bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global Epiproteomic Signatures Distinguish Embryonic Stem Cells from Differentiated Cells
Authors: Dai Bo , Rasmussen Theodore P. 
Published: July 2007

AbstractComplex organisms contain a variety of distinct cell types but only a single genome. Therefore, cellular identity must be specified by the developmentally regulated expression of a subset of genes from an otherwise static genome. In mammals, genomic DNA is modified by cytosine methylation, resulting in a pattern that is distinctive for each cell type (the epigenome). Because nucleosomal histones are subject to a wide variety of post-translational modifications (PTMs), we reasoned that an analogous “epiproteome” might exist that could also be correlated with cellular identity. Here, we show that the quantitative evaluation of nucleosome PTMs yields epiproteomic signatures that are useful for the investigation of stem cell differentiation, chromatin function, cellular identity, and epigenetic responses to pharmacologic agents. We have developed a novel enzyme-linked immunosorbent assay-based method for the quantitative evaluation of the steady-state levels of PTMs and histone variants in preparations of native intact nucleosomes. We show that epiproteomic responses to the histone deacetylase inhibitor trichostatin A trigger changes in histone methylation as well as acetylation, and that the epiproteomic responses differ between mouse embryonic stem cells and mouse embryonic fibroblasts (MEFs). ESCs subjected to retinoic acid-induced differentiation contain reconfigured nucleosomes that include increased content of the histone variant macroH2A and other changes. Furthermore, ESCs can be distinguished from embryonal carcinoma cells and MEFs based purely on their epiproteomic signatures. These results indicate that epiproteomic nucleosomal signatures are useful for the investigation of stem cell identity and differentiation, nuclear reprogramming, epigenetic regulation, chromatin dynamics, and assays for compounds with epigenetic activities.Disclosure of potential conflicts of interest is found at the end of this article.
The effect of viscosity on surface tension measurements by the drop weight method
Authors: Kaully T. , Siegmann A. , Shacham D. , Marmur A. 
Published: July 2007

AbstractViscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the “drop weight” method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ≥0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Combining Models ADM1 and ASM2d in a Sequencing Batch Reactor Simulation
Authors: Kauder J. , Boes N. , Pasel C. , Herbell J.‐D. 
Published: July 2007

AbstractThe Anaerobic Digestion Model No. 1 (ADM) and the Activated Sludge Model No. 2d (ASM) have been combined in a sequencing batch reactor simulation using a FORTRAN ODE solver. Special attention has been paid to the interface definition between the two models which use different biological state variables. The simulation results demonstrate the alternating treatment characteristics resulting from the sequence of anaerobic and aerobic steps. A parameter study reveals the process optimization potential of the model. Some numerical issues of the ADM are discussed in detail. The Jacobian matrix is provided, and the error handling of negative gas‐rates and negative concentrations is described from a numerical point of view.
Study of the Preparation of Flavone Imprinted Silica Microspheres and Their Molecular Recognition Function
Authors: Zhang Y.‐Q. , Qin Z. , Tu Z.‐Y. 
Published: July 2007

AbstractThe aim of this study is to prepare flavone imprinted silica with good sphericity. Previous studies have demonstrated that imprinted silica can be synthesized using a simple sol‐gel method and a grinding‐sieving process. Despite the simplicity of the synthetic method, the appearance of the final product obtained is often very irregular and nonuniform. This product has many utilization issues and problems, e.g., residues and low operability. In this study, one type of novel spherical flavone imprinted silica was synthesized. A sol‐gel method and molecular imprinting technique were employed. By using luteolin as a template molecule, aminopropyltriethoxysilane (APTS) as the functional monomer, tetraethoxysilane (TEOS) as the cross‐linking agent, molecularly imprinted silica microspheres were prepared via a two‐stage reaction. The preparation conditions were monitored by the appearance of the products. SEM images show that under optimum conditions, the diameters of these microspheres are ca. 20–30 μm. The amino group adsorption peaks can be seen from the IR spectra. Results from elemental analysis indicate that 3.206 μmol of amino groups were successfully introduced into 1 g of product. This microspheric adsorbent has a high adsorption capacity to the template molecule, high adsorption selectivity and reproducibility. The adsorption capacity amounted to 32.987 mg/g and the separation factor was up to 84.3, while the adsorption capacity hardly decreased after 15 cycles.
Velocity Profiles of Suspension Flows through an Abrupt Contraction Measured by Magnetic Resonance Imaging
Authors: Yasuda K. , Ohara N. , Muguruma M. 
Published: July 2007

AbstractVelocity profiles in steady flows of fluid/particle mixtures through a duct with an abrupt contraction were measured by magnetic resonance imaging. Aqueous solutions of carboxymethyl cellulose containing particles, including spheres, disk‐like particles, and short fibers, at high volume fractions were used. As a result, a plug‐like velocity profile was observed in a straight duct flow for every suspension, but the velocity profile depends on the particle shape at contraction. Disk‐like particles caused an unsteady flow, and short fibers caused a concave shape in the velocity profile near the centerline upstream of the contraction. Spheres did not affect the flow field. The concave profile became obvious with increased volume fraction of fiber. This result is caused by the larger elongational viscosity of the fiber suspension near the centerline of the channel, as compared with that of the sphere suspension.
Photocatalytic Degradation of Benzene in Air Streams in an Optical Fiber Photoreactor
Authors: Ma C. M. , Wang W. , Ku Y. , Jeng F. T. 
Published: July 2007

AbstractPhotocatalytic decomposition of gaseous benzene at room temperature was studied with a differential‐type optical fiber reactor using TiO2 as the photocatalyst. The effects of humidity, UV light intensity and benzene concentration on the performance of the reactor for benzene decomposition were investigated. It was observed that both the apparent quantum yields of benzene decomposition and CO2 production were superior to the traditional photoreactor, especially under limited UV light supply. In addition, deactivation of the TiO2 catalyst heavily relied on the humidity contained in the airflow. Purging with ozone‐containing air rapidly decomposed the organic residues adhering to the TiO2 surface and regenerated the deactivated catalyst within 30 minutes.
Synthesis and Structures of Alkali(alkoxy) Antimonates and Bismuthates
Authors: Veith Michael , Yu Eung‐Chul , Huch Volker 
Published: July 2007

AbstractAs(OtBu)3 does not form adducts with alkali metal tert‐butoxides MOtBu (M = Li, Na, K, Rb and Cs), whereas the corresponding Sb(OtBu)3 (2) and Bi(OtBu)3 (3) react with MOtBu (M = K, Rb, Cs) to yield M(OtBu)4Sb (M = K (6), Rb (7), Cs (8)) and M(O‐tBu)4Bi (M = 9), respectively. X‐ray structure determinations for 6 and 9 show them to be one‐dimensional coordination polymers composed of E(OtBu)4 (E = Sb, Bi) units linked through potassium atoms. These E(OtBu)4 units display a ψ‐trigonal‐bipyramidal coordination around the metal atom (SbO = 1.971(2) and 2.181(2) Å, BiO = 2.068(8) and 2.275(8) Å). Both the structures exhibit a planar four‐coordinate environment of oxygen around the potassium atoms (KO = 2.650(2)‐2.967(2) Å in 6, 2.53(1)‐3.15(1) Å in 9). Compound 2 reacts with two equivalents of KOtBu to afford K2Sb(OtBu)5 · dioxane (10), which contains Sb2K2O5 cage units and can be described as an O5 trigonal bipyramid with metal atoms inserted in the equatorial edges. Each metal atom is tetracoordinated by oxygen atoms of the cage (SbO = 1.979(3)‐2.144(3) Å. KO = 2.592(3)‐2.778(2) Å). The dioxane molecules increase the coordination number at each potassium atom to five by forming bridges between the molecules through KO bonds. Reaction of 2 and 3 with NaOtBu produce the cluster compounds Na4Sb2O(OtBu)8 (4) and Na4Bi2O‐(OtBu)8 (5) in high yields. K4Sb2O‐(OtBu)8 (11) is obtained in almost quantitative yield by heating KSb(OtBu)4 in benzene for 24 h. Compounds 4, 5 and 11 crystallise in rhombohedral lattices; the crystal structure analyses show a superposition of molecules. With an isotropic oxygen‐centred M6 octahedron. The formation of these oxo‐tert‐butoxides is accompanied by evolution of isobutene. Addition of four equivalents of THF to 11 gives K4Sb2O(OtBu)8 · 4 THF (12). X‐ray diffraction studies reveal a cis arrangement of the Sb atoms in the central OSb2K4 unit. K4Sb2O2(OiPr)12 (13) is obtained as the major product on heating KSb(OtBu)4 and subsequent reaction with isopropyl alcohol. In the crystal structure, two oxygen‐centred Sb2K2 tetrahedra (KO 2.693(4) Å, SbO = 1.982(5) Å) linked through iPrOK bonds (2.726(7)‐2.738(7) Å) are observed. In the reactions of KSb(OtBu)4 (6) with the metal halides CaCl2, TlCl and CuI, a halide ion is transferred to potassium; this results in formation of potassium halide, the corresponding alkoxide and Sb(OtBu)3.
Linear and Cyclic Platinum σ‐Acetylide Complexes of Tetraethynylethene
Authors: Faust Rüdiger , Diederich François , Gramlich Volker , Seiler Paul 
Published: July 2007

AbstractThe syntheses of the first organometallic mono‐ and dinuclear platinum complexes bearing the tetraethynylethene unit as an η1‐ligand are reported. Structural characterization of two of the trans σ‐bis(acetylide) derivatives by X‐ray crystallography reveals coplanarity of the acetylenic π‐ligands and indicates possible electronic delocalization across the metal center. This notion is further supported by comparing the electronic absorption spectra of the platinum‐containing compounds with those of related tetraethynylethene derivatives without metals. The solidstate structure of a dinuclear complex with two iodoplatinum fragments attached to one set of geminal acetylenes of tetraethynylethene was also investigated by X‐ray diffraction. Hay coupling of a mononuclear species leads to the incorporation of the σ‐bis(acetylide) moiety into a diplatinated metallacycle. This macrocyclic compound represents a novel structural motif in the design of a transition metal linked carbon network based on tetraethynylethene.
First Synthesis of the Functionalized Dioxatricyclic Core Structure of Dictyoxetane and Proposed Biogenesis in Dictyota Dichotoma
Authors: Reinecke Jens , Hoffmann H. M. R. 
Published: July 2007

Abstract6,8‐Dimethyl‐2,7‐dioxatricyclo[4.2.13,8]nonan‐4β‐ol (9aβ) has been prepared from readily accessible starting materials in eight steps (14% overall yield). The parent dioxatricyclic framework 11 was obtained from 1,5‐dimethyl‐8‐oxabicyclo[3.2.1]oct‐3‐en‐6α‐ol (7) in six steps (28% yield with respect to 7). Based on the experimental introduction of the oxetane moiety in vitro, a biosynthetic pathway is proposed for dictyoxetane (1) from a known dolabellane metabolite.
Total Synthesis of the Trehalase Inhibitor Salbostatin
Authors: Yamagishi Tatsuya , Uchida Chikara , Ogawa Seiichiro 
Published: July 2007

AbstractThe total synthesis of trehalase inhibitor salbostatin (1), recently discovered as a novel metabolite of Streptomyces albus species, has been achieved starting from the major product (58 % yield) from the coupling of the amine di‐O‐isopropylidene‐α‐valienamine and the electrophile 1,5 : 2,3‐dianhydro‐D‐mannitol in 2‐propanol. Deprotection with aqueous acetic acid and subsequent purification on a column of acidic resin afforded 1, which showed inhibitory activity (IC50 = 8.3 μML−1) against silkworm trehalase.
Centropentaindan, a Fenestrane Bearing Five Mutually Fused Indan Units: Syntheses, Molecular Structure, and Bridgehead Substitution
Authors: Kuck Dietmar , Schuster Andreas , Gestmann Detlef , Posteher Frank , Pritzkow Hans 
Published: July 2007

AbstractSyntheses, properties, and some reactions of a novel centropolycyclic hydrocarbon, centropentaindan (1), are described. The molecular structure of 1 consists of a tetrabenzo[5.5.5.5]fenestrane bearing a fifth centrically fused indan unit. Independent syntheses have been developed employing i) twofold cyclodehydrogenation of tribenzotriquinacene (7) with Pd/C at 500°C, which gives 1 in 50% yield, and ii) a two‐step procedure by tetrabromination of di‐fuso‐centrotriindan (8) followed by condensation with two molecules of benzene, which provides 1 in 88% yield. Some bridgehead‐substituted centropentaindans are described, including the highly labile dibromo derivative 19, and the centrohexacyclic, topologically nonplanar endo‐peroxide 26 and endo‐disulfide 28. The notably rigid ring fusion in the molecular framework of 1 is shown both by X‐ray structural analysis and by particular steric interactions of the two mutually compressed bridgehead substituents.
λ5‐Phosphetes, Benzo‐λ5‐Phosphetes, Naphtho‐λ5‐Phosphetes: Four‐π‐, Eight‐π‐, and Twelve‐π‐Electron Systems
Authors: Heim Udo , Pritzkow Hans , Fleischer Ulrich , Grützmacher Hansjörg , Sanchez Muriel , Réau Régis , Bertrand Guy 
Published: July 2007

AbstractA number of possible strategies for the preparation of λ5‐phosphetes were tested as follows: cyclopropenium 6 was treated with the lithium salt of diphenylphosphine to give phosphinocyclopropene 7, but 7 did not undergo ring expansion upon photolysis or thermolysis. P‐chloro‐Ctrimethylsilyl‐substituted ylide 8b reacted with two equivalents of dimethyl acetylenedicarboxylate to afford phosphinine 13 via a transient λ5‐phosphete 12. Addition of aluminum trichloride to P‐halogenated ylides 17a–b led to dihydrophosphetium salts 19a–b, which, upon treatment with pyridine, isomerized into the 1, 2‐dihydrophosphet‐2‐ium salts 20a–b. Hydrolysis of derivatives 20a–b cleanly afforded phosphoniums 21 a–b, which reacted with NaN(SiMe3)2 to give rise to the corresponding λ5‐phosphetes 22a–b. The benzo‐λ5‐phosphete 22a underwent ring expansion reactions with dimethyl acetylenedicarboxylate and acetonitrile, leading to benzo‐λ5‐phosphinine and benzo‐1, 4λ5‐azaphosphinine in good yields. Derivative 22b was characterized by X‐ray crystal structure analysis. Ab initio SCF calculations, IGLO‐13C chemical shifts and Δχ for various benzannulated derivatives and phosphorus heterocycles are presented.
Bimetallic Sesquifulvalene Complexes–Compounds with Unusually Large Hyperpolarizability β
Authors: Behrens Ulrich , Brussaard Hugo , Hagenau Ute , Heck Jürgen , Hendrickx Eric , Körnich Jan , Van Der Linden Johannes G. M. , Persoons André , Spek Anthony L. , Veldman Nora , Voss Bea , Wong Hans 
Published: July 2007

AbstractIn order to construct bimetallic organometallic donor–acceptor complexes with nonlinear optical (NLO) properties, the bimetallic sesquifulvalene complexes [{CpFe(η5‐C5H4)}Z{η7‐C7H6)Cr‐(CO)3}]BF4 (2BF4) have been synthesized with different bridging functions Z (2a: Z = ‐ 2b: Z = C2; 2c: Z  (E)‐C2H2). X‐ray structure determinations show that 2a BF4 and 2c BF4 crystallize in acentric space groups (P41, P212121), whereas crystalline 2b BF4 has the centric space group P21/c. The organometallic fragments in 2a adopt a transoid conformation, those in 2b and 2c are cisoid. The cyclo‐C5 and cyclo‐C7 rings of the sesquifulvalene ligands are almost coplanar; this allows an optimum electronic interaction between the ferrocenyl donor and the [η7‐C7H6)Cr(CO)3]+ acceptor moiety in the crystalline state. Cyclovoltammetric studies show an electrochemically reversible one‐electron oxidation ( > 0 mV vs. FeH/FcH+, FcH = ferrocene) and an irreversible one‐electron reduction (≤–900 mV), which are assigned to the ferrocenyl and [(η7‐C7H6)Cr(CO)3]+ units, respectively. UV/vis spectra reveal low‐energy absorptions for 2a–c at about λ=600 nm, showing strong negative solvatochromism. These absorption maxima are related to a charge‐transfer excitation between the ferrocenyl and the [(η7‐C7H6)Cr(CO)3]+ groups, indicating considerable nonlinear optical properties. Determination of the first hyperpolarizability β by means of hyper Rayleigh scattering yields exceptionally large β values: β(2b) = 570 × 10−30 esu and β(2c) = 320 × 10−30 esu. These unexpectedly large β values are explained by resonance enhancement.
Studies on the Topography of Biomembranes: Regioselective Photolabelling in Vesicles with the Tandem Use of Cholesterol and a Photoactivable Transmembrane Phospholipidic Probe
Authors: Nakatani Yoichi , Yamamoto Masakuni , Diyizou Yvonne , Warnock William , Dollé Valérie , Hahn Wolfgang , Milon Alain , Ourisson Guy 
Published: July 2007

Abstract2H NMR, DSC and UV studies of DMPC (1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine) vesicles have demonstrated the favourable physicochemical properties of the transmembrane phospholipid probes 1 a and 1 b for membrane topographical studies. In particular, in the presence of a physiological amount of cholesterol, only one transmembrane conformation is observed. The use of 1 a and cholesterol together for photolabelling experiments in DMPC vesicles led to a remarkable improvement in the regioselectivity of cross‐linking between 1 a and DMPC, and between 1 a and cholesterol: the myristoyl chains functionalized at C11, C12 and C13 made up 95% of the total photolabelled myristates, and cholesterol was principally functionalized at the C25 position on the side‐chain. This indicates the formation of a highly ordered bilayer structure and proves directly the orientation of cholesterol perpendicular to the membrane plane with its chain terminal buried in the middle of the bilayer.
The Pre‐Reactive Complex of H2S and BrCl; Observation and Characterisation by Rotational Spectroscopy
Authors: Bloemink Hannelore I. , Legon A. C. 
Published: July 2007

AbstractBy using a fast‐mixing nozzle in a Fourier transform microwave spectrometer, any chemical reaction accompanying mixing of H2S and BrCl was prevented, thus allowing the observation of the pre‐reactive complex H2S ··· BrCl. The rotational spectra of eight isotopomers of the complex were recorded. The analysis of the determined spectroscopic constants shows that the atoms S ··· BrCl are collinear or nearly so and that the H2S plane is approximately perpendicular to the S ··· BrCl axis with r(S ··· Br) = 3.094 (7) Å. This geometry is in agreement with previously stated rules for B ··· XY complexes, where B is a Lewis base and XY is an (inter)halogen molecule. The intermolecular interaction is shown to be relatively weak, both in terms of the intermolecular stretching force constant kσ and the intramolecular electric change redistribution δ within the BrCl subunit that accompanies formation of H2S ··· BrCl.
Synthesis and Properties of 4,4,9,9‐Tetramethyl‐1‐oxa‐cycloundecane‐5,6,7,8‐tetrone and 5,5,10,10‐Tetramethyl‐1‐oxa‐cyclotridecane‐6,7,8,9‐tetrone
Authors: Gleiter Rolf , Ackermann Uwe , Oeser Thomas , Irngartinger Hermann 
Published: July 2007

AbstractThe synthesis of 4,4,9,9‐tetramethyl‐1‐oxa‐cycloundecane‐5,6,7,8‐tetrone (9) and 5,5,10,10‐tetramethyl‐1‐oxa‐cyclotridecane‐6,7,8,9‐tetrone (10) has been achieved in a multistep procedure. The key steps in this synthesis were the ring closure of 23 and 24 to 25 and 26, respectively, and the oxidation of the triple bond with RuO2/NaIO4 to the dihydroxydiketones 31 and 32. Compound 9 is the first cyclic tetraketone for which an intramolecular donor‐acceptor stabilization has been found. A strong transannular interaction between the ether oxygen and the C4O4 unit in 9 was detected by X‐ray studies on single crystals of 9. The transannular distance is 2.7–2.8 Å. Further evidence for a strong transannular interaction was obtained from the comparison of the reduction potential and the first band in the UV/Vis spectrum with the corresponding values from other openchain tetraketones. These findings were substantiated by PE investigations on 9. The crystal structures of the dihydroxy‐diketones 31 a and 32 a showed that, in the case of the eleven‐membered ring (31 a), there are also short transannular distances between the ether oxygen and the C2O2 moiety (2.5 Å and 2.9 Å). In the case of the thirteen‐membered ring (32 a), no transannular interactions were found in the solid state.
Highly Selective Formation of tert‐Butyl Hydroperoxide from the Reaction of Isobutane and O2 in a Zeolite under Visible Light
Authors: Blatter Fritz , Sun Hai , Frei Heinz 
Published: July 2007

AbstractIsobutane and oxygen gas loaded into zeolite BaY react upon irradiation with green or blue light to yield tert‐butyl hydroperoxide in a single‐photon process. This was discovered when monitoring the reaction at room temperature in situ by FT‐infrared spectroscopy. Selectivity was 98%, even upon conversion of more than half of the reactants loaded into the zeolite. Diffuse reflectance spectra revealed a visible absorption tail which originates from an isobutane · O2 collision complex. It is attributed to the isobutane · O2 contact charge‐transfer absorption, whose onset is shifted from the UV into the visible region by the high electrostatic field of the zeolite.
Zirconium(II)‐ and Hafnium(II)‐Assisted Reductive Coupling of Coordinated Carbonyl Groups Leading to Ketenylidene Complexes of Zirconium(IV) and Hafnium(IV)
Authors: Calderazzo Fausto , Englert Ulli , Guarini Alessandro , Marchetti Fabio , Pampaloni Guido , Segre Annalaura , Tripepi Giovanna 
Published: July 2007

AbstractThe biscyclopentadienyldicarbonyl derivatives of zirconium(II) and hafnium(II) ([MCp2(CO)2]; MZr, Hf) promote the reductive coupling of coordinated carbon monoxide to give, in the presence of N,N‐dialkylcarbamtes of the tetravalent metals [M(O2CNR2)4], the ketenylidene complexes [M3Cp2(μ2‐CCO)‐(μ3‐O)(O2CNR2)6] (1 a: MZr, REt; 1 b: MZr, RiPr; 2: MHf, RiPr). The yields of the isolated zirconium complexes are as high as 60%, while that of the hafnium derivative is 40%. The X‐ray crystal structure analysis of 1 b shows that it consists of trinuclear molecules, with the three zirconium atoms held together by the bidentate C2O ligand, by the tridentate bridging oxide and by the bidentate carbamato groups. Labelling experiments with [ZrCp2(13CO)2] show that the ketenylidene ligand originates from the coordinated CO groups. These ketenylidene complexes, which are rare examples of compounds containing a CCO but no CO ligand, are characterized by an intense IR band at about 2015 cm−1, associated with the bridging C2O ligand. The ketenylidene group of 1 b was readily removed and replaced by a bidentate μ‐oxo ligand of the same hapticity by reaction with carbon dioxide or acetone or by thermal decomposition. The resulting product [Zr3Cp2(μ‐O)(μ3‐O)‐(O2CNiPr2)6] (3) crystallizes in the same space group as 1 b and with similar cell constants and bond parameters.