Synthesis and Characterization of Benzonitrile-Substituted Silyl Ethers

The silyl ethers (siloxanes) Me_{4? x}Si(OC₆H₅CN)_x (x = 1–4) (1–4), O(Si(OC₆H₄CN) (Me)₂)₂ (5), and Me₃Si–O–C₆F₄CN (6) have been synthesized by the reaction of the respective p-hydroxybenzonitriles and chlorosilanes in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) as hydrogen chloride acceptor. All compounds have been fully characterized by CHN-analysis, melting point, IR, Raman, mass spectroscopy, and ¹H, ¹³C, ²⁹Si NMR spectroscopy. Furthermore, the crystal structures of these compounds—with the exception of Me₂Si(OC₆H₅CN)₂, which is a liquid—were determined by X-ray diffractometry.     

Complexes of 4- and 5-bromo derivatives of 2-(hydroxymethyl)pyridine with copper(II) and cobalt(II) salts. Synthesis and X-ray crystal structures

Four copper(II) complexes (1–4) and a cobalt(II) complex (5) derived from 4-bromo-2-(hydroxymethyl)pyridine (L¹) or 5-bromo-2-hydroxymethyl)pyridine (L²) with Cu(NO₃)₂·3H₂O, CuCl₂·2H₂O and CoCl₂·6H₂O have been synthesized and their respective crystal structures studied. They show specific influences owing to the different kind of metal cations and counter anions, the hydration as well as the different position of the bromine substitution on both the coordination of the complex unit and the network structure of the crystal lattice. The Cu(II) complexes of L¹ are five-coordinate [Cu(L¹)₂NO₃]NO₃·H₂O (1) and [Cu(L¹)₂Cl]Cl·H₂O (2) species with distorted quadratic pyramidal and trigonal bipyramidal coordination geometries of the N₂O₃ and N₂O₂Cl donor atoms around the Cu(II), respectively. The Cu(II) complexes of L² are six-coordinate [Cu(L²)₂(NO₃)₂] (3) and [Cu(L²)₂Cl(H₂O)]Cl·H₂O (4) species with distorted octahedral coordination geometries of the N₄O₂ and N₂O₃Cl donor atoms. A distorted octahedral coordination geometry of the N₂O₂Cl₂ donor atoms is also found in the complex unit [Co(L²)₂Cl₂] of the Co(II) complex 5 but showing the oxygen atoms of the chelating ligand as well as the chloride ions in a cis-position. Depending on the complex, water molecules and chloride anions are shown to act as stabilizing components of the crystal structure. The comparative structural investigation includes also known structures of the bromine-free ligand analogue 2-(hydroxymethyl)pyridine, illustrating the basic implication of the bromine substitution, mostly perceptible in the different modes of crystal packing.     

Efficient numerical integration of arbitrarily broken cells using the moment fitting approach

The finite cell method is based on a fictitious domain approach, providing a simple and fast mesh generation of structures with complex geometries. However, this simplification leads to intersected cells where the standard Gauss quadrature does not perform well. To perform the numerical integration of these cells, we use the moment fitting approach that generates an individual quadrature rule for every broken cell. In this paper, we will perform a non-linear optimization approach to find the optimal position and number of the integration points. The findings show that the proposed method leads to efficient quadrature rules that require less integration points than other existing integration methods. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Excited state dynamics in recombinant water-soluble chlorophyll proteins (WSCP) from cauliflower investigated by transient fluorescence spectroscopy

The present study describes the fluorescence emission properties of recombinant water-soluble chlorophyll (Chl) protein (WSCP) complexes reconstituted with either Chl a or Chl b alone (Chl a only or Chl b only WSCP, respectively) or mixtures of both pigments at different stoichiometrical ratios. Detailed investigations were performed with time and space correlated ps fluorescence spectroscopy within the temperature range from 10 to 295 K. The following points were found: (a) The emission spectra at room temperature (295 K) are well characterized by bands with a dominating Lorentzian profile broadened due to phonon scattering and peak positions located at 677, 684 and 693 nm in the case of Chl a only WSCP and at 665, 675 and 689 nm for Chl b only WSCP. In addition, all spectra contain minor bands in the longer wavelength region. (b) The emission spectra at 10 K of samples suspended in buffer containing 50% glycerol are dominated by bands peaking at 668 nm for Chl b only WSCP and at 685 nm for Chl a only WSCP and samples reconstituted with mixtures of Chl a and Chl b. (c) At 10 K and in buffer with 50% glycerol the decay kinetics of WSCP samples with Chl a only are dominated by a component with a time constant of 6.2 (+/-0.2) ns at 685 nm while those of WSCP containing mixtures of Chl a and Chl b are characterized by a slightly shorter value of 6.0 (+/-0.2) ns. WSCP containing Chl b only exhibits a distinctly longer value of 7.0 (+/-0.3) ns at an emission wavelength of 668 nm. (d) The decay associated emission spectra at 10 K of all samples exhibit at least 3 decay components with time constants of 80-120 ps, 2-4 ns and 6-7 ns in 50% glycerol. These results are consistently described within the framework of our previously presented model (J. Phys. Chem. B 2007, 111, No. 46, 13325; J. Phys. Chem. B 2007, 111, No. 35, 10487) , for the structural motifs of chlorophyll binding to the tetrameric protein matrix of WSCP. It is shown that formation of strongly coupled open sandwich dimers does not lead to quenching of 1Chl a* or 1Chl b*.     

Adducts of Cyclodiphosph(V)azenes: Synthesis and Structure

The reaction of Ph₂PCl and PhPCl₂ with bis(trimethylsilyl)sulfur diimide in the presence of GaCl₃ and AlCl₃ yields diadducts of the corresponding cyclodiphosph(V)azene: [Ph₂PN]₂·(GaCl₃)₂ ( 1 ), [Ph₂PN]₂·(AlCl₃)₂ ( 2 ), and [Ph(Cl)PN]₂·(AlCl₃)₂ ( 3 ). This reaction is triggered by Lewis acids, which catalyse the (CH₃)₃Si‐Cl and S₈ elimination. The structures of 1· 2 CH₂Cl₂, 2· 2 CH₂Cl₂ and 3 were determined by single crystal X‐ray studies ( 1 : triclinic, , a = 9.679(2) Å, b = 9.863(2) Å, c = 11.366(2) Å, α = 113.55(3)°; β = 99.59(3)°; γ = 106.67(3)°; V = 902.8(3) ų, Z = 1; 2 : triclinic, , a = 9.639(2) Å, b = 9.804(2) Å, c = 11.321(2) Å, α = 113.71(3)°; β = 99.44(3)°; γ = 106.70(3)°; V = 889.3(3) ų, Z = 1; 3 : orthorhombic, Pbca, a = 14.853(3) Å, b = 9.261(2) Å, c = 16.631(3) Å, V = 2287.7(8) ų, Z = 4.     

Substrate specificity analysis of protein kinase complex Dbf2-Mob1 by peptide library and proteome array screening

Background  

The mitotic exit network (MEN) is a group of proteins that form a signaling cascade that is essential for cells to exit mitosis in Saccharomyces cerevisiae. The MEN has also been implicated in playing a role in cytokinesis. Two components of this signaling pathway are the protein kinase Dbf2 and its binding partner essential for its kinase activity, Mob1. The components of MEN that act upstream of Dbf2-Mob1 have been characterized, but physiological substrates for Dbf2-Mob1 have yet to be identified.     

Absorptionsspektren von halogenierten Methanen im Bereich von 275 bis 160 run bei Temperaturen von 298 und 208 K

Ohne Zusammenfassung