Arabidopsis thaliana LUP1 converts oxidosqualene to multiple triterpene alcohols and a triterpene diol

The Arabidopsis thaliana LUP1 gene encodes an enzyme that converts oxidosqualene to pentacyclic triterpenes. Lupeol and beta-amyrin were previously reported as LUP1 products. Further investigation described here uncovered the additional products germanicol, taraxasterol, psi-taraxasterol, and 3,20-dihydroxylupane. These results suggest that the 80 known C(30)H(50)O compounds that are structurally consistent with being oxidosqualene cyclase products may be derived from fewer than 80 enzymes and that some C(30)H(52)O(2) compounds may be direct cyclization products of oxidosqualene.     

Cs4[Sc6C]Cl13 und Cs4[Pr6(C2)]I13 — zwei Beispiele für das fehlende Bindeglied bei der Verknüpfung der Baueinheiten [M6Z]XX

Cs₄[Sc₆C]Cl₁₃ and Cs₄[Pr₆(C₂)]I₁₃ — Two Examples for the Missing Link in the Connectivity of [M₆Z]X X Building Units Cs₄[Sc₆C]Cl₁₃ (tetragonal, I4₁/amd, a = 1 540.5(4), c = 1 017.9(7) pm, c/a = 0.661, Z = 4, R = 0.038, R_w = 0.026) and Cs₄[Pr₆(C₂)]I₁₃ (a = 1 804.9(3), c = 1 259.5(3) pm, c/a = 0.698, R = 0.106, R_w = 0.068) are obtained as green-black and blue-black single crystals with brass-like metallic lustre through metallothermic reduction of ScCl₃ and PrI₃, respectively, with cesium in the presence of carbon in sealed tantalum containers. The, overall, isotypic compounds contain isolated [Sc₆C] and [Pr₆(C₂)] clusters, respectively, that are surrounded by 18 halide (X) ligands (12 Xⁱ and 6 X^a; X = Cl or I). The connection is carried out via the motif [M₆Z]XXXX (M = Sc and Pr; Z = C and C₂, respectively) and is thereby the missing link of the motifs of connection for the composition A_x[M₆Z]X₁₃. Analogous interconnection of [TiO₆] octahedra is found in the anatase-type of structure of TiO₂.     

Interpretation of mass spectrometry data for high-throughput proteomics

Recent developments in proteomics have revealed a bottleneck in bioinformatics: high-quality interpretation of acquired MS data. The ability to generate thousands of MS spectra per day, and the demand for this, makes manual methods inadequate for analysis and underlines the need to transfer the advanced capabilities of an expert human user into sophisticated MS interpretation algorithms. The identification rate in current high-throughput proteomics studies is not only a matter of instrumentation. We present software for high-throughput PMF identification, which enables robust and confident protein identification at higher rates. This has been achieved by automated calibration, peak rejection, and use of a meta search approach which employs various PMF search engines. The automatic calibration consists of a dynamic, spectral information-dependent algorithm, which combines various known calibration methods and iteratively establishes an optimised calibration. The peak rejection algorithm filters signals that are unrelated to the analysed protein by use of automatically generated and dataset-dependent exclusion lists. In the "meta search" several known PMF search engines are triggered and their results are merged by use of a meta score. The significance of the meta score was assessed by simulation of PMF identification with 10,000 artificial spectra resembling a data situation close to the measured dataset. By means of this simulation the meta score is linked to expectation values as a statistical measure. The presented software is part of the proteome database ProteinScape which links the information derived from MS data to other relevant proteomics data. We demonstrate the performance of the presented system with MS data from 1891 PMF spectra. As a result of automatic calibration and peak rejection the identification rate increased from 6% to 44%.Abbreviations 2-DE Two-dimensional gel electrophoresis - MALDI Matrix-assisted laser desorption ionisation - PMF Peptide mass fingerprinting - MS Mass spectrometry - TOF Time of flight     

Überschreitungen der konventionellen Zahl von Clusterelektronen in Metallhalogeniden des M6X12‐Typs: W6Cl18, (Me4N)2[W6Cl18] und Cs2[W6Cl18]

Beyond the Conventional Number of Electrons in M₆X₁₂ Type Metal Halide Clusters: W₆Cl₁₈, (Me₄N)₂[W₆Cl₁₈], and Cs₂[W₆Cl₁₈] Black octahedral single crystals of W₆Cl₁₈ were obtained by reducing WCl₄ with graphite in a silica tube at 600 °C. The single crystal structure refinement (space group R 3¯, Z = 3, a = b = 1498.9(1) pm, c = 845.47(5) pm) yielded the W₆Cl₁₈ structure, already reported on the basis of X‐ray powder data. (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈] were obtained from methanolic solutions of W₆Cl₁₈ with Me₄NCl and CsCl, respectively. The structure of (Me₄N)₂[W₆Cl₁₈] was refined from X‐ray single crystal data (space group P 3¯m1, Z = 1, a = b = 1079.3(1) pm, c = 857.81(7) pm), and the structure of Cs₂[W₆Cl₁₈] was refined from X‐ray powder data (space group P 3¯, Z = 1, a = b = 932.10(7) pm, c = 853.02(6) pm). The crystal structure of W₆Cl₁₈ contains molecular W₆Cl₁₈ units arranged as in a cubic closest packing. The structures of (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈] can be considered as derivatives of the W₆Cl₁₈ structure in which 2/3 of the W₆Cl₁₈ molecules are substituted by Me₄N⁺ ions and Cs⁺ ions, respectively. The conventional number of 16 electrons/cluster is exceeded in these compounds, with 18 electrons for W₆Cl₁₈ and 20 electrons for (Me₄N)₂[W₆Cl₁₈] and Cs₂[W₆Cl₁₈]. Cs₂[W₆Cl₁₈] exhibits temperature independent paramagnetic behaviour.     

Determination of adenine,caffeine, theophylline and theobromine by HPLC with amperometric detection

A relatively simple method for quantifying caffeine, theobromine, theophylline and adenine by HPLC with amperometric detection was developed. A C₁₈-column and an isocratic elution with phosphate buffer pH 3.5/methanol (90 : 10) were employed for the chromatographic separation of the investigated compounds. The optimal detection potential was +1.4 V. The limits of detection were 0.4 ng for adenine, 1 ng for theophylline and 2.5 ng for caffeine and theobromine. The method was applied to the determination of these purine alkaloids in beverages, tea, coffee and cacao. The determination was carried out directly or after solid-phase extraction.     

[Cu4(NPMe3)3(O2C?CH3)5] – ein tetramerer Phosphaniminato-Komplex von Kupfer(II). Synthese,Kristallstruktur, magnetisches Verhalten und EPR-Spektrum

[Cu₄(NPMe₃)₃(O₂C? CH₃)₅] – a Tetrameric Phosphorane Iminato Complex of Copper(II). Synthesis, Crystal Structure, Magnetic Behaviour, and EPR Spectrum The title compound and the corresponding benzoate complex [Cu₄(NPMe₃)₃(O₂C? C₆H₅)₅] have been prepared by reactions of copper(II)acetate and copper(II)benzoate, respectively, with Me₃SiNPMe₃ in dichloromethane. Both complexes are characterized by IR spectroscopy. The acetate complex is additionally characterized by the measurement of the magnetic susceptibility, by its EPR spectrum, and by a crystal structure determination. [Cu₄(NPMe₃)₃(O₂C? CH₃)₅] · CH₂Cl₂: Space group I4₁/a, Z = 16, structure solution with 7 960 independent reflections, R = 0.044. Lattice dimensions at ?70°C: a = b = 3 670.6; c = 1 091.9 pm. The structure consists of four Cu atoms which are arranged at the corners of a distorted tetrahedron with Cu…?Cu distances between 290 and 318 pm. Three of the faces of the tetrahedron are linked by μ₃-N atoms of the phosphorane iminato groups. Three of the acetate ligands form chelates, the other two are monofunctionally coordinated. Three of the copper atoms have a planar surrounding, the forth Cu atom has a (4 + 1) coordination.     

New flexible synthesis of pyrazoles with different,functionalized substituents at C3 and C5

Syntheses of pyrazoles featuring a functionalized side chain attached to carbon 3 and varying alkyl and aryl substituents attached to carbon 5 are presented. Installation of R = methyl, isopropyl, tert-butyl, adamantyl, or phenyl groups at C5 is reported here, starting by coupling protected alkynols with acid chlorides RCOCl, forming alkynyl ketones, which are reacted with hydrazine to form the pyrazole nucleus. Alcohol deprotection and conversion to a chloride gave 5-substituted 3-(chloromethyl)- or 3-(2-chloroethyl)pyrazoles. This sequence can be done within 2 d on a 30 g scale in excellent overall yield. Through nucleophilic substitution reactions, the chlorides are useful precursors to other polyfunctional pyrazoles. In the work here, derivatives with side chains LCH(2)- and LCH(2)CH(2)- at C3 (L = thioether or phosphine) were made as ligands. The significance of the ligands made here is that by placing a ligating side chain on a ring carbon (C3), rather than on a ring nitrogen, the ring nitrogen not bound to the metal and its attached proton will be available for hydrogen bonding, depending on the steric environment created by R at C5.     

Zur Kenntnis von Dinitrito-kobalt(III)-Komplexen. I Darstellung und Absorptions-Spektren der Dinitrito-di(äthylendiamin)-kobalt(III)-perchlorate

On Dinitrito Cobalt(III) Complexes. I. Preparation and Absorption Spectra of Di(ethylenediamine) Cobalt(III) Perchlorates Cis and trans dinitrito diethylenediamine cobalt perchlorates could be prepared starting with carbonato and trans dichloro ethylenediamine cobalt perchlorate. Spectroscopic data are reported and compared with those of the corresponding dinitro complexes.     

Synthesis,Structure, and Properties of LiNb6Cl15

Black single crystals of LiNb₆Cl₁₅ were obtained from reactions of Nb powder, NbCl₅ and LiCl in sealed niobium tubes at 850°C. The heavy atom structure of LiNb₆Cl₁₅ (Ia3 d (no. 230), Z = 16, a = 2055.5(2) pm at 100 K, R(F) = 0.028, R(F²) = 0.053) is isotypic with the structure of Ta₆Cl₁₅. The [Nb₆Cl₁₂]²⁺ clusters in the structure are three-dimensionally interconnected via three additional Cl^a?a. These bridge all vertices of niobium clusters, consistent with [Nb₆Cl₁₂ⁱCl]^? (the Nb? Cl^a–a? Nb angles are 140°). At low temperatures the lithium ions are disordered over one-third of sites (48 f), occupying cavities inside of two distorted corner-sharing tetrahedra of chloride. These positions for lithium represent the narrowest sections of infinite channels in the structure built up by chloride. An increased lithium ion mobility is obtained above 170 K by ⁷Li-NMR measurements.     

Structure transfer from a polymeric melt to the solid state. Part II: Dependence on molecular weight

Melt spinning experiments of polyethylene, using a high quenching rate have been carried out. Molecular weight has been varied. From measurements of the mechanical properties of the monofilaments produced it is concluded that melt history influences the solid state behavior. This is reflected in the hypothesis of a transference of knots, preexisting in the melt into the solid state. Measurements of the elastic recovery allow to offer an interpretation, in which this network of knots does not percolate, until a critical value of the molecular weightM _{c knot}10⁵ is surpassed. The possible influence of these knots on the mobile entanglements is discussed.On leave from the Institut für Technische und Makromolekulare Chemie, Universität Hamburg, Hamburg, Germany.