bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Identification of
Campylobacter concisus
Authors: Matsheka M. I. , Lastovica A. J. , Elisha B. Gay
Published: July 2002

A 1.6-kb DNA fragment isolated from a
Campylobacter concisus
genomic library gave
C. concisus
-specific restriction fragment length patterns when it was used as a probe in hybridization studies. All of the strains tested, including type strains and clinical isolates, contained a 0.5-kb
Hin
dIII fragment that hybridized to the probe. DNA sequencing of the 1.6-kb fragment identified three open reading frames (ORFs). One of the ORFs encodes the carboxy terminus of GyrB, and the translational products of ORF2 and ORF3 showed similarity to hypothetical proteins, previously identified in
Campylobacter jejuni
. DNA-DNA hybridization studies with a fragment internal to ORF3 showed that this sequence was responsible for the signal observed with the 0.5-kb
Hin
dIII fragment. A rapid PCR assay was developed and evaluated. Primers that annealed to the extremities of the 1.6-kb fragment were used to obtain an amplicon of the correct size from both reference and clinical strains of
C. concisus
.
Characterization of Capsid Genes, Expressed in the Baculovirus System, of Three New Genetically Distinct Strains of “Norwalk-Like Viruses”
Authors: Belliot Gaël , Noel Jacqueline S. , Li Jin-Fen , Seto Yoshiyuki , Humphrey Charles D. , Ando Tamie , Glass Roger I. , Monroe Stephan S.
Published: July 2002

“Norwalk-like viruses” (NLVs), members of a newly defined genus of the family
Caliciviridae
, are the most common agents of outbreaks of gastroenteritis in the United States. Two features of NLVs have hindered the development of simple methods for detection and determination of serotype: their genetic diversity and their inability to grow in cell culture. To assess the immune responses of patients involved in outbreaks of gastroenteritis resulting from infection with NLVs, we previously used recombinant-expressed capsid antigens representing four different genetic clusters, but this panel proved insufficient for detection of an immune response in many patients. To extend and further refine this panel, we expressed in baculovirus the capsid genes of three additional genetically distinct viruses, Burwash Landing virus (BLV), White River virus (WRV), and Florida virus. All three expressed proteins assembled into virus-like particles (VLPs) that contained a full-length 64-kDa protein, but both the BLV and WRV VLPs also contained a 58-kDa protein that resulted from deletion of 39 amino acids at the amino terminus. The purified VLPs were used to measure the immune responses in 403 patients involved in 37 outbreaks of acute gastroenteritis. A majority of patients demonstrated a fourfold rise in the titer of immunoglobulin G to the antigen homologous to the outbreak strain, but most seroconverted in response to other genetically distinct antigens as well, suggesting no clear pattern of type-specific immune response. Further study of the antigenicity of the NLVs by use of VLPs should allow us to design new detection systems with either broader reactivity or better specificity and to define the optimum panel of antigens required for routine screening of patient sera.
Detection of Pathogenic
Yersinia enterocolitica
by a Rapid and Sensitive Duplex PCR Assay
Authors: Wannet Wim J. B. , Reessink Michiel , Brunings Henk A. , Maas Henny M. E.
Published: July 2002

A duplex PCR assay targeting the
ail
and 16S rRNA genes of
Yersinia enterocolitica
was developed to specifically identify pathogenic
Y. enterocolitica
from pure culture. Validation of the assay was performed with 215 clinical
Yersinia
strains and 40 strains of other bacterial species. Within an assay time of 4 h, this assay offers a very specific, reliable, and inexpensive alternative to the conventional phenotypic assays used in clinical laboratories to identify pathogenic
Y. enterocolitica
.
Use of
rpoB
Gene Analysis for Detection and Identification of
Bartonella
Species
Authors: Renesto Patricia , Gouvernet Joanny , Drancourt Michel , Roux Veronique , Raoult Didier
Published: July 2002

Identification of
Bartonella
species is of increasing importance as the number of infections in which these bacteria are involved increases. To date, these gram-negative bacilli have been identified by various serological, biochemical, and genotypic methods. However, the development of alternative tools is required, principally to circumvent a major risk of contamination during sample manipulation. The aim of our study was to investigate the possible identification of various
Bartonella
species by comparison of RNA polymerase beta-subunit gene (
rpoB
) sequences. This approach has previously been shown to be useful for the identification of members of the family
Enterobacteriaceae
(C. M. Mollet, M. Drancourt, and D. Raoult, Mol. Microbiol. 26:1005–1011, 1997). Following PCR amplification with specific oligonucleotides, a 825-bp region of the
rpoB
gene was sequenced from 13 distinct
Bartonella
strains. Analysis of these sequences allowed selection of three restriction enzymes (
Apo
I,
Alu
I, and
Afl
III) useful for discerning the different strains by PCR-restriction fragment length polymorphism (PCR-RFLP) analysis. To confirm the potential value of such an approach for identification of
Bartonella
, the
rpoB
PCR was then applied to 94 clinical samples, and the results obtained were identical to those obtained by our reference PCR method. Twenty-four isolates were also adequately identified by PCR-RFLP analysis. In all cases, our results were in accordance with those of the reference method. Moreover, conserved regions of DNA were chosen as suitable primer targets for PCR amplification of a 439-bp fragment which can be easily sequenced.
Simultaneous Detection of Measles Virus, Rubella Virus, and Parvovirus B19 by Using Multiplex PCR
Authors: del Mar Mosquera María , de Ory Fernando , Moreno Mónica , Echevarría Juan E.
Published: July 2002

We describe here a multiplex reverse transcription-PCR (RTMNPCR) assay designed to detect and differentiate measles virus, rubella virus, and parvovirus B19. Serial dilution experiments with vaccine strains that compared cell culture isolation of measles in B95 cells and rubella in RK13 cells showed sensitivity rates of 0.004 50% tissue culture infective dose (TCID
50
) for measles virus and 0.04 TCID
50
for rubella virus. This RTMNPCR can detect as few as 10 molecules for measles virus and rubella virus and one molecule for parvovirus B19 in dilution experiments with plasmids containing inserts of the primary reaction amplification products. Five pharyngeal exudates from measles patients and 2 of 15 cerebrospinal fluid samples from measles-related encephalitis were found to be positive for measles virus by this RTMNPCR. A total of 3 of 27 pharyngeal exudates from vaccinated children and 2 pharyngeal exudates, plus one urine sample from a case of congenital rubella syndrome, were found to be positive for rubella virus by RTMNPCR, whereas 16 of 19 sera from patients with erythema infectiosum were determined to be positive for parvovirus B19 by RTMNPCR. In view of these results, we can assess that this method is a useful tool in the diagnosis of these three viruses and could be used as an effective surveillance tool in measles eradication programs.
Assessment of Clarithromycin-Resistant
Helicobacter pylori
among Patients in Shanghai and Guangzhou, China, by Primer-Mismatch PCR
Authors: Pan Zhi-Jun , Su Wan-Wen , Tytgat Guido N. J. , Dankert Jacob , van der Ende Arie
Published: July 2002

Of 96
Helicobacter pylori
isolates from patients in Shanghai and Guangzhou, China, 5 had the A2143G 23S rRNA mutation as determined by primer-mismatch PCR and were resistant to clarithromycin by the E-test. The remaining isolates were primer-mismatch PCR negative and susceptible to clarithromycin. The conclusion is that the prevalence of clarithromycin-resistant
H. pylori
isolates among these Chinese patients is 5%.
Trypsin-Induced Structural Transformation in Aquareovirus
Authors: Nason Emma L. , Samal Siba K. , Venkataram Prasad B. V.
Published: July 2002

Aquareovirus
, a member of the family
Reoviridae
, is a large virus with multiple capsid layers surrounding a genome composed of 11 segments of double-stranded RNA. Biochemical studies have shown that treatment with the proteolytic agent trypsin significantly alters the infectivity of the virus. The most infectious stage of the virus is produced by a 5-min treatment with trypsin. However, prolonged trypsin treatment almost completely abolishes the infectivity. We have used three-dimensional electron cryomicroscopy to gain insight into the structural basis of protease-induced alterations in infectivity by examining the structural changes in the virion at various time intervals of trypsin treatment. Our data show that after 5 min of trypsinization, projection-like spikes made of VP7 (35 kDa), associated with the underlying trimeric subunits, are completely removed. Concurrent with the removal of VP7, conformational changes are observed in the trimeric subunit composed of putative VP5 (71 kDa). The removal of VP7 and the accompanied structural changes may expose regions in the putative VP5 important for cell entry processes. Prolonged trypsinization not only entirely removes the outer capsid layer, producing the poorly infectious core particle, but also causes significant conformational changes in the turret protein. These changes result in shortening of the turret and narrowing of its central channel. The turret, as in orthoreoviruses, is likely to play a major role in the capping and translocation of mRNA during transcription, and the observed conformational flexibility in the turret protein may have implications in rendering the particle transcriptionally active or inactive.
Sendai Virus C Proteins Must Interact Directly with Cellular Components To Interfere with Interferon Action
Authors: Garcin Dominique , Curran Joseph , Kolakofsky Daniel
Published: July 2002

Sendai virus (SeV) infection of interferon (IFN)-competent cells is one of the most efficient ways of inducing IFN production. Virus replication is nevertheless largely unaffected, since SeV infection also interfers with IFN action, a prerequisite for the establishment of an antiviral state. This property has been mapped by reverse genetics to the viral C gene, which is also known to act as a promoter-specific inhibitor of viral RNA synthesis. Using luciferase reporter plasmids containing IFN-responsive promoters, we have found that all four C proteins effectively interdict IFN signaling when expressed independently of SeV infection. The C proteins must therefore interact directly with cellular components to carry this out. The C gene in the context of an SeV infection was also found to induce STAT1 instability in some cells, whereas in other cells it apparently acts to prevent the synthesis of STAT1 in response to the virus infection or IFN treatment. The SeV C proteins appear to act in at least two ways to counteract the IFN induced by SeV infection.
Human Monoclonal Antibodies That Inhibit Binding of Hepatitis C Virus E2 Protein to CD81 and Recognize Conserved Conformational Epitopes
Authors: Hadlock Kenneth G. , Lanford Robert E. , Perkins Susan , Rowe Judy , Yang Qing , Levy Shoshana , Pileri Piero , Abrignani Sergio , Foung Steven K. H.
Published: July 2002

The intrinsic variability of hepatitis C virus (HCV) envelope proteins E1 and E2 complicates the identification of protective antibodies. In an attempt to identify antibodies to E2 proteins from divergent HCV isolates, we produced HCV E2 recombinant proteins from individuals infected with HCV genotypes 1a, 1b, 2a, and 2b. These proteins were then used to characterize 10 human monoclonal antibodies (HMAbs) produced from peripheral B cells isolated from an individual infected with HCV genotype 1b. Nine of the antibodies recognize conformational epitopes within HCV E2. Six HMAbs identify epitopes shared among HCV genotypes 1a, 1b, 2a, and 2b. Six, including five broadly reactive HMAbs, could inhibit binding of HCV E2 of genotypes 1a, 1b, 2a, and 2b to human CD81 when E2 and the antibody were simultaneously exposed to CD81. Surprisingly, all of the antibodies that inhibited the binding of E2 to CD81 retained the ability to recognize preformed CD81-E2 complexes generated with some of the same recombinant E2 proteins. Two antibodies that did not recognize preformed complexes of HCV 1a E2 and CD81 also inhibited binding of HCV 1a virions to CD81. Thus, HCV-infected individuals can produce antibodies that recognize conserved conformational epitopes and inhibit the binding of HCV to CD81. The inhibition is mediated via antibody binding to epitopes outside of the CD81 binding site in E2, possibly by preventing conformational changes in E2 that are required for CD81 binding.
Structural and Functional Dissection of Human Cytomegalovirus US3 in Binding Major Histocompatibility Complex Class I Molecules
Authors: Lee Sungwook , Yoon Juhan , Park Boyoun , Jun Youngsoo , Jin Mirim , Sung Ha Chin , Kim Ik-Hwan , Kang Seongman , Choi Eui-Ju , Ahn Byung Yoon , Ahn Kwangseog
Published: July 2002

The human cytomegalovirus US3, an endoplasmic reticulum (ER)-resident transmembrane glycoprotein, forms a complex with major histocompatibility complex (MHC) class I molecules and retains them in the ER, thereby preventing cytolysis by cytotoxic T lymphocytes. To identify which parts of US3 confine the protein to the ER and which parts are responsible for the association with MHC class I molecules, we constructed truncated mutant and chimeric forms in which US3 domains were exchanged with corresponding domains of CD4 and analyzed them for their intracellular localization and the ability to associate with MHC class I molecules. All of the truncated mutant and chimeric proteins containing the luminal domain of US3 were retained in the ER, while replacement of the US3 luminal domain with that of CD4 led to cell surface expression of the chimera. Thus, the luminal domain of US3 was sufficient for ER retention. Immunolocalization of the US3 glycoprotein after nocodazole treatment and the observation that the carbohydrate moiety of the US3 glycoprotein was not modified by Golgi enzymes indicated that the ER localization of US3 involved true retention, without recycling through the Golgi. Unlike the ER retention signal, the ability to associate with MHC class I molecules required the transmembrane domain in addition to the luminal domain of US3. Direct interaction between US3 and MHC class I molecules could be demonstrated after in vitro translation by coimmunoprecipitation. Together, the present data indicate that the properties that allow US3 to be localized in the ER and bind MHC class I molecules are located in different parts of the molecule.
Bcl-2 Blocks a Caspase-Dependent Pathway of Apoptosis Activated by Herpes Simplex Virus 1 Infection in HEp-2 Cells
Authors: Galvan Veronica , Brandimarti Renato , Munger Joshua , Roizman Bernard
Published: July 2002

Earlier reports have shown that herpes simplex virus 1 (HSV-1) mutants induce programmed cell death and that wild-type virus blocks the execution of the cell death program triggered by expression of viral genes, by the Fas and tumor necrosis factor pathways, or by nonspecific stress agents. In particular, an earlier report from this laboratory showed that the mutant virus
d
120 lacking the genes encoding infected cell protein 4 (ICP4), the major regulatory protein of the virus, induces a caspase-3-independent pathway of apoptosis in human SK-N-SH cells. Here we report that the pathway of apoptosis induced by the
d
120 mutant in human HEp-2 cells is caspase dependent. Specifically, in HEp-2 cells infected with
d
120, (i) a broad-range inhibitor of caspase activity, z-vad-FMK, efficiently blocked DNA fragmentation, (ii) cytochrome
c
was released into the cytoplasm, (iii) caspase-3 was activated inasmuch as poly(ADP-ribose) polymerase was cleaved, and (iv) chromatin condensation and fragmentation of cellular DNA were observed. In parallel studies, HEp-2 cells were transfected with a plasmid encoding human Bcl-2 and a clone (VAX-3) expressing high levels of Bcl-2 was selected. This report shows that Bcl-2 blocked all of the manifestations associated with programmed cell death caused by infection with the
d
120 mutant. Consistent with their resistance to programmed cell death, VAX-3 cells overproduced infected cell protein 0 (ICP0). An unexpected observation was that ICP0 encoded by the
d
120 mutant accumulated late in infection in small, quasi-uniform vesicle-like structures in all cell lines tested. Immunofluorescence-based colocalization studies indicated that these structures were not mitochondria or components of the endoplasmic reticulum or the late endosomal compartment. These studies affirm the conclusion that HSV can induce programmed cell death at multiple steps in the course of its replication, that the
d
120 mutant can induce both caspase-dependent and -independent pathways of programmed cell death, and that virus-induced stimuli of programmed cell death may differ with respect to the pathway that they activate.
Adaptive Mutations in Sindbis Virus E2 and Ross River Virus E1 That Allow Efficient Budding of Chimeric Viruses
Authors: Kim Kyongmin Hwang , Strauss Ellen G. , Strauss James H.
Published: July 2002

Alphavirus glycoproteins E2 and E1 form a heterodimer that is required for virus assembly. We have studied adaptive mutations in E2 of Sindbis virus (SIN) and E1 of Ross River virus (RR) that allow these two glycoproteins to interact more efficiently in a chimeric virus that has SIN E2 but RR E1. These mutations include K129E, K131E, and V237F in SIN E2 and S310F and C433R in RR E1. Although RR E1 and SIN E2 will form a chimeric heterodimer, the chimeric virus is almost nonviable, producing about 10
−7
as much virus as SIN at 24 h and 10
−5
as much after 48 h. Chimeras containing one adaptive change produced 3 to 20 times more virus than did the parental chimera, whereas chimeras with two changes produced 10 to 100 times more virus and chimeras containing three mutations produced yields that were 180 to 250 times better. None of the mutations had significant effects upon the parental wild-type viruses, however. Passage of the triple variants eight or nine times resulted in variants that produced virus rapidly and were capable of producing >10
8
PFU/ml of culture fluid within 24 h. These further-adapted variants possessed one or two additional mutations, including E2-V116K, E2-S110N, or E1-T65S. The RR E1-C433R mutation was studied in more detail. This Cys is located in the putative transmembrane domain of E1 and was shown to be palmitoylated. Mutation to Arg-433 resulted in loss of palmitoylation of E1. The positively charged arginine residue within the putative transmembrane domain of E1 would be expected to alter the conformation of this domain. These results suggest that interactions within the transmembrane region are important for the assembly of the E1/E2 heterodimer, as are regions of the ectodomains possibly identified by the locations of adaptive mutations in these regions. Further, the finding that four or five changes in the chimera allow virus production that approaches the levels seen with the parental SIN and exceeds that of the parental RR illustrates that the structure and function of SIN and RR E1s have been conserved during the 50% divergence in sequence that has occurred.
The Conserved Serine 177 in the Delta Antigen of Hepatitis Delta Virus Is One Putative Phosphorylation Site and Is Required for Efficient Viral RNA Replication
Authors: Mu Jung-Jung , Chen Ding-Shinn , Chen Pei-Jer
Published: July 2002

Hepatitis delta virus (HDV) small delta antigen (S-HDAg) plays a critical role in virus replication. We previously demonstrated that the S-HDAg phosphorylation occurs on both serine and threonine residues. However, their biological significance and the exact phosphorylation sites of S-HDAg are still unknown. In this study, phosphorylated S-HDAg was detected only in the intracellular compartment, not in viral particles. In addition, the number of phosphorylated isoforms of S-HDAg significantly increased with the extent of viral replication in transfection system. Site-directed mutagenesis showed that alanine replacement of serine 177, which is conserved among all the known HDV strains, resulted in reduced phosphorylation of S-HDAg, while the mutation of the other two conserved serine residues (2 and 123) had little effect. The S177A mutant dramatically decreased its capability in assisting HDV RNA replication, with a preferential and profound impairment of the antigenomic RNA replication. Furthermore, the viral RNA editing, a step relying upon antigenomic RNA replication, was also abolished by this mutation. These results suggested that phosphorylation of S-HDAg, with serine 177 as a presumable site, plays a critical role in viral RNA replication, especially in augmenting the replication of antigenomic RNA.
Activated Peripheral CD8 Lymphocytes Express CD4 In Vivo and Are Targets for Infection by Human Immunodeficiency Virus Type 1
Authors: Imlach S. , McBreen S. , Shirafuji T. , Leen C. , Bell J. E. , Simmonds P.
Published: July 2002

There is increasing evidence that CD8 lymphocytes may represent targets for infection by human immunodeficiency virus type 1 (HIV-1) in vivo whose destruction may contribute to the loss of immune function underlying AIDS. HIV-1 may infect thymic precursor cells destined to become CD4 and CD8 lymphocytes and contribute to the numerical decline in both subsets on disease progression. There is also evidence for the induction of CD4 expression and susceptibility to infection by HIV-1 of CD8 lymphocytes activated in vitro. To investigate the relationship between CD8 activation and infection by HIV-1 in vivo, activated subsets of CD8 lymphocytes in peripheral blood mononuclear cells (PBMCs) of HIV-seropositive individuals were investigated for CD4 expression and HIV infection. Activated CD8 lymphocytes were identified by expression of CD69, CD71, and the human leukocyte antigen (HLA) class II, the β-chain of CD8, and the RO isoform of CD45. CD4+and CD4−CD8 lymphocytes, CD4 lymphocytes, other T cells, and non-T cells were purified using paramagnetic beads, and proviral sequences were quantified by PCR using primers from the long terminal repeat region. Frequencies of activated CD8 lymphocytes were higher in HIV-infected study subjects than in seronegative controls, and they frequently coexpressed CD4 (mean frequencies on CD69+, CD71+, and HLA class II+cells of 23, 37, and 8%, respectively, compared with 1 to 2% for nonactivated CD8 lymphocytes). The level of CD4 expression of the double-positive population approached that of mature CD4 lymphocytes. That CD4 expression renders CD8 cell susceptible to infection was indicated by their high frequency of infection in vivo; infected CD4+CD8 lymphocytes accounted for between 3 and 72% of the total proviral load in PBMCs from five of the eight study subjects investigated, despite these cells representing a small component of the PBMC population (<3%). Combined, these findings provide evidence that antigenic stimulation of CD8 lymphocytes in vivo induces CD4 expression that renders them susceptible to HIV infection and destruction. The specific targeting of responding CD8 lymphocytes may provide a functional explanation for the previously observed impairment of cytotoxic T-lymphocyte (CTL) function disproportionate to their numerical decline in AIDS and for the deletion of specific clones of CTLs responding to HIV antigens.
Estimation of Critical Properties from the Number of Carbon Atoms in Homologous Series
Authors: Koutek Bohumír , Hoskovec Michal , Lazar Josef
Published: July 2002

Equations correlating the normal boiling points (TB), critical temperatures (TC) and critical pressures (PC) with the respective carbon numbers (n) were developed for the straight-chain homologous series H-(CH2)n-Y, where Y denotes CH3, OH, CH=O, OCOCH3 and COOH and n varies from 5 to 18. The estimates based on these equations were found to reproduce experimental data within the average errors less than 0.27% for TB and TC, and 1.45% for PC thus allowing a prediction of new data.
Kinetics and Mechanism of Reaction of 2,4-Dinitrobenzaldehyde with Hydroxide Ion
Authors: Macháček Vladimír , Manová Jana , Sedlák Miloš , Štěrba Vojeslav
Published: July 2002

The reaction of 2,4-dinitrobenzaldehyde with hydroxide ion in water is first order in the substrate. The reaction order in hydroxide ion varies from one to two at lower and higher OH- concentrations, respectively. The reaction mechanism has been suggested, the pKa value of reaction product 2-nitro-4-nitrosophenol and the equilibrium constant of formation of the Meisenheimer adduct from 2-nitro-4-nitrosophenoxide and hydroxide ion have been determined.
Electron Pairing and Chemical Bonds. Physical Meaning of Effective Pairs
Authors: Ponec Robert , Uhlík Filip
Published: July 2002

The physical meaning of the so-called effective pairs which have been introduced recently within the formalism of pair population analysis is discussed using the analysis of conditional probabilities of electron density distribution for electron 1 with the reference electron fixed in a certain point 2. It is demonstrated that from the point of view of the mutual coupling of electron motions, the effective pairs behave analogously to singlet pairs. Based on this finding, effective pairs can be interpreted as the fraction of singlet pairs that is directly involved in bonding.
Kinetics of Reactions of 9-Isothiocyanatoacridine with Aromatic and Aliphatic Amines and Fluorescence Properties of the 1-Acridin-9-yl-3-alkyl(aryl)thioureas Obtained
Authors: Mazagová Dana , Kristian Pavol , Suchár Gejza , Imrich Ján , Antalík Marián
Published: July 2002

Kinetics of nucleophilic addition reaction of 9-isothiocyanatoacridine with seventeen aliphatic and aromatic amines in organic solvents has been studied by the VIS spectroscopic method. 9-Isothiocyanatoacridine reacted by about two orders of magnitude faster than phenyl isothiocyanate. The reaction rates of aliphatic amines were markedly affected by steric effects. Excepting 1-acridin-9-yl-3-butylthiourea (IIIo), the products obtained exhibited weaker fluorescence than the starting 9-isothiocyanatoacridine.
Oxidation of Toluene by Air in the Presence of Oxygen Compounds on Vanadium Catalysts
Authors: Kaszonyi Alexander , Antol Marcel , Hronec Milan , Delahay Gérard , Ballivet-Tkatchenko Danielle
Published: July 2002

Addition of 10 - 30 vol.% of C1 - C4 alcohols, acetone, acetic acid or acetic anhydride to toluene increases several times the yield of benzaldehyde. The effect of these compounds over V2O5-K2SO4 catalysts supported on SiO2 is positive at molar ratio K2SO4 : V2O5 < 0.5. At the ratio K2SO4 : V2O5 ≥ 0.5 the effect is more complex and depends on the conditions used. In the case of V : Ag : K catalyst with the molar ratio 1 : 0.3 : 0.3, added compounds increase the yield of benzaldehyde, except 2-propanol. No effect of these additives was observed over H9PV6Mo6O40 catalyst supported on SiO2.
The Synthesis of Some 2,4-Disubstituted 6H-5,1,3-Benzothiadiazocines
Authors: Bodajla Michal , Stankovský Štefan , Špirková Katarína
Published: July 2002

The title compounds bearing a phenyl or morpholin-4-yl groups in position 2 were prepared from the corresponding 2-chloromethyl imidoyl isothiocyanate.
Chemometric Analysis of Substituent Effects. VIII. Alternative Interpretation of Substituent Effects (AISE)
Authors: Pytela Oldřich
Published: July 2002

Alternative interpretation of substituent effects (AISE) starts from the presumption that a substituent only possesses a single property described by a single substituent constant. This property is transmitted to the reaction centre by three different ways depending on the interaction type in the triad reaction centre - basic skeleton - substituent. For interpretation it is substantial whether or not the substituent has p electrons at the atom adjacent to the basic skeleton. If it has none, the substituent belongs to class I and operates only by its basic effect described by the mentioned single substituent constant. Substituents of class II possess a free electron pair at the atom adjacent to the basic skeleton, and those of class III have a multiple bond between the first and the second atoms which is polarized in the direction from the basic skeleton. Substituent effects in class I are described by a substituent constant identical with σI constant. Substituents in classes II and III show additional effects proportional to the same constant. Hence, a separate treatment of substituent effects in the individual classes provides three straight lines intersecting in a common point. Mathematically, the description of substituent effects in this approach is expressed by a family of lines with a single explaining variable. The point of intersection, which is referred to as the iso-effect point, is not identical with the classic standard substituent - hydrogen - but is near to CN substituent. The approach given has the advantage of adopting a single substituent constant whose scale can be adjusted relatively precisely. Its drawback (like in the case of the correlation equations derived from the principle of separation of substituent effects) lies in a more extensive set of substituents needed for a correlation. The AISE principle has been applied to 318 series of experimental data describing effects of 32 substituents in a large variety of chemical models (aliphatic, alicyclic, aromatic, heteroaromatic, with or without direct conjugation between reaction centre and substituent) in both chemical reactions and equilibria. A comparison with two other correlation relations with two and three substituent constants for interpretation of substituent effects based on the principle of separation of the individual substituent effects showed that the closeness of AISE based correlations is comparable with that of the correlation equations currently used. It was somewhat less successful in the models with direct conjugation between reaction centre and substituent but the AISE principle can be used even in these cases.
Reaction of Carbon Disulfide with Active Methylenes: Novel Synthesis of Thiophene, Thieno[2,3-b]thiophene, Thieno[3,2-c]pyrazole and Thieno[3,2-b]pyridine Derivatives
Authors: Mohareb Rafat M. , Sherif Sherif M. , Habashi Adiba , Abdel-Sayed Nadia I. , Osman Samia S.
Published: July 2002

The active methylene compounds - derivatives of malonic or 4-oxobutanoic acid - reacted with carbon disulfide in dimethyl formamide containing potassium hydroxide to yield the non-isolable dipotassium disulfide intermediates. The latter were cyclized by α-haloketones to give thiophene, thieno[2,3-b]thiophene, thieno[3,2-c]pyrazole and thieno[3,2-b]pyridine derivatives. The reactivity of the products toward various reagents was studied.
Neutralization Dialysis. Problems and Outlook
Authors: Tishchenko Galina A. , Denisov Genadii A. , Shataeva Larisa K. , Bleha Miroslav
Published: July 2002

Neutralization dialysis (ND) of model systems containing 0.1-0.5 M NaCl and various high-molecular-weight synthetic or natural substances have been investigated. Desalination experiments were carried out in a three-compartment spiral module equipped with heterogeneous Ralex or homogeneous Neosepta membranes. Practically complete desalination proceeds due to the neutralization reaction in the desalination compartment. The time of desalination depends only on the membrane permeability and on the initial salt concentration in solution. An important feature hindering larger application of this method is sharp pH changes occurring in the desalination solution. This phenomenon predicted theoretically is mainly caused by the difference in diffusivities of H+/Na+ and OH-/Cl- ion pairs. Independently of the type of membrane and desalinated solution, pH value jumps into acidic region at the beginning of the ND. In the course of the process the pH value increases and the ND proceeds mostly at pH < 7. On the basis of theoretical prediction, an experimental method consisting in adjustment of acid concentration is proposed, which makes it possible to maintain constant pH in the desalination compartment. The convenience of this method was demonstrated by the ND of protein solutions.
Dehalogenation of 4,4'-Dichlorobiphenyl with Sodium Dihydridobis(2-methoxyethoxo)aluminate
Authors: Včelák Jaroslav , Hetflejš Jiří
Published: July 2002

4,4'-Dichlorobiphenyl was reduced to biphenyl with sodium dihydridobis(2-methoxyethoxo)aluminate in toluene at 70-110 °C. The reaction course was described by two consecutive dehalogenation steps of the first order in the substrate. The dehalogenation was accelerated by catalytic amounts of Co(II) and Ni(II) 1,3-pentanedionates. Dependence of dehalogenation steps on temperature and metal pentanedionate is reported, and rate data are compared with those obtained for 4-chlorobiphenyl, dichlorobenzene, and chlorobenzene.
Surface Aeration Threshold in Agitated Vessels
Authors: Wichterle Kamil , Svěrák Tomáš
Published: July 2002

Violent agitation of liquids in mixing vessels may result in the regime of surface aeration being attained when the bubbles formed at the liquid surface enter the impeller region. Analysis of data on surface aeration for different liquids in a set of geometrically similar agitated vessels is presented. Data on the just aerated state as observed visually in transparent liquids, and data for the efficient aeration as determined from the break on the power number curve are considered. A simple model is developed for correlation of the data which enables the threshold of aeration to be predicted from the value of the recirculation number Nc = Nd (ρ/σg)1/4. The possibility of interpreting various literature data for the aeration threshold and for the power input with use of Nc is demonstrated. Similar modelling rules hold also for the correlation of beginning of the efficient liquid-liquid dispersion.
New Groups of Potential Antituberculotics: 5-Alkylthio-1-aryltetrazoles
Authors: Waisser Karel , Kuneš Jiří , Hrabálek Alexandr , Macháček Miloš , Odlerová Želmíra
Published: July 2002

A series of 5-alkylthio-1-aryltetrazoles 1-14 was prepared by alkylation of the corresponding 1-aryltetrazole-5-thiols with alkyl bromides in the cyclohexane-aqueous potassium hydroxide system. The new compounds were evaluated for their activity against Mycobacterium tuberculosis, M. kansasii, M. avium and M. fortuitum. The effects of aryl and alkyl fragments on minimum inhibitory concentrations (MIC) against M. tuberculosis and M. kansasii were analyzed by Free-Wilson method. On basis of calculated fragment contributions, 5-butylthio-1-(3,4-dimethylphenyl)tetrazole (15) was predicted to be the most antimycobacterially active derivative in the present series studied and its activity was verified experimentally. MIC values of 30 μmol l-1 and 61 μmol l-1 were obtained for its activity against M. tuberculosis and M. kansasii, respectively.
Performance of the Amperometric Biosensor with Immobilized Butyrylcholinesterase in Organic Solvents
Authors: Skládal Petr , Krejčí Jan
Published: July 2002

The disposable electrochemical sensors with platinum composite electrode were successfully used for amperometric measurement of thiocholine produced from butyrylthiocholine by enzyme hydrolysis with butyrylcholinesterase (BChE, EC 3.1.1.8). The optimum potential was +500 mV vs the internal Ag/AgI/iodide (1 mmol/l) reference electrode. BChE was crosslinked with albumin and glutaraldehyde over the working electrode. Thus obtained biosensor was tested in various organic solvents (values of the hydrophobicity parameter log P from -1 to 5), no loss of activity was detected after a 5 min incubation in the solvents with log P greater than 2.5. The inhibition of the biosensor with paraoxon was studied in water, toluene, hexane, heptane and nonane. The extent of inhibition increased with solvent hydrophobicity (toluene > hexane > heptane), the inhibition obtained in water was similar as in heptane. Lower response than expected was obtained in nonane. The liquid-liquid extraction of paraoxon from aqueous samples to heptane provided significant improvement of sensitivity of the method. By this method, the lowest detected concentration of paraoxon was 0.03 μmol/l, resulting in the 20% inhibition of the biosensor signal after 5 min preincubation in the heptane extract.
Chemometric Analysis of Substituent Effects. X. Unification and Reparametrization of Substituent Constants in Hammett-Type Equations by Means of Alternative Interpretation of Substituent Effects (AISE)
Authors: Pytela Oldřich
Published: July 2002

The paper deals with evaluation of validity of substituent scales σm, σp, σp0, σp+, and σp- in Hammett-type equations. Possible reasons of unreliability of these scales and conceivable ways of verification of individual substituent constants are discussed. On the basis of Alternative Interpretation of Substituent Effects (AISE) and four additional conditions, a regression nonlinear model has been suggested which includes the dependence of all above-mentioned substituent scales upon a single interpreting variable - the σi substituent constant. This model has been applied to the 32 most frequent substituents from each scale, i.e. altogether 160 substituent constants taken from literature. The optimization of 17 unknown regression parameters gave the residual standard deviation s = 0.180 and, after excluding 12 remote values, s = 0.061. The analysis of residua proved their standard and statistical appropriateness of the model. The agreement between literature values and predicted values of substituent constants was the best with the σm scale; on the other hand, the largest differences were encountered with the σp+ scale. The found differences above a current reliability limit of substituent constants were due first to unreliability of some literature data and next to solvent effects and (in some cases) specific properties of substituents.
The Structure of [6,6'-μ-S(1,7-C2B9H10)2-2-Co]-[PPh4]+
Authors: Plešek Jaromír , Franken Andreas , Fröhlich Roland
Published: July 2002

Single crystal X-ray structure of monoatomically bridged [6,6'-μ-S(1,7-C2B9H10)2-2-Co]-[PPh4]+ is reported and selected bond lengths and angles are tabulated. A distinctly smaller dihedral angle (12.2°) between both pentagonal ligand planes than found earlier in the formally related symmetric analogue 8,8'-μ-MeOCOCH2S(1,2-C2B9H10)2-3-Co (16.5°) is discussed. This is the first reported X-ray structure of a monoatomically bridged cobaltacarborane with nonadjacent carbon atoms in deltahedral ligands.
Synthesis of 2-Aryl[1]benzofuro[2,3-e][1,2,4]triazin-3(2H)-ones and Their Use for Preparation of 1-Aryl-5-(2-hydroxyphenyl)-6-azauracils
Authors: Stýskala Jakub , Slouka Jan , Hejsek Miloslav , Bekárek Vojtěch
Published: July 2002

A series of arylhydrazones 1a-1i was prepared by coupling of arene diazonium salts with ethyl N-(benzo[b]furan-2-yl)carbamate. The hydrazones 1 were thermally cyclized to the corresponding 2-aryl[1]benzofuro[2,3-e][1,2,4]triazin-3(2H)-ones 2a-2i, derivatives of a new fused ring system. Compounds 2 were transformed by hydrolytic splitting to the corresponding 1-aryl-5-(2-hydroxyphenyl)-6-azauracils 3a-3i.
Influence of Geometry on Pumping Characteristics of Screw Agitators in a Tube
Authors: Sedláček Libor , Rieger František
Published: July 2002

The pumping characteristics of screw agitators in tubes were measured using a new dynamic method. Two inductive sensors record the difference of liquid surfaces in the tank while the liquid is pumped out. The characteristics in the form of dependence of the dimensionless specific energy on the dimensionless pumping capacity were obtained over a wide range of Reynolds number values. Screw agitators with different root diameter, pitch and number of flights were used in the experiments. The influence of above-mentioned geometrical parameters on pumping characteristics is discussed.
Ultrafast Electronic Energy Flow in a Bichromophoric Molecule
Authors: Fidler Vlastimil , Kapusta Peter , Nepraš Miloš , Schroeder Jörg , Rubtsov Igor V. , Yoshihara Keitaro
Published: July 2002

The intramolecular electronic excitation energy flow was investigated in a specially designed bichromophoric molecule, 2-(3-benzanthronylamino)-4-(1-pyrenylamino)-6-chloro-1,3,5-triazine (1) and was compared with the behaviour of two relevant component model compounds that closely mimic the photophysical properties of acceptor and donor sub-units in the bichromophore. Electronic absorption and fluorescence spectroscopy was applied (including fluorescence anisotropy and decay kinetics measurements with nanosecond to femtosecond time resolution) in order to resolve the energy relaxation process on a real time. An unambiguous piece of evidence is reported for an ultrafast process which leads to practically instantaneous population of the emitting state of the acceptor sub-unit after selective ≈200-fs-excitation of the donor sub-unit. This first direct observation of extremely fast energy transfer in a stiff bichromophore is significant for further development of relevant theory. Two conceptually different approaches to explaining such fast energy flow are discussed.
Hydrogenation of a Tetrasubstituted Double Bond: Synthesis of 5-Methyl-19-nor-5β-pregnanes
Authors: Kasal Alexander , Polman Jiří , Buděšínský Miloš
Published: July 2002

Reduction of C=C and/or C=O bonds in 5-methyl-19-nor-5β-pregn-9-ene-3,20-dione (1) leads to saturated and unsaturated ketones and hydroxy ketones. The C=C reduction affords mainly 9β,10β and 9α,10β dihydro products. Reaction conditions of partial esterification, hydrolysis and oxidation were elaborated. Several analogues were prepared for the testing of gestagenic and neurosteroidal activities.
Steric Effects and Steric Inhibition of Resonance in Benzene Derivatives: 2,3-Dimethylbenzoic Acid
Authors: Císařová Ivana , Podlaha Jaroslav , Böhm Stanislav , Exner Otto
Published: July 2002

Structure of 2,3-dimethylbenzoic acid was determined both by single-crystal X-ray diffraction and by ab initio calculation at an RHF/6-31+G** level. Comparing with a previous X-ray analysis of another crystal modification of the same compound, it was possible to estimate the effect of crystal forces on the conformation. The isolated molecule is not planar as deduced previously, mainly from IR spectra, but the carboxyl group is twisted out of the ring plane by a torsion angle ϕ = 12°. In the crystal, the molecule is more flat and ϕ is reduced to 7 and 1° in the two modifications, respectively. Further significant differences between the modifications were not detected. The flattening in the crystal structure is accompanied by additional small changes in the geometry, connected with greater steric crowding in the less twisted molecule: the example shows well the limits in which molecular structure can be deduced from the solid-state structure. Previous division of methylated benzoic acids into two subgroups, planar and nonplanar, is to be formulated with more precision: the former group includes even acids with nearly planar conformation (ϕ up to 15°).
Nitrosyl Tris(3,5-dimethylpyrazolyl)borato Complexes of Molybdenum Binding Pyridine Ligands with Electron-Withdrawing Groups at the 3-Position
Authors: Stobie Keira , Bell-Reeves Zoe R. , Ward Michael D. , McCleverty Jon A.
Published: July 2002

The octahedral nitrosyl complexes [MoCl(NO)(3-PhCH=CHCOpy)(TpMe,Me)] and [MoCl(NO){3,5-(MeCO)2py}(TpMe,Me)] (py = pyridyl) were synthesized and characterized spectroscopically. Both complexes underwent reduction and oxidation giving anionic and cationic species, respectively. Both complexes were also characterized by X-ray crystallography that confirmed their essential octahedral geometry and showed that the Mo-NO bond distance reflected the acceptor ability of the pyridine ligands.
Nonlinear Hammett Relationships in the Reaction of Peroxomonosulfate Anion (HOOSO3-) with meta- and para-Substituted Anilines in Alkaline Medium
Authors: Meenakshisundaram Subbiah , Sockalingam Ramanathan
Published: July 2002

The HOOSO3- oxidation of eleven meta- and para-substituted anilines to the corresponding nitrosobenzenes at pH ≈ 11 was characterized by the rate equation v = kK[OX][An]/(1 + K[An]). Formation constant of the reactive intermediate and its rate of decomposition were evaluated separately for ascertaining the structure-reactivity relationships. Under the experimental conditions the dianion, -O-O-SO3- is probably the effective electrophile. Kinetic data can be rationalized by a bimolecular process which involves the attack of nucleophilic nitrogen atom on the peroxidic oxygen. The highlight of the study is the opposite curvatures observed in the nonlinear Hammett plots of first-order rate constant k and the "equilibrium" constant K, being concave downward and upward, respectively.
Excimer Formation in Oligo[2,5-bis(hexadecyloxy)-1,4-phenylene]s Followed by Fluorescence Spectroscopy
Authors: Výprachtický Drahomír , Cimrová Věra , Machová Luďka , Pokorná Veronika
Published: July 2002

Using the steady-state and time-resolved fluorescence spectroscopy, the behavior of "hairy-rod" oligo- and poly[2,5-bis(hexadecyloxy)-1,4-phenylene]s in tetrahydrofuran solutions was investigated. The materials were prepared by the Yamamoto coupling reaction using zinc as a reducing metal, the nickel(II)/triphenylphosphine complex as a catalyst, and 2,2'-bipyridine as a coligand. The appropriate oligomer fractions were separated by fractional precipitation and characterized by GPC and end group analysis. The fluorescence quantum yield of oligomers and polymers increased with their increasing conjugation length. The fluorescence emission spectra of polymers and longer oligomers exhibited one emission maximum at 390 nm with a single-exponential decay and fluorescence lifetimes (τ) around 1 ns. The substitution in positions 2 and 5 forces the adjacent backbone benzene units out of the plane, which results in twist angles 60-80°, and the bulky substituents exclude the cofacial sandwich-type configuration necessary for excimer formation. However, with shorter oligomers, another emission band at 460 nm appeared. Fluorescence decays at 460 nm were found to be double-exponential with longer excited-state lifetimes [e.g. τ1 = 6.9 ns (76%), τ2 = 2.4 ns (24%)]. With shorter oligomers (dimer, trimer), we assume a sandwich-type configuration with sufficiently close interchain distance and hence the excimer can form. Hydrophobic interactions of long aliphatic side chains in a polar medium play an important role in the excimer formation.
Composite girder design by CAN/CSA S6-00: generalized design equations
Authors: Bobey Bill , Azarnejad Azita , McWhinnie Ken , Loov Robert
Published: July 2002

This paper presents generalized design equations for concretesteel composite girders. The equations evaluate the ultimate positive and negative flexural resistances of a composite section by addressing the issues of different design classes, varying locations of the neutral axis, and the possibility for either pseudoplastic or elastoplastic design. The equations may be readily implemented into design programs or spreadsheets.Key words: bridge, composite girders, design equations, elastic, elastoplastic, plastic, psuedoplastic.