Triazolium-containing metal-organic frameworks: Control of catenation in 2-D Copper(II) paddlewheel structures

Paper accepted for publication 6th November 2012One approach to exploit MOFs as heterogeneous catalyst platforms requires the development of materials containing groups that can be utilised to anchor a catalytic moiety into the links within the structure. Here we report the synthesis of the first integrated triazolium-containing MOF linker and the first MOFs containing linkers of this type. 1,4-Bis(4-benzoic acid)-1-methyl-1H-1,2,3-triazolium chloride, H₂L1ᴹᵉ, was synthesised in three steps by a 'Click' reaction of methyl 4-ethynylbenzoate with methyl 4-azidobenzoate, methylation using methyl triflate, followed by ester hydrolysis in overall 74% yield. The equivalent neutral triazole precursor, 1,4-bis(4-benzoic acid)-1H-1,2,3-triazole hydrochloride, H₂L1(HCl), was also prepared and a comparison of the chemistry with Zn(NO₃)2·6H₂O and Cu(NO₃)₂·3H₂O is presented. [Zn(L1)₂(H₂O)₂] is a 2-D MOF with infinite chains of zinc carboxylates bridged by L1, while an equivalent structure is not observed for L1ᴹᵉ. In turn, two catenation isomers of [Cu₂(DMF)2(L1ᴹᵉ)2](NO3)₂ were isolated from a single reaction of L1ᴹᵉ and Cu(NO₃)₂·3H₂O. The α-form, a close-packed 3-fold interpenetrated structure, was obtained from reactions undertaken in the presence of nitric acid or at lower temperatures, while undertaking the reaction at higher temperatures leads to a predominance of the 2-fold interpenetrated and potentially porous β-form of the structure. The work presented provides further support for the use of reaction conditions to control interpenetration and additional evidence that charge on structurally similar ligands can drastically alter the types of structures that are accessible due to the requirements for charge balance in the final product.Alexandre M. Burgun, Christian J. Doonan, and Christopher J. Sumb

A new and updated resource for codon usage tables

Abstract Background Due to the degeneracy of the genetic code, most amino acids can be encoded by multiple synonymous codons. Synonymous codons naturally occur with different frequencies in different organisms. The choice of codons may affect protein expression, structure, and function. Recombinant gene technologies commonly take advantage of the former effect by implementing a technique termed codon optimization, in which codons are replaced with synonymous ones in order to increase protein expression. This technique relies on the accurate knowledge of codon usage frequencies. Accurately quantifying codon usage bias for different organisms is useful not only for codon optimization, but also for evolutionary and translation studies: phylogenetic relations of organisms, and host-pathogen co-evolution relationships, may be explored through their codon usage similarities. Furthermore, codon usage has been shown to affect protein structure and function through interfering with translation kinetics, and cotranslational protein folding. Results Despite the obvious need for accurate codon usage tables, currently available resources are either limited in scope, encompassing only organisms from specific domains of life, or greatly outdated. Taking advantage of the exponential growth of GenBank and the creation of NCBI’s RefSeq database, we have developed a new database, the High-performance Integrated Virtual Environment-Codon Usage Tables (HIVE-CUTs), to present and analyse codon usage tables for every organism with publicly available sequencing data. Compared to existing databases, this new database is more comprehensive, addresses concerns that limited the accuracy of earlier databases, and provides several new functionalities, such as the ability to view and compare codon usage between individual organisms and across taxonomical clades, through graphical representation or through commonly used indices. In addition, it is being routinely updated to keep up with the continuous flow of new data in GenBank and RefSeq. Conclusion Given the impact of codon usage bias on recombinant gene technologies, this database will facilitate effective development and review of recombinant drug products and will be instrumental in a wide area of biological research. The database is available at hive.biochemistry.gwu.edu/review/codon

An der grünen Mur : für Männerchor mit Clavierbegleitung : op. 37

componiert von Franz Blümel ; Worte von Hans VischerErscheinungsjahr aus dem Inventarisierungsjahr der UB Graz ermittelt(VLID)220966

Diffractive Dijet Production with a Leading Proton in ep Collisions at HERA

The cross section of the diffractive process e^+p -> e^+Xp is measured at a centre-of-mass energy of 318 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities Q^2 <2 GeV^2 and in deep-inelastic scattering with 4 GeV^2<Q^2<80 GeV^2. The results are compared to next-to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering

Measurement of Dijet Production in Diffractive Deep-Inelastic ep Scattering at HERA

A measurement is presented of single- and double-differential dijet cross sections in diffractive deep-inelastic $ep$ scattering at HERA using data collected by the H1 experiment corresponding to an integrated luminosity of 290 pb^{-1}. The investigated phase space is spanned by the photon virtuality in the range of 4<Q^{2}<100 GeV^{2} and by the fractional proton longitudinal momentum loss x_pom<0.03. The resulting cross sections are compared with next-to-leading order QCD predictions based on diffractive parton distribution functions and the value of the strong coupling constant is extracted