bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro- and In Vivo-Generated Defective RNAs of Satellite Panicum Mosaic Virus Define
cis
-Acting RNA Elements Required for Replication and Movement
Authors: Qiu Wenping , Karen-Beth Scholthof G.
Published: July 2002

Satellite panicum mosaic virus (SPMV) depends on its helper virus, panicum mosaic virus (PMV), to provide
trans
-acting proteins for replication and movement. The 824-nucleotide (nt) genome of SPMV possesses an open reading frame encoding a 17.5-kDa capsid protein (CP), which is shown to be dispensable for SPMV replication. To localize
cis
-acting RNA elements required for replication and movement, a comprehensive set of SPMV cDNA deletion mutants was generated. The results showed that the 263-nt 3′ untranslated region (UTR) plus 73 nt upstream of the CP stop codon and the first 16 nt in the 5′ UTR are required for SPMV RNA amplification and/or systemic spread. A region from nt 17 to 67 within the 5′ UTR may have an accessory role in RNA accumulation, and a fragment bracketing nt 68 to 104 appears to be involved in the systemic movement of SPMV RNA in a host-dependent manner. Unexpectedly, defective RNAs (D-RNAs) accumulated de novo in millet plants coinfected with PMV and either of two SPMV mutants: SPMV-91, which is incapable of expressing the 17.5-kDa CP, and SPMV-GUG, which expresses low levels of the 17.5-kDa CP. The D-RNA derived from SPMV-91 was isolated from infected plants and used as a template to generate a cDNA clone. RNA transcripts derived from this 399-nt cDNA replicated and moved in millet plants coinoculated with PMV. The characterization of this D-RNA provided a biological confirmation that the critical RNA domains identified by the reverse genetic strategy are essential for SPMV replication and movement. The results additionally suggest that a potential “trigger” for spontaneous D-RNA accumulation may be associated with the absence or reduced accumulation of the 17.5-kDa SPMV CP. This represents the first report of a D-RNA associated with a satellite virus.
A Single-Amino-Acid Substitution of a Tyrosine Residue in the Rubella Virus E1 Cytoplasmic Domain Blocks Virus Release
Authors: Yao Jiansheng , Gillam Shirley
Published: July 2002

Rubella virus particles, consisting of a nucleocapsid surrounded by a lipid envelope in which two virus-encoded glycoproteins E1 and E2 are embedded, assemble on intracellular membranes and are secreted from cells, possibly via the cellular secretory pathway. We have recently demonstrated that the cytoplasmic domain of E1 (residues 469 to 481, KCLYYLRGAIAPR) is required for virus release. Alteration of cysteine 470 to alanine did not affect virus release, whereas mutation of leucine 471 to alanine reduced virus production by 90%. In the present study, substitutions of remaining amino acids in the E1 cytoplasmic domain were made in order to investigate the role of each amino acid in regulating rubella virus release. Generated mutants were analyzed in the context of infectious full-length cDNA clone and virus-like particles using combined genetic, biochemical, and electron microscopic approaches. Substitution of a single residue of tyrosine 472 to alanine or tyrosine 473 to serine resulted in a block in virus release without affecting protein transport and virus budding into the lumen of the Golgi complexes. Infectious RNA transcripts bearing these mutations were incapable of forming plaques. Mutants with substitutions at the amino-terminal region (leucine 474, arginine 475, and glycine 476) in the E1 cytoplasmic domain had reduced virus release and small-plaque phenotype, while mutants with substitutions at the carboxy-terminal region (alanine 477, isoleucine 478, alanine 479, proline 480, and arginine 481) had only marginal defects in virus release. Plaque-forming revertants could be isolated from mutants Y472A and Y473S. Sequencing analysis revealed that the substituted serine residue in mutant Y473S reverted to the original tyrosine residue, whereas the substituted alanine residue in mutant Y472A was retained. These results indicate that the E1 cytoplasmic domain modulates virus release in a sequence-dependent manner and that the tyrosine residues are critical for this function. We postulate that residues YYLRG constitute a domain in the E1 tail that may interact with other proteins and this interaction is involved in regulating virus release.
NP and L Proteins of Lymphocytic Choriomeningitis Virus (LCMV) Are Sufficient for Efficient Transcription and Replication of LCMV Genomic RNA Analogs
Authors: Lee Ki Jeong , Novella Isabel S. , Teng Michael N. , Oldstone Michael B. A. , de la Torre Juan Carlos
Published: July 2002

The genome of lymphocytic choriomeningitis virus (LCMV) consists of two negative-sense single-stranded RNA segments, designated L and S. Both segments contain two viral genes in an ambisense coding strategy, with the genes being separated by an intergenic region (IGR). We have developed a reverse genetic system that allows the investigation of
cis
-acting signals and
trans
-acting factors involved in transcription and replication of LCMV. To this end, we constructed an LCMV S minigenome consisting of a negative-sense copy of the chloramphenicol acetyltransferase (CAT) reporter gene flanked upstream by the S 5′ untranslated region (UTR) and IGR and downstream by the S 3′ UTR. CAT expression was detected in LCMV-infected cells transfected with the minigenome RNA. Intracellular coexpression of the LCMV minigenome and LCMV L and NP proteins supplied from cotransfected plasmids driven by the T7 RNA polymerase provided by the recombinant vaccinia virus vTF7-3 resulted in high levels of CAT activity and synthesis of subgenomic CAT mRNA and antiminigenome RNA species. Thus, L and NP represent the minimal viral
trans
-acting factors required for efficient RNA synthesis mediated by LCMV polymerase.
Passive Transfer of Antibodies Protects Immunocompetent and Immunodeficient Mice against Lethal Ebola Virus Infection without Complete Inhibition of Viral Replication
Authors: Gupta Manisha , Mahanty Siddhartha , Bray Mike , Ahmed Rafi , Rollin Pierre E.
Published: July 2002

Ebola hemorrhagic fever is a severe, usually fatal illness caused by Ebola virus, a member of the filovirus family. The use of nonhomologous immune serum in animal studies and blood from survivors in two anecdotal reports of Ebola hemorrhagic fever in humans has shown promise, but the efficacy of these treatments has not been demonstrated definitively. We have evaluated the protective efficacy of polyclonal immune serum in a mouse model of Ebola virus infection. Our results demonstrate that mice infected subcutaneously with live Ebola virus survive infection and generate high levels of anti-Ebola virus immunoglobulin G (IgG). Passive transfer of immune serum from these mice before challenge protected upto 100% of naive mice against lethal Ebola virus infection. Protection correlated with the level of anti-Ebola virus IgG titers, and passive treatment with high-titer antiserum was associated with a delay in the peak of viral replication. Transfer of immune serum to SCID mice resulted in 100% survival after lethal challenge with Ebola virus, indicating that antibodies alone can protect from lethal disease. Thus antibodies suppress or delay viral growth, provide protection against lethal Ebola virus infection, and may not require participation of other immune components for protection.
Telomerase Activation by Human Papillomavirus Type 16 E6 Protein: Induction of Human Telomerase Reverse Transcriptase Expression through Myc and GC-Rich Sp1 Binding Sites
Authors: Oh Stephen T. , Kyo Saturo , Laimins Laimonis A.
Published: July 2002

High-risk human papillomaviruses (HPVs) immortalize keratinocytes by disrupting the retinoblastoma protein (Rb)/p16 pathway and activating telomerase. The E7 oncoprotein targets Rb, while the E6 oncoprotein induces telomerase activity in human keratinocytes. This study has examined the mechanism by which E6 activates telomerase. Expression of human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase, was found to be increased in keratinocytes stably expressing HPV type 16 E6, suggesting that E6 acts to increase hTERT transcription. hTERT expression and telomerase activity were activated to significantly higher levels in cells expressing both E6 and E7 than in cells expressing E6 alone. This indicates that E7 may augment E6-mediated activation of hTERT transcription. In transient-transfection assays using hTERT reporters, the induction of hTERT expression by E6 was found to be mediated by a 258-bp fragment of the hTERT promoter, proximal to the ATG initiation codon. Previous studies have demonstrated that overexpression of Myc can activate hTERT expression, suggesting that Myc may be a mediator of E6-mediated hTERT induction. However, in cells stably expressing E6, no strict correlation between the level of Myc and the activation of hTERT was found. Consistent with this observation, mutation of the two Myc binding sites in the hTERT promoter only modestly reduced responsiveness to E6 in transient reporter assays. This indicates that activation of Myc-dependent transcription is not essential for E6-mediated upregulation of hTERT expression. The hTERT promoter also contains five GC-rich elements that can bind Sp1. Mutation of these sites within the 258-bp fragment partially reduced hTERT induction by E6. However, when mutations in the Sp1 sites were combined with the mutated Myc binding sites, all activation by E6 was lost. This indicates that it is the combinatorial binding of factors to Myc and Sp1
cis
elements that is responsible for hTERT induction by E6.
Virus Reconstituted from Infectious Bacterial Artificial Chromosome (BAC)-Cloned Murine Gammaherpesvirus 68 Acquires Wild-Type Properties In Vivo Only after Excision of BAC Vector Sequences
Authors: Adler Heiko , Messerle Martin , Koszinowski Ulrich H.
Published: July 2002

We studied the in vivo biological properties of viruses reconstituted from the genome of murine gammaherpesvirus 68 (MHV-68) cloned as an infectious bacterial artificial chromosome (BAC). Recombinant virus RγHV68A98.01, containing BAC vector sequences, is attenuated in vivo as determined by (i) viral titers in the lungs during the acute phase of infection, (ii) the extent of splenomegaly, and (iii) the number of latently infected spleen cells reactivating virus in an ex vivo reactivation assay. Since the BAC vector sequences were flanked by
lox
P sites, passaging the virus in fibroblasts expressing Cre recombinase resulted in the generation of recombinant virus RγHV68A98.02, with biological properties comparable to those of wild-type MHV-68. On the basis of these data we conclude (i) that excision of BAC vector sequences from cloned MHV-68 genomes is critical for reconstitution of the wild-type phenotypic properties of this virus and (ii) that the BAC-cloned MHV-68 genome is suitable for the construction of mutants and mutant libraries whose phenotypes can be reliably assessed in vivo.
Evidence that
Equine Rhinitis A Virus
VP1 Is a Target of Neutralizing Antibodies and Participates Directly in Receptor Binding
Authors: Warner Simone , Hartley Carol A. , Stevenson Rachel A. , Ficorilli Nino , Varrasso Annalisa , Studdert Michael J. , Crabb Brendan S.
Published: July 2002

Equine rhinitis A virus
(ERAV) is a respiratory pathogen of horses and is classified as an
Aphthovirus
, the only non-
Foot-and-mouth disease virus
(FMDV) member of this genus. In FMDV, virion protein 1 (VP1) is a major target of protective antibodies and is responsible for viral attachment to permissive cells via an RGD motif located in a distal surface loop. Although both viruses share considerable sequence identity, ERAV VP1 does not contain an RGD motif. To investigate antibody and receptor-binding properties of ERAV VP1, we have expressed full-length ERAV VP1 in
Escherichia coli
as a glutathione
S
-transferase (GST) fusion protein (GST-VP1). GST-VP1 reacted specifically with antibodies present in serum from a rabbit immunized with purified ERAV virions and also in convalescent-phase sera from horses experimentally infected with ERAV. An antiserum raised in rabbits to GST-VP1 reacted strongly with viral VP1 and effectively neutralized ERAV infection in vitro. Using a flow cytometry-based binding assay, we found that GST-VP1, but not other GST fusion proteins, bound to cell surface receptors. This binding was reduced in a dose-dependent manner by the addition of purified ERAV virions, demonstrating the specificity of this interaction. A separate cell-binding assay also implicated GST-VP1 in receptor binding. Importantly, anti-GST-VP1 antibodies inhibited the binding of ERAV virions to Vero cells, suggesting that these antibodies exert their neutralizing effect by blocking viral attachment. Thus ERAV VP1, like its counterpart in FMDV, appears to be both a target of protective antibodies and involved directly in receptor binding. This study reveals the potential of recombinant VP1 molecules to serve as vaccines and diagnostic reagents for the control of ERAV infections.
Infection and Activation of Monocytes by Marburg and Ebola Viruses
Authors: Ströher Ute , West Elmar , Bugany Harald , Klenk Hans-Dieter , Schnittler Hans-Joachim , Feldmann Heinz
Published: July 2002

In this study we investigated the effects of Marburg virus and Ebola virus (species Zaire and Reston) infections on freshly isolated suspended monocytes in comparison to adherent macrophages under culture conditions. Our data showed that monocytes are permissive for both filoviruses. As is the case in macrophages, infection resulted in the activation of monocytes which was largely independent of virus replication. The activation was triggered similarly by Marburg and Ebola viruses, species Zaire and Reston, as indicated by the release of the proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor α, and IL-6 as well as the chemokines IL-8 and gro-α. Our data suggest that infected monocytes may play an important role in the spread of filoviruses and in the pathogenesis of filoviral hemorrhagic disease.
Expression of Mouse Interleukin-4 by a Recombinant Ectromelia Virus Suppresses Cytolytic Lymphocyte Responses and Overcomes Genetic Resistance to Mousepox
Authors: Jackson Ronald J. , Ramsay Alistair J. , Christensen Carina D. , Beaton Sandra , Hall Diana F. , Ramshaw Ian A.
Published: July 2002

Genetic resistance to clinical mousepox (ectromelia virus) varies among inbred laboratory mice and is characterized by an effective natural killer (NK) response and the early onset of a strong CD8+cytotoxic T-lymphocyte (CTL) response in resistant mice. We have investigated the influence of virus-expressed mouse interleukin-4 (IL-4) on the cell-mediated response during infection. It was observed that expression of IL-4 by a thymidine kinase-positive ectromelia virus suppressed cytolytic responses of NK and CTL and the expression of gamma interferon by the latter. Genetically resistant mice infected with the IL-4-expressing virus developed symptoms of acute mousepox accompanied by high mortality, similar to the disease seen when genetically sensitive mice are infected with the virulent Moscow strain. Strikingly, infection of recently immunized genetically resistant mice with the virus expressing IL-4 also resulted in significant mortality due to fulminant mousepox. These data therefore suggest that virus-encoded IL-4 not only suppresses primary antiviral cell-mediated immune responses but also can inhibit the expression of immune memory responses.
Recombinant Human Parvovirus B19 Vectors: Erythrocyte P Antigen Is Necessary but Not Sufficient for Successful Transduction of Human Hematopoietic Cells
Authors: Weigel-Kelley Kirsten A. , Yoder Mervin C. , Srivastava Arun
Published: July 2002

The blood group P antigen, known to be abundantly expressed on erythroid cells, has been reported to be the cellular receptor for parvovirus B19. We have described the development of recombinant parvovirus B19 vectors with which high-efficiency, erythroid lineage-restricted transduction can be achieved (S. Ponnazhagan, K. A. Weigel, S. P. Raikwar, P. Mukherjee, M. C. Yoder, and A. Srivastava, J. Virol. 72:5224–5230, 1998). However, since a low-level transduction of nonerythroid cells could also be detected and since P antigen is expressed in nonerythroid cells, we reevaluated the role of P antigen in the viral binding and entry into cells. Cell surface expression analyses revealed that ∼75% of primary human bone marrow mononuclear erythroid cells and ∼31% of cells in the nonerythroid population were positive for P antigen. Two human erythroleukemia cell lines, HEL and K562, and a human promyelocytic leukemia cell line, HL-60, were also examined for P antigen expression and binding and entry of the vector. HEL and K562 cells showed intermediate levels, whereas HL-60 cells demonstrated high levels of expression of P antigen. However, the efficiency of vector binding to these cells did not correlate with P antigen expression. Moreover, despite P antigen positivity and efficient viral binding, HEL, K562, and HL-60 cells could not be transduced with the vector. Low levels of P antigen expression could also be detected in two primary cell types, human umbilical vein endothelial cells (HUVEC) and normal human lung fibroblasts (NHLF). In addition, vector binding occurred in both cell types and was inhibited by globoside, indicating the involvement of P antigen in virus binding to these cells. These primary cells could be efficiently transduced with the recombinant vector. These data suggest that (i) P antigen is expressed on a variety of cell types and is involved in binding of parvovirus B19 to human cells, (ii) the level of P antigen expression does not correlate with the efficiency of viral binding, (iii) P antigen is necessary but not sufficient for parvovirus B19 entry into cells, and (iv) parvovirus B19 vectors can be used to transduce HUVEC and NHLF. These studies further suggest the existence of a putative cellular coreceptor for efficient entry of parvovirus B19 into human cells.
Group A Rotavirus Infection and Age-Dependent Diarrheal Disease in Rats: a New Animal Model To Study the Pathophysiology of Rotavirus Infection
Authors: Ciarlet Max , Conner Margaret E. , Finegold Milton J. , Estes Mary K.
Published: July 2002

Group A rotaviruses are major pathogens causing acute gastroenteritis in children and animals. To determine if group A rotavirus replicates and induces disease in rats, antibody-negative Lewis neonatal or adult rats were inoculated orally with tissue culture-adapted human (Wa, WI61, and HAL1166), simian (rhesus rotavirus [RRV] and SA11), bovine (WC3), lapine (ALA), or porcine (OSU) rotavirus strains, wild-type murine (EC
wt
) rotavirus strain, or phosphate-buffered saline (PBS). Rotavirus infection in rats was evaluated by (i) clinical findings, (ii) virus antigen shedding or infectious virus titers in the feces or intestinal contents measured by enzyme-linked immunosorbent assay or fluorescent-focus assay, (iii) histopathological changes in the small intestine, (iv) distribution of rotavirus antigen in small-intestine sections by immunofluorescence, and (v) growth rate. Rotavirus infection of 5-day-old but not ≥21-day-old rats resulted in diarrhea that lasted from 1 to 10 days postinoculation. The severity of disease and spread of infection to naÏve littermates differed depending on the virus strain used for inoculation. The duration of virus antigen shedding following infection was considerably prolonged (up to 10 days) in neonatal rats compared to that in 21-day-old rats (1 or 2 days). Based on lack of virus antigen shedding and disease induction, the murine EC
wt
rotavirus was the only strain tested that did not infect rats. Histopathological changes in the small-intestine mucosa of 5-day-old RRV-inoculated rats but not of PBS-inoculated rats was limited to extensive enterocyte vacuolation in the ileum. In RRV-inoculated neonatal rats, rotavirus antigen was detected in the epithelial cells on the upper half of the intestinal villi of the jejunum and ileum. In addition, infection of neonatal rats with RRV but not with PBS resulted in reduced weight gain. Rats infected with group A rotaviruses provide a new animal model with unique features amenable to investigate rotavirus pathogenesis and the molecular mechanisms of intestinal development, including physiological factors that may regulate age-dependent rotavirus-induced diarrhea.
Functional Interaction between the pp71 Protein of Human Cytomegalovirus and the PML-Interacting Protein Human Daxx
Authors: Hofmann Heike , Sindre Hilde , Stamminger Thomas
Published: July 2002

The tegument protein pp71 (UL82) of human cytomegalovirus (HCMV) has previously been shown to transactivate the major immediate-early enhancer-promoter of HCMV. Furthermore, this protein is able to enhance the infectivity of viral DNA and to accelerate the infection cycle, suggesting an important regulatory function during viral replication. To gain insight into the underlying mechanisms that are used by pp71 to exert these pleiotropic effects, we sought for cellular factors interacting with pp71 in a yeast two-hybrid screen. Here, we report the isolation of the human Daxx (hDaxx) protein as a specific interaction partner of HCMV pp71. hDaxx, which was initially described as an adapter protein involved in apoptosis regulation, has recently been identified as a nuclear protein that interacts and colocalizes with PML in the nuclear domain ND10. In order to assess whether pp71 can also be detected in ND10 structures, a vector expressing pp71 in fusion with the green fluorescent protein was used for transfection of human fibroblasts. This revealed a colocalization of pp71 with the ND10 proteins PML and Sp100. In addition, cotransfection of a hDaxx expression vector resulted in an enhanced recruitment of pp71 to ND10. Targeting of pp71 to nuclear dots could also be observed in infected human fibroblasts in the absence of de novo viral protein synthesis. Moreover, cotransfection experiments revealed that pp71-mediated transactivation of the major immediate-early enhancer-promoter was synergistically enhanced in the presence of hDaxx. These results suggest an important role of hDaxx for pp71 protein function.
Safety and Immunogenicity in Neonatal Mice of a HyperattenuatedListeriaVaccine Directed against Human Immunodeficiency Virus
Authors: Rayevskaya Marina , Kushnir Natasha , Frankel Fred R.
Published: July 2002

CD8+T cells are a major component of the adaptive response of a host to infections by viruses and other intracellular pathogenic agents. However, because of the intrinsic immaturity of the immune system of neonatal animals, neonates are highly sensitive to a variety of pathogens and may be unable to respond in a protective manner. Here we explore whether a hyperattenuated strain ofListeria monocytogenesthat can be used as a live vaccine vector in adults is safe and able to induce an effective response in neonates. We answer both questions affirmatively.
Direct Preparation of 1,2:3,5-Di-O-cyclohexylidene-α-D-xylofuranose from Corncobs and Its Conversion to 1-O-Acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose
Authors: Popsavin Mirjana , Popsavin Velimir , Vukojevic Nada , Miljković Dušan
Published: July 2002

A novel synthesis of 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (I) has been described starting from 1,2:3,5-di-O-cyclohexylidene-α-D-xylofuranose (II), obtained directly from the crude xylose syrup originated from corncobs. Partial acid hydrolysis of II gave 1,2-O-cyclohexylidene-α-D-xylofuranose (III). Selective benzoylation of primary C-5 hydroxyl group of III followed by tosylation of C-3 hydroxyl group afforded IV in an overall yield of 67%. Mild acid methanolysis of IV gave the corresponding methyl xylofuranosides V which were further benzoylated to afford 2,5-di-O-benzoyl derivatives VI in 65% yield. Solvolysis of VI in 95% DMF gave a mixture of 2,5- and 3,5-di-O-benzoylribofuranosides VII, which were subsequently converted into the corresponding tribenzoates VIII. An acetolysis of VIII afforded I in an overall yield of 96% related to VI.
Hydroxylation of Phenol over Ti-MCM-41 and TS-1
Authors: Kulawik Kornelia , Schulz-Ekloff Günter , Rathouský Jiří , Zukal Arnošt , Had Jiří
Published: July 2002

In the oxidation of phenol by hydrogen peroxide over titanium containing MCM-41 materials, practically only para isomers are formed. The exclusive para selectivity is proposed to be due to the different strength of adsorption for the para and ortho isomers influencing the overall reaction rate or the faster polymerization of the ortho product. The former mechanism is more probable.
Functional Derivatives of Sterically Hindered Amines. Polyalkylpiperidine Diesters
Authors: Vašš František , Lustoň Jozef
Published: July 2002

Several diesters of dicarboxylic acids with pendant polyalkylpiperidine structural units were prepared from α-bromo and α,α'-dibromo substituted aliphatic dicarboxylic acid diesters by a nucleophilic replacement reaction with 2,2,6,6-tetramethyl-4-hydroxypiperidine, 1,2,2,6,6-pentamethyl-4-hydroxypiperidine, and 2,2,6,6-tetramethyl-4-aminopiperidine, by a nucleophilic addition of amino derivative to the α,β-unsaturated dicarboxylic acid diester and by an acid catalyzed condensation of 2,2,6,6-tetramethyl-4-oxopiperidine with diethyl bis(hydroxymethyl)malonate.
Electrically Induced Structural Changes in Quaternized Methyl Methacrylate-N-[2-methyl-5-(dimethylamino)phenyl]maleimide Copolymer Membranes
Authors: Kůdela Vlastimil , Lokaj Jan
Published: July 2002

Homogeneous membranes were prepared by casting chloroform solutions of methyl methacrylate-N-[2-methyl-5-(dimethylamino)phenyl]maleimide copolymers containing 2.3-8.7 mole % of the imide. After quaternization with methyl iodide, diffusive permeabilities and electric resistances (both with alternating and direct current) of the membranes were determined. During the passage of electric current a substantial decrease (2-10 fold) in the membrane resistance was observed; the lower the imide content was, the greater was the effect. The decrease suggests structural changes in the membranes due to electrohydrodynamic convection of unstable polymer chains caused by electric force. Significant correlations between the imide content and the resistance, both before and after the treatment with electric current, were found. According to oriented concentration potentials, the internal symmetry of the membranes was also affected by electric current.
Synthesis of Poly(ethylene glycol) Block Copolymers as Potential Water-Soluble Drug Carriers
Authors: Pechar Michal , Strohalm Jiří , Ulbrich Karel
Published: July 2002

The synthesis of a model water-soluble drug carrier based on poly(ethylene glycol) (PEG) block copolymers is described. In the copolymers, two blocks of PEG are linked by a biodegradable oligopeptide or amino acid linkage containing the glutamic acid residue. 4-Nitroaniline as a drug model is attached to the γ-carboxyl group of glutamic acid of the polymer carrier via an enzymatically degradable oligopeptide spacer. The oligopeptides used were potential substrates for chymotrypsin. The relationship between the structure of oligopeptides linking two PEG blocks and the rate of chymotrypsin-catalyzed polymer chain degradation as well as the relationship between the structure of the spacer and kinetics of drug model release from the carrier after incubation in chymotrypsin solution is discussed in detail. The results showed that by modifying the structure of oligopeptides in the polymer construct, changes in the rates of both polymer degradation and the drug model release can be achieved in a very broad range.
Melting and Crystallization of Poly(oxyethylene) Mixtures
Authors: Lapeš Ivo , Baldrian Josef , Biroš Ján , Pouchlý Julius , Mio Hanes
Published: July 2002

Solid-liquid eutectic phase diagrams of mixtures of poly(oxyethylene) (M.w. 2 000) with hydroxy and methoxy endgroups, crystallizing in extended-chain macroconformation only, with glutaric acid, benzoic acid or 1,2-diphenylethane are given. The composition dependence of the melting temperature can be fitted by the Flory-Huggins equation. Interaction parameters X and interaction energy densities B evaluated from the diluent branch of the phase diagram are consistent with those obtained from the polymer branch provided the calorimetric value of enthalpy of polymer fusion is used in the latter computation. Measurements of small- and wide-angle X-ray scatterings showed a stacked lamellar structure of POE. Below the eutectic melting point, the long period of the polymer is almost independent of the diluent concentration. On raising temperature gradually from this melting point to the melting point of pure polymer, the increasing long period indicates the penetration of the diluent between the lamellae. As follows from SAXS measurements, the crystallinity of poly(oxyethylene) in the mixtures remains unchanged compared to that of the pure polymer.
Synthesis of Disubstituted 6-Chloro-5-methyl-4H-1,4-benzothiazines: Novel Heterocycles
Authors: Rathore Ram K. , Gupta Radha R.
Published: July 2002

2-Amino-4-chloro-3-methylbenzenethiol in the form of dimer condensed with 8 β-diketones or β-ketoesters to form an enaminoketone or ester intermediate which underwent spontaneous oxidative cyclization to form 6-chloro-5-methyl-2,3-disubstituted 4H-1,4-benzothiazines.
Gould-Jacobs Reaction of 5- and 6-Amino-2-substituted Benzoxazoles. I. Reaction with Diethyl Ethoxymethylenemalonate
Authors: Ilavský Dušan , Heleyová Katarína , Nádaská Jana , Bobošík Vladimír
Published: July 2002

Reaction of 2-substituted 5- and 6-aminobenzoxazoles 1 and 2 with diethyl ethoxymethylenemalonate afforded the corresponding diethyl 3-N-(5- and 6-benzoxazolyl)aminomethylenemalonates 3 and 4. Under conditions of the Gould-Jacobs reaction, the compounds 3 gave a mixture of angularly and linearly annelated oxazolo[4,5-f]quinolones 5 and oxazolo[5,4-g]quinolones 6, and compounds 4 afforded a mixture of oxazolo[5,4-f]quinolones 7 and oxazolo[4,5-g]quinolones 8.
Diels-Alder Reactions of Cyclopentadiene with Several Ferrocenyl- and η6-Phenyltricarbonylchromium Analogues of Chalcone. Catalytic Effect of SiO2
Authors: Prokešová Monika , Rihs Grety , Toma Štefan
Published: July 2002

The Diels-Alder reaction of cyclopentadiene with eight electron deficient dienophiles was studied. The reaction was performed at room temperature using silica gel as an inorganic support, without solvent. Only one of the two possible Diels-Alder adducts was isolated in moderate to good yield. The structure of products with endo-oriented electron-withdrawing group was proved by 1H NMR spectrum and in one case (9b) by X-ray analysis.
Synthesis of 5-Phenyl-2(1H)-pyrimidinone Nucleosides
Authors: Krečmerová Marcela , Hřebabecký Hubert , Masojídková Milena , Holý Antonín
Published: July 2002

Reaction of 2-phenyltrimethinium salt 1 with thiourea and subsequent reaction with chloroacetic acid afforded 5-phenyl-2(1H)-pyrimidinone (3). Its silyl derivative 4 was condensed with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose under catalysis with tin tetrachloride or trimethylsilyl trifluoromethanesulfonate to give protected nucleoside 5 together with 5',O6-cyclo-5-phenyl-1,3-bis- (β-D-ribofuranosyl)-6-hydroxy-5,6-dihydro-2(1H,3H)-pyrimidinone (7). The greatest amounts of 7 were formed with the latter catalyst. Nucleosidation of the silyl derivative 4 with protected methyl 2-deoxy-D-ribofuranoside 8 or 2-deoxy-D-ribofuranosyl chloride 9 afforded 1-(2-deoxy-3,5-di-O-p-toluoyl-β-D-ribofuranosyl)-5-phenyl-2(1H)-pyrimidinone (10) and its α-anomer 11. Reaction of 10 and 11 with methanolic ammonia gave free 2'-deoxynucleosides 12 and 13. Compound 13 was converted into 5'-O-tert-butyldiphenylsilyl-3'-O-mesyl derivative 14 which on heating with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and subsequent cleavage with tetrabutylammonium fluoride afforded 2',3'-dideoxy-2',3'-didehydronucleoside 15. Reaction of the silyl derivative 4 with 1,2-di-O-acetyl-3,5-di-O-benzoylxylofuranose (18), catalyzed with tin tetrachloride, furnished 1-(2-O-acetyl-3,5-di-O-benzoyl-β-D-xylofuranosyl)-2(1H)-pyrimidinone (19) which was deprotected to give the β-D-xylofuranosyl derivative 22. As a side product, the nucleosidation afforded the β-D-xylopyranosyl derivative 23. Deacetylation of compound 19 gave 1-(3,5-di-O-benzoyl-β-D-xylofuranosyl)-5-phenyl-2(1H)-pyrimidinone (24) which on reaction with thionyl chloride afforded 2'-chloro-2'-deoxynucleoside 25 and 2',O6-cyclonucleoside 26. Heating of compound 25 with DBU in dimethylformamide furnished the lyxo-epoxide 27 which on reaction with methanolic ammonia was converted into free 1-(2,3-anhydro-β-D-lyxofuranosyl)-5-phenyl-2(1H)-pyrimidinone (28). Reaction of 1,2-di-O-acetyl-5-O-benzoyl-3-O-methanesulfonyl-D-xylofuranose (30) with silyl derivative 4 gave the nucleoside 31 which by treatment with DBU was converted into an equilibrium mixture of 5'-benzoylated arabinofuranoside 33a and its 2',6-anhydro derivative 33b.
Preparation of 5-Benzyluracil and 5-Benzylcytosine Nucleosides as Potential Inhibitors of Uridine Phosphorylase
Authors: Krečmerová Marcela , Hřebabecký Hubert , Holý Antonín
Published: July 2002

Reaction of 3,4,6-tri-O-acetyl-2-deoxyglucopyranosyl bromide (1) with silylated 5-benzyluracil and subsequent ammonolysis afforded α- and β-anomers of 5-benzyl-1-(2-deoxy-D-glucopyranosyl)uracil (2 and 3). Under catalysis with tin tetrachloride, silylated 5-benzyluracil reacted with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose to give 2',3',5'-tri-O-benzoyl-5-benzyluridine (10), which was converted into the 4-thio derivative 11 by reaction with Lawesson reagent. Debenzoylation of compound 11 afforded 5-benzyl-4-thiouridine (12), whereas its reaction with methyl iodide and deblocking gave 4-methylthiopyrimidine nucleoside 14. Amonolysis of derivative 12 at elevated temperature afforded 5-benzylcytidine (15). This reacted with thionyl chloride at room temperature to give cyclic sulfite 16 which on heating at 100 °C in dimethylformamide was converted into 5-benzyl-2,2'-cyclocytidine (17). Mild alkaline hydrolysis of compound 17 afforded 1-(β-D-arabinofuranosyl)-5-benzylcytosine (18). With boiling thionyl chloride, compound 15 formed 2',3'-cyclic sulfite 19 which on alkaline hydrolysis gave 5-benzyl-5'-chloro-5'-deoxycytidine (20). Compound 20 was reduced with tributylstannane to 5-benzyl-5'-deoxycytidine (21). Reaction of silylated 5-benzyluracil with 2-deoxy-3,5-bis(O-p-toluoyl)-D-ribofuranosyl chloride, catalyzed with mercury(II) bromide, afforded 5-benzyl-2'-deoxy-3',5'-bis(O-p-toluoyl)uridine (22) and its α-anomer 23. With Lawesson reagent, compound 22 gave 5-benzyl-4-thiouracil derivative 24 which was ammonolyzed to give 5-benzyl-2'-deoxycytidine (25). Analogously, compound 23 was converted into 5-benzyl-2-deoxy-α-cytidine (27). 5'-O-Benzoyl-5-benzyluridine (29) was converted into the 2,2'-anhydro derivative 30 which on reaction with hydrogen chloride afforded 3'-chloro-3'-deoxynucleoside 31. This compound was reduced with tributylstannane and the obtained 2'-deoxynucleoside 32 on treatment with thionyl chloride gave a mixture of erythro- and threo-3'-chloro-2',3'-dideoxynucleosides (33 and 34, respectively) which were reduced to 5'-O-benzoyl-5-benzyl-2',3'-dideoxyuridine (35). Compound 35 reacted with Lawesson reagent under formation of 4-thiouracil derivative 36 and this was deblocked to 5-benzyl-4-thio-2',3'-dideoxyuridine (37). On heating with ammonia, compound 37 was converted into 5-benzyl-2',3'-dideoxycytidine (38). Reaction of 4-thiouracil derivative with methyl iodide and subsequent hydrazinolysis afforded 4-hydrazino derivative 40 which was heated with silver oxide in ethanol to give a mixture of anomeric 5-benzyl-1-(2,3-dideoxyribofuranosyl)-2(1H)-pyrimidinones (42).
Oxidation of Azo Dyes by Peroxidase: Additional Evidence of a One-Electron Mechanism of Oxidation of Dimethylaminoazobenzene and Sudan I (Solvent Yellow 14)
Authors: Stiborová Marie , Asfaw Befekadu , Frei Eva , Schmeiser Heinz H.
Published: July 2002

In the presence of hydrogen peroxide, peroxidase oxidized aminoazo dyes, the non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I, Solvent Yellow 14), and its C-hydroxy derivatives. The oxidation of azo dyes is a pH-dependent reaction; while slightly acidic conditions are optimal for the aminoazo dyes, a basic pH suits better for Sudan I and its hydroxy derivatives. The oxidation of the carcinogenic Sudan I and dimethylaminoazobenzene catalyzed by peroxidase was investigated in detail. Oxygen consumption was not observed in incubations of peroxidase, azo dyes and hydrogen peroxide. However, oxygen uptake was observed after the addition of glutathione, which indicates that free radical metabolites of these compounds are formed by peroxidase. The results suggest that peroxidase metabolizes Sudan I and dimethylaminoazobenzene through a one-electron oxidation mechanism, giving rise to free radicals. Three of the products of Sudan I oxidation by peroxidase with a hitherto unknown structure were characterized partly by UV/VIS and mass spectroscopy.
Potential Antagonists of Excitatory Amino Acids and Anticonvulsants: Some Heterocyclic (±)-Pyrrolidine-2-carboxamides
Authors: Valenta Vladimír , Dobrovský Karel , Krejčí Ivan , Polívka Zdeněk
Published: July 2002

The benzylpyrrolidine amides 1a-1d, 3a-3e, 5a, and 5b were prepared from N-benzyl-L-proline methyl ester with corresponding diamines. Compounds 2a-2d, 4b, and 4e have similarly been synthesized from L-proline methyl ester and the corresponding diamines in refluxing methanol. In both cases, the reactions were accompanied by racemization. Prepared amides were transformed to salts, suitable for pharmacological testing (hydrogen maleates, hydrogen oxalates and hydrochlorides). The products were tested by selected methods of biochemical and behavioural pharmacology.
Radical Addition of 2-Propanol to Trifluoroethylene. Preparation of Trifluoroethylene Oligomersfrom Chlorotrifluoroethylene Oligomers
Authors: Fikar Jiří , Trška Petr , Pech Pavel , Liška František
Published: July 2002

Photochemically initiated addition of 2-propanol to trifluoroethylene afforded the 1 : 1 adducts 3,3,4-trifluoro-2-methyl-2-butanol 1 and 3,4,4-trifluoro-2-methyl-2-butanol 2, as well as the 1 : 2 telomers 3,4,4,5,5,6-hexafluoro-2-methyl-2-hexanol 3 and 3,4,4,5,6,6-hexafluoro-2-methyl-2-hexanol 4. The other possible 1 : 2 and 1 : 3 telomers, in which the CF2-CFH- groups regularly alternate ("head-tail") - 3,3,4,5,5,6-hexafluoro-2-methyl-2-hexanol 13 and 3,3,4,5,5,6,7,7,8-nonafluoro-2-methyl-2-octanol 14 - and which did not arise in the reaction, were obtained by photochemical reduction of addition products of 2-propanol to chlorotrifluoroethylene (alcohols 15-17) with secondary and tertiary amines. Dehydrofluorination of alcohols 1 and 2 gave 3,3-difluoro-2, 2-dimethyloxetane 18 and 3-difluoromethyl-2,2-dimethyloxirane 19.
New Synthesis of Important Prostanoid Intermediate
Authors: Svoboda Jiří , Kozmík Václav , Veselý Ivan , Paleček Jaroslav
Published: July 2002

New synthesis of intermediates for the preparation of prostaglandin analogs of the E1 series is described. The simple synthesis starts from commercially accessible Corey acetate 1 and makes use of simultaneous protection of the two hydroxy groups in the form of cyclic acetal. No expensive protecting reagents are required and the synthetic sequence leading to the end product is shorter.
NMR and AM1 Quantum Chemical Study of the Regioselectivity of the Reaction of 2-Hydroxyethyl Methacrylate with 3-Nitrophthalic Anhydride
Authors: Kříž Jaroslav , Dybal Jiří , Sedláková Zdeňka
Published: July 2002

The reaction of 2-hydroxyethyl methacrylate with 3-nitrophthalic anhydride catalyzed with triethylamine results in the 3 : 1 mixture of two possible monoesters, the more populated one being that with the ester group in ortho position to the nitro group. The isomers were identified and quantified by 1H and 13C 1D and 2D techniques including APT, INEPT, superselective long-range (SSLR) INEPT, SSLR HHCR, COSY, NOESY, HETCOR and COLOC. Theoretical analysis was done on the model reaction of methanol with the anhydride using semiempirical AM1 quantum chemical calculations. The results indicate that the relative regioselectivity of the reaction is due to both the electron distribution in the anhydride molecule and hydrogen bonding in the stages immediately preceding the transition state.
Chiral Forms of 4-(2',4'-Difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic Acid (Flobufen) and Its Metabolite.Synthesis and Basic Biological Properties
Authors: Kuchař Miroslav , Poppová Marie , Jandera Antonín , Panajotovová Vladimíra , Zůnová Hana , Buděšínský Miloš , Tomková Hana , Jegorov Alexandr , Taimr Jan
Published: July 2002

4-(2',4'-Difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic acid (1, flobufen) is subjected to clinical testing in the treatment of rheumatoid arthritis. Owing to the occurrence of a centre of chirality, the compound exists in two enantiomers, and its major human metabolite, viz. 4-(2',4'-difluorobiphenyl-4-yl)-4-hydroxy-2-methylbutanoic acid isolated in the lactone form (2), possesses two chiral centres, making possible the existence of four stereoisomers. All of the optical isomers of the substances 1 and 2 were prepared. For flobufen (1), the racemate was separated into the stereoisomers by using the salts 3 with R-(+)- or S-(-)-1-phenylethylamine. The pairs of stereoisomers of 2, obtained by reduction of R-(+)-flobufen or the S-(-)-enantiomer, were separated by column chromatography. The physico-chemical parameters of the optical isomers were determined and some biological activities were evaluated in both in vitro and in vivo models.
Axially Chiral Synthons for Dendrimer Synthesis
Authors: Lellek Vít , Stibor Ivan
Published: July 2002

Axially chiral synthons for chiral dendrimer construction based on 2,2'-dihydroxy-1,1'-binaphthalene-3,3'-dicarboxylic acid were prepared, namely, chiral connecting units (3, 6, 8), chiral branching units (10, 12, 14), and chiral surface units (5, 17). Regioselective chloromethylation of methyl 3'-acetoxymethyl-2,2'-dimethoxy-1,1'-binaphthalene-3-carboxylate (7) was also studied.
Diagrams Er-mKOH for Iron at 25-125 °C and at Total Pressure of 1-30 Bar
Authors: Balej Jan , Divisek Jiri
Published: July 2002

Taking into consideration the water activity aH2O, the equilibrium pressure of water vapour pH2O in or above KOH solutions of different molality (2-18 mol kg-1) and temperature (0-200 °C), the relations for the quantitative evaluation of the equilibrium conditions of individual reactions in the Fe-KOH-H2O system were derived in potential range from -0.3 to +1.8 V (RHE). With the aid of standard thermodynamic data for individual reaction components, Er-mKOH diagrams were constructed for iron at 25, 100 and 125 °C and a total pressure of 1, 10 and 30 bar (0.1, 1 and 3 MPa). Under standard conditions (aH2O = 1.0), Fe(OH)2(s) may result at temperatures of up to 63.1 °C, while at higher temperatures solid magnetite, Fe3O4, is directly formed as the thermodynamically stable primary corrosion product. The region of existence of solid Fe(OH)2 is influenced by the molality and temperature of KOH solutions in contact with metallic iron. For example, at 25 °C Fe(OH)2 can only arise as the primary corrosion product in KOH solutions mKOH ≤ 6.34 mol kg-1, which cannot be concluded from the usual Er-pH diagram after Pourbaix.
Molecular Structure of cis- and trans-Tergurides
Authors: Hušák Michal , Kratochvíl Bohumil , Sedmera Petr , Havlíček Vladimír , Votavová Hana , Cvak Ladislav , Bulej Petr , Jegorov Alexandr
Published: July 2002

Four isomers of terguride, a semisynthetic ergot alkaloid derivative, have been prepared by catalytic hydrogenation of (5R,8S)- and (5S,8S)-lisuride [1,1-diethyl-3-(6-methyl-8-ergolenyl)urea]. Relative stereochemistry of the isomers is based on NMR and CD spectra. Absolute configuration of all the series has been confirmed by the X-ray crystal structure determination of (5R,8S,10S)-terguride 2-bromobenzoate [1,1-diethyl-3-(6-methyl-8-isoergolenyl)urea, cis-dihydrolisuride].
Synthesis and Immunomodulating Activity of Lipophilic Analogs of N-Acetylnormuramoyl-L-2-aminobutanoyl-D-isoglutamine
Authors: Ledvina Miroslav , Ježek Jan , Šaman David , Hříbalová Věra
Published: July 2002

N-Acetylnormuramoyl-L-2-aminobutanoyl-D-isoglutamine (7) and its lipophilic 6-O-octadecanoyl (8) and 6-O-(2-tetradecylhexadecanoyl) (9) derivatives were prepared and their immunoadjuvant activity and pyrogenicity were tested. Compounds 8 and 9 are less pyrogenic than muramoyl-dipeptide (MDP) and norMDP analog 7. Both lipophilic derivatives 8 and 9 are better adjuvants than MDP in cell mediated immunity.
Synthesis and Biological Activity of N4-Methyl-5-azacytidines
Authors: Hanna Naeem B. , Masojídková Milena , Pískala Alois
Published: July 2002

Protected N4-methyl and N4,N4-dimethyl derivatives of 5-azacytidine 3 and 4 were prepared by selective aminolysis of benzoylated 4-methoxy-1-(β-D-ribofuranosyl)-1,3,5-triazin-2(1H)-one 5, by glycosylation of silylated N4-methyl- or N4,N4-dimethyl-5-azacytosines 7 and 8 with 2,3,5-tri-O-benzoyl-α,β-D-ribofuranosyl chloride (11) or by several modifications of the isocyanate method. By the isocyanate approach, also the α-D anomer of protected N4-methyl-5-azacytidine 17 was obtained as a minor product. The protected dimethyl derivative 4 was also obtained by the reaction of isobiuret 22 with dimethylformamide dimethyl acetal. The free nucleosides 1 and 2 were obtained either by aminolysis of the free methoxy nucleoside 23 with methylamine or dimethylamine, respectively, or by methanolysis or ammonolysis of the corresponding benzoyl derivatives 3 and 4. The free α-D anomer 24 was obtained by methanolysis of its tribenzoate 17. Nucleosides 1 and 2 exhibited a lower antibacterial, antitumor and antiviral activity than the unsubstituted 5-azacytidine.
Two Classes of ZEKE Spectroscopy
Authors: Selzle Heinrich L. , Schlag Edward W. , Remacle Françoise , Levine Raphael D.
Published: July 2002

A classification of ZEKE spectra into two classes based on operational criteria is useful for discussion. The proposal is that some of the different and seemingly conflicting effects reported for different molecular (or the same molecule for different excitations), such as the role of an external field, are due to these two distinct classes of states which can be optically accessed. Class A is the direct, "front door" entry where the states excited are those which are detected by the delayed ionization. Class B is a very prevalent but indirect "backdoor" route where it is only the interaction of the Rydberg electron with the core, possibly aided by external perturbations, that allows a signal to be detected upon ionization. The operational criteria for distinguishing between or even exploiting the features of the two classes are discussed. Such attention might be useful as new techniques for class B spectra are developed.
Generation and Reactivity of Chromium Fluoride Cations (CrF+n, n = 0-4) in the Gas Phase
Authors: Mazurek Ulf , Schröder Detlef , Schwarz Helmut
Published: July 2002

Gaseous chromium fluoride monocations CrFn+ (n = 1-4) can be prepared by sequential fluorine-atom transfer from nitrogen trifluoride, NF3, to chromium cation. In addition, formal F- anion transfer to CrFn+ (n = 2-4) to yield the corresponding neutral chromium fluorides CrFn+1 is observed. In conjunction with a re-evaluation of previous data, the present results provide a consistent picture of the thermochemistry of neutral and cationic chromium fluorides. The reactivity of the CrFn+ ions towards alkanes is investigated in a Fourier-transform ion cyclotron resonance mass spectrometer. While "bare" Cr+ does not react with alkanes, the chromium fluoride cations CrFn+ do; CrF3+ and CrF4+ are even capable of activating methane. With both increasing oxidation state of chromium and increasing chain lengths of the alkane, the branching ratio of the possible reaction pathways shifts from homolytic C-H and C-C bond activation to hydride- and methanide-ion transfer to yield carbocations, and finally electron transfer generating hydrocarbon radical cations.