations for Sauter diameter d32 in pulsed and reciprocating plate columns are compared with drop size measurements from seven different data sources. The correlation of Kumar and Hartland gives the best fit of data in the whole range of agitation rates. Also the semiempiric equations of Misek and of Boyadzhiev and Spassov are of general validity at higher agitation levels. A new semiempiric equation covering the whole range of agitation rates and describing experimental data with a standard deviation of 10% is presented.
33S NMR spectra of some sulfonated naphthalenes, naphthols, and their anions
Authors: Jirman Josef , Lyčka Antonín
Published: February 2010

The 33S NMR spectra of 11 naphthalenesulfonates, 11 hydroxynaphthalenesulfonates, two dihydroxynaphthalenesulfonates, and their anions have been measured in aqueous solutions. The 33S NMR chemical shifts of these compounds exhibit upfield shifts when related to ammonium sulfate as the standard. Introduction of a further sulfonic group causes a small upfield shift (up to 3 ppm). Introduction of a hydroxyl group causes a downfield shift (up to 5 ppm) unless the ring is further substituted. Formation of the anion from hydroxyl group causes an additional downfield shift (up to 6 ppm). The half-width of 33S NMR signals of sulfonated naphthalenes, naphthols, and their anions vary from 10 to 400 Hz.
Direct esterification of 2-methoxy-2-phenyl-3,3,3-trifluoropropionic acid: A reinvestigation
Authors: Svatoš Aleš , Valterová Irena , Šaman David , Vrkoč Jan
Published: February 2010

The direct esterification of enantiomeric 2-methoxy-2-phenyl-3,3,3-trifluoropropionic acids (MTPA) was reinvestigated. Preferential formation of one of the diastereoisomeric esters was avoided by using three equivalents of MTPA. Chromatographic behaviour of the obtained MTPA esters is discussed.
Nitriles in heterocyclic synthesis: A novel route for the synthesis of naphthodipyrans, pyridines. 2H- and 4H-Pyrans
Authors: Elagamey Abdel Ghani A. , El-Taweel Fathy M. A. , Sowellim Salah Z. A. , Sofan Mamdouh A. , Elnagdi Mohamed H.
Published: February 2010

Naphtho[2,1-b:5,6-b']dipyrans and naphtho[1,2-b:6,5-b']dipyrans were synthesized by the reaction of cinnamonitriles with 2,3-, 1,5-, 1,6-naphthalenediols, respectively. Polysubstituted pyridines, 2H-pyrans and 4H-pyrans were also synthesized from cinnamonitriles, 2-hydroxyacetophenone and 3-acetyl-4-hydroxy-1-methylcarbostyril, respectively.
Reaction of mercaptoacetic acid and chloroacetyl chloride with benzalamino thiazolyl coumarins
Authors: Veerabhadraiah Udarapu , Rajeswar Rao Vedeela , Padmanabha Rao Tadepalcy Venkata
Published: February 2010

2-Aryl-3-[4-(2-oxo-2H-1-benzopyran-3-yl)-2-thiazolyl]-4-thiazolidinones (III), have been synthesized by the reaction of Schiff's bases (II) derived from 3-(2-amino-4-thiazolyl)-2H-1-benzopyran-2-ones (I) with mercaptoacetic acid. The Schiff's bases on reaction with chloroacetyl chloride in the presence of triethylamine in dioxane gave chloroacetamido derivative (IV) instead of expected compound V.
Detergentless microemulsions as media for enzymatic reactions: Catalytic properties of laccase in the ternary system hexane-2-propanol-water
Authors: Khmelnitsky Yurii L. , Gladilin Alexander K. , Neverova Irina N. , Levashov Andrei V. , Martinek Karel
Published: February 2010

The catalytic activity and stability of laccase in the detergentless ternary system hexane - 2-propanol - water were studied. In the microemulsion region of the phase diagram the enzyme exhibited the highest catalytic activity and stability, which were comparable to those in aqueous solution. The character of the microenvironment inside microemulsion droplets was studied using nitrate anion as spectral probe and its polarity was found to correspond to that of 75% v/v aqueous 2-propanol. In principle, laccase can be recovered many times from the microemulsion without loss of catalytic activity.
Isolation and purification of proteinase inhibitors from developing embryos of Hyalomma dromedarii
Authors: Hamed Ragaa R. , Ibrahim Mahmoud A. , Kamel Mamdouh Y.
Published: February 2010

The changes in the level of trypsin, chymotrypsin, subtilisin and papain inhibitors were examined during embryonic development of H. dromedarii. The high level of trypsin and chymotrypsin inhibitors in the oviposited eggs did not change during embryogenesis and was followed by a sharp drop after hatching. On the other hand, the papain inhibitor exhibited very low level throughout embryonic development and was followed by a significant increase in the newly hatched larvae. A purification scheme for trypsin and chymotrypsin inhibitors which involved chromatography on DEAE-cellulose, cellulose phosphate and Ultrogel AcA 54 was established. Using synthetic substrates six multiple forms of proteinase inhibitors with different molecular weights and properties were isolated. They were classified into three specific trypsin inhibitors F1a, F4a, and F4b, one specific chymotrypsin inhibitor F1b and to mixed trypsin-chymotrypsin inhibitors F2 and F3. Although treatment that may cause fragmentation of the native inhibitors were avoided during purification, multiple forms of trypsin and chymotrypsin inhibitor were isolated. The significancy of such multiplicity is not understood.
Antisense oligonucleotides modified at 5'-end by fatty radicals effectively inhibit reproduction of influenza virus
Authors: Kabanov Alexander V. , Vinogradov Sergei V. , Ovcharenko Alexander V. , Krivonos Alexander V. , Melik-Nubarov Nikolai S. , Kiselev Vsevolod I. , Severin Eugenii S.
Published: February 2010

To enhance penetration of oligonucleotides ("oligos") into cells it was suggested that they should be chemically modified by fatty radicals at 5'-end. Two modified by undecanol at 5'-end phosphate group oligos, namely, oligo complementary to the protein binding sites, located at the influenza virus polymerases encoding RNA, and oligo complementary to the polyadenylation signal of the polymerase 3 encoding RNA were synthesized using DNA-synthetisator. These modified oligos effectively suppressed the influenza A/PR8/34 virus reproduction and inhibited the synthesis of virus-specific proteins in MDCK cells. The non-modified antisense oligos and modified nonsense oligos did not affect the virus development under the same conditions.
Topological aspects of chemical reactivity. Relation between the overlap determinant method and the least motion principle
Authors: Ponec Robert , Strnad Martin
Published: February 2010

The recently suggested approach to the study of chemical reactivity in terms of the generalized and integral similarity indices is analyzed and discussed from the point of view of its compatibility with the principle of least motion. It is shown that the formulations of the similarity approach as initially introduced on an intuitive basis are consistent with that principle.
The crystal and molecular structure of tetramethylammonium 1-dimethylamino-1-carba-undecahydro-closo-dodecaborate
Authors: Novák Ctirad , Šubrtová Věra , Petříček Václav , Hummel Ludvík , Hašek Jindřich
Published: February 2010

The title compound crystallizes in the trigonal system and in the P3 space group. The unit cel parameters are a = b = 2 717.1(8) pm, c = 1 222.5(3) pm, V = 7 816 . 106 pm3. Z = 18 density calculated Dc = 0.995 Mg m-3. Radiation used CuKα, λ = 154.18 pm, intensities measured at room temperature. Mr = 260.34, linear absorption coefficient μ = 0.342 mm-1, F(000) = 2 520. Final R = 0.077 for 3 096 observed independent reflections. There is an unusual number of six isomers in the asymmetric unit. The structure is built up from CB11H11·N(CH3)2 anions and N(CH3)4 cations. The dimethylamino group attached to the carbon atom of the carbaborane icosahedron in not planar (as usual in aromatic compounds), but has an almost tetrahedral form, which reveals the presence of the sp3 hybridization of the orbitals of the nitrogen atom. The C-N-C bond angles are 117.6(3)°, 112.7(3)° and 111.8(3)° on average. The comparison of the monocarbaborane CB11H11 with the B12H12 framework showed an overall contraction of the first one - the averaged C-B bond lengths are shorter by 6 pm and the B-B bond lengths by up to 3 pm then the B-B bond lengths in B12H12. Cartesian coordinates of the averaged framework are given. The mutual arrangement of the ions simulates fairly well the space group R3, but the symmetry is reduced to P3 due to the presence of the orientational (but not positional) disorder of the anions and of the cations. The centroids of the anions form a nearly perfect primitive cubic point lattice. The cations are positioned in the proximity of the center of the cube formed by the anions and consequently, their central nitrogen atoms simulate the same cubic point lattice. The arrangement of the building units resembles the B2 structure type with one exception: the positions on the 3-fold axes (two vertices of each cube) are vacant.
Crystal structures of some 3-(hydroxymethylene)dihydro-2(3H)-furanone derivatives
Authors: Głowiak Tadeusz , Žák Zdirad , Jonas Jaroslav
Published: February 2010

The crystal structures of (Z)-3-(p-toluenesulfonyloxymethylene)dihydro-2(3H)-furanone (I), (E)-3-(methanesulfonyloxymethylene)dihydro-2(3H)-furanone (II), and (E)-3-(benzoyloxymethylene)dihydro-2(3H)-furanone (III) were solved by direct methods. The intensities of the diffractions were recorded using MoKα graphite monochromatized radiation, λ = 0.07107 nm. The compound I is monoclinic, space group P21/n, with a = 0.8615(2), b = 0.5955(2), c = 2.3883(5) nm, β = 93.27(2)°, V = 1.223(1) nm3, Z = 4, F(000) = 560, Dm = 1.43, Dx = 1.46 Mg m-3, μ = 0.27 mm-1. The structure was refined to R = 0.042 for 1 341 independent diffractions. Compound II is triclinic, space group P1, with a = 0.5840(2), b = 0.8232(2), c = 0.9827(3) nm, α = 97.68(3), β = 110.82(3), γ = 108.62(3)°, V = 0.402(1) nm3, Z = 2, F(000) = 200, Dm = 1.55, Dx = 1.59 Mg m-3, μ = 0.38 mm-1. The structure was refined to R = 0.041 for 952 independent diffractions. Compound III is monoclinic, space group P2/m with a = 0.9665(3), b = 1.1861(3), c = 0.9906(3) nm, β = 112.85(3)°, V = 1.046(2) nm3, Z = 4, F(000) = 456, Dm = 1.35, Dx = 1.38 Mg m-3, μ = 0.11 mm-1. The structure was refined to R = 0.048 for 1 115 independent diffractions. The configurations of the compounds I, II, and III are in agreement with the assignments made on the basis of the NMR spectra.
Laser induced gas phase reaction between chromyl chloride and some polyhalogenoethenes
Authors: Pola Josef , Vítek Josef
Published: February 2010

Gas phase reaction between chromyl chloride and some polyhalogenoethenes induced with the radiation of continuous-wave CO2 laser yields carbonyl halides and compounds arising from oxygen donation to alkene and 1,2-rearrangement of halogen.
Reactions of aromatic radical-anions and ethyllithium with silica gel and Brönsted acids
Authors: Kratochvíla Jan , Salajka Zdeněk , Kazda Antonín , Kadlc Zbyněk , Gheorghiu Mihnea
Published: February 2010

Electric conductivities of radical-anions prepared from several aromatic compounds (biphenyl, naphthalene, benzophenone, anthracene, phenanthrene) and sodium in tetrahydrofuran have been measured and a suitability of radical-anions for titration of silica gel and acid impurities in liquid media have been investigated. The reactivity of the radical-anions and ethyllithium with acidic hydrogen of silica gel hydroxy groups is approximately equal in spite of substantial differences in structure and bonding character of the above compounds. Highest amounts of radical-anions and ethyllithium are decomposed by thermally non-activated silica gel (1.7 to 1.8 mmol g-1 for Davison, grade 952). With the increasing temperature of dehydration of silica gel (200-900 °C), the amount of decomposed organometallic compounds decreases approximately linearly.
On the origin of base concentration effect on stereo- and regioselectivity in alkoxide-promoted E2 reactions: A consequence of substrate solvation by metal ions
Authors: Závada Jiří , Pánková Magdalena , Vítek Antonín
Published: February 2010

The title problem has been investigated in the reaction of 2-decyl bromide with t-C4H9OK/t-C4H9OH system employing 18-crown-6 ether and an "inert" salt (t-C4H9OLi) as mechanistic probes. From olefin-distribution data and a subsidiary kinetic evidence it has been inferred that the investigated effect originates from a concentration-dependent substrate solvation by metal ions in the transition state.
Intramolecular cyclization of O-alkyl-N-(3-phenylpropenoyl)thiocarbamates catalyzed by boron trifluoride
Authors: Dzurilla Milan , Kutschy Peter , Koščík Dušan , Toma Štefan
Published: February 2010

2-Alkoxy-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones, 6-phenyl-1,3-perhydrothiazine-2,4-dione and S-methyl N-(3-phenylpropenoyl)thiocarbamate are the products of intramolecular rearrangement of O-alkyl N-(3-phenylpropenoyl)thiocarbamates catalyzed by boron trifluoride; their formation depends on the nature of the alkyl group. The rearrangement was shown to proceed intermolecularly by investigating the reaction of O-methyl N-(3-phenylpropenoyl)thiocarbamate to an S-methyl ester by the method of a crossover experiment.
Heterocyclic synthesis from 3-amino-4-cyanopyrazole
Authors: Deeb Ali , El-Mobayed Medhat , Essawy Abdel Naby , El-Hamid Adel Abd , El-Hamid Atef Mohamid Abd
Published: February 2010

3-Amino-4-cyanopyrazole I reacts with hydroxylamine and with hydrazine to yield 1H,6H-3-aminopyrazolo[3,4-c]pyrazole (III and IV). Diazotized IV couples with 2-naphthol to give the arylazo derivative VI which cyclizes to 9H-naphthol[2,1-e]pyrazolo[3',4':3,4]pyrazolo[5,1-c]-[1,2,4]triazine VII by means of acetic acid. The pyrazol-5-ylthiourea obtained from I and phenyl isothiocyanate undergoes base-catalyzed cyclization to give pyrazolo[3,4-d]pyrimidinethione derivative IX. Compound I reacts with cyclohexane in the presence of zinc chloride to give the tetrahydropyrazolo[3,4-b]quinoline derivative XI. The reaction of I with pyridine 1-oxide affords 4H,5H-pyrazolo[5',1':2,3] [1,2,4]triazolo[1,5-a]pyridine-3-carbonitrile XII.
Synthesis of some biologically active derivatives of 2-hydroxymethyl-5-hydroxy-4H-pyran-4-one
Authors: Veverka Miroslav , Kraľovičová Eva
Published: February 2010

Depending on reaction conditions, acylation of the phenolic and primary alcoholic group in 2-hydroxymethyl-5-hydroxy-4H-pyran-4-one leads to mono- or disubstituted products. Also described is acylation of the phenolic group in 2-chloromethyl- or 2-bromomethyl-5-hydroxy-4H-pyran-4-one as well as the nucleophilic replacement of the halogen by azide group. The prepared derivatives exhibit herbicidal and growth regulatory activity.
Extracellular proteinase from Brevibacterium linens. Purification and characterization
Authors: Juhász Ondrej , Knošková Danka , Zemanovič Jaroslav , Škárka Bohumil
Published: February 2010

Brevibacterium linens produces proteolytic enzymes in cultivation broth. One of them was purified by application of a two step procedure involving ultrafiltration and molecular sieving. The isolated enzyme hydrolyzed natural substrates: casein, hemoglobin, ovalbumin and bovine serum albumin with rations 22.2, 3.5, 1.6, 1.2 nkat mg-1, respectively. For casein the apparent Km 1.8 mg ml-1 was determined. The proteinase is fairly stable at pH 8.0 at 30 °C. Short term incubation at 50 °C denaturated the proteinase. SDS PAGE revealed an Mr of the proteolytic enzyme about 52 000 to 55 000.
The influence of the initial concentrations of glucose and yeast extract on the ethanolic fermentation by Pachysolen tannophilus
Authors: Bravo Rodríguez V. , Camacho Rubio F. , Sánchez Villasclaras S. , Castro Vico M.
Published: February 2010

The ethanolic fermentation in batch cultures of Pachysolen tannophilus was studied experimentally varying the initial concentrations of two of the components in the culture medium: glucose between 0 and 200 g l-1 and yeast extract between 0 and 8 g l-1. The yeast extract appears to be a significant component both in cell growth and for ethanol production.
A novel approach to the characterization of molecular similarity. The 2nd order similarity index
Authors: Ponec Robert , Strnad Martin
Published: February 2010

The topological similarity index rAB introduced recently is generalized by using reduced 2nd order density matrices. The comparison with the results of our previous study demonstrates enhanced ability to discriminate between allowed and forbidden reactions.
Voltammetric study of the electrochemical stripping of galenite using a rotating ring-disk electrode
Authors: Hošková Šárka , Beran Přemysl , Beran Tomáš
Published: February 2010

A study was carried out of the electrochemical stripping of galenite in the form of a disk electrode with a gold ring, in 0.1M-NaClO4 base electrolyte. It was found that lead is reduced from the galenite at potentials more negative than -1 V and remains on the surface of the electrode. The reduced lead is electrochemically stripped from the electrode at potentials more positive than -0.5 V. At potentials more positive than +0.4 V, PbS is further oxidized to Pb(IV). The degree of oxidation increases with increasing potential.
Zur sauerstoffreduktion an n-GaAs-elektroden
Authors: Schlesinger Roland , Janietz Peter Johannes
Published: February 2010

Die elektrochemische Reduktion von Sauerstoff an n-GaAs(100) in sauren und alkalischen Elektrolyten wird mittels zyklischer Voltammetrie untersucht. Es wird eine ungewohnliche Abhangigkeit des Reduktionspeaks von der Umdrehungsgeschwindigkeit der Elektrode in 0.5M-H2SO4 gefunden. Die Gestalt der Zyklovoltammogramme wird qualitativ auf der Basis eines Ladungstransfer-Modells erklart. Es wird postuliert, dass der Elektronentransfer durch sauerstoffadsorptionsinduzierte, nahe der Leitungsbandkante lokalisierte Oberflachenzustande vermittelt wird. Es werden Argumente dafur geliefert, dass ein in der Literatur beschriebener Reduktionspeak in der potentiodynamischen Dunkelstromkurve fur n-GaAs/0.5M-H2SO4 nicht der Reduktion von Arsenoxidationsprodukten, sondern der Reduktion von im Elektrolyten gelosten Sauerstoff zuzuordnen ist.
A contribution to the identification in fuzzy-logic control
Authors: Vrba Josef , Purová Ywetta
Published: February 2010

A linguistic identification of a system controlled by a fuzzy-logic controller is presented. The information about the behaviour of the system, concentrated in time-series, is analyzed from the point of its description by linguistic variable and fuzzy subset as its quantifier. The partial input/output relation and its strength is expressed by a sort of correlation tables and coefficients. The principles of automatic generation of model statements are presented as well.
A hybrid form of fuzzy-logic controller
Authors: Vrba Josef , Purová Ywetta
Published: February 2010

A hybrid form of a fuzzy-logic controller with linguistic and numerical variables and fuzzy subset as their common quantifier is presented. It is typical for the controller that the role of conditional statements of its linguistic model is optionally combined with a set of numerical parameters. The statements are automatically generated according to the given state of the system under control, it brings the necessary feature of adaptivity and self-tuning ability. The efficiency of the controller is checked on a set of simulated systems and a real one with pH control as well.
The specific interfacial area in an airlift tower reactor
Authors: Potůček František
Published: February 2010

This study deals with the oxygen transfer in the gas-liquid dispersion systems. The sulfite oxidation method was used to determine the specific interfacial area in the airlift tower reactor with and without motionless mixers. The experimental results obtained were described by the correlation equations and compared with those already published in the literature.
The change in the standard Gibbs energy ΔG0 in the formation of double selenates K2MII(SCo4)2·x H2O (MII = Mn, Co, Ni, Cu, Zn; x = 6 or 2)
Authors: Vojtíšek Pavel , Ebert Miroslav
Published: February 2010

The heterogeneous K2SeO4-MIISeO4-H2O system (MII = Mn, Co, Ni, Cu, Zn) at 298 K was studied using the Filippov eutonic method, yielding values for the change in the standard Gibbs energy ΔG0 for the formation of double selenates in the range 16.2-30.3 kJ/mol. It follows from the ΔG0 values that, in systems without strong interactions in the liquid phase, the formation of poorly soluble double selenates from readily soluble selenates is energetically most favourable.
Oxidation of 1,2,3,4-tetrahydronaphthalene by dioxygen. Effect of the free radical initiators 1,2,3,4-tetrahydro-1-naphthylhydroperoxide and 2,2'-azobis(2-methylpropionitrile) on the reaction catalyzed by 2,4-pentanedionates of 3d transition metals
Authors: Luňák Stanislav , Vašková Marie , Lederer Pavel
Published: February 2010

The effect of the free radical initiators 1,2,3,4-tetrahydro-1-naphthylhydroperoxide and 2,2'-azobis(2-methylpropionitrile) on the oxidation of 1,2,3,4-tetrahydronaphthalene (tetraline) by dioxygen catalyzed by Cr(III), Mn(III), Fe(III), Co(II), Co(III) and Cu(II) 2,4-pentanedionates (acac) has been investigated. It has been found that the addition of a free radical initiator can increase the rate of catalyzed oxidation or decrease it. Which effect will operate depends on the kind of the catalyzing transition metal ion and its oxidation state. The results obtained indicate that the above free radical initiators act on the catalyzed oxidation of tetraline by affecting the catalyst activity.