109 research outputs found

    Additional data to the stratigraphy and the chronology of the Kostenki 1 (Poliakov) sequence, Voronezh, Russia:Le Sungirien, Saint-Petersbourg 2016

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    Kostenki 1 is one of the many sites of the Kostenki- Borshchevo site cluster south of Voronezh, which has a long sequence covering the Early and Mid Upper Palaeo- lithic, including the Streletskian Cultural Layer V. Here we present stratigraphic data from our 1994 eldwork (sections of the 1981-1982 excavations) and radiocarbon dates for the CL IV and V. For dating we used our cross- dating approach on high quality conifer charcoal with ABA and ABOx-SC pre-treatment on sub-samples of the same charcoal sample. Our results show that the Strelets- kian CL V dates to ~42,500 14C uncal BP and is signi - cantly older than previously though

    G-quadruplex DNA motifs in the malaria parasite Plasmodium falciparum and their potential as novel antimalarial drug targets

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    G-quadruplexes are DNA or RNA secondary structures that can be formed from guanine-rich nucleic acids. These four-stranded structures, composed of stacked quartets of guanine bases, can be highly stable and have been demonstrated to occur in vivo in the DNA of human cells and other systems, where they play important biological roles, influencing processes such as telomere maintenance, DNA replication and transcription, or, in the case of RNA G-quadruplexes, RNA translation and processing. We report for the first time that DNA G-quadruplexes can be detected in the nuclei of the malaria parasite Plasmodium falciparum, which has one of the most A/T-biased genomes sequenced and therefore possesses few guanine-rich sequences with the potential to form G-quadruplexes. We show that despite this paucity of putative G-quadruplex-forming sequences, P. falciparum parasites are sensitive to several G-quadruplex-stabilizing drugs, including quarfloxin, which previously reached phase 2 clinical trials as an anticancer drug. Quarfloxin has a rapid initial rate of kill and is active against ring stages as well as replicative stages of intraerythrocytic development. We show that several G-quadruplex-stabilizing drugs, including quarfloxin, can suppress the transcription of a G-quadruplex-containing reporter gene in P. falciparum but that quarfloxin does not appear to disrupt the transcription of rRNAs, which was proposed as its mode of action in both human cells and trypanosomes. These data suggest that quarfloxin has potential for repositioning as an antimalarial with a novel mode of action. Furthermore, G-quadruplex biology in P. falciparum may present a target for development of other new antimalarial drugs

    Solution structures of the Bacillus cereus metallo-β-lactamase BcII and its complex with the broad spectrum inhibitor R-thiomandelic acid

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    Metallo-β-lactamases, enzymes which inactivate β-lactam antibiotics, are of increasing biological and clinical significance as a source of antibiotic resistance in pathogenic bacteria. In the present study we describe the high-resolution solution NMR structures of the Bacillus cereus metallo-β-lactamase BcII and of its complex with R-thiomandelic acid, a broad-spectrum inhibitor of metallo-β-lactamases. This is the first reported solution structure of any metallo-β-lactamase. There are differences between the solution structure of the free enzyme and previously reported crystal structures in the loops flanking the active site, which are important for substrate and inhibitor binding and catalysis. The binding of R-thiomandelic acid and the roles of active-site residues are defined in detail. Changes in the enzyme structure upon inhibitor binding clarify the role of the mobile β3–β4 loop. Comparisons with other metallo-β-lactamases highlight the roles of individual amino-acid residues in the active site and the β3–β4 loop in inhibitor binding and provide information on the basis of structure–activity relationships among metallo-β-lactamase inhibitors

    Ligand Binding Study of Human PEBP1/RKIP: Interaction with Nucleotides and Raf-1 Peptides Evidenced by NMR and Mass Spectrometry

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    Background Human Phosphatidylethanolamine binding protein 1 (hPEBP1) also known as Raf kinase inhibitory protein (RKIP), affects various cellular processes, and is implicated in metastasis formation and Alzheimer's disease. Human PEBP1 has also been shown to inhibit the Raf/MEK/ERK pathway. Numerous reports concern various mammalian PEBP1 binding ligands. However, since PEBP1 proteins from many different species were investigated, drawing general conclusions regarding human PEBP1 binding properties is rather difficult. Moreover, the binding site of Raf-1 on hPEBP1 is still unknown. Methods/Findings In the present study, we investigated human PEBP1 by NMR to determine the binding site of four different ligands: GTP, FMN, and one Raf-1 peptide in tri-phosphorylated and non-phosphorylated forms. The study was carried out by NMR in near physiological conditions, allowing for the identification of the binding site and the determination of the affinity constants KD for different ligands. Native mass spectrometry was used as an alternative method for measuring KD values. Conclusions/Significance Our study demonstrates and/or confirms the binding of hPEBP1 to the four studied ligands. All of them bind to the same region centered on the conserved ligand-binding pocket of hPEBP1. Although the affinities for GTP and FMN decrease as pH, salt concentration and temperature increase from pH 6.5/NaCl 0 mM/20°C to pH 7.5/NaCl 100 mM/30°C, both ligands clearly do bind under conditions similar to what is found in cells regarding pH, salt concentration and temperature. In addition, our work confirms that residues in the vicinity of the pocket rather than those within the pocket seem to be required for interaction with Raf-1.METASU

    Palynological and chemical volatile components of tipically autumnal honeys of the western Mediterranean

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    [EN] Twenty-five samples of autumnal honeys from the western Mediterranean (Mallorca and Eivissa, Balearic Islands) were examined for pollen content (qualitative and quantitative melissopalynological analysis), moisture, electrical conductivity, colour, sensorial qualities and volatile components. Quantitative analysis showed that the honey contained Maurizio's Class II: 64%, Class III: 28%, Class IV: 4% and Class V: 4%. Fifty-four pollen types, with an average number of 16.68 per sample, were identified, belonging to 29 botanical families. Only two taxa (Ceratonia siliqua and Erica multiflora) were found in all samples. Seventeen samples were unifloral (68%) - ten (40%) of C. siliqua, six (24%) of E. multiflora and one (4%) of Hedera helix. All honeys have a low honeydew index (<?0.09%), while the values for electrical conductivity and water content were high. 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