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41.
Jiong Wang Liyong Gan Qianwen Zhang Vikas Reddu Yuecheng Peng Zhichao Liu Xinghua Xia Cheng Wang Xin Wang 《Liver Transplantation》2019,9(3)
A structurally simple molecular 1,10‐phenanthroline‐Cu complex on a mesostructured graphene matrix that can be active and selective toward CO2 reduction over H2 evolution in an aqueous solution is reported. The active sites consist of Cu(I) center in a distorted trigonal bipyramidal geometry, which enables the adsorption of CO2 with η1‐COO‐like configuration to commence the catalysis, with a turnover frequency of ≈45 s?1 at ?1 V versus reversible hydrogen electrode. Using in situ infrared spectroelectrochemical investigation, it is demonstrated that the Cu complex can be reversibly heterogenized near the graphene surface via potential control. An increase of electron density in the complex is observed as a result of the interaction from the electric field, which further tunes the electron distribution in the neighboring CO2. It is also found that the mesostructure of graphene matrix favored CO2 reduction on the Cu center over hydrogen evolution by limiting mass transport from the bulk solution to the electrode surface. 相似文献
42.
Serious environmental problems, growing demand for energy, and the pursuit of environmental‐friendly, sustainable, and effective energy technologies to store and transform clean energy have all drawn great attention recently. As a part of the special issue “Energy Research in National Institute of Advanced Industrial Science and Technology (AIST)” this review systematically summarizes the research progress of metal–organic framework (MOF) composites and derivatives in energy applications, including catalytic CO oxidation, liquid‐phase chemical hydrogen storage, and electrochemical energy storage and conversion. Furthermore, the correlation between MOF‐based structures, synthetic strategies, and their corresponding performances is carefully discussed. The further scope and opportunities, expected improvements and challenges are also discussed. This review will not only benefit development of more feasible protocols to fabricate nanostructures for energy systems but also stimulate further interest in MOF composites and derivatives, for energy applications. 相似文献
43.
Stéphane Sengmany Mathilde Sitter Eric Léonel Erwan Le Gall Gervaise Loirand Thierry Martens Didier Dubreuil Florian Dilasser Morgane Rousselle Vincent Sauzeau Jacques Lebreton Muriel Pipelier Rémy Le Guével 《Bioorganic & medicinal chemistry letters》2019,29(5):755-760
Various 3-amino-, 3-aryloxy- and alkoxy-6-arylpyridazines have been synthesized by an electrochemical reductive cross-coupling between 3-amino-, 3-aryloxy- or 3-alkoxy-6-chloropyridazines and aryl or heteroaryl halides. In vitro antiproliferative activity of these products was evaluated against a representative panel of cancer cell lines (HuH7, CaCo-2, MDA-MB-231, HCT116, PC3, NCI-H727, HaCaT) and oncogenicity prevention of the more efficient derivatives was highlighted on human breast cancer cell line MDA-MB 468-Luc prior establishing their interaction with p44/42 and Akt-dependent signaling pathways. 相似文献
44.
45.
Four methods have been screened for the synthesis of some alpha-D-glucopyranosides, with the recently reported (Mukaiyama) combination of 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl iodide and triphenylphosphine oxide being the most successful, especially in the diastereoselectivity exhibited. The alpha-D-glucopyranosides so obtained have been deprotected to yield 2-, 3-, 4- and 6-O-alpha-D-glucopyranosyl-D-galactopyranose. Only the last disaccharide showed any hydrolysis by alpha-glycosidases but this success was not emulated by mucosal extracts from the small intestine of the pig. 相似文献
46.
Varga B Barabás O Kovári J Tóth J Hunyadi-Gulyás E Klement E Medzihradszky KF Tölgyesi F Fidy J Vértessy BG 《FEBS letters》2007,581(24):4783-4788
Human dUTPase, essential for DNA integrity, is an important survival factor for cancer cells. We determined the crystal structure of the enzyme:alpha,beta-imino-dUTP:Mg complex and performed equilibrium binding experiments in solution. Ordering of the C-terminus upon the active site induces close juxtaposition of the incoming nucleophile attacker water oxygen and the alpha-phosphorus of the substrate, decreasing their distance below the van der Waals limit. Complex interactions of the C-terminus with both substrate and product were observed via a specifically designed tryptophan sensor, suitable for further detailed kinetic and ligand binding studies. Results explain the key functional role of the C-terminus. 相似文献
47.
Dyguda-Kazimierowicz E Sokalski WA Leszczyński J 《Journal of molecular modeling》2007,13(6-7):839-849
The subject of this study was an analysis of the role of active site residues in the phosphoryl transfer reaction catalyzed
by 4-methyl-5-β-hydroxyethylthiazole kinase (ThiK). The ThiK-catalyzed reaction is of special interest due to the lack of
a highly conserved aspartate residue serving as a catalytic base. ONIOM(B3LYP:PM3) models of stationary points along the reaction
pathway consisted of reactants, two magnesium ions and several highly conserved ThiK active site residues. The results indicate
that an SN2-like mechanism of ThiK, with γ-phosphate acting as an alcohol-activating base is reasonable. Geometries of substrates, transition
state and products were utilized in the non-empirical analysis of the physical nature of catalytic interactions taking place
in the ThiK active site. The role of particular residues was investigated in terms of their ability to preferentially stabilize
the transition state relative to substrates (differential transition state stabilization, DTSS) or products (differential
product stabilization, DPS). It seems that Mg2, Glu126 and Cys198 play a major catalytic role, whereas Mg1 and the same Cys198
are responsible for product release. It is remarkable that no dominant role of an electrostatic term in the interactions involved
in catalytic activity is observed for product release. Determination of catalytic fields expressing differential electrostatic
potential of the transition state with respect to substrates revealed the optimal electrostatic features of an ideal catalyst
for the studied reaction. The predicted catalytic environment is in agreement with experimental data showing increased catalytic
activity of ThiK upon mutation of Cys198 to aspartate.
Figure Catalytic fields for ThiK-catalyzed reaction juxtaposed with the positions of active site residues of a model system. Magnesium
ions are considered part of the transition state/reactants. The surface of constant electronic density is colored according
to differential electrostatic potential of transition state with respect to reactants. The sign of the differential potential
reflects the electrostatic properties of a complementary molecular environment. Red (green) color denotes regions where a negative (positive) charge would be optimal for catalytic activity 相似文献
48.
Chirality plays a pivotal role in an uncountable number of biological processes, and nature has developed intriguing mechanisms to maintain this state of enantiopurity. The strive for a deeper understanding of the different elements that constitute such self‐sustaining systems on a molecular level has sparked great interest in the studies of autoinductive and amplifying enantioselective reactions. The design of these reactions remains highly challenging; however, the development of generally applicable principles promises to have a considerable impact on research of catalyst design and other adjacent fields in the future. Here, we report the realization of an autoinductive, enantioselective self‐inhibiting hydrogenation reaction. Development of a stereodynamic catalyst with chiral sensing abilities allowed for a chiral reaction product to interact with the catalyst and change its selectivity in order to suppress its formation, which caused a reversal of selectivity over time. 相似文献
49.
Shoichiro Horita Michihiko Kataoka Nahoko Kitamura Takuya Miyakawa Jun Ohtsuka Yuko Maejima 《Bioscience, biotechnology, and biochemistry》2019,83(3):456-462
Old yellow enzymes (OYEs) are potential targets of protein engineering for useful biocatalysts because of their excellent asymmetric reductions of enone compounds. Two OYEs from different yeast strains, Candida macedoniensis AKU4588 OYE (CmOYE) and Pichia sp. AKU4542 OYE (PsOYE), have a sequence identity of 46%, but show different substrate preferences; PsOYE shows 3.4-fold and 39-fold higher catalytic activities than CmOYE toward ketoisophorone and (4S)-phorenol, respectively. To gain insights into structural basis of their different substrate preferences, we have solved a crystal structure of PsOYE, and compared its catalytic site structure with that of CmOYE, revealing the catalytic pocket of PsOYE is wider than that of CmOYE due to different positions of Phe246 (PsOYE)/Phe250 (CmOYE) in static Loop 5. This study shows a significance of 3D structural information to explain the different substrate preferences of yeast OYEs which cannot be understood from their amino acid sequences.
Abbreviations: OYE: Old yellow enzymes, CmOYE: Candida macedoniensis AKU4588 OYE, PsOYE: Pichia sp. AKU4542 OYE 相似文献
50.
Arianna?BassanEmail author Margareta?R.?A.?Blomberg Per?E.?M.?Siegbahn 《Journal of biological inorganic chemistry》2004,9(4):439-452
The catalytic mechanism of naphthalene 1,2-dioxygenase has been investigated by means of hybrid density functional theory. This Rieske-type enzyme, which contains an active site hosting a mononuclear non-heme iron(II) complex, uses dioxygen and two electrons provided by NADH to carry out the cis-dihydroxylation of naphthalene. Since a (hydro)peroxo-iron(III) moiety has been proposed to be involved in the catalytic cycle, it was probed whether and how this species is capable of cis-dihydroxylation of the aromatic substrate. Different oxidation and protonation states of the Fe–O2 complex were studied on the basis of the crystal structure of the enzyme with oxygen bound side-on to iron. It was found that feasible reaction pathways require a protonated peroxo ligand, FeIII–OOH; the deprotonated species, the peroxo-iron(III) complex, was found to be inert toward naphthalene. Among the different chemical patterns which have been explored, the most accessible one involves an epoxide intermediate, which may subsequently evolve toward an arene cation, and finally to the cis-diol. The possibility that an iron(V)-oxo species is formed prior to substrate hydroxylation was also examined, but found to implicate a rather high energy barrier. In contrast, a reasonably low barrier might lead to a high-valent iron-oxo species [i.e. iron(IV)-oxo] if a second external electron is supplied to the mononuclear iron center before dioxygenation.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00775-004-0537-0 相似文献