Metabolic engineering of aminocoumarins: inactivation of the methyltransferase gene cloP and generation of new clorobiocin derivatives in a heterologous host

Aminocoumarin antibiotics are highly potent inhibitors of bacterial gyrase and represent a class of antibiotics that are very suitable for the generation of new compounds by metabolic engineering. In this study, the putative methyltransferase gene cloP in the biosynthetic gene cluster of clorobiocin was inactivated. Expression of the modified gene cluster in the heterologous host Streptomyces coelicolor M512 gave three new aminocoumarin antibiotics. The structures of the new compounds were elucidated by MS and 1H NMR, and their antibacterial activities were determined. All three compounds lacked clorobiocin's methyl group at 4-OH of the deoxysugar moiety, noviose. They differed from each other in the position of the 5-methylpyrrole-2-carbonyl group, which was found to be attached to either 2-OH, 3-OH or 4-OH of noviose. Attachment at 4-OH resulted in the highest antibacterial activity. This is the first time that an aminocoumarin antibiotic acylated at 4-OH in noviose has been detected.     

Identification of Novel Genes Involved in Hyperglycemia in Mice

Current attempts to prevent and manage type 2 diabetes have been moderately effective, and a better understanding of the molecular roots of this complex disease is important to develop more successful and precise treatment options. Recently, we initiated the collective diabetes cross, where four mouse inbred strains differing in their diabetes susceptibility were crossed with the obese and diabetes-prone NZO strain and identified the quantitative trait loci (QTL) Nidd13/NZO, a genomic region on chromosome 13 that correlates with hyperglycemia in NZO allele carriers compared to B6 controls. Subsequent analysis of the critical region, harboring 644 genes, included expression studies in pancreatic islets of congenic Nidd13/NZO mice, integration of single-cell data from parental NZO and B6 islets as well as haplotype analysis. Finally, of the five genes (Acot12, S100z, Ankrd55, Rnf180, and Iqgap2) within the polymorphic haplotype block that are differently expressed in islets of B6 compared to NZO mice, we identified the calcium-binding protein S100z gene to affect islet cell proliferation as well as apoptosis when overexpressed in MIN6 cells. In summary, we define S100z as the most striking gene to be causal for the diabetes QTL Nidd13/NZO by affecting β-cell proliferation and apoptosis. Thus, S100z is an entirely novel diabetes gene regulating islet cell function.     

Protein adsorption kinetics in charged agarose gels: Effect of agarose content and modeling

The adsorption kinetics of myoglobin in charged gels of varying agarose content have been measured macroscopically, through batch uptake experiments, and microscopically, using light microscopy with gels supported in microfluidics chips. The apparent effective pore diffusivities, determined by fitting either set of rate data to the shrinking core model, were greater than the free solution diffusivity and concentration‐dependent. Moreover, the microscopically derived concentration profiles were qualitatively different from the predicted ones. Therefore, a new model taking into account an assumed favorable partitioning of the protein in the pore liquid is proposed to describe the adsorption kinetics. The new model yields effective pore diffusivities that are in approximate agreement with the values determined chromatographically under nonbinding conditions and with hindered diffusion theory. In addition, it predicts concentration profiles in the gel that are consistent with those observed microscopically. The overall increase in mass transfer is attributed to the favorable partitioning of the protein in the pores at low ionic strength, which results in a greater diffusional driving force. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

Catalytic porous ceramic prepared in‐situ by sol‐gelation for butane‐to‐syngas processing in microreactors

In this study, a novel flow‐based method is presented to place catalytic nanoparticles into a reactor by sol‐gelation of a porous ceramic consisting of Rh/ceria/zirconia nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam‐like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior. To investigate the catalytic activity, microreactors containing this foam‐like ceramic are employed for the production of hydrogen and carbon monoxide‐rich syngas from butane. The effect of operating parameters such as the inlet flow rate on the hydrocarbon processing is analyzed and the limitation of the reactor by diffusion mass transport is investigated. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Maximierung der Samenerträge und wertgebenden Inhaltsstoffe von Fenchel (Foeniculum vulgare M.) I

Maximizing the Yield of Seeds and the Yield of Petroselinic Acid and Essential Oils of Fennel (Foeniculum vulgare M.) I It was the object of this trials to maximize the yield of seeds and the yield of petroselinic acid and essential oils of fennel with a comparison of cultivation and freely sowen seeds, with optimum amount of nitrogen and adapted harvest times in dependence of different ecological conditions. Fennel was investigated in 1990 and 1991 at 2 locations in Durmersheim (Rheintal) and Ensmad (Schwäbische Alb) with an average temperature of 9.8°C and 6.9°C over many years. With cultivation instead of freely sowen seed, fennel obtained in Durmersheim the highest seed yields in both years. The highest yields of petroselinic acid and essential oils were achieved with both, cultivation and freely sowen variants. In Ensmad only the cultivation-variants developed harvestable seeds. With an increase of N-application fennel attained a higher seed yield. The N-application induced a higher yield of petroselinic acid and of essential oils, too. During the maturity of the fennel fruits the seed yield and the yield of petroselinic acid and of essential oils decreased.     

Heterocyclen aus o-Aminoketonen. XXIII [1]. Umsetzung von o-Aminoketonen mit Dicarbonsäuren

Heterocyclic Compounds from 2-Aminoketones. XXIII. Reaction of o-Aminoketones with Dicarboxylic Acids Saturated aliphatic dicarboxylic acids (C₄ C₇ and C₁₀) react with 2-aminobenzophenones in polyphosphoric acid (PPA) to form substituted derivatives of partial hydrogenated benzo[b][1,8]naphthyridines 2a–d and 2-anilino-quinoline-3-alkanoic-acids 5a–h . The heterologous derivatives of glutaric acid — containing S or N instead of β-CH₂ — with aminoketon undergo ring closure to give thiazino- and oxazino[3,2-b]quinolines 2e–h . Aromatic o-dicarboxylic acids with a –CH₂ CO- group react with aminoketones to yield anilinosubstituted 5i or pyrano[b]-condensed quinolines 6 . N,N′-Di-(2-benzoylphenyl)-dicarboxylicacid-diamides 3 with ammonia undergo cyclisation to α,ω-di-(4′phenyl-quinazolinyl-(2′))-alkanes 4 .     

Near-infrared absorbing acidochromic nonsymmetric Trimethinium Dyes containing acridinium and pyrylium end groups

A series of new acidochromic dyes absorbing in the NIR spectral region (up to 900 nm) has been synthesized with a systematic variation of the underlying nonsymmetric pyrylium trimethinium acridine structure. The dyes exhibit pK_a-values between 5.7 and 6.7. Semiempirical MO-calculations were performed to elucidate the essentials of the chromophores.