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Iron(II) cage complexes with terminal 4-pyridyl groups can be incorporated in metal-organic frameworks (MOFs) via solvent-assisted ligand exchange (SALE). Paddle -wheeled MOFs with N,N'-di-4-pyridylnaphthalenete-tracarboxydiimide pillars were used as starting materials. Pillar exchange was nearly quantitative, despite the fact that the cage complexes are long (similar to 15 angstrom) and sterically demanding. The reactions provide products of high crystallinity, and the structures of daughter MOFs were determined by single crystal X-ray diffraction. The crystallographic analyses showed that some of the SALE experiments led to topological changes of the MOF structures.

to the editor: With great interest we have read the article by Wang and colleagues recently published in this journal ([26][1]). Wang et al. describe a method to assess glucose production rates in rodents from the kinetics of an IP injected glucose tracer, i.e. , U-13C-glucose. The authors compared

This work was supported by The Scientific and Technological Research Council of Turkey TUBITAK under the contract No. 214M397. For work at Northwestern, J. T. H. and O. K. F. and gratefully acknowledge support from the Dept. of Energy, Office of Science, Basic Energy Science through grant DE-FG02-08ER155967. Bridging ligand replacement in zeolitic imidazolate frameworks, ZIF-8 and ZIF-67, by 1,2,3-triazole was investigated. A complete substitution of 2-methylimidazole by 1,2,3-triazole resulted in a topological transformation of the parent framework from a sodalite (SOD) network to a diamond (DIA) network. Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) 214M397 Dept. of Energy, Office of Science, Basic Energy Science DE-FG02-08ER155967

Mitochondrial fatty acid oxidation (mFAO) is considered to be essential for driving gluconeogenesis (GNG) during fasting. However, quantitative in vivo data on de novo synthesis of glucose-6-phosphate upon acute inhibition of mFAO are lacking. We assessed hepatic glucose metabolism in vivo after acute inhibition of mFAO by 30 mg kg(-1) 2-tetradecylglycidic acid (TDGA) in hypoketotic hypoglycemic male C57BL/6J mice by the infusion of [U-C-13]glucose, [2-C-13]glycerol, [1-H-2] galactose, and paracetamol for 6 hours, which was followed by mass isotopomer distribution analysis in blood glucose and urinary paracetamol-glucuronide. During TDGA treatment, endogenous glucose production was unaffected (127 +/- 10 versus 118 +/- 7 mu mol kg(-1) minute(-1), control versus TDGA, not significant), but the metabolic clearance rate of glucose was significantly enhanced (15.9 +/- 0.9 versus 26.3 +/- 1.1 mL kg(-1) minute(-1), control versus TDGA, P

Nucleotide sugar transport across Golgi membranes is essential for the luminal biosynthesis of glycan structures. Here we identify GDP-fucose transporter 1 (GFT1), an Arabidopsis nucleotide sugar transporter that translocates GDP-L-fucose into the Golgi lumen. Using proteo-liposome-based transport assays, we show that GFT preferentially transports GDP-L-fucose over other nucleotide sugars in vitro, while GFT1-silenced plants are almost devoid of L-fucose in cell wall-derived xyloglucan and rhamnogalacturonan II. Furthermore, these lines display reduced L-fucose content in N-glycan structures accompanied by severe developmental growth defects. We conclude that GFT1 is the major nucleotide sugar transporter for import of GDP-L-fucose into the Golgi and is required for proper plant growth and development., Nucleotide sugars are transported from the cytoplasm to the Golgi lumen where they are incorporated into cell wall polysaccharides and used for glycosylation of proteins and lipids. Here the authors identify GFT1, an Arabidopsis Golgi-localized GDP-fucose transporter that is required for plant growth and development

Viral RNA-dependent RNA polymerases (RdRps) responsible for the replication of single-strand RNA virus genomes exert their function in the context of complex replication machineries. Within these replication complexes the polymerase activity is often highly regulated by RNA elements, proteins or other domains of multi-domain polymerases. Here, we present data of the influence of the methyltransferase domain (NS5-MTase) of dengue virus (DENV) protein NS5 on the RdRp activity of the polymerase domain (NS5-Pol). The steady-state polymerase activities of DENV-2 recombinant NS5 and NS5-Pol are compared using different biochemical assays allowing the dissection of the de novo initiation, transition and elongation steps of RNA synthesis. We show that NS5-MTase ensures efficient RdRp activity by stimulating the de novo initiation and the elongation phase. This stimulation is related to a higher affinity of NS5 toward the single-strand RNA template indicating NS5-MTase either completes a high-affinity RNA binding site and/or promotes the correct formation of the template tunnel. Furthermore, the NS5-MTase increases the affinity of the priming nucleotide ATP upon de novo initiation and causes a higher catalytic efficiency of the polymerase upon elongation. The complex stimulation pattern is discussed under the perspective that NS5 adopts several conformations during RNA synthesis.

Total synthesis of the bacillosamine containing L-serine linked O-trisaccharide of Neisseria meningitidis is described. The synthesis entails installation of two consecutive alpha-linkages including the coupling of bacillosamine with L-serine derivative. (C) 2014 Elsevier Ltd. All rights reserved.

International audience; Glutamine amidotransferase/aminodeoxychorismate synthase (GAT-ADCS) is a bifunctional enzyme involved in the synthesis of p-aminobenzoate, a central component part of folate cofactors. GAT-ADCS is found in eukaryotic organisms autonomous for folate biosynthesis, such as plants or parasites of the phylum Apicomplexa. Based on an automated screening to search for new inhibitors of folate biosynthesis, we found that rubreserine was able to inhibit the glutamine amidotransferase activity of the plant GAT-ADCS with an apparent IC(50) of about 8 μm. The growth rates of Arabidopsis thaliana, Toxoplasma gondii, and Plasmodium falciparum were inhibited by rubreserine with respective IC(50) values of 65, 20, and 1 μm. The correlation between folate biosynthesis and growth inhibition was studied with Arabidopsis and Toxoplasma. In both organisms, the folate content was decreased by 40-50% in the presence of rubreserine. In both organisms, the addition of p-aminobenzoate or 5-formyltetrahydrofolate in the external medium restored the growth for inhibitor concentrations up to the IC(50) value, indicating that, within this range of concentrations, rubreserine was specific for folate biosynthesis. Rubreserine appeared to be more efficient than sulfonamides, antifolate drugs known to inhibit the invasion and proliferation of T. gondii in human fibroblasts. Altogether, these results validate the use of the bifunctional GAT-ADCS as an efficient drug target in eukaryotic cells and indicate that the chemical structure of rubreserine presents interesting anti-parasitic (toxoplasmosis, malaria) potential.

SUMMARYThe biological membranes ofTrypanosoma bruceicontain a complex array of phospholipids that are synthesizedde novofrom precursors obtained either directly from the host, or as catabolised endocytosed lipids. This paper describes the use of nanoflow electrospray tandem mass spectrometry and high resolution mass spectrometry in both positive and negative ion modes, allowing the identification of ~500 individual molecular phospholipids species from total lipid extracts of cultured bloodstream and procyclic formT. brucei. Various molecular species of all of the major subclasses of glycerophospholipids were identified including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol as well as phosphatidic acid, phosphatidylglycerol and cardolipin, and the sphingolipids sphingomyelin, inositol phosphoceramide and ethanolamine phosphoceramide. The lipidomic data obtained in this study will aid future biochemical phenotyping of either genetically or chemically manipulated commonly used bloodstream and procyclic strains ofTrypanosoma brucei. Hopefully this will allow a greater understanding of the bizarre world of lipids in this important human pathogen.

Sphingomyelin is the main sphingolipid in Trypanosoma brucei, the causative agent of African sleeping sickness. In vitro and in vivo characterization of the T. brucei neutral sphingomyelinase demonstrates that it is directly involved in sphingomyelin catabolism. Gene knockout studies in the bloodstream form of the parasite indicate that the neutral sphingomyelinase is essential for growth and survival, thus highlighting that the de novo biosynthesis of ceramide is unable to compensate for the loss of sphingomyelin catabolism. The phenotype of the conditional knockout has given new insights into the highly active endocytic and exocytic pathways in the bloodstream form of T. brucei. Hence, the formation of ceramide in the endoplasmic reticulum affects post-Golgi sorting and rate of deposition of newly synthesized GPI-anchored variant surface glycoprotein on the cell surface. This directly influences the corresponding rate of endocytosis, via the recycling endosomes, of pre-existing cell surface variant surface glycoprotein. The trypanosomes use this coupled endocytic and exocytic mechanism to maintain the cell density of its crucial variant surface glycoprotein protective coat. TbnSMase is therefore genetically validated as a drug target against African trypanosomes, and suggests that interfering with the endocytic transport of variant surface glycoprotein is a highly desirable strategy for drug development against African trypanosomasis. Publisher PDF

Besides its well established role in control of cellular cholesterol homeostasis, the liver X receptor (LXR) has been implicated in the regulation of hepatic gluconeogenesis. We investigated the role of the major hepatic LXR isoform in hepatic glucose metabolism during the feeding-to-fasting transition in vivo. In addition, we explored hepatic glucose sensing by LXR during carbohydrate refeeding. Lxr alpha(-/-) mice and their wild-type littermates were subjected to a fasting-refeeding protocol and hepatic carbohydrate fluxes as well as whole body insulin sensitivity were determined in vivo by stable isotope procedures. Lxr alpha(-/-) mice showed an impaired response to fasting in terms of hepatic glycogen depletion and triglyceride accumulation. Hepatic glucose 6-phosphate turnover was reduced in 9-h fasted Lxr alpha(-/-) mice as compared with controls. Although hepatic gluconeogenic gene expression was increased in 9-h fasted Lxr alpha(-/-) mice compared with wild-type controls, the actual gluconeogenic flux was not affected by Lxr alpha deficiency. Hepatic and peripheral insulin sensitivity were similar in Lxr alpha(-/-) and wildtype mice. Compared with wild-type controls, the induction of hepatic lipogenic gene expression was blunted in carbohydrate-refed Lxr alpha(-/-) mice, which was associated with lower plasma triglyceride concentrations. Yet, expression of "classic" LXR target genes Abca1, Abcg5, and Abcg8 was not affected by Lxr alpha deficiency in carbohydrate-refed mice. In summary, these studies identify LXR alpha as a physiologically relevant mediator of the hepatic response to fasting. However, the data do not support a role for LXR in hepatic glucose sensing.

Bacteria have unusual glycans which are not accessible by isolation. Herein, we describe a general and divergent strategy for the synthesis of the rare, bacterial deoxy amino hexopyranoside building blocks from d-mannose. The methodology is applied to the first total synthesis of the l-serine linked trisaccharide of Neisseria meningitidis.

Summary The effect of silymarin, an antihepatotoxic compound extracted from Silybum Marianum , upon phospholipid metabolism of liver and brain microsomal membranes has been investigated by examining in vitro the de novo synthesis and breakdown of lecithin and phosphatidylethanolamine, and the base-exchange system between serine (ethanolamine) and endogenous membrane phospholipids. Silymarin inhibits to a considerable extent the synthesis and breakdown of the two lipids. Pre-incubation of the membranes with the drug is a prerequisite for the inhibitory effect. Silymarin inhibits also the base-exchange enzymic reaction in liver and brain at 1.0 – 0.1 mM concentration, both in pre-incubation and non pre-incubation experiments. Suggestion is made that the drug might exert stabilizing effects at the membrane level, by virtue of its action upon membrane-bound enzymic activities.

The visible-light-driven rotation of an overcrowded alkene-based molecular motor strut in a dual-function metal-organic framework (MOF) is reported. Two types of functional linkers, a palladium-porphyrin photosensitizer and a bispyridine-derived molecular motor, were used to construct the framework capable of harvesting low-energy green light to power the rotary motion. The molecular motor was introduced in the framework using the postsynthetic solvent-assisted linker exchange (SALE) method, and the structure of the material was confirmed by powder (PXRD) and single-crystal X-ray (SC-XRD) diffraction. The large decrease in the phosphorescence lifetime and intensity of the porphyrin in the MOFs upon introduction of the molecular motor pillars confirms efficient triplet-to-triplet energy transfer between the porphyrin linkers and the molecular motor. Near-infrared Raman spectroscopy revealed that the visible light-driven rotation of the molecular motor proceeds in the solid state at rates similar to those observed in solution.