bluuebunny/crossref_metadata_2025 huggingface dataset:
Inactivation of p21 by E1A Leads to the Induction of Apoptosis in DNA-Damaged Cells
Authors: Chattopadhyay Debasis , Ghosh Mrinal K. , Mal Asoke , Harter Marian L.
Published: July 2002

A major impediment to successful chemotherapy is the propensity for some tumor cells to undergo cell cycle arrest rather than apoptosis. It is well established, however, that the adenovirus E1A protein can sensitize these cells to the induction of apoptosis by anticancer agents. To further understand how E1A enhances chemosensitivity, we have made use of a human colon carcinoma cell line (HCT116) which typically undergoes cell cycle arrest in response to chemotherapeutic drugs. As seen by the analysis of E1A mutants, we show here that E1A can induce apoptosis in these cells by neutralizing the activities of the cyclin-dependent kinase inhibitor p21. E1A's ability to interact with p21 and thereby restore Cdk2 activity in DNA-damaged cells correlates with the reversal of G
1
arrest, which in turn leads to apoptosis. Analysis of E1A mutants failing to bind p300 (also called CBP) or Rb shows that they are almost identical to wild-type E1A in their ability to initially overcome a G
1
arrest in cells after DNA damage, while an E1A mutant failing to bind p21 is not. However, over time, this mutant, which can still target Rb, is far more efficient in accumulating cells with a DNA content greater than 4
N
but is similar to wild-type E1A and the other E1A mutants in releasing cells from a p53-mediated G
2
block following chemotherapeutic treatment. Thus, we suggest that although E1A requires the binding of p21 to create an optimum environment for apoptosis to occur in DNA-damaged cells, E1A's involvement in other pathways may be contributing to this process as well. A model is proposed to explain the implications of these findings.
Mapping the Sequences That Mediate Interaction of the Equine Herpesvirus 1 Immediate-Early Protein and Human TFIIB
Authors: Jang Hyung K. , Albrecht Randy A. , Buczynski Kimberly A. , Kim Seong K. , Derbigny Wilbert A. , O'Callaghan Dennis J.
Published: July 2002

The sole immediate-early (IE) gene of equine herpesvirus 1 encodes a 1,487-amino-acid (aa) regulatory phosphoprotein that independently activates expression of early viral genes. Coimmunoprecipitation assays demonstrated that the IE protein physically interacts with the general transcription factor TFIIB. Using a variety of protein-binding assays that employed a panel of IE truncation and deletion mutants expressed as in vitro-synthesized or glutathione
S
-transferase fusion proteins, we mapped a TFIIB-binding domain to aa 407 to 757 of the IE protein. IE mutants carrying internal deletions of aa 426 to 578 and 621 to 757 were partially defective for TFIIB binding, indicating that aa 407 to 757 may harbor more than one TFIIB-binding domain. The interaction between the IE protein and TFIIB is of physiological importance, as evidenced by transient-cotransfection assays. Partial deletion of the TFIIB-binding domain within the IE protein inhibited its ability to activate expression of the viral thymidine kinase gene, a representative early promoter, and of the IR5 gene, a representative late promoter, by greater than 20 and 50%, respectively. These results indicate that the interaction of the IE protein with TFIIB is necessary for its full transactivation function and that the IE-TFIIB interaction may be part of the mechanism by which the IE protein activates transcription.
Human Immunodeficiency Virus Type 1 Env Sequences from Calcutta in Eastern India: Identification of Features That Distinguish Subtype C Sequences in India from Other Subtype C Sequences
Authors: Shankarappa Raj , Chatterjee Ramdas , Learn Gerald H. , Neogi Dhruba , Ding Ming , Roy Pratima , Ghosh Adhir , Kingsley Lawrence , Harrison Lee , Mullins James I. , Gupta Phalguni
Published: July 2002

India is experiencing a rapid spread of human immunodeficiency virus type 1 (HIV-1), primarily through heterosexual transmission of subtype C viruses. To delineate the molecular features of HIV-1 circulating in India, we sequenced the V3-V4 region of viral
env
from 21 individuals attending an HIV clinic in Calcutta, the most populous city in the eastern part of the country, and analyzed these and the other Indian sequences in the HIV database. Twenty individuals were infected with viruses having a subtype C
env
, and one had viruses with a subtype A
env
. Analyses of 192 subtype C sequences that included one sequence for each subject from this study and from the HIV database revealed that almost all sequences from India, along with a small number from other countries, form a phylogenetically distinct lineage within subtype C, which we designate C
IN
. Overall, C
IN
lineage sequences were more closely related to each other (level of diversity, 10.2%) than to subtype C sequences from Botswana, Burundi, South Africa, Tanzania, and Zimbabwe (range, 15.3 to 20.7%). Of the three positions identified as signature amino acid substitution sites for C
IN
sequences (K340E, K350A, and G429E), 56% of the C
IN
sequences contained all three amino acids while 87% of the sequences contained at least two of these substitutions. Among the non-C
IN
sequences, all three amino acids were present in 2%, while 22% contained two or more of these amino acids. These results suggest that much of the current Indian epidemic is descended from a single introduction into the country. Identification of conserved signature amino acid positions could assist epidemiologic tracking and has implications for the development of a vaccine against subtype C HIV-1 in India.
An Attenuating Mutation in the 2A Protease of Swine Vesicular Disease Virus, a Picornavirus, Regulates Cap- and Internal Ribosome Entry Site-Dependent Protein Synthesis
Authors: Sakoda Yoshihiro , Ross-Smith Natalie , Inoue Toru , Belsham Graham J.
Published: July 2002

Virulent and avirulent strains of swine vesicular disease virus (SVDV), a picornavirus, have been characterized previously. The major determinants for attenuation have been mapped to specific residues in the 1D-2A-coding region. The properties of the 2A proteases from the virulent and avirulent strains of SVDV have now been examined. Both proteases efficiently cleaved the 1D/2A junction in vitro and in vivo. However, the 2A protease of the avirulent strain of SVDV was much less effective than the virulent-virus 2A protease at inducing cleavage of translation initiation factor eIF4GI within transfected cells. Hence the virulent-virus 2A protease is much more effective at inhibiting cap-dependent protein synthesis. Furthermore, the virulent-virus 2A protease strongly stimulated the internal ribosome entry sites (IRESs) from coxsackievirus B4 and from SVDV, while the avirulent-virus 2A protease was significantly less active in these assays. Thus, the different properties of the 2A proteases from the virulent and avirulent strains of SVDV in regulating protein synthesis initiation reflect the distinct pathogenic properties of the viruses from which they are derived. A single amino acid substitution, adjacent to His21 of the catalytic triad, is sufficient to confer the characteristics of the virulent-strain 2A protease on the avirulent-strain protease. It is concluded that the efficiency of picornavirus protein synthesis, controlled directly by the IRES or indirectly by the 2A protease, can determine virus virulence.
A Short N-Proximal Region in the Large Envelope Protein Harbors a Determinant That Contributes to the Species Specificity of Human Hepatitis B Virus
Authors: Chouteau P. , Le Seyec J. , Cannie I. , Nassal M. , Guguen-Guillouzo C. , Gripon P.
Published: July 2002

Infection by hepatitis B virus (HBV) is mainly restricted to humans. This species specificity is likely determined at the early phase of the viral life cycle. Since the envelope proteins are the first viral factors to interact with the cell, they represent attractive candidates for controlling the HBV host range. To investigate this assumption, we took advantage of the recent discovery of a second virus belonging to the primate
Orthohepadnavirus
genus, the woolly monkey HBV (WMHBV). A recombinant plasmid was constructed for the expression of all WMHBV envelope proteins. In additional constructs, N-terminal sequences of the WMHBV large envelope protein were substituted for their homologous HBV counterparts. All wild-type and chimeric WMHBV surface proteins were properly synthesized by transfected human hepatoma cells, and they were competent to replace the original HBV proteins for the production of complete viral particles. The resulting pseudotyped virions were evaluated for their infectious capacity on human hepatocytes in primary culture. Virions pseudotyped with wild-type WMHBV envelope proteins showed a significant loss of infectivity. By contrast, infectivity was completely restored when the first 30 residues of the large protein originated from HBV. Analysis of smaller substitutions within this domain limited the most important region to a stretch of only nine amino acids. Reciprocally, replacement of this motif by WMHBV residues in the context of the HBV L protein significantly reduced infectivity of HBV. Hence this short region of the L protein contributes to the host range of HBV.
The Pattern of Tegument-Capsid Interaction in the Herpes Simplex Virus Type 1 Virion Is Not Influenced by the Small Hexon-Associated Protein VP26
Authors: Chen Dong-Hua , Jakana Joanita , McNab David , Mitchell Joyce , Zhou Z. Hong , Dougherty Matthew , Chiu Wah , Rixon Frazer J.
Published: July 2002

Examination of the three-dimensional structure of intact herpes simplex virus type 1 (HSV-1) virions had revealed that the icosahedrally symmetrical interaction between the tegument and capsid involves the pentons but not the hexons (Z. H. Zhou, D. H. Chen, J. Jakana, F. J. Rixon, and W. Chiu, J. Virol. 73:3210–3218, 1999). To account for this, we postulated that the presence of the small capsid protein, VP26, on top of the hexons was masking potential binding sites and preventing tegument attachment. We have now tested this hypothesis by determining the structure of virions lacking VP26. Apart from the obvious absence of VP26 from the capsids, the structures of the VP26 minus and wild-type virions were essentially identical. Notably, they showed the same tegument attachment patterns, thereby demonstrating that VP26 is not responsible for the divergent tegument binding properties of pentons and hexons.
Mature Dendritic Cells Infected with Canarypox Virus Elicit Strong Anti-Human Immunodeficiency Virus CD8+and CD4+T-Cell Responses from Chronically Infected Individuals
Authors: Engelmayer Jose , Larsson Marie , Lee Andrew , Lee Marina , Cox William I. , Steinman Ralph M. , Bhardwaj Nina
Published: July 2002

Recombinant canarypox virus vectors containing human immunodeficiency virus type 1 (HIV-1) sequences are promising vaccine candidates, as they replicate poorly in human cells. However, when delivered intramuscularly the vaccines have induced inconsistent and in some cases transient antigen-specific cytotoxic T-cell (CTL) responses in seronegative volunteers. An attractive way to enhance these responses would be to target canarypox virus to professional antigen-presenting cells such as dendritic cells (DCs). We studied (i) the interaction between canarypox virus and DCs and (ii) the T-cell responses induced by DCs infected with canarypox virus vectors containing HIV-1 genes. Mature and not immature DCs resisted the cytopathic effects of canarypox virus and elicited strong effector CD8+T-cell responses from chronically infected HIV+individuals, e.g., cytolysis, and secretion of gamma interferon (IFN-γ) and β-chemokines. Furthermore, canarypox virus-infected DCs were >30-fold more efficient than monocytes and induced responses that were comparable to those induced by vaccinia virus vectors or peptides. Addition of exogenous cytokines was not necessary to elicit CD8+effector cells, although the presence of CD4+T cells was required for their expansion and maintenance. Most strikingly, canarypox virus-infected DCs were directly able to stimulate HIV-specific, IFN-γ-secreting CD4 helper responses from bulk as well as purified CD4+T cells. Therefore, these results suggest that targeting canarypox virus vectors to mature DCs could potentially elicit both anti-HIV CD8+and CD4+helper responses in vivo.
Generation and Characterization of a Mammalian Cell Line Continuously Expressing Japanese Encephalitis Virus Subviral Particles
Authors: Konishi Eiji , Fujii Atsuko , Mason Peter W.
Published: July 2002

We have generated a cell line (F cells) producing a secreted form of Japanese encephalitis virus (JEV) subviral particle (extracellular particles [EPs]) that contains the JEV envelope glycoprotein (E) and a precursor (prM) of the virion membrane protein (M). The F cells were engineered to synthesize these JEV products from a cDNA encoding a mutated (furin proteinase resistant) form of prM, since stable cell lines expressing E and the authentic form of prM could not be obtained, due (in part) to the cell-fusing ability of EPs containing E and M. Our biochemical alteration of the prM protein was critical for the successful production of EP-producing cell lines. EPs produced by F cells share the biochemical properties of empty viral particles produced by JEV-infected cells, except that the F-cell EPs lack hemagglutinating activity and M. F-cell EPs were recognized by a panel of monoclonal antibodies to E, and EPs were shown to be useful as vaccine candidates in mice and as diagnostic reagents in evaluating human immune responses to JE vaccination. The amounts of E antigen released into the culture fluid of F cells were similar to those found in virion fractions of JEV-infected cell culture fluids or JEV-infected weanling mouse brains (the current source of antigen used to produce human vaccines for JE). Thus, the F-cell line would appear to be a useful source of antigen for JE vaccines and diagnostics.
Differential CD4/CCR5 Utilization, gp120 Conformation, and Neutralization Sensitivity between Envelopes from a Microglia-Adapted Human Immunodeficiency Virus Type 1 and Its Parental Isolate
Authors: Martı́n Julio , LaBranche Celia C. , González-Scarano Francisco
Published: July 2002

Human immunodeficiency virus type 1 (HIV-1) infects and induces syncytium formation in microglial cells from the central nervous system (CNS). A primary isolate (HIV-1
BORI
) was sequentially passaged in cultured microglia, and the isolate recovered (HIV-1
BORI-15
) showed high levels of fusion and replicated more efficiently in microglia (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. González-Scarano, J. Virol. 70:7654–7662, 1996). The parent and adapted viruses used CCR5 as coreceptor. Recombinant viruses demonstrated that the syncytium-inducing phenotype was associated with four amino acid differences in the V1/V2 region of the viral gp120 (J. T. C. Shieh, J. Martin, G. Baltuch, M. H. Malim, and F. González-Scarano, J. Virol. 74:693–701, 2000). We produced luciferase-reporter,
env
-pseudotyped viruses using plasmids containing
env
sequences from HIV-1
BORI
, HIV-1
BORI-15
, and the V1/V2 region of HIV-1
BORI-15
in the context of HIV-1
BORI
env
(named rBORI, rB15, and rV1V2, respectively). The pseudotypes were used to infect cells expressing various amounts of CD4 and CCR5 on the surface. In contrast to the parent recombinant, the rB15 and rV1V2 pseudotypes retained their infectability in cells expressing low levels of CD4 independent of the levels of CCR5, and they infected cells expressing CD4 with a chimeric coreceptor containing the third extracellular loop of CCR2b in the context of CCR5 or a CCR5 Δ4 amino-terminal deletion mutant. The VH-rB15 and VH-rV1V2 recombinant viruses were more sensitive to neutralization by a panel of HIV-positive sera than was VH-rBORI. Interestingly, the CD4-induced 17b epitope on gp120 was more accessible in the rB15 and rV1V2 pseudotypes than in rBORI, even before CD4 binding, and concomitantly, the rB15 and rV1V2 pseudotypes were more sensitive to neutralization with the human 17b monoclonal antibody. Adaptation to growth in microglia—cells that have reduced expression of CD4 in comparison with other cell types—appears to be associated with changes in gp120 that modify its ability to utilize CD4 and CCR5. Changes in the availability of the 17b epitope indicate that these affect conformation. These results imply that the process of adaptation to certain tissue types such as the CNS directly affects the interaction of HIV-1 envelope glycoproteins with cell surface components and with humoral immune responses.
The Human Cytomegalovirus US8 Glycoprotein Binds to Major Histocompatibility Complex Class I Products
Authors: Tirabassi Rebecca S. , Ploegh Hidde L.
Published: July 2002

Human cytomegalovirus US8 is a type I membrane protein that partially colocalizes with cellular endosomal and lysosomal proteins. Although US8 does not have discernible effects on the processing and cell surface distribution of major histocompatibility complex (MHC) class I products, we have demonstrated that US8 binds to MHC class I heavy chains in the endoplasmic reticulum.
Identification of a Type 1 Peroxisomal Targeting Signal in a Viral Protein and Demonstration of Its Targeting to the Organelle
Authors: Mohan K. V. K. , Som I. , Atreya C. D.
Published: July 2002

Peroxisomes are unimembrane, respiratory organelles of the cell. Transport of cellular proteins to the peroxisomal matrix requires a type 1 peroxisomal targeting signal (PTS1) which essentially constitutes a tripeptide from the consensus sequence S/T/A/G/C/N-K/R/H-L/I/V/M/A/F/Y. Although PTS-containing proteins have been identified in eukaryotes, prokaryotes, and parasites, viral proteins with such signals have not been identified so far. We report here the first instance of a virus, the rotavirus, which causes infantile diarrhea worldwide, containing a functional C-terminal PTS1 in one of its proteins (VP4). Analysis of 153 rotavirus VP4-deduced amino acid sequences identified five groups of conserved C-terminal PTS1 tripeptide sequences (SKL, CKL, GKL, CRL, and CRI), of which CRL is represented in approximately 62% of the sequences. Infection of cells by a CRL-containing representative rotavirus (SA11 strain) and confocal immunofluorescence analysis revealed colocalization of VP4 with peroxisomal markers and morphological changes of peroxisomes. Further, transient cellular expression of green fluorescent protein (GFP)-fused VP4CRL resulted in transport of VP4 to peroxisomes, whereas the chimera lacking the PTS1 signal, GFP-VP4ΔCRL, resulted in diffuse cytoplasmic staining, suggesting a CRL-dependent targeting of the protein. The present study therefore demonstrates hitherto unreported organelle involvement, specifically of the peroxisomes, in rotaviral infections as demonstrated by using the SA11 strain of rotavirus and opens a new line of investigation toward understanding viral pathogenesis and disease mechanisms.
In Adenovirus Type 12 Tumorigenic Cells, Major Histocompatibility Complex Class I Transcription Shutoff Is Overcome by Induction of NF-κB and Relief of COUP-TFII Repression
Authors: Hou Shihe , Guan Hancheng , Ricciardi Robert P.
Published: July 2002

The surface levels of major histocompatibility complex class I antigens are diminished on tumorigenic adenovirus type 12 (Ad12)-transformed cells, enabling them to escape from immunosurveillant cytotoxic T lymphocytes (CTLs). This is due to the down-regulation of the class I transcriptional enhancer, in which there is strong binding of the repressor COUP-TFII and lack of binding of the activator NF-κB. Even though NF-κB (p65/p50) translocates to the nuclei of Ad12-transformed cells, it fails to bind to DNA efficiently due to the hypophosphorylation of the p50 subunit. In this study, tumor necrosis factor alpha (TNF-α) and interleukin 1β (IL-1β) were shown to promote degradation of the NF-κB cytoplasmic inhibitor IκBα and permit the nuclear translocation of a phosphorylated form of NF-κB that is capable of binding DNA. Interestingly, when Ad12-transformed cells were treated with TNF-α or IL-1β, class I gene transcription substantially increased when transcriptional repression by COUP-TFII was blocked. This indicates that in cytokine-treated Ad12-transformed cells, COUP-TFII is able to repress activation of class I transcription by newly nucleus-localized NF-κB. Our results suggest that Ad12 likely employs a “fail-safe” mechanism to ensure that the transcription of class I genes remains tightly repressed under various physiological conditions, thus providing tumorigenic Ad12-transformed cells with a means of escaping CTL recognition and lysis.
Intramolecular Complementing Mutations in
Tobacco Mosaic Virus
Movement Protein Confirm a Role for Microtubule Association in Viral RNA Transport
Authors: Boyko Vitaly , Ashby Jamie Alan , Suslova Elena , Ferralli Jacqueline , Sterthaus Oliver , Deom Carl M. , Heinlein Manfred
Published: July 2002

The movement protein (MP) of
Tobacco mosaic virus
(TMV) facilitates the cell-to-cell transport of the viral RNA genome through plasmodesmata (Pd). A previous report described the functional reversion of a dysfunctional mutation in MP (Pro81Ser) by two additional amino acid substitution mutations (Thr104Ile and Arg167Lys). To further explore the mechanism underlying this intramolecular complementation event, the mutations were introduced into a virus derivative expressing the MP as a fusion to green fluorescent protein (GFP). Microscopic analysis of infected protoplasts and of infection sites in leaves of MP-transgenic
Nicotiana benthamiana
indicates that MP
P81S
-GFP and MP
P81S;T104I;R167K
-GFP differ in subcellular distribution. MP
P81S
-GFP lacks specific sites of accumulation in protoplasts and, in epidermal cells, exclusively localizes to Pd. MP
P81S;T104I;R167K
-GFP, in contrast, in addition localizes to inclusion bodies and microtubules and thus exhibits a subcellular localization pattern that is similar, if not identical, to the pattern reported for wild-type MP-GFP. Since accumulation of MP to inclusion bodies is not required for function, these observations confirm a role for microtubules in TMV RNA cell-to-cell transport.
Reaction of 4-Amino-4,5-dihydro-1H-1,2,4-triazol-5-ones with 2,5-Dimethoxytetrahydrofuran
Authors: Ikizler Aykut A. , Yüksek Haydar
Published: July 2002

A number of studies involving some reactions of 4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones have been made in recent years. On the other hand, the reactions of some N-aminoheteroaryls with 1,4-diketones or 1,4-dialdehydes to give N,N'-linked biheteroaryls have also been reported. In the present study, a series of 3-alkyl-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones I were condensed in good yields with the succinaldehyde equivalent, 2,5-dimethoxytetrahydrofuran to give N,N'-bis(3-alkyl-4,5-dihydro-1H-1,2,4-triazol-5-on-4-yl)-1,4-butanediimines II or 1-(3-alkyl-4,5-dihydro-1H-1,2,4-triazol-5-on-4-yl)pyrroles III in nitrobenzene or acetic acid medium, respectively. To obtain more information on type II compounds, 3-methyl-4-ethylidenamino-4,5-dihydro-1H-1,2, 4-triazol-5-one (IV) was synthesized.
Intramolecular Hydrogen Bonds and Fermi Resonance in N-Substituted N'-(2-Fluorobenzoyl)thiourea Derivatives
Authors: Hritzová Oľga , Koščík Dušan
Published: July 2002

The presence of intramolecular NH...O=C bonds was proved in N-substituted N'-(2-fluorobenzoyl)thiourea derivatives by analysis of their infrared spectra. The intramolecular vibrational effects bring about a shift of the ν(NH) vibrational band to lower frequencies to the extent that the band gets into a vicinity to the δ(NH) overtone and Fermi resonance occurs between them. In addition, the ν(NH) vibration is also affected by Fermi resonance with the ν(CO) + δ(NH) combination. Double absorption bands were observed in the ν(CO) region for some of the derivatives. Based on perturbation theory applied to three-level interactions and using the Langseth and Lord equations, the band frequencies corrected for Fermi resonance were calculated and the hydrogen bond strength was examined in the compounds studied.
13C NMR Chemical Shift Assignments of Alkyl Chains of Histamine Analogous ω-Aminoalkylheterocycles and Bicyclic Derivatives
Authors: Pohl Martin , Bloedorn Wolf-Dieter , Mügge Clemens , Liebscher Jürgen
Published: July 2002

ω-Aminoalkylheterocycles and aromatics as well as bicyclic azolodiazepine derivatives were investigated by means of CH-COSY and INADEQUATE experiments. The 13C NMR shifts of all carbon atoms of the aminopropyl and aminobutyl moieties could be assigned. The benzylic position of the ω-aminopropyl moieties appears most upfield rather than more downfield like erroneously reported in the literature.
Preparation and Spectroscopic Properties of Spirocyclic 1-Methyl-2,4,4,6-tetraaryl-1,4-dihydropyridines
Authors: Böhm Stanislav , Hocek Michal , Němeček Jan , Havlíček Vladimír , Kuthan Josef
Published: July 2002

1,5-Diones Ib - Ie were converted to spirocyclic 1,4-dihydropyridines IIb - IIe by treatment with methanolic methylamine. The starting diketones Ib - Ie were obtained from corresponding acetophenones 4-X-C6H4COMe and fluorenone with sodium amide except of If where only ketone III and 1,4-dione IV were isolated. Molecular spectra (UV-VIS, NMR, IR and MS) of compounds Ib - Ie, IIa - IIe, III, and IV were assigned and interpreted.
Potential Nootropic Agents: Synthesis of Some 1,4-Disubstituted 2-Oxopyrrolidines and Some Related Compounds
Authors: Valenta Vladimír , Urban Jiří , Taimr Jan , Polívka Zdeněk
Published: July 2002

4-(Aminomethyl)-1-benzyl-2-oxopyrrolidine (VI) was transformed by treatment with (4-benzhydrylpiperazin-1-yl)carbonyl chlorides IIIb - IIId and with (4-methylpiperazin-1-yl)carbonyl chloride (IIIa) to the carboxamides IVa - IVd. Heating of 1-(ethoxycarbonylmethyl)-2,4-dioxopyrrolidine (XIX) in acetonitrile in the presence of water afforded XVIIIa. Treatment with ammonia led to the diamide XVIIIc, while alkaline hydrolysis of XVIIIa gave the dicarboxylic acid XVIIIb. 4-(Aminomethyl)-1-(4-methylthiobenzyl)-2-oxopyrrolidine (XII) was prepared by the reaction of 4-(methylthio)benzylamine with itaconic acid and the following sequence of reactions starting from the obtained carboxylic acid VII including esterification, reduction and treatment the obtained alcohol IX with thionyl chloride, synthesis of phthalimido derivative XI and hydrazinolysis. Amine XII added to 4-chlorophenyl isocyanate formed XIII. The compounds prepared were tested for nootropic activity.
Batch Precipitation of Lead Iodide
Authors: Nývlt Jaroslav , Žáček Stanislav
Published: July 2002

Lead iodide was precipitated by a procedure in which an aqueous solution of potassium iodide at a concentration of 0.03, 0.10 or 0.20 mol l-1 was stirred while an aqueous solution of lead nitrate at one-half concentration was added at a constant rate. The mean size of the PbI2 crystals was determined by evaluating the particle size distribution, which was measured sedimentometrically. The dependence of the mean crystal size on the duration of the experiment exhibited a minimum for any of the concentrations applied. The reason for this is discussed.
Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2
Authors: Žertová Miroslava , Slaninová Jiřina , Procházka Zdenko
Published: July 2002

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.
Kinetics of the Reaction of Solid Anhydrous Potassium Carbonate with Gaseous Sulfur Dioxide
Authors: Lippert Erich , Mocek Karel , Erdös Emerich
Published: July 2002

Results are presented of an experimental kinetic study of the heterogeneous reaction between gaseous sulfur dioxide and solid anhydrous potassium carbonate. The measurements were carried out in an all glass kinetic flow apparatus with nitrogen as the carrier gas and a fixed bed of the solid working in the differential regime at atmospheric pressure and a temperature of 423 K (150 °C). The reaction course was studied in dependence on the partial pressures of sulfur dioxide (pSO2) and water vapour (pH2O) in concentration ranges pSO2 = 13 - 430 Pa and pH2O = 0 - 2 100 Pa. In the reaction, water vapour acts as a gaseous catalyst. Based on the experimental data, the corresponding kinetic equation was found together with the numerical values of the relevant rate and equilibrium adsorption constants.
Sterically Crowded Heterocycles. II. Conformational Structure of 2-Phenyl-3-[(Z)-1,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridine and Related Compounds
Authors: Böhm Stanislav , Kubík Richard , Hradilek Martin , Němeček Jan , Hušák Michal , Kratochvíl Bohumil , Kuthan Josef
Published: July 2002

Conformational behaviour of 2-phenyl-3-[(Z)-1,3-diphenyl-3-oxopropenyl]imidazo[1,2- a]pyridine I is studied using a molecular isoenergy map calculated by the PM3 method. A predicted potency of this approach is discussed with respect to the experimental solid state structures of related compounds I - IV. Complete X-ray structures of 7-methyl derivative IV and 11-phenyl derivative V are reported.
Radical Additions to Fluoroolefins: Experimental Evidence for a Free-Radical Chain Mechanism in the Photo-Initiated Addition of Alcohols to Fluoroolefins
Authors: Paleta Oldřich , Kvíčala Jaroslav , Budková Zuzana , Timpe Hans-Joachim
Published: July 2002

Photo-initiated addition of 2-propanol to two fluoroolefinic compounds, i.e. methyl 2,4,4,5,6,6-hexafluoro-3-oxa-2-(trifluoromethyl)hex-5-enoate (IV) containing perfluoroallyloxy group and 8,9-dichloro-1,1,2,4,4,5,7,7,8,9,9-undecafluoro-3,6-dioxa-5-(t rifluoromethyl)dodec-1-ene (V) containing trifluorovinyloxy group were used to verify a free-radical chain mechanism by means of quantum yield measurements based on substrate-decay kinetic. UV-Light energy (254 nm) was transferred to the reaction system via triplet-excited acetone. Quantum yields Fi of the addition products (X, XI) reached values 68 and 42, respectively, and thus confirmed the chain mechanism. The olefinic compounds IV and V were synthesized on the basis of the reaction of 2,3-dichloro-2,3,3-trifluoropropanoyl fluoride (I) with hexafluoropropene-1,2-oxide. The photoaddition of 2-propanol to both olefins took place with complete regioselectivity.
ESR Spin Trapping Study of Sodium and Tetramethylammonium Mercaptoundecahydro-closo-dodecaborates(2-) and Sodium Tetraborate Aqueous Solutions Irradiated by UV Light at Room Temperature
Authors: Štrouf Oldřich , Stopka Pavel
Published: July 2002

The superoxide anion radicals O2-• were identified and determined in aqueous solutions of sodium and tetramethylammonium salts of mercaptoundecahydro-closo-dodecaborate(2-) (mercaptoborate), and sodium tetraborate, irradiated by high pressure mercury discharge lamp at room temperature by the of ESR spin trapping method. The quantity of the generated O2-. depends on the initial oxygen concentration in the irradiated solutions. The radical generation can play a crucial role in the application of mercaptoborate in boron neutron capture therapy (BNCT) of brain tumours.
Effect of Molecular Weight on Mechanical Behaviour of Segmented Polyurethanes
Authors: Ilavský Michal , Fähnrich Jaromír , Pakula Tadeusz , Lantman Christopher
Published: July 2002

The effect of molecular weight of polyurethanes on their dynamic mechanical and ultimate behaviour was investigated in wide frequency and temperature ranges. The polyurethanes were prepared from α,ω-dihydroxy-poly(oxypropylene), 1,4-butanediol, 1-butanol and 4,4'-dicyclohexylmethane diisocyanate at constant stoichiometric molar ratio of OH and NCO groups. Molecular weight (MW) of the copolymers was varied by replacing partly the butanediol by equivalent amounts of butanol; the calculated values of MW ranged from 6 000 to infinity. In all samples the constant soft-segment concentrations (~50 wt.%) were obtained. Two transition regions located around -30 °C and 70 °C, corresponding to the soft polyether and hard polyurethane domains, respectively, were observed with all samples in the temperature dependences of both components of the dynamic modulus measured at 1 Hz. Due to high miscibility of the phases, both transitions overlap; the two-phase character of the structure increases with decreasing MW. At T > 120 °C the samples are homogeneous and the frequency-temperature superposition could be applied. Quenching of the samples from 150 °C down to -80 °C preserves quasi-homogeneous structure; the rate of re-establishment of the two-phase structure increases with decreasing MW. The ultimate properties, strain-at-break and tensile strength measured at room temperature decrease with decreasing MW.
Experimental Evidence of the Isoperichoric Focusing of Nanosize Polyaniline Particles in Density Gradient Formed by Colloidal Silica
Authors: Janča Josef , Špírková Milena
Published: July 2002

The isoperichoric focusing transport phenomena were recently described by a rigorous theoretical model. Contrary to the generally accepted supposition that a density gradient forming liquid in isopycnic focusing should behave as continuum regarding the focused species, the model predicts the focusing with no a priori imposed size ratio of the focused to the density gradient forming species. This prediction was evidenced by focusing of the polyaniline nanosize particles in a density gradient formed by colloidal silica particles suspended in water. The size ratio of the polyaniline to silica particles was low.
Polarographic Studies on Selenite Ions in Aqueous Hypophosphorous Acid Solutions
Authors: El-Shatoury Salah A.
Published: July 2002

The polarographic behaviour and determination of Se(IV) in hypophosphorous acid solutions of concentrations varying from 0.05 mol l-1 to 4.0 mol l-1 at 25 ± 0.1 °C were investigated. It was shown that the reduction of 5 . 10-4 mol l-1 Se(IV) at the DME takes place in two waves independent on the acid concentration. The reduction waves correspond to the transfer of 6 electrons. A mechanism of the reduction at the DME has been suggested. A method for the analytical determination of Se(IV) species in 0.1 mol l-1 and 0.05 mol l-1 hypophosphorous acid in absence and in presence of 3 . 10-6 mol l-1 Cd(II) and Zn(II) was developed using a differential pulse technique.
Effect of Ultrasound on Voltammetric Measurements on a Miniaturized Mercury Electrode; Sonovoltammetry and Sonopolarography
Authors: Novotný Ladislav
Published: July 2002

The influence of ultrasound on voltammetric measurements at a mechanically stable renewed mercury electrode was described. The measurements were carried out in a solution of 4,4'-bipyridyl in 0.1 M KCl + 0.01 M NaOH, in 1 . 10-4 M CdSO4 + 5 . 10-6 M tribenzylamine in 0.1 M H2SO4 and in 3 . 10-3 M CdSO4 + 1 . 10-4 M tribenzylamine hydrochloride. Possible development and applications of related electroanalytical techniques by using mercury and solid electrodes were discussed. A pronounced influence of ultrasound was observed mainly in cases where the kinetics and irreversibility of the electrochemical and related processes played an important role.
NMR Complexation Study of Several Oxyethylated Calix[4]arenes with Lithium, Sodium and Potassium Ions
Authors: Havlíček Jaroslav , Tkadlecová Marcela , Vyhnánková Michaela , Pinkhassik Evgueni , Stibor Ivan
Published: July 2002

The influence of calix[4]arene upper rim substitution on the complexation with Li+, Na+, K+ was studied by 1H NMR spectroscopy. Calix[4]arenes 1-4 namely 25,26,27,28-tetrakis(3-oxapentyloxy)calix[4]arene (1), its 5,17-diamino (2) and 5,17-dinitro derivative (3) as well as 25,26,27,28-tetrakis(3,6,9-trioxadecyloxy)calix[4]arene (4) having four monoalkyloligoethylene glycol chains on the lower rim have been studied. No complexation has been observed for Li+. Two electron-donating NH2 groups on the calixarene upper rim (compound 2) improve the complexation ability for Na+ and K+ compared with parent calixarene 1. The electron-withdrawing nitro groups in 3 have the opposite influence. It seems that the complexation of alkali metal ions studied is not significantly influenced by the increasing number of donor atoms (from eight in 1 to sixteen in 4) available for complexation on the lower rim. The position of sodium cation in 1 . Na+ and 4. Na+ is supposed to be in close proximity of phenolic oxygens based on 1H and 13C NMR data. The error analysis is given for the stability constant determination from NMR data.
Stereochemical Factors of γ-H Eliminationin Cyclopentadienylvinylnickel Compounds
Authors: Pietrzykowski Antoni , Pasynkiewicz Stanisław , Buchalski Piotr
Published: July 2002

The reactions of nickelocene with cis-1,2-diphenylpropylmagnesium bromide and with trans-1,2-diphenylpropenyllithium had been studied. It was found that cis-1,2-diphenylpropenylcyclopentadienylnickel underwent γ-H elimination to form a mixture of (η5-cyclopentadienyl)[η3-1,2-(anti)-diphenylpropenyl]nickel and (η5-cyclopentadienyl)[η3-1,2-(syn)-diphenylpropenyl]nickel as the main products. The mechanism of this reaction has been discussed. Dihydrotetra(cyclopentadienylnickel) cluster (NiCp)4H2 was the main organometallic product of the reaction of nickelocene with trans-1,2-diphenylpropenyllithium. There was no γ-H elimination products formed in this reaction. It has been concluded that γ-H elimination in cyclopentadienylvinylnickel compounds is stereochemically controlled process and can occur only if a distance of γ-hydrogen from the nickel atom is relatively small.
Surface Cluster Models for V2O5 - Studies of the Importance of Local Geometry
Authors: Witko Małgorzata , Tokarz Renata , Hermann Klaus
Published: July 2002

Catalytic properties of the vanadium pentoxide (010) surface are discussed based upon semiempirical quantum chemical calculations using cluster models. Special attention is paid to the role of the second layer in discussing the geometrical factor by using the semiempirical ZINDO approach. Local electronic properties near the different surface oxygen sites are analyzed with the help of Mulliken populations and Meyer bond order indices. Different optimization procedures (with various boundary conditions) are performed for diverse V-O clusters modeling one and two layers. Electronic parameters of the clusters are found to be similar for the cluster in the bulk and optimized geometry. The optimized geometry of the cluster remains much closer to the surface geometry when the optimization is done for the whole cluster, excluding the saturated hydrogen atoms. Optimization of the small fragment of the cluster, results in the significant rearrangement of the cluster structure and leads to the "warped" geometry (bridging oxygen as well as vanadium atoms are shifted out of the surface). Two types of boundary conditions assumed during the optimization process lead to similar results, the optimization of all atoms in the cluster (with saturating hydrogen atoms kept frozen) and the same optimization in the presence of the second layer. The presence of the second layer stabilizes the surface geometry. The role of the second layer is also shown in a formation of an oxygen vacancy at the bridging position.
Synthesis of Acyclic Nucleotide Analogues Derived from 6-(sec- or tert-Alkyl)purines via Coupling of 6-Chloropurine Derivatives with Organocuprates
Authors: Dvořáková Hana , Dvořák Dalimil , Holý Antonín
Published: July 2002

Coupling of 9-[2-(diisopropyloxyphosphonylmethoxy)ethyl]-6-chloropurine (23) (and (R)-9-[2-(diisopropyloxyphosphonylmethoxy)propyl]-6-chloropurine (24), respectively) with organocuprates derived from Grignard reagents afforded after deprotection 6-(sec- or tert-alkyl) substituted phosphonates 31-36. As a model a series of 6-(sec- or tert-alkyl)purines 2-12 was also prepared.
Kinetics of Methanolysis of Substituted Benzamide O-(Phenoxycarbonyl)- and O-(Alkoxycarbonyl)oximes Catalyzed by Sodium Methanolate
Authors: Dušek Libor , Kaválek Jaromír , Štěrba Vojeslav
Published: July 2002

The kinetics of methanolysis of substituted benzamide O-(phenoxycarbonyl)- and O-(alkoxycarbonyl)oximes catalyzed by sodium methanolate was studied at 25 °C. The reaction proceeds in two steps. In the first, faster step, the substituted phenoxy group is exchanged for a methoxy group giving rise to substituted O-(methoxycarbonyl)oximes. In the second step, a benzamide oxime is eliminated and dimethyl carbonate is formed. The slope of the plot of the rate constant in dependence on the sodium methanolate concentration has an increasing tendency in both steps. In the presence of 18-crown-6, the plots are linear and the rate constants are lower than in the absence of the crown ether. The rate constants of the reaction of the substrate with the methanolate ion and with the MeONa ion pair were determined assuming that the sodium cation-catalyzed reactions constitute the rate-determining step of the reaction of the substrate with the MeONa ion pair. For the elimination of the aryloxy group and of the substituted benzamide oxime, the rate constants of the reaction with the ion pair are roughly twelvefold and twentyfold higher, respectively, than in the uncatalyzed reaction. The slope of the dependence of log k on the pKa of the substituted phenols (βlg) has the value of -0.52 for the uncatalyzed reaction of elimination of the substituted phenoxy group, -0.83 for the elimination of the benzamide oxime group, and -0.53 for the reaction with the ion pair. In the first step and probably also in the second step, the reaction proceeds by the concerted mechanism. The relatively high ρ value of methanolysis of substituted benzamide O-(4-nitrophenoxycarbonyl)oximes, 0.63, suggests that the structure of the transition state approaches that of the tetrahedral intermediate.
Fluorescence Anisotropy and Mobility of Dansyl Fluorophore in Labelled Homologous Alkanes
Authors: Výprachtický Drahomír , Pokorná Veronika , Pecka Jan , Mikeš František
Published: July 2002

Using the steady-state and time-resolved fluorescence anisotropy, the mobility of 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore in homologous 1-[2-acetamido-3-(1H-indol-3-yl)propanamido]-n-[5-(dimethylamino)naphthalene-1-sulfonamido]alkanes 1 was studied in binary solvents glycerol-water. Steady-state fluorescence data were evaluated by the generalized Perrin equation and the micro-Brownian motion of dansyl fluorophore was described by means of average characteristics (rotational relaxation times) of the rotational relaxation spectrum. The rotational relaxation time of "fast" motions caused by torsional vibrations of single bonds within the rotational-isomeric states decreases with increasing number of methylene groups in homologous compounds. The rotational relaxation time of "slow" motions due to conformational changes of the chain between the tryptophane and dansyl fluorophore remains at first approximately constant with increasing number of methylene groups but increases considerably for long aliphatic chains. The observed decrease in the rate of conformational changes of a long aliphatic chain is probably due to intramolecular interaction of parts of the methylene chain in a medium with high water content. The values of activation enthalpy ∆H≠ and activation entropy ∆S≠ calculated from experimental data corroborate such interpretation. Time-resolved anisotropy of dansyl fluorophore at a particular binary solvent composition confirmed the shape of rotational relaxation spectrum and the measured rotational correlation times have been discussed. The time-dependent decays of anisotropy supported our previous interpretation in terms of intramolecular association of the long aliphatic chain in polar medium.
Elimination of Substituted Fluoren-9-ylmethyl Benzenesulfonates: Hammett Substituent Effects at a Mechanistic Borderline
Authors: Larkin Finbar G. , More O'Ferrall Rory A. , Murphy Donal G.
Published: July 2002

Rates of elimination of fourteen substituted fluoren-9-ylmethyl benzenesulfonates have been measured in methanolic sodium methoxide and 90% aqueous ethanolic solutions of triethylamine, trimethylamine and 4-methyl morpholine. For the sodium methoxide, a linear Hammett plot with ρ = 0.74, consistent with reaction by an E2 mechanism, is observed. For the amine bases the Hammett plots are curved, suggesting a transition from an E2 mechanism for electron-withdrawing substituents to an irreversible E1cB mechanism with a smaller value of ρ for electron-donating substituents. The evidence for a change of mechanism is weakened by systematic and random deviations of substituents from correlations which span small changes in reactivity (less than ten-fold), by a surprisingly large value of ρ = 2 implied for the concerted (E2) reaction and by the possible influence of negative hyperconjugation. Nevertheless, it is consistent with independent evidence that the borderline between concerted and stepwise mechanisms is associated with chemically distinguishable reaction paths, even though pronounced carbanion character (and probably a small extent of bond-breaking to the leaving group) ensures a degree of similarity of structure and sensitivity to substituents of their transition states.
Franck-Condon Dominated Chemistry. Formation and Dissociations of the Dimethylhydroxysulfuranyl Radical
Authors: Tureček František
Published: July 2002

The structure and energetics of the hydroxyl radical adduct to dimethyl sulfide (DMS) was revisited using high level ab initio calculations. Density functional theory B3LYP/6-31++G(2d,p) and perturbational MP2(FULL)/6-31++G(2d,p) calculations found a weakly bound structure, (CH3)2SOH•, with a long S-O bond that was a local energy minimum. Single point calculations at the effective QCISD(T)/6-311++G(3df,2p) level of theory, denoted as G2++(MP2), found the (CH3)2S-OH• bonding energy to be 40 kJ mol-1 at 298 K. The standard heat of formation of (CH3)2SOH• was assessed from dissociation and isodesmic reactions as -45 ± 4 kJ mol-1. No other local minima corresponding to C2H7OS radicals were found at the present level of theory that could be derived from DMS or dimethyl sulfoxide (DMSO). A very weak complex, CH3S(H)-•OCH3, was found that was bound by mere 4 kJ mol-1 against dissociation to CH3SH and •OCH3. Vertical electron capture by (CH3)2SOH+ is predicted to form (CH3)2SOH• with a highly non-relaxed geometry corresponding to a vibrational excitation of 138 kJ mol-1 above the local minimum and 88 kJ mol-1 above the dissociation threshold to DMS and OH•. Unimolecular dissociation of (CH3)2SOH• to methanesulfenic acid (CH3SOH) and •OCH3 faces an energy barrier that diminishes at shorter S-O distances. The dipole-allowed electronic excitation in (CH3)2SOH• was calculated with CIS/6-311++G(2df,p) to have λmax = 248 nm in the gas phase. The resulting B state represents a charge-transfer complex of (CH3)2S+• and OH-. The present computational results allowed us to explain the existing controversy between the experimental results obtained by gas-phase flow kinetics, radiolysis in aqueous solution, and neutralization-reionization mass spectrometry.