129 results on '"Laus, G."'
Search Results
102. Crystal structure of 3-bromo-4-di-methyl-amino-1-methyl-1,2,4-triazol-5(4H)-one.
- Author
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Laus G, Gelbrich T, Wurst K, and Schottenberger H
- Abstract
The title compound, C5H9BrN4O, was obtained as a minor by-product in the synthesis of 4-di-methyl-amino-1-methyl-1,2,4-triazolin-5-one. Except for the methyl groups of the 4-dimethylamino moiety, all the non-H atoms lie on a crystallographic mirror plane." In the crystal, the mol-ecules are linked by C-Br⋯O=C inter-actions [Br⋯O = 2.877 (2) Å, C-Br⋯O = 174.6 (1)°] into infinite chains in the c-axis direction.
- Published
- 2015
- Full Text
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103. Crystal Structures of New Ammonium 5-Aminotetrazolates.
- Author
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Lampl M, Salchner R, Laus G, Braun DE, Kahlenberg V, Wurst K, Fuhrmann G, Schottenberger H, and Huppertz H
- Abstract
The crystal structures of three salts of anionic 5-aminotetrazole are described. The tetramethylammonium salt ( P [Formula: see text]) forms hydrogen-bonded ribbons of anions which accept weak C-H⋯N contacts from the cations. The cystamine salt ( C 2/ c ) shows wave-shaped ribbons of anions linked by hydrogen bonds to screw-shaped dications. The tetramethylguanidine salt ( P 2
1 / c ) exhibits layers of anions hydrogen-bonded to the cations.- Published
- 2014
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104. Draft genome sequence analysis of a Pseudomonas putida W15Oct28 strain with antagonistic activity to Gram-positive and Pseudomonas sp. pathogens.
- Author
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Ye L, Hildebrand F, Dingemans J, Ballet S, Laus G, Matthijs S, Berendsen R, and Cornelis P
- Subjects
- Anti-Bacterial Agents pharmacology, Bacterial Proteins classification, Bacterial Proteins genetics, Bacterial Proteins metabolism, DNA Transposable Elements, High-Throughput Nucleotide Sequencing, Membrane Proteins classification, Membrane Proteins genetics, Membrane Proteins metabolism, Microbial Sensitivity Tests, Multigene Family, Mutagenesis, Oligopeptides antagonists & inhibitors, Oligopeptides genetics, Oligopeptides metabolism, Phylogeny, Pseudomonas drug effects, Pseudomonas metabolism, Pseudomonas putida classification, Pseudomonas putida drug effects, Pseudomonas putida genetics, Sequence Analysis, DNA, Genome, Bacterial, Pseudomonas genetics
- Abstract
Pseudomonas putida is a member of the fluorescent pseudomonads known to produce the yellow-green fluorescent pyoverdine siderophore. P. putida W15Oct28, isolated from a stream in Brussels, was found to produce compound(s) with antimicrobial activity against the opportunistic pathogens Staphylococcus aureus, Pseudomonas aeruginosa, and the plant pathogen Pseudomonas syringae, an unusual characteristic for P. putida. The active compound production only occurred in media with low iron content and without organic nitrogen sources. Transposon mutants which lost their antimicrobial activity had the majority of insertions in genes involved in the biosynthesis of pyoverdine, although purified pyoverdine was not responsible for the antagonism. Separation of compounds present in culture supernatants revealed the presence of two fractions containing highly hydrophobic molecules active against P. aeruginosa. Analysis of the draft genome confirmed the presence of putisolvin biosynthesis genes and the corresponding lipopeptides were found to contribute to the antimicrobial activity. One cluster of ten genes was detected, comprising a NAD-dependent epimerase, an acetylornithine aminotransferase, an acyl CoA dehydrogenase, a short chain dehydrogenase, a fatty acid desaturase and three genes for a RND efflux pump. P. putida W15Oct28 genome also contains 56 genes encoding TonB-dependent receptors, conferring a high capacity to utilize pyoverdines from other pseudomonads. One unique feature of W15Oct28 is also the presence of different secretion systems including a full set of genes for type IV secretion, and several genes for type VI secretion and their VgrG effectors.
- Published
- 2014
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105. Crystal structure of 4-amino-1-benzyl-1,2,4-triazolin-5-one.
- Author
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Laus G, Kahlenberg V, and Schottenberger H
- Abstract
The title compound, C9H10N4O, was obtained unintentionally by hydrolysis of 4-amino-1-benzyl-5-methyl-sulfanyl-1,2,4-triazolium tetra-fluoro-borate in the presence of sodium azide. In the crystal, alternating layers of polar amino-triazolinone and apolar benzene moieties are observed. N-H⋯O hydrogen bonds between the amino and carbonyl groups form infinite chains along [010]. These infinite chains are linked by additional C-H⋯O contacts.
- Published
- 2014
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106. A combinatorial approach to the structure elucidation of a pyoverdine siderophore produced by a Pseudomonas putida isolate and the use of pyoverdine as a taxonomic marker for typing P. putida subspecies.
- Author
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Ye L, Ballet S, Hildebrand F, Laus G, Guillemyn K, Raes J, Matthijs S, Martins J, and Cornelis P
- Subjects
- Pseudomonas putida classification, Oligopeptides chemistry, Pseudomonas putida metabolism, Siderophores chemistry
- Abstract
The structure of a pyoverdine produced by Pseudomonas putida, W15Oct28, was elucidated by combining mass spectrometric methods and bioinformatics by the analysis of non-ribosomal peptide synthetase genes present in the newly sequenced genome. The only form of pyoverdine produced by P. putida W15Oct28 is characterized to contain α-ketoglutaric acid as acyl side chain, a dihydropyoverdine chromophore, and a 12 amino acid peptide chain. The peptide chain is unique among all pyoverdines produced by Pseudomonas subspecies strains. It was characterized as -L-Asp-L-Ala-D-AOHOrn-L-Thr-Gly-c[L-Thr(O-)-L-Hse-D-Hya-L-Ser-L-Orn-L-Hse-L-Ser-O-]. The chemical formula and the detected and calculated molecular weight of this pyoverdine are: C65H93N17O32, detected mass 1624.6404 Da, calculated mass 1624.6245. Additionally, pyoverdine structures from both literature reports and bioinformatics prediction of the genome sequenced P. putida strains are summarized allowing us to propose a scheme based on pyoverdines structures as tool for the phylogeny of P. putida. This study shows the strength of the combination of in silico analysis together with analytical data and literature mining in determining the structure of secondary metabolites such as peptidic siderophores.
- Published
- 2013
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107. 5,5'-Azoxytetrazolates--a new nitrogen-rich dianion and its comparison to 5,5'-azotetrazolate.
- Author
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Fischer N, Hüll K, Klapötke TM, Stierstorfer J, Laus G, Hummel M, Froschauer C, Wurst K, and Schottenberger H
- Subjects
- Anions chemistry, Azo Compounds chemical synthesis, Crystallization, Crystallography, X-Ray, Molecular Conformation, Nitrogen chemistry, Tetrazoles chemical synthesis, Azo Compounds chemistry, Tetrazoles chemistry
- Abstract
A modification of the synthesis of sodium 5,5'-azotetrazolate pentahydrate, described by Thiele in 1898, yields the unknown and unexpected corresponding 5N-oxido derivative sodium 5,5'-azoxybistetrazolate pentahydrate (Na(2)zTO·5H(2)O, 1). Purification was achieved by recrystallization based on the better solubility of Na(2)zTO·5H(2)O in water. Different nitrogen-rich salts, such as the diammonium (3), the dihydroxylammonium (4), the bis-diaminoguanidinium (5), the bis-triaminoguanidinium (6) and the diaminouronium salt (7), have been prepared using metathesis reactions starting from barium 5,5'-azoxybistetrazolate pentahydrate (2) and ammonium, hydroxylammonium, diaminoguanidinium or diaminouronium sulfate and triaminoguanidinium chloride, respectively. The nitrogen rich azoxy-derivatives 3-7 were characterized using NMR, IR and Raman spectroscopy, mass spectrometry and elemental analysis. Additionally the solid state structures of 3, 4, 5 and 7 were determined by single crystal X-ray diffraction. The heats of formation of 3 and 4 and their corresponding azo-tetrazolate derivatives were calculated by the atomization method based on CBS-4M enthalpies. With these values and the crystal densities, several detonation parameters such as the detonation velocity, detonation pressure and specific impulse were calculated (EXPLO5) and compared. The sensitivities towards shock (BAM drophammer), friction (BAM friction tester) and electrostatic discharge of the described compounds were determined.
- Published
- 2012
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108. Dialkyl phosphate-related ionic liquids as selective solvents for xylan.
- Author
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Froschauer C, Hummel M, Laus G, Schottenberger H, Sixta H, Weber HK, and Zuckerstätter G
- Subjects
- Eucalyptus chemistry, Particle Size, Solvents chemistry, Surface Properties, Ionic Liquids chemistry, Organophosphorus Compounds chemistry, Xylans chemistry
- Abstract
Herein we describe a possibility of selective dissolution of xylan, the most important type of hemicellulose, from Eucalyptus globulus kraft pulp using ionic liquids (ILs). On the basis of the IL 1-butyl-3-methylimidazolium dimethyl phosphate, which is well-known to dissolve pulp, the phosphate anion was modified by substituting one oxygen atom for sulfur and selenium, respectively. This alteration reduces the hydrogen bond basicity of the IL and therefore prevents dissolution of cellulose fibers, whereas the less ordered xylan is still dissolved. (1)H NMR spectra of model solutions and Kamlet-Taft parameters were used to quantify the solvent polarity and hydrogen bond acceptor properties of the ILs. These parameters have been correlated to their ability to dissolve xylan and cellulose, which was monitored by (13)C NMR spectroscopy. It was found that the selectivity for xylan dissolution increases to a certain extent with decreasing hydrogen-bond-accepting ability of anions of the ILs.
- Published
- 2012
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109. Mössbauer spectroscopy and X-ray diffraction study of Fe-labeled tetrachloroferrate(III)-based magnetic ionic liquids.
- Author
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Herber RH, Nowik I, Kostner ME, Kahlenberg V, Kreutz C, Laus G, and Schottenberger H
- Subjects
- Crystallography, X-Ray, Iron Isotopes chemistry, Isotope Labeling, Molecular Conformation, Spectroscopy, Mossbauer, Ionic Liquids chemistry, Iron chemistry, Magnetics
- Abstract
Four (57)Fe-labeled tetrachloroferrates(III) of organic cations (1-butyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, 1-methyl-1-propylpyrrolidinium, tetraphenylphosphonium) were examined by temperature-dependent Mössbauer spectroscopy. The hyperfine and dynamic parameters of the iron(III) site were determined. Single crystal X-ray diffraction data of [Ph(4)P][FeCl(4)] were collected at four temperatures (295, 223, 173, and 123 K), and the dynamics of the iron atom inferred from the Mössbauer data and the single crystal U(i,j) parameters have been compared.
- Published
- 2011
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110. Siderophore-mediated iron acquisition in the entomopathogenic bacterium Pseudomonas entomophila L48 and its close relative Pseudomonas putida KT2440.
- Author
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Matthijs S, Laus G, Meyer JM, Abbaspour-Tehrani K, Schäfer M, Budzikiewicz H, and Cornelis P
- Subjects
- Animals, Bacterial Outer Membrane Proteins genetics, Bacterial Outer Membrane Proteins metabolism, Base Sequence, Benzamides chemistry, Drosophila melanogaster microbiology, Genes, Bacterial physiology, Isoelectric Focusing, Microbial Interactions, Molecular Conformation, Molecular Sequence Data, Molecular Typing, Oligopeptides chemistry, Pseudomonas Infections microbiology, Pseudomonas putida genetics, Pseudomonas putida metabolism, Siderophores chemistry, Benzamides metabolism, Iron metabolism, Oligopeptides biosynthesis, Siderophores biosynthesis
- Abstract
Pseudomonas entomophila L48 is a recently identified entomopathogenic bacterium which, upon ingestion, kills Drosophila melanogaster, and is closely related to P. putida. The complete genome of this species has been sequenced and therefore a genomic, genetic and structural analysis of the siderophore-mediated iron acquisition was undertaken. P. entomophila produces two siderophores, a structurally new and unique pyoverdine and the secondary siderophore pseudomonine, already described in P. fluorescens species. Structural analysis of the pyoverdine produced by the closely related P. putida KT2440 showed that this strain produces an already characterised pyoverdine, but different from P. entomophila, and no evidence was found for the production of a second siderophore. Growth stimulation assays with heterologous pyoverdines demonstrated that P. entomophila is able to utilize a large variety of structurally distinct pyoverdines produced by other Pseudomonas species. In contrast, P. putida KT2440 is able to utilize only its own pyoverdine and the pyoverdine produced by P. syringae LMG 1247. Our data suggest that although closely related, P. entomophila is a more efficient competitor for iron than P. putida.
- Published
- 2009
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111. Ionic liquids as superior solvents for headspace gas chromatography of residual solvents with very low vapor pressure, relevant for pharmaceutical final dosage forms.
- Author
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Laus G, Andre M, Bentivoglio G, and Schottenberger H
- Subjects
- Ceftizoxime analogs & derivatives, Ceftizoxime chemistry, Imidazoles chemistry, Organophosphorus Compounds chemistry, Pharmaceutical Preparations chemistry, Reproducibility of Results, Sensitivity and Specificity, Thiophenes chemistry, Vapor Pressure, Cefpodoxime Proxetil, Excipients analysis, Gas Chromatography-Mass Spectrometry methods, Ionic Liquids chemistry, Solvents analysis
- Abstract
1-n-Butyl-3-methylimidazolium dimethyl phosphate (BMIM DMP) was identified as the most suitable ionic liquid as solvent for the headspace gas chromatographic analysis of solvents with very low vapor pressure such as dimethylsulfoxide, N-methylpyrrolidone, sulfolane, tetralin, and ethylene glycol in a realistic matrix of commonly used excipients (carboxymethylcellulose, magnesium stearate, guar flour, and corn starch) in pharmaceutical products. Limits of quantification and limits of detection were in the low microgram per gram range. The detection of traces of sulfolane in a real sample of tablets containing the drug cefpodoxim proxetil demonstrated the applicability of the method.
- Published
- 2009
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112. Sequence-dependent, synergistic antiproliferative and proapoptotic effects of the combination of cytotoxic drugs and enzastaurin, a protein kinase Cbeta inhibitor, in non-small cell lung cancer cells.
- Author
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Morgillo F, Martinelli E, Troiani T, Laus G, Pepe S, Gridelli C, and Ciardiello F
- Subjects
- Blotting, Western, Carcinoma, Non-Small-Cell Lung enzymology, Cell Cycle drug effects, Cell Line, Tumor, Cell Proliferation drug effects, Drug Screening Assays, Antitumor, Drug Synergism, Humans, Intracellular Space drug effects, Intracellular Space metabolism, Lung Neoplasms enzymology, Protein Kinase C beta, Signal Transduction drug effects, Apoptosis drug effects, Carcinoma, Non-Small-Cell Lung pathology, Cytostatic Agents pharmacology, Indoles pharmacology, Lung Neoplasms pathology, Protein Kinase C antagonists & inhibitors, Protein Kinase Inhibitors pharmacology
- Abstract
Enzastaurin, an acyclic bisindolymaleimide, is a potent and selective competitive inhibitor of protein kinase Cbeta, which has been shown to inhibit cancer cell proliferation and angiogenesis in human cancer cell lines. Gemcitabine and pemetrexed are two cytotoxic drugs that are currently used in non-small cell lung cancer (NSCLC) therapy. In this study, we have investigated whether the addition of enzastaurin to gemcitabine or to pemetrexed is able to increase their antitumor activity to establish an effective schedule of combined treatment. The effects on cancer cell proliferation, cell cycle distribution, intracellular mitogenic and antiapoptotic signaling pathways, and induction of apoptosis were evaluated in three different combination sequences (concomitant treatment, sequential treatment with the cytotoxic drug followed by enzastaurin, or sequential treatment with enzastaurin followed by the cytotoxic drug) in a panel of human NSCLC cell lines. The combination of enzastaurin with either gemcitabine or pemetrexed caused different antiproliferative and proapoptotic effects depending on the treatment schedule. A synergistic antiproliferative and proapoptotic activity was only obtained when chemotherapy was followed by treatment with enzastaurin. These effects were accompanied by the arrest of the surviving cancer cells in the S phase, thus limiting their ability to proceed through the cell cycle, and by a maximum inhibition in the activated, phosphorylated forms of Akt and mitogen-activated protein kinase. In contrast, the concomitant treatments or the sequential treatments, in which enzastaurin was given before chemotherapy, resulted in significant antagonistic effects.
- Published
- 2008
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113. Inhibition of NF-kappaB activation by the histone deacetylase inhibitor 4-Me2N-BAVAH induces an early G1 cell cycle arrest in primary hepatocytes.
- Author
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Papeleu P, Wullaert A, Elaut G, Henkens T, Vinken M, Laus G, Tourwé D, Beyaert R, Rogiers V, and Vanhaecke T
- Subjects
- Animals, Apoptosis drug effects, Cells, Cultured, Cyclin D, Cyclins genetics, Down-Regulation drug effects, Enzyme Inhibitors pharmacology, G1 Phase drug effects, Genes, Reporter, Hepatocytes cytology, Hepatocytes metabolism, Luciferases genetics, Rats, Transcription, Genetic drug effects, Hepatocytes drug effects, Histone Deacetylase Inhibitors, Hydroxamic Acids pharmacology, NF-kappa B antagonists & inhibitors, Pentanoic Acids pharmacology
- Abstract
Objective: Benzoylaminoalkanohydroxamic acids, including 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxamide (4-Me(2)N-BAVAH), are structural analogues of Trichostatin A, a naturally occurring histone deacetylase inhibitor (HDACi). 4-Me(2)N-BAVAH has been shown to induce histone hyperacetylation and to inhibit proliferation in Friend erythroleukaemia cells in vitro. However, the molecular mechanisms have remained unidentified., Materials and Methods: In this study, we evaluated the effects of 4-Me(2)N-BAVAH on proliferation in non-malignant cells, namely epidermal growth factor-stimulated primary rat hepatocytes., Results and Conclusion: We have found that 4-Me(2)N-BAVAH inhibits HDAC activity at non-cytotoxic concentrations and prevents cells from responding to the mitogenic stimuli of epidermal growth factor. This results in an early G(1) cell cycle arrest that is independent of p21 activity, but instead can be attributed to inhibition of cyclin D1 transcription through a mechanism involving inhibition of nuclear factor-kappaB activation. In addition, 4-Me(2)N-BAVAH delays the onset of spontaneous apoptosis in primary rat hepatocyte cultures as evidenced by down-regulation of the pro-apoptotic proteins Bid and Bax, and inhibition of caspase-3 activation.
- Published
- 2007
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114. Synergistic antitumour effect of raltitrexed and 5-fluorouracil plus folinic acid combination in human cancer cells.
- Author
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Avallone A, Di Gennaro E, Bruzzese F, Laus G, Delrio P, Caraglia M, Pepe S, Comella P, and Budillon A
- Subjects
- Antineoplastic Combined Chemotherapy Protocols administration & dosage, Apoptosis drug effects, Blotting, Western, Cell Cycle drug effects, Cell Line, Tumor, Cell Proliferation drug effects, Dose-Response Relationship, Drug, Drug Synergism, Fluorouracil administration & dosage, Humans, Inhibitory Concentration 50, Leucovorin administration & dosage, Quinazolines administration & dosage, Thiophenes administration & dosage, Antineoplastic Combined Chemotherapy Protocols pharmacology, Carcinoma, Squamous Cell drug therapy, Colorectal Neoplasms drug therapy, Head and Neck Neoplasms drug therapy
- Abstract
5-Fluorouracil, usually in combination with folinic acid, is widely used in the treatment of both colorectal and head and neck squamous cell cancer patients. Since 5-fluorouracil plus folinic acid and the antifolate thymidylate synthase inhibitor; raltitrexed have distinct mechanisms of action and toxicity profiles, we have evaluated the potential synergistic antitumor interaction between these two agents combined with a sequential schedule of administration in KB (wt-p53) and Cal27 (mut-p53) head and neck squamous cell carcinomas, and LoVo (wt-p53) and HT29 (mut-p53) colorectal cell lines. The combination between a 24-h exposure to raltitrexed followed by a 4-h exposure to 5-fluorouracil plus folinic acid was globally synergistic, as assessed by the median effect principle and combination index. A specific contribution of folinic acid to the cytotoxic effect of the raltitrexed/5-fluorouracil combination was clearly demonstrated by the evaluation of the potentiation factor. In all cell lines, a 1.5- up to 17-fold reduction in the IC50 of both raltitrexed and 5-fluorouracil plus folinic acid was observed in the combination setting compared with the concentrations of the each drug used alone. Moreover, we demonstrated that raltitrexed/5-fluorouracil plus folinic acid induced a distinct S-phase block of the cell cycle, as well as a potentiation of the apoptotic cell death, compared with 5-fluorouracil plus folinic acid or raltitrexed/5-fluorouracil combination. This preclinical work represents, at least to our knowledge, the first demonstration of a synergistic interaction between raltitrexed and 5-fluorouracil modulated by folinic acid, and could represent a rationale for further clinical investigation of raltitrexed/5-fluorouracil plus folinic acid combination.
- Published
- 2007
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115. Thioquinolobactin, a Pseudomonas siderophore with antifungal and anti-Pythium activity.
- Author
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Matthijs S, Tehrani KA, Laus G, Jackson RW, Cooper RM, and Cornelis P
- Subjects
- Antifungal Agents chemistry, Antifungal Agents isolation & purification, DNA Transposable Elements, Heme biosynthesis, Hydrolysis, Molecular Sequence Data, Mutation, Oligopeptides genetics, Oligopeptides metabolism, Phenotype, Pseudomonas fluorescens genetics, Pseudomonas fluorescens metabolism, Pythium growth & development, Quinolines chemistry, Quinolines isolation & purification, Quinolines metabolism, Siderophores chemistry, Siderophores isolation & purification, Sulfur metabolism, Antifungal Agents pharmacology, Pseudomonas fluorescens chemistry, Pythium drug effects, Quinolines pharmacology, Siderophores pharmacology
- Abstract
Under conditions of iron limitation Pseudomonas fluorescens ATCC 17400 produces two siderophores, pyoverdine, and a second siderophore quinolobactin, which itself results from the hydrolysis of the unstable molecule 8-hydroxy-4-methoxy-2-quinoline thiocarboxylic acid (thioquinolobactin). Pseudomonas fluorescens ATCC 17400 also displays a strong in vitro antagonism against the Oomycete Pythium, which is repressed by iron, suggesting the involvement of a siderophore(s). While a pyoverdine-negative mutant retains most of its antagonism, a thioquinolobactin-negative mutant only slowed-down Pythium growth, and a double pyoverdine-, thioquinolobactin-negative mutant, which does not produce any siderophore, totally lost its antagonism against Pythium. The siderophore thioquinolobactin could be purified and identified from spent medium and showed anti-Pythium activity, but it was quickly hydrolysed to quinolobactin, which we showed has no antimicrobial activity. Analysis of antagonism-affected transposon mutants revealed that genes involved in haem biosynthesis and sulfur assimilation are important for the production of thioquinolobactin and the expression of antagonism.
- Published
- 2007
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116. Poly(ADPR)polymerase-1 signalling of the DNA damage induced by DNA topoisomerase I poison in D54(p53wt) and U251(p53mut) glioblastoma cell lines.
- Author
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Cimmino G, Pepe S, Laus G, Chianese M, Prece D, Penitente R, and Quesada P
- Subjects
- Apoptosis drug effects, Blotting, Western, Brain Neoplasms enzymology, Brain Neoplasms genetics, Cell Line, Tumor, Cell Nucleus chemistry, Cell Nucleus enzymology, Densitometry, Dose-Response Relationship, Drug, Drug Synergism, Enzyme Inhibitors poisoning, Flow Cytometry, Glioblastoma enzymology, Glioblastoma genetics, Humans, In Situ Nick-End Labeling, Indicators and Reagents, Mutation physiology, Poly (ADP-Ribose) Polymerase-1, Quinazolines pharmacology, Signal Transduction drug effects, Topotecan poisoning, Tumor Suppressor Protein p53 genetics, Brain Neoplasms physiopathology, DNA Damage physiology, DNA Topoisomerases, Type I, Glioblastoma physiopathology, Poly(ADP-ribose) Polymerases physiology
- Abstract
Glioblastomas are widely characterised by the mutation of the p53 gene and p53 disruption sensitizes glioblastoma cells to DNA topoisomerase I (TOPO I) inhibitor-mediated apoptosis. We investigated the effects of combined treatments with the DNA topoisomerase I inhibitor Topotecan and the poly(ADPR)polymerase-1 inhibitor NU1025 in D54(p53wt) and U251(p53mut) glioblastoma cell lines. Analysis of cell growth and cell cycle kinetics showed a synergistic anti-proliferative effect of 10 nM TPT and 10 microM NU1025 and a G2/M block of the cell cycle. We also evaluated, the influence of TPT+/-NU1025 treatment on PARP-1 and p53 activity. We got evidences of a TPT-dependent increase of PARP-1 auto-modification level in both the cells. Moreover, in the D54(p53wt) cells we found that in co-treatments NU1025 incremented the TPT-dependent stimulation of p53 transcriptional activity and increased the p21 nuclear amount. Conversely, in U251(p53mut) cells we found that NU1025 incremented the TPT-dependent apoptosis characterised by PARP-1 proteolysis. Our findings suggest that the modulation of PARP-1 can be considered a strategy in the potentiation of the chemotherapeutic action of TOPO I poisons in glioblastoma cells apart from their p53 status.
- Published
- 2007
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117. Mechanistic diversity of the van Leusen reaction applied to 6-ketomorphinans and synthetic potential of the resulting acrylonitrile substructures.
- Author
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Schütz J, Windisch P, Kristeva E, Wurst K, Ongania KH, Horvath UE, Schottenberger H, Laus G, and Schmidhammer H
- Subjects
- Catalysis, Crystallography, X-Ray, Molecular Structure, Morphinans chemical synthesis, Nitriles chemical synthesis, Morphinans chemistry, Nitriles chemistry
- Abstract
Tosylmethyl isocyanide was used to convert 7,8-didehydro-6-ketomorphinans to 6,7-didehydromorphinan-6-carbonitriles with retainment of the 4,5-epoxy ring. However, ring opening occurred in the presence of NaH giving 5,6,7,8-tetradehydromorphinan-6-carbonitriles. Addition of nucleophiles such as Li diisopropylamide or Grignard reagents to the acrylonitrile substructure yielded ring-opened 5,6-didehydro products. Seven products were characterized by X-ray crystal structure analysis and revealed insight into the mechanistic diversity of the van Leusen reaction.
- Published
- 2005
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118. A new structural motif for mu-opioid antagonists.
- Author
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Van den Eynde I, Laus G, Schiller PW, Kosson P, Chung NN, Lipkowski AW, and Tourwé D
- Subjects
- Animals, Benzazepines chemistry, Benzazepines pharmacology, Electric Stimulation, Guinea Pigs, Ileum drug effects, Ileum physiology, In Vitro Techniques, Muscle Contraction, Muscle, Smooth drug effects, Muscle, Smooth physiology, Propane analogs & derivatives, Propane chemical synthesis, Propane chemistry, Propane pharmacology, Radioligand Assay, Receptors, Opioid, mu physiology, Stereoisomerism, Structure-Activity Relationship, Benzazepines chemical synthesis, Receptors, Opioid, mu antagonists & inhibitors
- Abstract
On the basis of the structural features of the Dmt-Tic pharmacophore, a new motif leading to a fairly potent mu-opioid antagonist is described. This motif contains the 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-one skeleton as a substitute for the Tic residue, which provides the conformational constraint compatible with the mu-opioid receptor. The stereoselective synthesis of four stereoisomers is performed starting from homochiral 2',6'-dimethyltyrosine (Dmt) and o-aminomethylphenylalanine.
- Published
- 2005
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119. 57Fe-labeled octamethylferrocenium tetrafluoroborate. X-ray crystal structures of conformational isomers, hyperfine interactions, and spin-lattice relaxation by Moessbauer spectroscopy.
- Author
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Schottenberger H, Wurst K, Griesser UJ, Jetti RK, Laus G, Herber RH, and Nowik I
- Abstract
X-ray structure determinations of two different single crystals of octamethylferrocenium tetrafluoroborate (OMFc(+)BF(4)(-)) revealed conformational polymorphism with ligand twist angles of 180 degrees and 108 degrees , respectively. Their concomitant occurrence could be explained by the small lattice energy difference of 3.2 kJ mol(-1). Temperature-dependent Moessbauer spectroscopy of (57)Fe-labeled OMFc(+)BF(4)(-) over the range 90 < T < 370 K did not show the anomalous sudden increase in the motion of the metal atom as observed in neutral OMFc. Broadened absorption curves characteristic of relaxation spectra were obtained with an isomer shift of 0.466(6) mm s(-1) at 90 K. The temperature dependence of the isomer shift corresponded to an effective vibrating mass of 79 +/- 10 Da and, in conjunction with the temperature dependence of the recoil-free fraction, to a Moessbauer lattice temperature of 89 K. The spin relaxation rate could be better described by an Orbach rather than a Raman process. At 400 K, a reversible solid-solid transition to a plastic crystalline mesophase was noted.
- Published
- 2005
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120. Identification of ethylsuccinylcarnitine present in some human urines.
- Author
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Libert R, Van Hoof F, Laus G, De Nayer P, Habib Jiwan JL, de Hoffmann E, and Schanck A
- Subjects
- Adult, Aged, Carnitine chemistry, Carnitine urine, Child, Child, Preschool, Female, Humans, Male, Middle Aged, Carnitine analogs & derivatives
- Abstract
Ethylsuccinylcarnitine, a previously undescribed acylcarnitine, was identified in urines obtained from 81% of adult volunteers. Its chemical structure was obtained by 1H nuclear magnetic resonance spectroscopy of the urinary purified compound and confirmed by its chemical synthesis. Its urinary excretion followed a circadian rhythm with a maximum occurring between 8 p.m. and 1 a.m. Excretion of this compound was enhanced after a load of L-carnitine and in this case, total 24-h urinary excretion may raise up to about 75 microM. It was observed that the day after adryamicine treatment, the compound was no more excreted. This molecule was absent or in trace amounts in urines obtained from few adults as well as in urines obtained from young subjects. In the positive urines, we detected an unknown organic acid whose excretion was almost parallel to that of ethylsuccinylcarnitine.
- Published
- 2005
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121. Rat hepatocyte suspensions as a suitable in vitro model for studying the biotransformation of histone deacetylase inhibitors.
- Author
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Elaut G, Török G, Papeleu P, Vanhaecke T, Laus G, Tourwé D, and Rogiers V
- Subjects
- Animals, Biotransformation, Chromatography, High Pressure Liquid, Hepatocytes cytology, Hydroxamic Acids pharmacokinetics, In Vitro Techniques, Male, Microsomes, Liver metabolism, Rats, Rats, Sprague-Dawley, Tandem Mass Spectrometry, Hepatocytes metabolism, Histone Deacetylase Inhibitors pharmacokinetics
- Abstract
This paper focuses on the use of liver-derived in vitro systems for biotransformation studies during early drug development, as exemplified by the two molecules recently studied in our laboratory: Trichostatin A (TSA) and its structural analogue 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxamide (4-Me2N-BAVAH). Phase I biotransformation of TSA, a histone deacetylase inhibitor with promising antifibrotic and antitumoural properties, was investigated in liver microsomal (rat and human) and in hepatocyte (rat) suspensions. Within 40 minutes, 50 microM of TSA was completely metabolised by 2 x 10(6) hepatocytes/ml. Reduction of the hydroxamic acid function to its corresponding amide and N-demethylation were the two major phase I biotransformation pathways, while hydrolysis products of TSA were minor metabolites. Lower concentrations of TSA (5 microM and 25 microM) were N-demethylated faster. Liver microsomes, however, metabolised TSA incompletely with the formation of two major metabolites, N-mono- and N-didemethylated TSA. Unlike TSA, 4-Me2N-BAVAH (50 microM) could still be detected after 3 hours of incubation with 2 x 10(6) rat hepatocytes/ml suspension. Hydrolysis and reduction of the hydroxamic acid function to its corresponding acid and amide, respectively, were shown to be the major phase I biotransformation pathways. Lower concentrations of 4-Me2N-BAVAH were hydrolysed more readily. 4-Me2N-BAVAH and its metabolites were less subjected to N-demethylation than TSA.
- Published
- 2004
- Full Text
- View/download PDF
122. Advances in chemistry and bioactivity of the genus Uncaria.
- Author
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Laus G
- Subjects
- Alkaloids chemistry, Alkaloids pharmacokinetics, Flavonoids chemistry, Flavonoids pharmacokinetics, Humans, Terpenes chemistry, Terpenes pharmacokinetics, Phytotherapy, Plant Extracts chemistry, Plant Extracts pharmacokinetics, Uncaria
- Abstract
The alkaloids of the pantropical genus Uncaria (Rubiaceae) were reviewed extensively by Phillipson et al. in (1978) Since then a host of papers with new results has been published. The compounds discovered are from three major groups: (1) alkaloids; (2) terpenoids; and (3) flavonoids. Some highly unusual structures have been reported. Although there are at least 35 species of Uncaria known, recent research focussed on a relatively small number of species. During recent years bioactivity of extracts and pure compounds isolated from Uncaria species have been increasingly investigated. These include anticonvulsive, antiinflammatory, antimutagenic, antioxidant, cytoprotective, hypotensive, and immunoregulatory effects. The literature since 1978 is reviewed and 133 references are given., (Copyright 2004 John Wiley & Sons, Ltd.)
- Published
- 2004
- Full Text
- View/download PDF
123. Electrochemical synthesis and X-ray crystal structures of beta-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and alpha-D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose.
- Author
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Predojević J, Vukićević MD, Wurst K, Ongania KH, Laus G, and Vukićević RD
- Subjects
- Crystallography, X-Ray, Electrochemistry, Molecular Conformation, Oligosaccharides chemistry, Stereoisomerism, Glycosides chemical synthesis, Mannosides chemical synthesis, Oligosaccharides chemical synthesis, Pyrans chemistry, Selenium chemistry
- Abstract
Electrochemical acetoxyphenylselenation of 3,4-dihydro-2H-pyran and D-3,4,6-tri-O-acetylglucal was studied. The constant current electrolysis (50mA) of dihydropyran and diphenyl diselenide in an acetic acid solution of tetramethylammonium chloride was performed at room temperature in an undivided cell using a graphite anode and an aluminum cathode and yielded trans-DL-2-acetoxy-3-phenylselenyltetrahydropyran (27%), in agreement with Markovnikov's rule. The analysis of the 1H NMR spectral data showed that the acetoxy and phenylselenyl groups adopt axial positions in the most stable conformation of this compound due to the anomeric effect. Under the same conditions D-3,4,6-tri-O-acetylglucal afforded D-2-phenylselenyl-1,3,4,6-tetra-O-acetylglucopyranose and D-2-phenylselenyl-1,3,4,6-tetra-O-acetylmannopyranose, which were separated by column chromatography and isolated in 87% overall yield (isomer ratio 60:40). The structures of these compounds were established by spectral data. Single crystal X-ray structure determinations of the diastereomers are reported.
- Published
- 2004
- Full Text
- View/download PDF
124. Solvatochromism, halochromism, and preferential solvation of new dipolar guaiazulenyl 1,4-benzoquinone methides.
- Author
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Laus G, Schottenberger H, Wurst K, Schütz J, Ongania KH, Horvath UE, and Schwärzler A
- Abstract
The synthesis and the solvatochromic properties of five dyes, obtained by condensation of guaiazulene with 4-hydroxybenzaldehydes, are described. Crystal structures of a quinoid dye and a phenolic dye precursor are presented. The dyes are sensitive to the dipolarity-polarizability of the medium and to the hydrogen-bond donor ability of protic solvents. Their solvatochromism is discussed in terms of Kamlet-Taft's pi* and alpha scales, and their difference in behaviour is interpreted. Alkali and alkaline earth metal salts effect halochromism, with one exception due to extreme steric hindrance. Thus, this dye is capable of measuring solvent polarities without sensing the presence of electrolytes. Preferential solvation of the dyes in a series of binary solvent mixtures is explained quantitatively by solvent-exchange models.
- Published
- 2003
- Full Text
- View/download PDF
125. The essential catalytic redox couple in arsenate reductase from Staphylococcus aureus.
- Author
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Messens J, Hayburn G, Desmyter A, Laus G, and Wyns L
- Subjects
- Adenosine Triphosphatases biosynthesis, Adenosine Triphosphatases genetics, Adenosine Triphosphatases isolation & purification, Amino Acid Sequence, Arsenite Transporting ATPases, Catalysis, Chromatography, High Pressure Liquid, Chromatography, Ion Exchange, Circular Dichroism, Cysteine genetics, Escherichia coli genetics, Mass Spectrometry, Molecular Sequence Data, Mutagenesis, Site-Directed, Oxidation-Reduction, Protein Structure, Secondary, Thioredoxin-Disulfide Reductase biosynthesis, Thioredoxin-Disulfide Reductase genetics, Adenosine Triphosphatases chemistry, Ion Pumps, Multienzyme Complexes, Staphylococcus aureus enzymology
- Abstract
Arsenate reductase (ArsC) encoded by Staphylococcus aureus arsenic-resistance plasmid pI258 reduces intracellular As(V) (arsenate) to the more toxic As(III) (arsenite), which is subsequently extruded from the cell. ArsC couples to thioredoxin, thioredoxin reductase, and NADPH to be enzymatically active. A novel purification method leads to high production levels of highly pure enzyme. A reverse phase method was introduced to systematically analyze and control the oxidation status of the enzyme. The essential cysteinyl residues and redox couple in arsenate reductase were identified by a combination of site-specific mutagenesis and endoprotease-digest mass spectroscopy analysis. The secondary structures, as determined with CD, of wild-type ArsC and its Cys mutants showed a relatively high helical content, independent of the redox status. Mutation of Cys 10, 82, and 89 led to redox-inactive enzymes. ArsC was oxidized in a single catalytic cycle and subsequently digested with endoproteinases ArgC, AspN, and GluC. From the peptide-mass profiles, cysteines 82 and 89 were identified as the redox couple of ArsC necessary to reduce arsenate to arsenite.
- Published
- 1999
- Full Text
- View/download PDF
126. Pentacyclic oxindole alkaloids from Uncaria tomentosa induce human endothelial cells to release a lymphocyte-proliferation-regulating factor.
- Author
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Wurm M, Kacani L, Laus G, Keplinger K, and Dierich MP
- Subjects
- Cell Line, Endothelium cytology, Endothelium metabolism, Humans, Indoles pharmacology, Alkaloids pharmacology, B-Lymphocytes cytology, Cell Division, Endothelium drug effects, Rubiaceae chemistry, T-Lymphocytes cytology
- Abstract
In the present study we show that pentacyclic but not tetracyclic oxindole alkaloids from Uncoria tomentosa (Willd.) DC. (Rubiaceae) induced EA.hy926 endothelial cells to release some yet to be determined factor(s) into the supernatant; this factor was shown to significantly enhance proliferation of normal human resting or weakly activated B and T lymphocytes. In contrast, proliferation of normal human lymphoblasts and of both the human lymphoblastoid B cell line Raji and the human lymphoblastoid T cell line Jurkat was inhibited significantly while cell viability was not affected. Tetracyclic oxindole alkaloids dose-dependently reduce the activity of pentacyclic oxindole alkaloids on human endothelial cells.
- Published
- 1998
- Full Text
- View/download PDF
127. Reconsidering the energetics of ribonuclease catalysed RNA hydrolysis.
- Author
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Loverix S, Laus G, Martins JC, Wyns L, and Steyaert J
- Subjects
- Catalysis, Energy Metabolism, Hydrolysis, Kinetics, RNA metabolism, Ribonucleases metabolism
- Abstract
In principle, all biochemical reactions are reversible, though some are more reversible than others. The classical ribonuclease mechanism involves a reversible transphosphorylation step, followed by quasi irreversible hydrolysis of the cyclic intermediate. We performed isotope-exchange and intermediate-trapping experiments showing that the second hydrolysis step is readily reversible in the presence of RNase A or RNase T1. As a consequence, the equilibrium between a phosphodiester and a 2',3'-cyclophosphate accounts for all catalysed reactions, even if the leaving/attacking group is a water molecule. Therefore, ribonucleases are transferases rather than hydrolases. The equilibrium constant for the catalysed interconversion is close to 1 M. From this result, we estimate the effective concentration of the 2'-hydroxyl nucleophile in the cyclization step to be 10(7) M. The high effective concentration of the vicinal hydroxyl group balances the strain-associated and solvation-associated instability of the pentacyclic phosphodiester.
- Published
- 1998
- Full Text
- View/download PDF
128. Location of the three disulfide bonds in an antimicrobial peptide from Amaranthus caudatus using mass spectrometry.
- Author
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el Bouyoussfi M, Laus G, Verheyden P, Wyns L, Tourwe D, and Van Binst G
- Subjects
- Amino Acid Sequence, Disulfides, Endopeptidases, Molecular Sequence Data, Spectrometry, Mass, Fast Atom Bombardment methods, Anti-Infective Agents chemistry, Peptide Fragments chemistry, Peptides chemistry, Seeds chemistry
- Abstract
The disulfide bridge pairing of Ac-AMP2, a 30-residue peptide isolated from the seeds of Amaranthus caudatus, is determined using a fast method involving enzymatic fragmentation followed by identification of the fragments with FAB mass spectrometry. The results confirm the location of the three disulfide bridges as previously established by NMR spectroscopy and molecular modelling.
- Published
- 1997
- Full Text
- View/download PDF
129. An evaluation of microwave heating for the rapid hydrolysis of peptide samples for chiral amino acid analysis.
- Author
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Péter A, Laus G, Tourwé D, Gerlo E, and Van Binst G
- Subjects
- Amino Acid Sequence, Gas Chromatography-Mass Spectrometry, Hot Temperature, Hydrolysis, Molecular Sequence Data, Stereoisomerism, Amino Acids analysis, Microwaves, Peptides chemistry
- Abstract
The hydrolysis of peptide samples in 6 N deuterium chloride by microwave heating has been investigated. The influence of the power and time of heating on the recovery of the amino acids and on their racemization was studied. A high recovery of sensitive amino acids and minimal racemization, as determined by the amount of deuterium incorporation, is obtained by using an intermediate irradiation power and 30 min reaction time.
- Published
- 1993
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