[N(2-ammoniumethyl)piperazinium]tetrachloromono-bromocuprate(II) monohydrate: A compound containing a discrete square-pyramidal unit

The crystal and molecular structure of the [N(2-ammoniumethyl)piperazinium]tetra-chloromonobromocuprate(II) monohydrate is reported. The crystals are monoclinic, space groupP2₁/c,Z=4, witha=9.560(2),b=9.240(3),c=18.270(7)Å,=99.20(2)°. The structure consists of discrete N(2-ammoniumethyl)piperazinium cations, uncoordinated water molecules and [CuCl₄Br]^3– anions, in which four coplanar chlorine atoms occupy the square-basal plane and one bromine atom the axial position, giving the copper(II) ion a moderately elongated square-pyramidal geometry. The structure was refined to a finalR index of 0.0765.     

Crystal and molecular structure of 1-epi-delphisine and nmr assignments for delphisine, 1-epi-delphisine and delphinine

The crystal and molecular structure of the norditerpenoid alkaloid 1-epi-delphisine (5), C₂₈H₄₃NO₈, M _r 521.66, has been confirmed by as X-ray diffraction study using the SIR 88 analysis program. The alkaloid crystallizes in the space groupP2₁ with cell parameters:a=11.853(1)Å,b=10.511(1)Å,c=11.854(1)Å,=112.58(1),V=1363.61(0)ų,Z=2,D _calc=1.27 g/cm³, (CuK)=1.54184 Å, (CuK=7.2 cm^–1,F(000)=564, temperature 23°C,R=0.052, for 2907 reflections. Ring A of 1-epi-delphisine exists in a chair conformation. By comparison, delphisine which bears a C-1 hydroxyl group, has ring A in a boat conformation stabilized by an intramolecular N----H-O hydrogen bond. Ring D of both of these alkaloids exists in a boat form. Unambiguous proton and carbon-13 nmr assignments for delphisine, 1-epi-delphisine and delphinine have been made by a detailed analysis of the DEPT, COSY, HETCOR, COLOC, DIFNOE, and selective INEPT nmr techniques.Dedicated to the memory of Dr. K. Krishna Bhandary (1946–1992).     

Syntheses and structural characterization of two novel α-diketone bisacylhydrazones

Benzil bis(3,4,5-trimethoxybenzohydrazone) (I) and 3,3-dimethoxybenzil bis(benzohydrazone) (II) were synthesized by condensation, acid catalyzed, of the proper -diketone and the corresponding hydrazide. Compound I crystallizes in the monoclinic system, space group P2₁/n, with a = 11.464(2), b = 21.098(4), c = 13.837(2) Å, = 109.50(1)° V = 3154.8(9) ų and D _c = 1.319 g/cm³ for Z = 4. Compound II crystallizes in the triclinic system, space group P , with a = 11.106(3), b = 11.728(10), c = 10.656(5) Å, = 91.86(2), = 92.68(3), = 110.00(2)° V = 1301.1(7) ų and D _c = 1.293 g/cm³ for Z = 2.     

Heptacoordination in MnII,NiII, and CuII complexes of 2,6-diacetylpyridine bis (acetylhydrazone)

Manganese(II), nickel(II), and copper(II) complexes of 2,6-diacetylpyridine bis (acetylhydrazone) (H₂dapac) have been synthesized and structurally characterized by X-ray diffraction methods. [Mn(H₂dapac) (OH₂)₂](NO₃)₂ crystallizes in the monoclinic space groupP2₁/c witha=11.145(3),b=10.723(4),c=17.189(2) Å, =92.81(2)° andZ=4; [Ni(H₂dapac)(OH₂)₂] (NO₃)₂·H₂O crystallizes in the monoclinic space groupP2₁ witha=9.994(3),b=14.423(4),c=7.697(2)Å, =100.37(2)°, andZ=2; [Cu(H₂dapac)(OH₂)₂](NO₃)₂·H₂O crystallizes in the orthorhombic space groupPbcn witha=20.986(5),b=14.552(3),c=6.905(1)Å andZ=4. In each case the metal atom has a slightly distorted pentagonal bipyramidal environment, the equatorial positions being occupied by three nitrogen and two oxygen atoms from the hydrazone ligand and the apices by two water molecules. The crystalline cohesion in ensured by a three-dimensional network of hydrogen bonds involving the complex cations, the nitrate anions, and, where present, the uncoordinate water molecules.     

Novel route to dendritic structures and their application for surface modification

Monodisperse branched polyurethanes containing long alkyl chains have been prepared by a new convergent synthesis. This synthesis comprises two steps, with hexamethylene diisocyanate uretdione as the starting molecule. The free isocyanate groups of this monomer are reacted with long‐chain alkanols. These diurethane uretdiones are then reacted with amines or amino alcohols under ring opening and the formation of a biuret group. Branching points are not, as usual, part of the monomer but are formed during preparation. The structure of these dendrons has been established with NMR spectroscopy, elemental analysis, mass spectroscopy, and gel permeation chromatography. The dendritic polyurethanes are thermally stable up to 200 °C. Surfaces coated with these materials are hydrophobic. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1372–1386, 2006     

Kautschuk

Ohne Zusammenfassung     

Estimating sufficient statistics in co-evolutionary analysis by mutual information

Mutual information (MI) is a standard measure in information theory to observe and quantify correlated signals and events in both, empirical data sets and theoretical models. In the field of computational biology the MI turned out to be particularly useful in studies on co-evolutionary signals of sites within biomolecules. A key issue in the applicability of the MI is, however, a correct reference system or null model to understand finite-size effects in the underlying, finite data set. Although some bioinformatics studies exist with rigorous results for theoretical, well-designed random distributions, data from real-world proteins was never used to quantify the effect of finite-size samples. The impact of real-world statistics is, however, most relevant for researchers in all fields concerned with detecting evolutionary signals within biological sequences. We present results on such effects in finite-sized biological data sets and point to future research directions. We are most of all concerned with bacterial, ribosomal proteins as a prototypical example in molecular evolution. We compare to previous published suggestions, give an empirical formula, and propose a protocol to guide future research projects.     

Confocal microscopy of whole mount embryonic cartilage: Intracellular localization of F-actin, chick prolyl hydroxylase and type II collagen mRNA

We show that whole mount preparations of embryonic chick sterna can be analyzed with confocal laser scanning microscopy (CLSM). This technique replaces the traditional sectioning of cartilage or culturing of chondrocytes. Whole ‘chunks’ of cartilage can be stained with dyes, used for immunohistochemistry or in situ hybridization. Although other stains have been used, the stains presented include phalloidin and propidium iodide which stain filamentous actin (F-actin) and the DNA and RNA of cells, respectively. Collagen secreting endoplasmic reticulum (ER) was localized with a primary antibody to chick prolyl hydroxylase (CPH) that was detected with a secondary antibody conjugated to FITC. The intracellular localization of type II collagen mRNA was analyzed using in situ hybridization. The cDNA probe specific for the C-propeptide region of the 1 type (II) collagen mRNA was nick translated and labeled with biotin-16-dUTP. Biotin labeled probes were visualized with avidin-FITC. Depending on the intensity of the stain, we were able to analyze approximately 3–10 layers of chondrocytes. Stains penetrated into the cartilage better than antibodies and biotin-avidin labeled cDNA probes. The F-actin was located as bands of filaments in the superficial layers of the cartilage and was associated with the membranes that marked cell boundaries as deep as 10 layers of chondrocytes. The ER stained with anti-chick prolyl hydroxylase was prominent in perinuclear regions of the cells, but the antibody was only able to penetrate 4–5 cell layers. Single label in situ hybridization studies show that chondrocytes are positive for type II collagen mRNA. Similar to the immunohistochemistry, in situ hybridization probes were only able to penetrate 4–5 cell layers. The type II collagen mRNA appeared perinuclear in the chondrocytes, similar to the ER staining pattern.