Browsing by Author "Mtashobya, Lewis"

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    Effects of Sugar Functional Groups, Hydrophobicity, and Fluorination on Carbohydrate–DNA Stacking Interactions in Water
    (American Chemical Society, 2014) Lucas, Ricardo; Peñalver, Pablo; Gómez-Pinto, Irene; Vengut-Climent, Empar; Mtashobya, Lewis; Cousin, Jonathan; Maldonado, Olivia S; Perez, Violaine; Reynes, Virginie; Aviñó, Anna; Eritja, Ramón; González, Carlos; Linclau, Bruno; Morales, Juan C.
    Carbohydrate−aromatic interactions are highly relevant for many biological processes. Nevertheless, experimental data in aqueous solution relating structure and energetics for sugar−arene stacking interactions are very scarce. Here, we evaluate how structural variations in a monosaccharide including carboxyl, N-acetyl, fluorine, and methyl groups affect stacking interactions with aromatic DNA bases. We find small differences on stacking interaction among the natural carbohydrates examined. The presence of fluorine atoms within the pyranose ring slightly increases the interaction with the C−G DNA base pair. Carbohydrate hydrophobicity is the most determinant factor. However, gradual increase in hydrophobicity of the carbohydrate does not translate directly into a steady growth in stacking interaction. The energetics correlates better with the amount of apolar surface buried upon sugar stacking on top of the aromatic DNA base pair.
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    Influence of Alcohol β‐Fluorination on Hydrogen‐Bond Acidity of Conformationally Flexible Substrates
    (Wiley Online Library, 2016) Graton, Jérôme; Compain, Guillaume; Besseau, François; Bogdan, Elena; Watts, Joe; Mtashobya, Lewis; Wang, Zhong; Weymouth-Wilson, Alex; Galland, Nicolas; Questel, Jean-Yves Le; Linclau, Bruno
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    Influence of Fluorination on the Conformational Properties and Hydrogen-Bond Acidity of Benzyl Alcohol Derivatives
    (WILEY-VCH Verlag, 2015) Bogdan, Elena; Compain, Guillaume; Mtashobya, Lewis; Le Questel, Jean-Yves; Besseau, François; Galland, Nicolas; Linclau, Bruno; Graton, Jérôme
    Abstract: The effect of fluorination on the conformational and hydrogen-bond (HB)-donating properties of a series of benzyl alcohols has been investigated experimentally by IR spectroscopy and theoretically with quantum chemical methods (ab initio (MP2) and DFT (MPWB1K)). It was found that o-fluorination generally resulted in an increase in the HB acidity of the hydroxyl group, whereas a decrease was observed upon o,o’-difluorination. Computational analysis showed that the conformational landscapes of the title compounds are strongly influenced by the presence of o-fluorine atoms. Intramolecular interaction descriptors based on AIM, NCI and NBO analyses reveal that, in addition to an intramolecular OH···F interaction, secondary CH···F and/or CH···O interactions also occur, contributing to the stabilisation of the various conformations, and influencing the overall HB properties of the alcohol group. The benzyl alcohol HB-donating capacity trends are properly described by an electrostatic potential based descriptor calculated at the MPWB1K/6-31+ G(d,p) level of theory, provided solvation effects are taken into account for these flexible HB donors.
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    Levels of Pesticide Residues in the Eastern Arc Mountains Part of Tanzania
    (International Journal of AgriScience, 2014-08) Mtashobya, Lewis; Nyambo, Brigitte
    A baseline study to document current farmers’ practices in relation to the use of synthetic pesticides in vegetable and spices production was conducted in Muheza district Eastern Usambara Mountains and Kilolo district in the Udzungwa Mountains, both located in the Eastern Arc Mountains of Tanzania. The study combined assessment of vegetable growers’ knowledge, attitude and practice (KAP) in selected villages and sampling and analysis of pesticide residues. Tomato production among other vegetables is the most popular enterprise grown all year round and therefore was selected as the model crop for this study. The crop is routinely sprayed using a wide range of broad spectrum pesticides from nursery up to the last harvest. In contrast, farmers in Muheza produce an array of spices but these are not sprayed with any synthetic pesticide. Analysis of clean sample extracts on a GC/ECD and confirmed on the GC/MS revealed dominance of organochlorine pesticides. Endosulfan was the only pesticide mentioned by the Kilolo vegetable growers that was detected. In general, sediment samples were found to have higher levels of pesticide residues than the other sample matrices. The implications of the findings to biodiversity conservation in the Eastern Arc Mountain hotspot are discussed.
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    The synthesis of mono- and difluorinated 2,3-dideoxy-d-glucopyranoses
    (Journal of Fluorine Chemistry, 2015) Mtashobya, Lewis; Quiquempoix, Lucas; Linclau, Bruno
    The synthesis of 2,3-dideoxy-2,3-difluoro-d-glucose and 2,3-dideoxy-3-fluoro-d-glucose is reported in, respectively, 5 and 6 steps from d-glucal, using a fluorination strategy.