bluuebunny/crossref_metadata_2025_split huggingface dataset:
Palladium(II)‐katalysierte C‐H‐Aktivierung/C‐C‐Kreuzkupplung: Vielseitigkeit und Anwendbarkeit
Authors: Chen Xiao , Engle Keary M. , Wang Dong‐Hui , Yu Jin‐Quan 
Published: June 2009

AbstractKatalyse mit Methode: Eine ganze Reihe katalytischer Palladiumsysteme für die C‐H‐Aktivierung/C‐C‐Kupplung (siehe Schema) wurde in jüngerer Zeit entwickelt. Ein besonderer Schwerpunkt ist die PdII‐katalysierte Kupplung von C‐H‐Bindungen mit metallorganischen Reagentien durch PdII/Pd0‐Katalysezyklen. Die Vielseitigkeit dieser Katalysemethode wird demonstriert, zudem werden offene Fragen sowie das Entwicklungspotenzial des Gebietes angesprochen.magnified imageIn den letzten zehn Jahren wurde die palladiumkatalysierte C‐H‐Aktivierung/C‐C‐Kupplung zu einer vielversprechenden katalytischen Umwandlung entwickelt. Allerdings sind die Möglichkeiten auf diesem Gebiet bisher noch nicht so umfangreich wie bei den Kreuzkupplungen, bei denen Aryl‐ und Alkylhalogenide eingesetzt werden. Dieser Aufsatz stellt vier ausführlich untersuchte Katalysemethoden zur C‐C‐Bindungsbildung ausgehend von C‐H‐Bindungen vor: PdII/Pd0‐, PdII/PdIV‐, Pd0/PdII/PdIV‐ und Pd0/PdII‐Katalyse. Außerdem werden neuere Entwicklungen bei der PdII‐katalysierten Kupplung von C‐H‐Bindungen mit metallorganischen Reagentien durch einen PdII/Pd0‐Katalysezyklus vorgestellt. Ungeachtet aller bisherigen Fortschritte verbleibt es eine wichtige Aufgabe, die Vielseitigkeit und Anwendbarkeit dieser Reaktionen auf eine breitere Grundlage zu stellen.
Titelbild: Spectroscopic Tracking of Molecular Transport Junctions Generated by Using Click Chemistry (Angew. Chem. 28/2009)
Authors: Chen Xiaodong , Braunschweig Adam B. , Wiester Michael J. , Yeganeh Sina , Ratner Mark A. , Mirkin Chad A. 
Published: June 2009

AbstractDie In‐situ‐Erzeugung von Molekülbrücken über Nanolücken, die durch “On‐Wire”‐Lithographie erzeugt wurden, gelingt mithilfe der Klickchemie. C. A. Mirkin et al. zeigen in der Zuschrift auf S. 5280 ff., dass diese molekularen Kontakte in hohen Ausbeuten entstehen, und schildern, wie das Verfahren für eine Vielfalt von Molekülarchitekturen verallgemeinert werden kann. Die molekulare Selbstorganisation in den Nanolücken lässt sich dank ihres starken elektromagnetischen Feldes verfolgen.magnified image
Inside Cover: Adsorption, Diffusion, and Self‐Assembly of an Engineered Gold‐Binding Peptide on Au(111) Investigated by Atomic Force Microscopy (Angew. Chem. Int. Ed. 28/2009)
Authors: So Christopher R. , Tamerler Candan , Sarikaya Mehmet 
Published: June 2009

AbstractThe binding, diffusion, and aggregation mechanism of an engineered binding peptide on Au(111), showing non‐equilibrium surface structures that lead to the formation of a confluent monolayer, is described by M. Sarikaya et al. in their Communication on page 5174 ff. The observed dynamic structural evolution involving the surface diffusion of peptides and multiple stages of molecular thin film topology are explained. Ersin Emre Oren is thanked for the design of the graphic.magnified image
Cationization of cellulose by using N‐oxiranylmethyl‐N‐methylmorpholinium chloride and 2‐oxiranylpyridine as etherification agents
Authors: Hasani Merima , Westman Gunnar , Potthast Antje , Rosenau Thomas 
Published: June 2009

AbstractCationization of cellulose under aqueous alkaline conditions was studied. Two new epoxy reagents, N‐oxiranylmethyl‐N‐methylmorpolinium chloride and 2‐oxiranylpyridine, were used for preparation of cationic cellulose ethers. Using the first agent, cationic ethers were obtained in one step, whereas the latter one yielded a reactive intermediate used as a precursor for two different cationizations. Etherification with the commonly used 2,3‐epoxypropyltrimethylammonium chloride was also performed and used as a reference reaction. By changing water content in the reaction mixture two groups cellulose ethers with different degrees of cationization were prepared. As expected, reducing the water content resulted in a higher degree of etherification and hence a more pronounced cationic character of the obtained ethers. Characterization by FTIR, elemental‐ and gravimetric analysis confirmed the formation of the desired ethers. Their ability to interact with water and adsorb the acid dye, methyl orange, was also studied, confirming further introduction of the cationic substituents and revealing different reactivities of the used epoxy reagents. From characterization, it could be concluded that N‐oxiranylmethyl‐N‐methylmorpholinium chloride exhibits higher reactivity toward cellulose than both the reference compounds and 2‐oxiranylpyridine. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Expression, purification, and characterization of pro‐phenoloxidase‐activating serine protease from Spodoptera litura
Authors: Arora Naresh , Hoque M. E. , Rajagopal R. , Sachdev Bindiya , Bhatnagar Raj K. 
Published: June 2009

AbstractOne of the important trigger molecules for innate immunity is a serine protease that activates zymogen phenol oxidase (PPO). Central to wound healing response is the activation of phenol oxidase zymogen. Molecular characterization of phenol oxidase has been recently reported by us. Here, we report isolation, cloning, expression, and purification of prophenol oxidase activating enzyme 1 (slppae1) from polyphagous pest, Spodoptera litura. SLPPAE1 is induced within 6 h of physical injury. The structural features of the mature polypeptide are reminiscent of other lepidopteran PPAE in having a signal peptide, propeptide, and catalytically active polypeptide. The cDNA has been expressed in Sf21 cells using baculovirus expression vector. Fractionation of expressing Sf21 cells revealed its expression in the membranes. The recombinant protein was solubilized from membranes and purified by Ni‐NTA affinity chromatography. The purified enzyme is catalytically active on chromogenic substrate, activates recombinantly expressed prophenol oxidase (PPO) of S. litura, and is sensitive to inhibition by aprotenin. N‐terminal sequencing of processed phenol oxidase revealed 11 kDa propeptide instead of in‐silico predicted 6 kDa polypeptide. © 2009 Wiley Periodicals, Inc.
Hemolymph ecdysteroids during the last three molt cycles of the blue crab, Callinectes sapidus: quantitative and qualitative analyses and regulation
Authors: Chung J. Sook 
Published: June 2009

AbstractThe profiles of circulating ecdysteroids during the three molt cycles prior to adulthood were monitored from the juvenile blue crab, Callinectes sapidus. Ecdysteroid patterns are remarkably similar in terms of peak concentrations ranging between 210–330 ng/ml hemolymph. Analysis of hemolymph at late premolt stage revealed six different types of ecdysteroids with ponasterone A (PoA) and 20‐OH ecdysone (20‐OH E) as the major forms. This ecdysteroid profile was consistent in all three molt cycles. Bilateral eyestalk ablation (EA) is a procedure that removes inhibitory neurohormones including crustacean hyperglycemic hormone (CHH) and molt‐inhibiting hormone (MIH) and often results in precocious molting in crustaceans. However, the inhibitory roles of these neuropeptides in vivo have not yet been tested in C. sapidus. We determined the regulatory roles of CHH and MIH in the circulating ecdysteroid from ablated animals through daily injection. A daily administration of purified native CHH and MIH at physiological concentration maintained intermolt levels of ecdysteroids in the EA animals. This suggests that Y organs (YO) require a brief exposure to CHH and MIH in order to maintain the low level of ecdysteroids. Compared to intact animals, the EA crabs did not exhibit the level of peak ecdysteroids, and the major ecdysteroid turned out to be 20‐OH E, not PoA. These results further underscore the important actions of MIH and CHH in ecdysteroidogenesis, as they not only inhibit, but also control the composition of output of the YO activity. © 2009 Wiley Periodicals, Inc.
Polyunsaturated fatty acids inhibit PI3K activity in a yeast‐based model system
Authors: Couplan Elodie , Le Cann Marie , Le Foll Christelle , Corporeau Charlotte , Blondel Marc , Delarue Jacques 
Published: June 2009

AbstractThe phosphatidylinositol 3‐kinase (PI3K) pathway controls the regulation of cell growth, proliferation, migration and apoptosis. In many tumors, the PI3K gene is mutated or overexpressed, and/or the PI3K pathway is hyperactive. PI3K is therefore a potential pharmacological target for the development of anti‐tumor drugs. Some polyunsaturated fatty acids (PUFA), when given in the diet, may lead to a decrease in PI3K activity. We used a yeast‐based model to reconstitute the PI3K/PTEN/Akt pathway to study the effects of long‐chain polyunsaturated n‐3 fatty acids on PI3K, and found that various PUFA were able to alleviate toxicity induced by overexpression of PI3K. The various PUFA had no significant effect on the steady‐state level of PI3K catalytic subunit proteins (p110α) in yeast. However, depletion of phosphatidylinositol 4,5‐bisphosphate due to overexpression of the p110α subunit was significantly reduced by treating the yeast cells with the various PUFA. The inhibition of mammalian PI3K, expressed in an exogenous cellular context in yeast, is likely to be a direct effect of these PUFA on PI3K rather than on other mammalian endogenous or environmental factors. These results are particularly promising given the abundance of active PUFA in marine foodstuffs and especially fish oils.
Cloning and overexpression of a thermostable signal peptide peptidase (SppA) from Thermoplasma volcanium GSS1 in E. coli
Authors: Kocabıyık Semra , Demirok Burçak 
Published: June 2009

AbstractIn this study, a gene coding for thermophilic serine protease of the ClpP class from the thermoacidophilic archaeon Thermoplasma volcanium (Tpv) was cloned and expressed in Escherichia coli. The primary sequence and domain analysis of this enzyme showed similarities (50–60% similarity) to signal peptide peptidases (SppA) of bacteria and other archaea. An increase of about tenfold in the activity was achieved by overexpression of Tpv SppA in E. coli, as detected by enzyme assays conducted using Ala‐Ala‐Phe‐pNa and N‐Suc‐Ala‐Ala‐Pro‐Phe‐pNA as substrates. The recombinant enzyme, purified using an anion exchange column chromatography, displayed an apparent molecular mass of 26 kDa on SDS‐PAGE analysis. Purified Tpv SppA was active in a broad range of pH and temperature with maximal activity at 60°C and between pH 7.5 and pH 8.0. The activity of the enzyme was strongly inhibited by inhibitors typical for serine proteases, i.e., chymostatin and PMSF. The activity of the Tpv SppA and the stability at high temperature were significantly enhanced in the presence of 5 mM Ca2+ ions. Our multiple sequence alignment data revealed a conserved Ser/Lys catalytic dyad in Tpv SppA that comprised Ser76 (nucleophile) and Lys128 (general base) residues. A search for a transmembrane domain using automated programs did not predict any signal peptide associated with the Tpv SppA and, therefore, suggested a cytoplasmic location for this enzyme.
Metals sorption from aqueous solutions by Kluyveromyces marxianus: Process optimization, equilibrium modeling and chemical characterization
Authors: Pal Rama , Tewari Saumyata , Rai Jai P. N. 
Published: June 2009

AbstractThe dead Kluyveromyces marxianus biomass, a fermentation industry waste, was used to explore its sorption potential for lead, mercury, arsenic, cobalt, and cadmium as a function of pH, biosorbent dosage, contact time, agitation speed, and initial metal concentration. The equilibrium data fitted the Langmuir model better for cobalt and cadmium, but Freundlich isotherm for all metals tested. At equilibrium, the maximum uptake capacity (Qmax) was highest for lead followed by mercury, arsenic, cobalt, and cadmium. The RL values ranged between 0–1, indicating favorable sorption of all test metals by the biosorbent. The maximum Kf value of Pb showed its efficient removal from the solution. However, multi‐metal analysis depicted that sorption of all metals decreased except Pb. The potentiometric titration of biosorbent revealed the presence of functional groups viz. amines, carboxylic acids, phosphates, and sulfhydryl group involved in heavy metal sorption. The extent of contribution of functional groups and lipids to biosorption was in the order: carboxylic>lipids>amines>phosphates. Blocking of sulfhydryl group did not have any significant effect on metal sorption.
A putative role for human BFK in DNA damage‐induced apoptosis
Authors: Özören Nesrin , Inohara Naohiro , Núñez Gabriel 
Published: June 2009

AbstractHuman BFK (BCL‐2 family kin) is a novel pro‐apoptotic BCL‐2 family member specifically expressed in the gastrointestinal tract. BFK has the characteristic BH3 domain, which was shown to be essential for the apoptosis‐inducing activity of pro‐apoptotic BCL‐2 family members. When overexpressed, BFK interacts with BCL‐XL and BCL‐W but not BCL‐2 or BAD in co‐immunoprecipitations studies. We find that BFK exhibits striking similarity to BID in the way it is activated through cleavage during apoptosis. The endogenous and cleaved versions of BFK are readily recognized by the rabbit and mouse sera raised against human BFK. An ideal caspase 3 or 7 target sequence, DEVD (amino acids 38–41), is evident N‐terminal to the BH3 domain. A recombinant version of the protein containing all residues downstream of the putative caspase cleavage site induces apoptosis in human colon cancer cells, HCT116, and in wild‐type mouse embryonic fibroblasts (MEFs), which can be reversed by co‐expression of BCL‐XL or BCL‐W. BFK becomes activated through caspase‐dependent cleavage during DNA damage‐induced apoptosis. The cleaved form of the protein is dependent on the presence of BAX or BAK for its ability to induce apoptosis, since BAX–/–‐BAK–/– double‐knockout MEFs are completely resistant to BFK‐induced apoptosis.
Using microarray technology to select housekeeping genes in Chinese hamster ovary cells
Authors: Bahr Scott M. , Borgschulte Trissa , Kayser Kevin J. , Lin Nan 
Published: June 2009

AbstractIn the present study, we have identified species‐specific housekeeping genes (HKGs) for Chinese Hamster Ovary (CHO) cells using data from microarray gene expression profiling. HKGs suitable for quantitative RT‐PCR normalization should display relatively stable expression levels across experimental conditions. We analyzed transcription profiles of several IgG‐producing recombinant CHO cell lines under numerous culture conditions using a custom CHO DNA microarray platform and calculated relative expression variability from 124 microarrays. We selected a novel panel of candidate HKGs based on their low variability in expression from the microarray data. Compared to three traditional HKGs (Gapdh, Actb, and B2m), the majority of genes on this panel demonstrated lower or equal variability. Each candidate HKG was then validated using qRT‐PCR. Final selection of CHO‐specific HKGs include Actr5, Eif3i, Hirip3, Pabpn1, Vezt, Cog1, and Yaf2. The results reported here provide a useful tool for gene expression analyses in CHO cells, a critical expression platform used in biotherapeutics. Biotechnol. Bioeng. 2009; 104: 1041–1046. © 2009 Wiley Periodicals, Inc.
Noncovalent Modulation of pH‐Dependent Reactivity of a Mn–Salen Cofactor in Myoglobin with Hydrogen Peroxide
Authors: Zhang Jun‐Long , Garner Dewain K. , Liang Lei , Barrios David A. , Lu Yi 
Published: June 2009

AbstractTo demonstrate protein modulation of metal‐cofactor reactivity through noncovalent interactions, pH‐dependent sulfoxidation and 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid) (ABTS) oxidation reactivity of a designed myoglobin (Mb) containing non‐native Mn–salen complex (1) was investigated using H2O2 as the oxidant. Incorporation of 1 inside the Mb resulted in an increase in the turnover numbers through exclusion of water from the metal complex and prevention of Mn–salen dimer formation. Interestingly, the presence of protein in itself is not enough to confer the increase activity as mutation of the distal His64 in Mb to Phe to remove hydrogen‐bonding interactions resulted in no increase in the turnover numbers, while mutation His64 to Arg, another residue with ability to hydrogen‐bond interactions, resulted in an increase in reactivity. These results strongly suggest that the distal ligand His64, through its hydrogen‐bonding interaction, plays important roles in enhancing and fine‐tuning reactivity of the Mn–salen complex. Nonlinear least‐squares fitting of rate versus pH plots demonstrates that 1⋅Mb(H64X) (X=H, R and F) and the control Mn–salen 1 exhibit pKa values varying from pH 6.4 to 8.3, and that the lower pKa of the distal ligand in 1⋅Mb(H64X), the higher the reactivity it achieves. Moreover, in addition to the pKa at high pH, 1⋅Mb displays another pKa at low pH, with pKa of 5.0±0.08. A comparison of the effect of different pH on sulfoxidation and ABTS oxidation indicates that, while the intermediate produced at low pH conditions could only perform sulfoxidation, the intermediate at high pH could oxidize both sulfoxides and ABTS. Such a fine‐control of reactivity through hydrogen‐bonding interactions by the distal ligand to bind, orient and activate H2O2 is very important for designing artificial enzymes with dramatic different and tunable reactivity from catalysts without protein scaffolds.
Stanislao Cannizzaro and the Development of Chemistry in Palermo from 1862 to 1871
Authors: Zingales Roberto 
Published: June 2009

AbstractStanislao Cannizzaro worked at Palermo University for about ten years. There he managed to establish a modern and well‐equipped chemical laboratory. His international fame attracted co‐workers even from abroad: Naquet, Lieben, and Körner came to Palermo to work with him. This greatly improved the quality of teaching and of research in Palermo, which became a worldwide acknowledged center of chemical culture. In Palermo, atomic‐molecular theory was extensively taught and research was carried out on chemical atomicity (valence) and spatial structures of both aliphatic and aromatic organic molecules: Körner found the relative positions of substituent groups on the benzene ring, Paternò proved the equivalence of the four positions around each carbon atom. Thanks to Cannizzaro′s and Paternò′s efforts, a new journal, Gazzetta Chimica Italiana, was printed in Palermo. The journal collected original papers from Italian chemists, and summaries or translations of foreign ones. When Cannizzaro moved to Rome in 1872, Emanuele Paternò, the youngest of his pupils, took his place. Eventually, Paternò also moved to Rome, and the leading role of Palermo in Italian chemistry faded.
Photophysics of an Intramolecular Hydrogen‐Evolving Ru–Pd Photocatalyst
Authors: Tschierlei Stefanie , Presselt Martin , Kuhnt Christian , Yartsev Arkady , Pascher Torbjörn , Sundström Villy , Karnahl Michael , Schwalbe Matthias , Schäfer Bernhard , Rau Sven , Schmitt Michael , Dietzek Benjamin , Popp Jürgen 
Published: June 2009

AbstractPhotoinduced electron‐transfer processes within a precatalyst for intramolecular hydrogen evolution [(tbbpy)2Ru(tpphz)PdCl2]2+(RuPd; tbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, tpphz=tetrapyrido[3,2‐a:2′,3′c:3′′,2′′,‐h:2′′′,3′′′‐j]phenazine) have been studied by resonance Raman and ultrafast time‐resolved absorption spectroscopy. By comparing the photophysics of the [(tbbpy)2Ru(tpphz)]2+subunitRuwith that of the supramolecular catalystRuPd, the individual electron‐transfer steps are assigned to kinetic components, and their dependence on solvent is discussed. The resonance Raman data reveal that the initial excitation of the molecular ensemble is spread over the terminal tbbpy and the tpphz ligands. The subsequent excited‐state relaxation of bothRuandRuPdon the picosecond timescale involves formation of the phenazine‐centered intraligand charge‐transfer state, which inRuPdprecedes formation of the Pd‐reduced state. The photoreaction in the heterodinuclear supramolecular complex is completed on a subnanosecond timescale. Taken together, the data indicate that mechanistic investigations must focus on potential rate‐determining steps other than electron transfer between the photoactive center and the Pd unit. Furthermore, structural variations should be directed towards increasing the directionality of electron transfer and the stability of the charge‐separated states.
Treatment of Terminal Alkynes R–C≡C–H with Dialkylaluminum Hydrides: Hydroalumination versus Deprotonation
Authors: Uhl Werner , Er Elif , Hepp Alexander , Kösters Jutta , Layh Marcus , Rohling Martina , Vinogradov Andrej , Würthwein Ernst‐Ulrich , Ghavtadze Nugzar 
Published: June 2009

AbstractDialkylaluminum hydrides R2Al–H (R = Me, Et, iBu, CH2tBu, tBu), reacted with tert‐butylethyne, H–C≡C–CMe3, by hydroalumination and formation of the corresponding vinylic compounds, R2Al–C(H)=C(H)–CMe3. The products are dimeric in the solid state with the negatively charged vinylic carbon atoms in the bridging positions and adopt usually a centrosymmetric structure with the C=C double bonds on different sides of the central Al2C2 heterocycle. Only with R = Me the C2v structure with the cis arrangement of the alkenyl groups was found. Complicated mixtures of isomeric substances were detected in solution. Quantum‐chemical calculations revealed a considerable charge separation in the C=C double bonds of the dimeric formula units. The α‐carbon atoms coordinated by both aluminum atoms show high negative NBO charges of about –1.0, while the β‐carbon atoms are almost uncharged (0.0 to –0.1). The rotational barriers decreased upon dimerization. Hence, the formation of such dimers may be the key step in the well‐known cis/trans isomerization process of hydroalumination and hydrogallation products. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Mononuclear and Dinuclear NiII and CuII Complexes with a Pyrrolecarboxamide Ligand: Core Conversions and Unusual Presence of a Dimer and Two Monomers in the Same Unit Cell
Authors: Singh Jyoti , Hundal Geeta , Gupta Rajeev 
Published: June 2009

AbstractA potential tetradentate pyrrolecarboxamide ligand, H4L1, coordinates to metal ions (M = Ni or Cu) either in tetraanionic or trianionic fashion to afford mononuclear [M(L1)]2–, dinuclear [M2(HL1)2]2–, or adduct [{M2(HL1)2}{M(L1)}2]6– complexes, respectively. The dinuclear complexes can be converted into the mononuclear complexes by the addition of NaOH due to the presence of protonated sites. On the other hand, Cu‐monomer can be converted into the Cu adduct after treating with water. Interestingly, the crystal structure of the adduct shows the unusual presence of a Cu2‐dimer and two Cu‐monomers in the same unit cell. The structure shows extensive network of H‐bonds between the Cu2‐dimer and Cu‐monomers through two water molecules. Further, this adduct can be assembled by mixing isolated one mole of Cu2‐dimer and two moles of Cu‐monomers. Crystallographic studies depict several interesting weak interactions in these complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Semi In Situ Synthesis of NHTS: A New Hollow Titanium Silicalite Modified by a Noble Metal
Authors: Shi Chunfeng , Zhu Bin , Lin Min , Long Jun 
Published: June 2009

AbstractA new hollow titanium silicalite with a noble metal incorporated into it (denoted as NHTS) was synthesized by a semi in situ method. This NHTS has intraparticle voids and exhibits bifunctional catalytic performance. It was characterized by various techniques, and its catalytic performance for the direct epoxidation of propylene was investigated. The results show that NHTS, with a highly ordered MFI topological and hollow structure, together with a noble metal, can be employed in catalytic oxidations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)