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Shanmugam S.R.,University of Windsor | Lalman J.A.,University of Windsor | Chaganti S.R.,University of Windsor | Heath D.D.,University of Windsor | And 3 more authors.
Renewable Energy

In this study, the long term effect of different microbial stressing agents on hydrogen (H2) production was examined using repeated batch cultivations. When compared to thermophilic cultures, higher H2 yields were observed in mesophilic cultures receiving repeated glucose addition. Methane production was only observed in control mesophilic cultures receiving repeated 5 glucose additions. Lower hydrogenase evolution specific activity was observed in thermophilic cultures (except alkali-treated cultures) compared to mesophilic cultures. For both mesophilic and thermophilic cultures, the hydrogenase uptake specific activity of the untreated control cultures exhibited higher levels of activity than the pretreated cultures. A flux balance analysis (FBA) showed negligible homoacetogenic flux in mesophilic cultures pretreated with linoleic acid (LA) and loading shock (LS) after successive batch cultivations. The homoacetogenic flux accounted for approximately 98% loss in the H2 yield in untreated mesophilic control cultures. Both homoacetogens (Eubacterium sp.) and aceticlastic methanogens (Methanosaeta sp. and Methanosarcina sp.) were abundant in the control cultures. In comparison, Clostridium sp. were dominant in mesophilic stress treated cultures whereas under thermophilic conditions, the dominant microorganisms were Flavobacterium sp., Bacillus sp., Thermoanaerobacter sp., Bacteroides sp., Lactobacillus sp. and Thioalkalivibrio sp. © 2015 Elsevier Ltd. Source

Ortgies D.H.,Concordia University at Montreal | Chen F.,Concordia University at Montreal | Forgione P.,Concordia University at Montreal | Forgione P.,Center for Green Chemistry and Catalysis
European Journal of Organic Chemistry

A range of aryl sulfinates can be oxidatively dimerized to generate substituted biphenyls with concomitant extrusion of sulfur dioxide with a palladium catalyst. Catalytic amounts of TEMPO and excess oxygen are utilized as oxidants to regenerate the palladium catalyst. TEMPO acts as catalytic primary oxidant in conjunction with molecular oxygen to regenerate a palladium catalyst for a desulfinative homocoupling reaction of aryl sulfinates. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Gobeil S.M.C.,Laval University | Gobeil S.M.C.,University of Montreal | Clouthier C.M.,Laval University | Clouthier C.M.,University of Montreal | And 13 more authors.
Chemistry and Biology

Summary Proteins are dynamic systems, and understanding dynamics is critical for fully understanding protein function. Therefore, the question of whether laboratory engineering has an impact on protein dynamics is of general interest. Here, we demonstrate that two homologous, naturally evolved enzymes with high degrees of structural and functional conservation also exhibit conserved dynamics. Their similar set of slow timescale dynamics is highly restricted, consistent with evolutionary conservation of a functionally important feature. However, we also show that dynamics of a laboratory-engineered chimeric enzyme obtained by recombination of the two homologs exhibits striking difference on the millisecond timescale, despite function and high-resolution crystal structure (1.05 Å) being conserved. The laboratory-engineered chimera is thus functionally tolerant to modified dynamics on the timescale of catalytic turnover. Tolerance to dynamic variation implies that maintenance of native-like protein dynamics may not be required when engineering functional proteins. © 2014 Elsevier Ltd. Source

Ortgies D.H.,Autonomous University of Madrid | Ortgies D.H.,Instituto Ramon Y Cajal Of Investigacion Sanitaria Irycis | Hassanpour A.,Concordia University at Montreal | Chen F.,Concordia University at Montreal | And 3 more authors.
European Journal of Organic Chemistry

As carbon-carbon bonds are an essential bond type in Nature, reactions that form C-C bonds are of great interest in organic chemistry. Among the most popular C-C bond formation methods with aromatic systems are palladium-catalyzed coupling reactions, such as the Heck, Suzuki, Negishi and Stille reactions. Even though these methods are efficient, they produce stoichiometric amounts of high molecular weight byproducts, placing them in conflict with the increasingly important ideas of sustainable reactions and green chemistry. In contrast, palladium-catalyzed desulfinative coupling reactions produce minimal waste; in general, only hydrogen halides or alkali halides are formed as byproducts in addition to SO2 gas, which can potentially be recycled. This microreview provides a brief historic overview on palladium-catalyzed coupling reactions with organosulfur compounds, with the main focus on the use of sulfinate salts as nucleophilic or electrophilic reaction partners. Various methods to access the sulfinate salts, and the coupling reactions of sulfonyl precursors that proceed through sulfinic acid/salt intermediates generated in situ are also discussed. Organosulfur compounds have gained increasing attention as coupling partners for palladium-catalyzed C-C bond formation. This microreview provides a critical analysis of desulfinative reactions for these couplings, from their origins to the current state-of-the-art to their future prospects for sustainable chemistry. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Morley K.L.,National Research Council Canada | Lau P.C.K.,McGill University | Lau P.C.K.,Center for Green Chemistry and Catalysis | Berghuis A.M.,McGill University
ACS Chemical Biology

The Baeyer-Villiger monooxygenases (BVMOs) are microbial enzymes that catalyze the synthetically useful Baeyer-Villiger oxidation reaction. The available BVMO crystal structures all lack a substrate or product bound in a position that would determine the substrate specificity and stereospecificity of the enzyme. Here, we report two crystal structures of cyclohexanone monooxygenase (CHMO) with its product, ε-caprolactone, bound: the CHMOTight and CHMOLoose structures. The CHMOTight structure represents the enzyme state in which substrate acceptance and stereospecificity is determined, providing a foundation for engineering BVMOs with altered substrate spectra and/or stereospecificity. The CHMOLoose structure is the first structure where the product is solvent accessible. This structure represents the enzyme state upon binding and release of the substrate and product. In addition, the role of the invariant Arg329 in chaperoning the substrate/product during the catalytic cycle is highlighted. Overall, these data provide a structural framework for the engineering of BVMOs with altered substrate spectra and/or stereospecificity. © 2014 American Chemical Society. Source

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