bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Structural Variants of Homoserine Lactones in Bacteria
Authors: Thiel Verena , Kunze Brigitte , Verma Pankaj , Wagner‐Döbler Irene , Schulz Stefan 
Published: June 2009

AbstractN‐Acylhomoserine lactones (AHLs) are used by a wide variety of bacteria for cell–cell communication in “quorum‐sensing”. These compounds are derived from L‐homoserine lactone and a fatty acid, which varies in chain‐length, degree of saturation, and the presence or absence of an oxygen atom at C‐3. In this study we describe for the first time the occurrence of acyl chains carrying a methyl branch, and present a GC‐MS‐based method that can be used to distinguish these compounds from unbranched isomers. The bacterium Aeromonas culicicola produces several methyl branched AHLs. In Jannaschia helgolandensis—a marine bacterium of the Roseobacter clade—a doubly unsaturated AHL, (2E,9Z)‐N‐(2,9‐hexadecadienoyl)‐L‐homoserine lactone, occurs. The location and configuration of the double bonds was proven by spectrometric investigation and synthesis. Finally, a method was developed to establish the absolute configuration of 3‐hydroxyalkanoyl‐HSLs by mild cleavage and chiral gas chromatography. The AHLs synthesized during this study were tested in sensor systems specific for certain AHL types. The results show that these compounds display varying responses to the respective sensors; this underlines the importance of determining the whole bouquet of AHLs and its function to fully understand their importance for regulatory functions in bacteria.
Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae
Authors: Yildizhan Selma , van Loon Joop , Sramkova Anna , Ayasse Manfred , Arsene Cristian , ten Broeke Cindy , Schulz Stefan 
Published: June 2009

AbstractPheromonally yours: The aphrodisiac pheromones of male Cabbage White butterflies were identified. The small butterfly uses the smaller molecule ferrulactone (1) to enhance its mating success, while the large butterfly uses the larger compound brassicalactone (2), which is a new natural product. Both compounds are active in combination with hexahydrofarnesylacetone and phytol.magnified imageThe small and large cabbage butterflies, Pieris rapae and P. brassicae, are found worldwide and are of considerable economic importance. The composition of the male scent‐producing organs present on the wings was investigated. More than 120 components were identified, but only a small portion proved to be male specific. Major components were the known beetle pheromone ferrulactone (1) in P. rapae and its previously unknown larger analogue, brassicalactone (2), in P. brassicae. The latter carries an additional isoprene unit and is closely related to 1. Other components present in larger amounts on male relative to female wings were hexahydrofarnesylacetone (18) and phytol (23). Brassicalactone (2) was fully characterized by synthesis of its various diastereomers by using ring‐closing metathesis. A similar approach to ferrulactone (1) failed, presumably because of its smaller ring size. Instead, this compound was synthesized by using a modified literature procedure. The biological activity of the compounds in the extract was tested by coupled gas chromatographic‐electroantennographic (GC‐EAD) analysis, which showed that both macrolides and the other major components of the wings can be detected by the antennae of the conspecific female butterflies. Other detectable compounds included several alkanes, which are typical constituents of the butterfly cuticula, derivatives of phytol (23) and long‐chain secondary alcohols. Finally, bioassays with males showed that the mixture of 1 (P. rapae) or 2 (P. brassicae) together with 18 and 23 applied to freshly eclosed males increased mating success compared to untreated males. Therefore, the two macrolides 1 and 2 are aphrodisiac pheromone components of male small and large cabbage white butterflies, respectively.
Time‐Resolved Tracking of a Minimum Gene Expression System Reconstituted in Giant Liposomes
Authors: Saito Hirohide , Kato Yusho , Le Berre Maël , Yamada Ayako , Inoue Tan , Yosikawa Kenichi , Baigl Damien 
Published: June 2009

AbstractIndividual expression: We describe a method that allows the observation of real‐time gene expression in a large number of individual giant liposomes encapsulating identical genetic material. We followed the gene expression profiles from DNA and mRNA templates coding for different proteins. Although the average profiles of individual liposomes were similar to those measured in bulk solution, strong variability between individual liposomes was observed at both transcription and translation.magnified image
Expanding RNA Silencing Approaches by U1 Adaptors
Authors: Grünweller Arnold , Hartmann Roland K. 
Published: June 2009

AbstractSilent partner: In a recent publication, Gunderson and co‐workers described an approach to recruit the abundant U1 snRNP, a splicing subparticle, to the last exon of a pre‐mRNA, in a sequence‐specific manner. This mediates interaction of the U1‐70K protein subunit with poly(A) polymerase, thus blocking polyadenylation and inducing pre‐mRNA degradation. This novel promising strategy expands the repertoire of gene‐silencing concepts.magnified image
Hacking the Genetic Code of Mammalian Cells
Authors: Schwarzer Dirk 
Published: June 2009

AbstractA genetic shuttle: The highlighted article, which was recently published by Schultz, Geierstanger and co‐workers, describes a straightforward scheme for enlarging the genetic code of mammalian cells. An orthogonal tRNA/aminoacyl‐tRNA synthetase pair specific for a new amino acid can be evolved in E. coli and subsequently transferred into mammalian cells. The feasibility of this approach was demonstrated by adding a photocaged lysine derivative to the genetic repertoire of a human cell line.magnified image
On the Size of Ions Solvated in Helium Clusters
Authors: Ferreira da Silva Filipe , Waldburger Philipp , Jaksch Stefan , Mauracher Andreas , Denifl Stephan , Echt Olof , Märk Tilmann D. , Scheier Paul 
Published: June 2009

AbstractHelium nanodroplets are doped with SF6, C4F8, CCl4, C6H5Br, CH3I, and I2. Upon interaction with free electrons a variety of positively and negatively charged cluster ions X±Hen are observed where X±=F±, Cl±, Br±, I+, I2+, or CH3I+. The yield of these ions versus cluster size n drops at characteristic sizes ns that range from ns=10.2±0.6 for F+ to ns=22.2±0.2 for Br−. ns values for halide anions are about 70 % larger than for the corresponding cations. The steps in the ion yield suggest closure of the first solvation shell. We propose a simple classical model to estimate ionic radii from ns. Assuming the helium density in the first solvation shell equals the helium bulk density one finds that radii of halide anions in helium are nearly twice as large as in alkali halide crystals, indicating the formation of an anion bubble due to the repulsive forces that derive from the exchange interaction. In spite of the simplicity of our model, anion radii derived from it agree within approximately 10 % with values derived from the mobility of halide anions in superfluid bulk helium, and with values computed by quantum Monte Carlo methods for X−Hen cluster anions.
Dendrimer Disassembly in the Gas Phase: A Cascade Fragmentation Reaction of Fréchet Dendrons
Authors: Baytekin Bilge , Baytekin H. Tarik , Hahn Uwe , Reckien Werner , Kirchner Barbara , Schalley Christoph A. 
Published: June 2009

AbstractThe mass spectrometric characterization of Fréchet‐type dendrons is reported. In order to provide the charges necessary for electrospray ionization, dendrons bearing an OH group at the focal point can be deprotonated and observed in the negative ion mode. Alternatively, the corresponding bromides can be converted to quaternary ammonium ions that can easily be detected in the positive mode. If the latter ions are subjected to collision‐induced dissociation experiments, a fragmentation cascade begins with the dissociation of the focal amine. The focal benzyl cation quickly decomposes in a fragmentation cascade from the focal point to the periphery until the peripheral benzyl (or naphthylmethyl) cations are formed. Five different mechanisms are discussed in detail, three of which can be excluded based on experimental evidence. The cascade fragmentation is reminiscent of self‐immolative dendrimers.
Structurally Defined Potassium‐Mediated Zincation of Pyridine and 4‐R‐Substituted Pyridines (R=Et, iPr, tBu, Ph, and Me2N) by Using Dialkyl–TMP–Zincate Bases
Authors: Clegg William , Conway Ben , Graham David V. , Hevia Eva , Kennedy Alan R. , Mulvey Robert E. , Russo Luca , Wright Dominic S. 
Published: June 2009

AbstractTwo potassium–dialkyl–TMP–zincate bases [(pmdeta)K(μ‐Et)(μ‐tmp)Zn(Et)] (1) (PMDETA=N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine, TMP=2,2,6,6‐tetramethylpiperidide), and [(pmdeta)K(μ‐nBu)(μ‐tmp)Zn(nBu)] (2), have been synthesized by a simple co‐complexation procedure. Treatment of 1 with a series of substituted 4‐R‐pyridines (R=Me2N, H, Et, iPr, tBu, and Ph) gave 2‐zincated products of the general formula [{2‐Zn(Et)2‐μ‐4‐R‐C5H3N}2⋅2{K(pmdeta)}] (3–8, respectively) in isolated crystalline yields of 53, 16, 7, 23, 67, and 51 %, respectively; the treatment of 2 with 4‐tBu‐pyridine gave [{2‐Zn(nBu)2‐μ‐4‐tBu‐C5H3N}2⋅2{K(pmdeta)}] (9) in an isolated crystalline yield of 58 %. Single‐crystal X‐ray crystallographic and NMR spectroscopic characterization of 3–9 revealed a novel structural motif consisting of a dianionic dihydroanthracene‐like tricyclic ring system with a central diazadicarbadizinca (ZnCN)2 ring, face‐capped on either side by PMDETA‐wrapped K+ cations. All the new metalated pyridine complexes share this dimeric arrangement. As determined by NMR spectroscopic investigations of the reaction filtrates, those solutions producing 3, 7, 8, and 9 appear to be essentially clean reactions, in contrast to those producing 4, 5, and 6, which also contain laterally zincated coproducts. In all of these metalation reactions, the potassium–zincate base acts as an amido transfer agent with a subsequent ligand‐exchange mechanism (amido replacing alkyl) inhibited by the coordinative saturation, and thus, low Lewis acidity of the 4‐coordinate Zn centers in these dimeric molecules. Studies on analogous trialkyl–zincate reagents in the absence and presence of stoichiometric or substoichiometric amounts of TMP(H) established the importance of ZnN bonds for efficient zincation.
Structural Study and Conformational Behavior of the Two Different Lipopolysaccharide O‐Antigens Produced by the Cystic Fibrosis Pathogen Burkholderia multivorans
Authors: Ieranò Teresa , Silipo Alba , Cescutti Paola , Leone Maria Rosaria , Rizzo Roberto , Lanzetta Rosa , Parrilli Michelangelo , Molinaro Antonio 
Published: June 2009

AbstractLipopolysaccharides (LPSs) are virulence factors expressed by Gram‐negative bacteria; they are among those mainly responsible for bacterial virulence. In this work we define the primary structure and the conformational features of the O‐chain from the LPS produced by the highly virulent clinical isolate Burkholderia multivorans strain C1576, an opportunistic human pathogen isolated in a cystic fibrosis center and causative of an outbreak with lethal outcome. We demonstrate that the LPS from this clinical isolate consists of two O‐polysaccharide chains present in different amounts and made up of repeating units, both containing deoxy sugar. Additionally, conformational studies have been performed to establish and compare the spatial arrangements of the two polysaccharides and differences in their shape have been highlighted. The comprehension of the structural and conformational features of the two repeating units may help to explain their biological significance, the molecular shape of the bacterial external surface, and the comprehension at the molecular level of the recognition mechanisms of the antibodies.
Arene Control over Thiolate to Sulfinate Oxidation in Albumin by Organometallic Ruthenium Anticancer Complexes
Authors: Hu Wenbing , Luo Qun , Ma Xiaoyan , Wu Kui , Liu Jianan , Chen Yi , Xiong Shaoxiang , Wang Jianping , Sadler Peter J. , Wang Fuyi 
Published: June 2009

AbstractArene control: Anticancer complexes [Ru(arene)Cl(en)]+ (arene=p‐cymene or biphenyl; en=ethylenediamine) bind to surface histidine (His128, His247, His510) and methionine (Met298) residues in human albumin, but only the p‐cymene complex can gain entry to the crevice containing the free cysteine thiolate (Cys34) and induce oxidation to sulfinate.magnified imageInteractions of organometallic ruthenium anticancer complexes [Ru(η6‐arene)Cl(en)][PF6] (arene=p‐cymene (1) or biphenyl (2), en=ethylenediamine) with human serum albumin were investigated by means of mass spectrometry combined with trypsin digestion, specific sidechain modifications and computational modelling. Both complexes were shown to bind to surface histidine (His128, His247, His510) and methionine (Met298) residues in human albumin, but only the p‐cymene complex can gain entry to the crevice containing the free cysteine thiolate (Cys34) and induce oxidation to sulfinate. The two complexes exhibit a similar coordination preference for histidine and methionine residues on the protein surface. His128 binding is favoured both kinetically and thermodynamically. At 310 K, six days of incubation of recombinant human albumin (rHA) with complex 1 (rHA:Ru 50:250 μM) led to about 18 % ruthenation of His128 in the protein. However, the extent of ruthenation of albumin by complex 2 was less than that by 1, due to the steric hindrance from the biphenyl ligand. These results imply that the arene ligand in the organometallic ruthenium anticancer complexes plays a crucial role in interactions with proteins.
Synthesis and Evaluation of New Antagonists of Bacterial Quorum Sensing in Vibrio harveyi
Authors: Peng Hanjing , Cheng Yunfeng , Ni Nanting , Li Minyong , Choudhary Gaurav , Chou Han Ting , Lu Chung‐Dar , Tai Phang C. , Wang Binghe 
Published: June 2009

AbstractBacterial quorum sensing has received much attention in recent years because of its relevance to pathological events such as biofilm formation. Based on the structures of two lead inhibitors (IC50: 35–55 μM) against autoinducer‐2‐mediated quorum sensing identified through virtual screening, we synthesized 39 analogues and examined their inhibitory activities. Twelve of these new analogues showed equal or better inhibitory activities than the lead inhibitors. The best compound showed an IC50 value of ∼6 μM in a whole‐cell assay using Vibrio harveyi as the model organism. The structure–activity relationship is discussed herein.
Corporate social responsibility: management and methods
Authors: Dobers Peter 
Published: June 2009

AbstractThis article gives an overview of recent Corporate Social Responsibility (CSR) handbooks to illustrate that the field is of immediate interest and relevance for scholars and practitioners. It gives a background to CSR and how the field relates to management and methods and introduces the four articles of this special issue. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.
Against corporate responsibility: critical reflections on thinking, practice, content and consequences
Authors: Fougère Martin , Solitander Nikodemus 
Published: June 2009

AbstractThis article critically reflects on today's dominant articulation of corporate responsibility (CR) in terms of thinking, practice, content and consequences. We examine what has and has not changed since a seminal critique of the notion of business social responsibility put forward by Theodore Levitt 50 years ago. We illustrate our argument with the case of Botnia in Uruguay, which has recently generated much discussion in international media, and other examples that are illuminating on the problematic nature of contemporary CR. We find that little in fact has changed between the 1958 and 2008 versions of CR except for the context of (global) business, especially the threat posed by sustainability questions and the more systematic ideological rejection of regulation. As opposed to these contemporary evolutions, we call for alternative, regulation‐based articulations of CR, which would improve corporate accountability on social and environmental questions. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.
Moral landscapes – understanding agency in corporate responsibility initiatives
Authors: Larssaether Stig , Nijhof André 
Published: June 2009

AbstractDrawing on literature in the field of Science Technology Studies (STS) it is argued in this article that including influences of non‐human actors in the design of corporate responsibility programs has the potential to improve significantly the associated social and ecological effects. For this we turn to the concept of moral landscapes, where agency primarily is seen as a distributed effect along a trajectory of connected practices, rather than as the result of intrinsic properties of individual decision‐makers. It is the objective of this article to present a perspective on corporate responsibility initiatives based on such a distributed view of agency. By using this framework as an analytical tool, managers and scholars can improve the overall effect of corporate responsibility initiatives by paying more attention to potential incongruence with other practice areas within or beyond their primary domain of influence. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.
Nonanuclear Coordination Compounds Featuring {M9L12}6+ Cores (M = NiII, CoII, or ZnII; L = 1,2,3‐Benzotriazolate)
Authors: Biswas Shyam , Tonigold Markus , Speldrich Manfred , Kögerler Paul , Volkmer Dirk 
Published: June 2009

AbstractSyntheses, characterization, and magnetic properties of three nonanuclear coordination compounds with the molecular formulae [Ni9(bta)12(NO3)6(MeOH)6]·4THF (1) (btaH = 1,2,3‐benzotriazole; THF = tetrahydrofuran), [Co9(bta)12(MeOH)18][(NO3)6]·9C6H6 (C6H6 = benzene) (2), and [Zn9(Me2bta)12(CH3COO)6]·3DMF (Me2btaH = 5,6‐dimethyl‐1,2,3‐benzotriazole; DMF = N,N′‐dimethylformamide) (3) are presented. The solid‐state structures of all the compounds were determined by single‐crystal X‐ray structure analysis revealing the presence of structurally similar {M9L12}6+ cores (M = NiII, CoII, or ZnII; L = 1,2,3‐benzotriazolate) in which the metal centers are bridged by μ3‐benzotriazolates. The charges of the cationic {M9L12}6+ moieties in 1 and 3 are balanced by six nitrate and acetate anions coordinated to the peripheral metal atoms, respectively, whereas 2 is a cationic metal complex with six noncoordinated nitrate counterions in the crystal lattice. All the metal centers in each compound are hexacoordinate, except for the peripheral metal centers in 3 which are pentacoordinate. The nonanuclear cores can be formally subdivided into two metallosupramolecular tetrahedra which bear five metal ions each, and share a common apex. All compounds have been prepared by using excess of ligand, which acts as an auxiliary base, serving to abstract protons from the coordinated benzotriazole ligand. Magnetic susceptibility studies (2–290 K) show net antiferromagnetic intramolecular coupling for 2, while 1 displays both ferro‐ and antiferromagnetic coupling contributions. Both compounds exhibit strong ligand field effects in their magnetic properties. Phase purity of the compounds was ascertained by X‐ray powder diffraction (XRPD) analysis, IR spectroscopy, and elemental analysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Push–Pull Azo‐Chromophores Containing Two Fused Pentatomic Heterocycles and Their Nonlinear Optical Properties
Authors: Centore Roberto , Fusco Sandra , Peluso Andrea , Capobianco Amedeo , Stolte Matthias , Archetti Graziano , Kuball Hans‐Georg 
Published: June 2009

AbstractWe have developed procedures for the synthesis of push–pull azo‐chromophores containing the s‐triazolo[3,4‐b]thiadiazole heterocycle compatible with the presence of electron‐acceptor groups (nitrophenyl group) as substituents on both the triazole and thiadiazole rings. The linear and non‐linear optical properties of the synthesized chromophores have been characterized by the EFISH technique, electro‐optical absorption spectroscopy and DFT calculations. The combined results indicate a significant modulation of the properties of the chromophores depending on the substitution pattern on the heterobicycle. Fast UV‐driven trans → cis and slower thermally driven cis → trans isomerizations around the N=N bond were observed and characterized for the chromophores. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Regioselective Reduction of 2,4‐Diacylpyrroles and the Synthesis of a 2,4‐Divinylpyrrole
Authors: Li Yan , Dolphin David 
Published: June 2009

AbstractReduction of 2,4‐diacylpyrroles followed by dehydration to prepare the divinylpyrroles has been studied. The N‐phenylsulfonyl group exhibited directing ability at the 4‐position during the reduction of 2,4‐diacylpyrrole and complete regioselectivity was achieved for formations of the 2‐ and 4‐carbinols; several new derivatives, including 2,4‐divinylpyrrole, have been prepared.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Generation of Prenylhafnium and α‐Selective Addition to Imines
Authors: Shibata Ikuya , Miyamoto Shinji , Tsunoi Shinji , Sakamoto Kazuya , Baba Akio 
Published: June 2009

AbstractAllylhafnium compounds were generated by transmetalation between allyl‐SnBu3 and HfCl4 in EtCN. A highly α‐selective addition reaction of prenyltributyltin to imines was observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Asymmetric Synthesis of α‐Allenylglycines
Authors: Bucuroaia Carmen , Groth Ulrich , Huhn Thomas , Klinge Michael 
Published: June 2009

AbstractThe coupling of the homocuprate of the bislactim ether of cyclo‐(‐L‐Val‐Gly‐) (9) with primary propargyl halides produces the allenyl‐substituted bislactim ethers 11 in a highly diastereoselective manner, whereas the alkylation of the lithiated bislactim ether of cyclo‐(‐L‐Val‐Gly‐) yields the propargyl‐substituted bislactim ethers 12. Subsequent hydrolysisaffords, after protection of the amino group, the methyl α‐allenylglycinates 15, the α‐allenylglycines 16, and the methyl α‐propargylglycinates 17. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)