Genome-wide high-throughput mining of natural-product biosynthetic gene clusters by phage display

We have developed a phage-display method for high-throughput mining of bacterial gene clusters encoding the natural-product biosynthetic enzymes, polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs). This method uses the phosphopantetheinyl transferase activity of Sfp to specifically biotinylate NRPS and PKS carrier-protein domains expressed from a library of random genome fragments fused to a gene encoding a phage coat protein. Subsequently, the biotinylated phages are enriched through selection on streptavidin-coated plates. Using this method, we isolated phage clones from the multiple NRPS and PKS gene clusters encoded in the genomes of Bacillus subtilis and Myxococcus xanthus. Due to the rapid and unambiguous identification of carrier domains, this method will provide an efficient tool for high-throughput cloning of NRPS and PKS gene clusters from many individual bacterial genomes and multigenome environmental DNA.     

Rare configuration of tautomeric benzimidazolecarboxylate ligands in cadmium(II) and copper(II) coordination polymers

Two Cd(HBimc)-based isomers, [Cd(HBimc^N)(HBimc^T)(H₂O)]·3.5H₂O·EtOH (1a·3.5H₂O·EtOH, H₂Bimc=1H-benzimidazole-5-carboxylic acid) and [Cd(HBimc^N)(HBimc^T)(H₂O)] (1b), and two Cu(HMBimc)-based coordination polymers, [Cu(HMBimc^N)₂(H₂O)]·1/2H₂O (2·1/2H₂O, H₂MBimc=2-methyl-1H-benzimidazole-5-carboxylic acid) and [Cu(HMBimc^T)₂]·2THF·H₂O (3·2THF·H₂O), were self-assembled from Cd(ClO₄)₂·6H₂O/H₂Bimc and Cu(ClO₄)₂·6H₂O/H₂MBimc systems, respectively. Compound 1a adopts a ladder-like chain structure, comprised of a hydrogen-bond-stabilized Cd₂(HBimc^N)₂-metallocyclic stair and a 1D straight -(Cd-HBimc^T)_n- edge, whereas compound 1b exhibits a 2D (4,4)-rhombus layered structure, intercrossed by 1D -(Cd-HBimc^N)_n- chains and -(Cd-HBimc^T)_n- chains. Compound 2 shows a 1D double-stranded wave-like chain from two single-stranded wave-like -(Cu-HMBimc^N)_n- chains and compound 3 adopts a 2D (4,4)-topological layer structure, intercrossed by subunits of 1D -(Cu-HMBimc^T)_n- chains. Interestingly, a pair of tautomeric HBimc building blocks—normal (N or HBimc^N) and tautomer (T or HBimc^T)—is simultaneously included in the structures of 1a and 1b, whilst the N- and T-configured HMBimc building blocks are present as separate entities in Cu species, 2 and 3, respectively. The existence of only a tautomer (T) mode of the benzimidazolecarboxylate-based ligand in a Cu(II) network is observed for the first time.     

Adsoption an Quecksilberober-fl?chen. II. Octadecan, Octadecylalkohol, Octadecylamin und Stearims?ure aus L?sung in Cyclihexan

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Vapour Phase Hydrogenation of Cinnamaldehyde over Nano Ni and Ni/SiMCM‐41 Catalysts

Ni nanoparticles (Ni(1) and Ni(2)) and Ni loaded SiMCM‐41 (15Ni/SiMCM‐41) were prepared and characterized with XRD, TEM, N₂ adsorption, CO chemisorption, and H₂‐TPR. The Ni specific surface area followed the order of 15Ni/SiMCM‐41 > Ni(1) >> Ni(2), whereas the Ni particle size exhibited the opposite trend. These catalysts were utilized for vapour phase hydrogenation of cinnamaldehyde at 1 atm and 200 °C in a fixed‐bed, down flow reactor. The main products include hydrocinnamaldehyde, styrene, ethylbenzene, and 2‐phenyl‐1‐propanol. The catalytic activity decreased in the same order as that of Ni specific surface areas. The SiMCM‐41 support possessed very large surface area, leading to enhanced dispersion and specific surface area of Ni nanoparticles. As a result, the 15Ni/SiMCM‐41 catalyst exhibited the highest activity. Based on the investigation of reaction pathways, it is important to emphasize that both hydrogenation and hydroelimination of formaldehyde (hydrodeformylation) occur in the vapour phase reaction.     

Applications of gas chromatography and gamma spectrometry to fission gas measurements

A gas sampler with lead shield has been designed for transferring the grab gas sample taken from the sampling station of Taiwan nuclear power reactor. The methods involving gas chromatography and gamma spectrometry have been developed for the determination of fission gases. A gas chromatograph equipped with TCD was used for measurement of gas composition. Column requirements are identified and optimum operating conditions are discussed. A single analysis is completed within 25 minutes for all of the gas constitutents and 12 minutes for only Xe and Kr. The detection limit is 0.005 mm partial pressure for Kr and Xe and a precision of ±1% relative is achieved for all the sample constituents. Combined error determinations for the method denote an attainable accuracy of less than ±2% for constituents at a sample pressure above 10 mm. Mixing and dispensing of the radioactive gases were carried out in a special gas mixing line. In experiment, calibration factors for measurement of¹³³Xe and⁸⁵Kr in ampules are determined in an isotope calibrator and by Ge(Li) gamma ray spectrometry. The relative precisions of 0.14% and 0.5% are readily achieved for⁸⁵Kr and¹³³Xe, respectively. The calibration uncertainty in⁸⁵Kr measurement is 0.4%.     

Synthesis and characterization of nonaqueous dispersion particles with photolabile α‐heptadecylphenacyl ester stabilizer chains

We describe a new method for the synthesis of core–shell photolabile nanoparticles. The synthesis begins with the batch emulsion copolymerization of n‐butyl methacrylate (BMA) and ethylene glycol dimethacrylate to form small (20‐nm‐diameter) crosslinked particles with a narrow size distribution. These seeds are then used for a second‐stage emulsion copolymerizations in which BMA and various polar monomers, including methacrylic acid, are added under monomer‐starved conditions. After characterization of the particles, they are transferred to an N,N‐dimethylformamide solution. The cesium salt of the carboxylic acid groups is reacted with 2‐bromo‐1‐phenyl‐octadecan‐1‐one to convert various fractions of the ? COOH groups to the corresponding 2‐benzoylheptadecyl ester groups. These aliphatic ester groups render the surface sufficiently hydrophobic that the particles can be dispersed in common aliphatic hydrocarbons solvents to yield colloidal dispersions, sterically stabilized by the dangling aliphatic chains. Ester groups with a phenyl ketone attached to the β‐carbon are photolabile. Irradiation of the particles with UV light detaches the sterically stabilizing chains from the particle and transforms the surface groups back to COOH groups. This leads to flocculation of the particles. The emphasis in this article is on the optimization of the particle synthesis and the characterization of the particles obtained. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2642–2657, 2001     

Effect of immobilization of polysaccharides on the biocompatibility of poly(butyleneadipate‐co‐terephthalate) films

Aiming to improve the hydrophilicity, antibacterial activity, cytocompatibility, and hemocompatibility of poly(butyleneadipate‐co‐terephthalate) (PBAT) films, PBAT films were treated with ozone, grafted with chitosan (CS), and followed by covalent immobilization of either heparin (HEP) or hyaluronic acid (HA). The surface graft density of modified PBAT films was detected by X‐ray photoelectron spectroscopy (XPS) and dyeing. The surface roughness of PBAT films was measured using an atomic force microscope (AFM). After immobilizing CS, PBAT films acquired antibacterial activity against Staphylococcus aureus and Escherichia coli. The adsorption of human serum albumin (HSA) and human plasma fibrinogen (HPF) on PBAT–CS–HEP and PBAT–CS–HA films was lower compared to that of native PBAT. Moreover, HEP immobilization could effectively reduce platelet adhesion and prolong the blood coagulation time, thereby improving the blood compatibility of PBAT. In addition, the growth of L929 fibroblasts was improved for HEP or HA immobilized PBAT, suggesting this surface modification was non‐cytotoxic. Furthermore, PBAT–CS–HEP and PBAT–CS–HA exhibited higher cell proliferation than native PBAT. Copyright © 2009 John Wiley & Sons, Ltd.     

Distribution of functional groups grafted onto an ethylene-propylene copolymer

A theoretical model, based on the binomial (Bernoullian) distribution function, was employed for the prediction of functional group distribution in an ethylene-propylene copolymer randomly grafted by maleic anhydride. Using the experimentally determined graft level and molecular weight distribution function, the fraction of polymer molecules with given number of functional groups was calculated. The result was checked experimentally by a fluorescence method based on the excimer formation of pyrene fluorophores attached to the anhydride pendants. The time-resolved fluorescence from the pyrene-labeled copolymer yielded the fraction of polymer molecules with a single functional group. The fraction of singly labeled molecules was compared to the calculated functional group distribution and a reasonable agreement was found between the two. The distribution of grafted maleic anhydride was found to be apparently random among polymer molecules. The distribution of distances was calculated between randomly attached consecutive functional groups along the polymer backbone also. The result indicated that the distance distribution function (similar to a decaying exponential) is dominated by short distances. © 1996 John Wiley & Sons, Inc.