bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elaboration of rac‐Like Active Species from Lewis Base Functionalized Unbridged Zirconocenes for Isospecific Propylene Polymerization
Authors: Kim Hwa Kyu , Kim Seong Kyun , Park Jun Ha , Yoon Seung Woong , Lee Min Hyung , Do Youngkyu 
Published: September 2008

AbstractA series of ortho or meta Lewis base functionalized unbridged zirconocenes, [{1‐(En‐Ph)‐3,4‐Me2C5H2}2ZrCl2] (E=NMe2, OMe; n=1, 2), and a half‐functionalized zirconocene, [{1‐(p‐Me2NC6H4)‐3,4‐Me2C5H2}{1‐(p‐tolyl)‐3,4‐Me2C5H2}ZrCl2], were prepared. The crystal structures of these compounds determined by X‐ray diffraction revealed the presence of only C2‐symmetric rac‐like isomers in the asymmetric units. In combination with methylaluminoxane (MAO) cocatalyst, the meta‐functionalized complexes afforded mixtures of polymers that exhibit multimelting transition temperatures and broad molecular‐weight distributions (MWDs) in propylene polymerization at atmospheric monomer pressure, whereas the ortho‐functionalized complexes did not give rise to polymerization. Stepwise solvent extraction of the polymer mixtures showed that the polymers consist of amorphous, moderately isotactic, and highly isotactic portions, the weight ratio of which is dependent on the reaction temperature. 13C NMR spectral analysis indicated that the [mmmm] methyl pentad value of the isotactic portion reached around 90 %. Among the meta‐functionalized zirconocenes, the di‐OMe‐substituted one afforded the largest amount of the isotactic portion at all temperatures, and the portion comprised 82 wt % of the crude polymer obtained at 25 °C. In contrast, propylene polymerization with the half‐functionalized unbridged zirconocene resulted in the formation of nearly atactic polypropylene with a narrow MWD of around 2. These results corroborate the proposition that the rigid rac‐like cation–anion ion pair of type [rac‐L2ZrP]+[Me‐MAO]− generated in situ, through Lewis acid–base interactions between the functional groups and [Me‐MAO]−, is responsible for the isospecific propylene polymerization with the given class of functionalized unbridged zirconocenes and further indicate that the formation of such ion pairs can be favored by difunctionalization at the meta position of the phenyl ring with OMe groups.
Solid state and solution conformations of a hybrid αγααγα hexapeptide. Characterization of a backbone expanded analog of the α‐polypeptide 310‐helix
Authors: Chatterjee Sunanda , Vasudev Prema G. , Raghothama Srinivasarao , Shamala Narayanaswamy , Balaram Padmanabhan 
Published: September 2008

AbstractThe stereochemically constrained γ amino acid residue gabapentin (1‐(aminomethyl)cyclohexaneacetic acid, Gpn) has been incorporated into a host α‐peptide sequence. The structure of a hybrid αγααγα peptide, Boc‐Leu‐Gpn‐Aib‐Leu‐Gpn‐Aib‐OMe in crystals reveals a continuous helical conformation stabilized by three intramolecular 4 → 1 C12 hydrogen bonds across the αγ/αγ segments and one C10 hydrogen bond across the central αα segment. This conformation corresponds to an expanded analog of the canonical all‐α polypeptide 310‐helix, with insertion of two additional backbone atoms at each γ residue. Solvent dependence of NH chemical shifts in CDCl3 solution are consistent with conformation in which the NH groups of Aib (3), Leu (4), Gpn (5), and Aib (6) are hydrogen bonded, a feature observed in the solid state. The nonsequential NOEs between Gpn (2) NH ↔ Leu (4) NH and Gpn (2) NH ↔ Gpn (5) NH support the presence of additional conformations in solution. Temperature‐dependent line broadening of NH resonances confirms the occurrence of rapid exchange between multiple conformations at room temperature. Two conformational models which rationalize the observed nonsequential NOEs are presented, both of which contain three hydrogen bonds and are consistent with the known stereochemical preferences of the Gpn residue. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 85:759–771, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Influence of charge and size of terminal amino‐acid residues on local conformational states and shape of alanine‐based peptides
Authors: Makowska Joanna , Bagińska Katarzyna , Skwierawska Agnieszka , Liwo Adam , Chmurzyński Lech , Scheraga Harold A. 
Published: September 2008

AbstractWe present results of conformational studies by Circular dichroism and NMR spectroscopy, differential scanning calorimetry, and molecular dynamics, of three alanine‐based peptides: Ac‐KK‐(A)7‐KK‐NH2 (KAK), Ac‐OO‐(A)7‐DD‐NH2 (OAD), and Ac‐KK‐(A)7‐EE‐NH2 (KAE), where A, K, O, D, and E, denote alanine, lysine, ornithine, aspartic acid, and glutamic acid residues, respectively. For OAD and KAE, canonical MD simulations with time‐averaged NMR‐derived restraints demonstrate the presence of an ensemble of structures with a variety of conformational states (polyproline II, α‐helical, α′, and extended, turn); for KAK the conformational states are predominantly polyproline II and extended. The OAD peptide exhibits a bent shape with its ends close to each other, whereas KAK and KAE are more extended. The bent shape was also observed in our earlier study of the Ac‐XX‐(A)7‐OO‐NH2 (XAO) peptide, where X denotes the diaminobutyric acid residue; therefore, the shape seems to depend on the size of the charged side chains at the ends of the alanine sequence and not on their kind. This suggests that the bent shape of the alanine sequence is formed to enable screening of this nonpolar sequence from the solvent by sufficiently short charged side chains. As in our previous study of the XAO peptide, no long polyproline II segments were observed. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 85:772‐782, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Conformational studies of the C‐terminal 16‐amino‐acid‐residue fragment of the B3 domain of the immunoglobulin binding protein G from Streptococcus
Authors: Skwierawska Agnieszka , Ołdziej Stanisław , Liwo Adam , Scheraga Harold A. 
Published: September 2008

AbstractThe structure and stability of the 16‐amino‐acid‐residue fragment [IG(46–61)] corresponding to the C‐terminal β‐hairpin of the B3 domain of the immunoglobulin binding protein G from Streptococcus was investigated by means of CD and NMR spectroscopy and by differential scanning calorimetry. The CD and 2D NMR experiments were carried out (i) in water at different temperatures and (ii) at one temperature (305 K), with only CD, at different TFE concentrations. Our results show that the IG(46–61) peptide possesses organized three‐dimensional structure at all investigated temperatures. The three‐dimensional structure of the IG(46–61) peptide resembles the general shape of a β‐hairpin that is also observed for this peptide in the experimental structure of the B3 domain in the whole G protein; the structure is stabilized by hydrophobic interactions between nonpolar side chains. Our study shows that the melting temperature of the IG(46–61) peptide is about 320 K which supports the hypothesis that the investigated peptide can serve as a folding initiation site of the B3 domain of the immunoglobulin binding protein G. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 37–51, 2009.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Polymorphisms of the matrix metalloproteinase 9 gene and abdominal aortic aneurysm
Authors: Smallwood L , Allcock R , van Bockxmeer F , Warrington N , Palmer L J , Iacopetta B , Golledge J , Norman P E 
Published: September 2008

AbstractBackgroundIncreased matrix metalloproteinase (MMP) 9 activity has been implicated in the formation of abdominal aortic aneurysm (AAA). The aim was to explore the association between potentially functional variants of the MMP-9 gene and AAA.MethodsThe − 1562C &gt; T and − 1811A &gt; T variants of the MMP-9 gene were genotyped in 678 men with an AAA (at least 30 mm in diameter) and 659 control subjects (aortic diameter 19–22 mm) recruited from a population-based trial of screening for AAA. Levels of MMP-9 were measured in a random subset of 300 cases and 84 controls. The association between genetic variants (including haplotypes) and AAA was assessed by multivariable logistic regression.ResultsThere was no association between the MMP-9 − 1562C &gt; T (odds ratio (OR) 0·70 (95 per cent confidence interval (c.i.) 0·27 to 1·82)) or − 1811A &gt; T (OR 0·71 (95 per cent c.i. 0·28 to 1·85)) genotypes, or the most common haplotype (OR 0·81 (95 per cent c.i. 0·62 to 1·05)) and AAA. The serum MMP-9 concentration was higher in cases than controls, and in minor allele carriers in cases and controls, although the differences were not statistically significant.ConclusionIn this study, the genetic tendency to higher levels of circulating MMP-9 was not associated with AAA.
Topical haemostatic agents
Authors: Seyednejad H , Imani M , Jamieson T , Seifalian A M 
Published: September 2008

AbstractBackgroundA variety of local haemostatic agents is now available to stop troublesome bleeding. These agents are indicated for use during surgical interventions where conventional methods of haemostasis are not applicable because of the site of surgery or the degree of bleeding.MethodA literature search using the PubMed and ISI Web of Knowledge databases identified relevant studies on topical haemostatic agents. Manufacturers' recommendations were also sought through commercial websites.Results and conclusionA significant body of evidence now exists to support the use of topical haemostatic agents in a wide variety of clinical situations. The advantages and disadvantages of many of these agents are highlighted.
Meta-analysis of sentinel node biopsy in ductal carcinoma in situ of the breast (Br J Surg 2008; 95: 547–554)
Authors: Meijnen P , Th. Rutgers E J 
Published: September 2008

Abstract
The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved,appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.
‘It's gotten a bit old, charity’: Young adults in New Zealand talk about poverty, charitable giving and aid appeals
Authors: Dalton S. , Madden H. , Chamberlain K. , Carr S. , Lyons A. C. 
Published: September 2008

AbstractAn extensive body of literature exists on the phenomena of poverty, charitable giving and the effectiveness of aid appeals. To date psychological research has predominantly focused on individualistic models to explain people's understandings of poverty and their charitable giving practices. Based upon a social constructionist epistemology, this study investigates how understandings of aid appeals, poverty and charitable giving are discursively produced and constructed in relation to one another through an analysis of New Zealand young adults' talk about these issues. Data were collected from three focus group discussions among pre‐existing friendship groups comprising three male and nine female students aged between 18 and 25. A brief video clip of aid appeals was used to stimulate discussion on poverty and charitable giving. Analysis of these discussions revealed three discursive themes relating to the aid appeals: local versus international need, emotional arousal and insufficient information. Drawing upon these themes the participants constructed poverty as relative or extreme, and largely explained by educational deficits. They constructed charitable giving as solicited through aid appeals, as compromised through immunity to such appeals, and as diminished through positionings of self‐help and self‐responsibility. These discursive constructions were drawn on by participants to legitimate their own non‐donor position. Copyright © 2008 John Wiley & Sons, Ltd.
Studies of the Structure of the N‐Terminal Domain from the Y4 Receptor—a G Protein‐Coupled Receptor—and its Interaction with Hormones from the NPY Family
Authors: Zou Chao , Kumaran Sowmini , Markovic Stefan , Walser Reto , Zerbe Oliver 
Published: September 2008

AbstractBinding of peptide hormones to G protein‐coupled receptors is believed to be mediated through formation of contacts of the ligands with residues of the extracellular loops of family 1 GPCRs. Here we have investigated whether additional binding sites exist within the N‐terminal domain, as studied in the form of binding of peptides from the neuropeptide Y (NPY) family to the N terminus of the Y4 receptor (N‐Y4). The N‐terminal domain of the Y4 receptor has been expressed in isotopically enriched form and studied by solution NMR spectroscopy. The peptide is unstructured in solution, whereas a micelle‐associated helical segment is formed in the presence of dodecylphosphocholine (DPC) or sodium dodecylsulfate (SDS). As measured by surface plasmon resonance (SPR) spectroscopy, N‐Y4 binds with approximately 50 μM affinity to the pancreatic polypeptide (PP), a high‐affinity ligand to the Y4 receptor, whereas binding to neuropeptide Y (NPY) and peptide YY (PYY) is much weaker. Residues critical for binding in PP and in N‐Y4 have been identified by site‐directed mutagenesis. The data indicate that electrostatic interactions dominate and that this interaction is mediated by acidic ligand and basic receptor residues. Residues of N‐Y4 are likely to contribute to the binding of PP, and in addition might possibly also help to transfer the hormone from the membrane‐bound state into the receptor binding pocket.
Reactions of Uranium Atoms with Ammonia: Infrared Spectra and Quasi‐Relativistic Calculations of the U:NH3, H2NUH, and HNUH2 Complexes
Authors: Wang Xuefeng , Andrews Lester , Marsden Colin J. 
Published: September 2008

AbstractAmmonia molecules interact with U atoms, and the resulting U:NH3 complex rearranges upon visible irradiation to form the H2NUH and HNUH2 molecules in excess argon. These products are identified by functional group frequencies, 15NH3 and ND3 isotopic shifts, and comparison to frequencies calculated by using density functional theory. The NU π bond in HNUH2 is enhanced by partial triple‐bond character through N(2p) to U(5f) conjugation, which is comparable to that found in the analogous HNThH2 molecule. These products also form complexes with additional ammonia molecules in the matrix. The interesting higher‐energy NUH3 complex is not formed.
Improving Photocurrent Generation: Supramolecularly and Covalently Functionalized Single‐Wall Carbon Nanotubes–Polymer/Porphyrin Donor–Acceptor Nanohybrids
Authors: Rahman G. M. Aminur , Troeger Anna , Sgobba Vito , Guldi Dirk M. , Jux Norbert , Balbino Domenico , Tchoul Maxim N. , Ford Warren T. , Mateo‐Alonso Aurelio , Prato Maurizio 
Published: September 2008

AbstractElectrostatic interactions: A versatile donor–acceptor system has been constructed by exploiting the electrostatic interactions between covalently and noncovalently polymer‐functionalized SWNTs (i.e., SWNT–PVBTAn+ and SWNT/PVBTAn+) and porphyrins (i.e., H2P8− or ZnP8−). The nanohybrids thus formed afford long‐lived radical–ion pairs and valuable photocurrent conversions (see figure).magnified imageNovel nanohybrids based on covalently and noncovalently functionalized single‐wall carbon nanotubes (SWNTs) have been prepared and assembled for the construction of photoactive electrodes. Polymer‐grafted SWNTs were synthesized by free‐radical polymerization of (vinylbenzyl)trimethylammonium chloride. Poly[(vinylbenzyl)trimethylammonium chloride] (PVBTAn+) was also noncovalently wrapped around SWNTs to form stable, positively charged SWNT/PVBTAn+ suspensions in water. Versatile donor–acceptor nanohybrids were prepared by using the electrostatic/van der Waals interactions between covalent SWNT–PVBTAn+ and/or noncovalent SWNT/PVBTAn+ and porphyrins (H2P8− and/or ZnP8−). Several spectroscopic, microscopic, transient, and photoelectrochemical measurements were taken to characterize the resulting supramolecular complexes. Photoexcitation of the nanohybrids afforded long‐lived radical ion pairs with lifetimes as long as 2.2 μs. In the final part, photoactive electrodes were constructed by using a layer‐by‐layer technique on an indium tin oxide covered glass support. Photocurrent measurements gave remarkable internal photon‐to‐current efficiencies of 3.81 and 9.90 % for the covalent ZnP8−/SWNT–PVBTAn+ and noncovalent ZnP8−/SWNT/PVBTAn+ complex, respectively, when a potential of 0.5 V was applied.
Reactions of 16e CpCo Half‐Sandwich Complexes Containing a Chelating 1,2‐Dicarba‐closo‐dodecaborane‐1,2‐dichalcogenolate Ligand with Ethynylferrocene and Dimethyl Acetylenedicarboxylate
Authors: Xu Bao‐Hua , Peng Xu‐Qing , Li Yi‐Zhi , Yan Hong 
Published: September 2008

AbstractThe reaction of the 16e half‐sandwich complex [CpCo(S2C2B10H10)] (1 S; Cp: cyclopentadienyl) with ethynylferrocene in CH2Cl2 at ambient temperature leads to [CpCo(S2C2B10H9)(CH2CFc)] (2 S; Fc: ferrocenyl) and 1,2,4‐triferrocenylbenzene. In 2 S, B substitution occurs at the carborane cage in the position B(3)/B(6) with the formation of a CB bond. In the presence of the protic solvent MeOH, 2 S loses a CpCo fragment to generate [(CH2CFc)(S2C2B10H9)] (3 S). On the other hand, 2 S can take a free CpCo fragment to form [(CpCo)2(S2C2B9H8)(CHCFc)] (4 S) containing a nido‐C2B9 unit. In sharp contrast, [CpCo(Se2C2B10H10)] (1 Se) does not react with the alkyne in CH2Cl2, but in MeOH [(CHCFc)(Se2C2B10H10)] (5 Se) is generated without the presence of a CpCo unit. The reaction of 1 with dimethyl acetylenedicarboxylate at ambient temperature leads to insertion compounds [CpCo(E2C2B10H10){(MeO2C)CC(CO2Me)}] (6 S, E=S; 6 Se, E=Se). Upon heating, 6 S rearranges to two geometrical isomers [CpCo(S2C2B10H9){(MeO2C)CCH(CO2Me)}] (7 S) and [CpCo(S2C2B10H9){(MeO2C)CHC(CO2Me)}] (8 S). In both, BH functionalization takes place at the carborane cage in the position B(3)/B(6), but 7 S is a 16e complex with an olefinic unit in a Z configuration, and 8 S is an 18e complex containing an alkyl BCH group. Further treatment of 7 S with dimethyl acetylenedicarboxylate at ambient temperature affords two B‐disubstituted complexes at the carborane cage in the positions of the B(3) and B(6) sites, that is, [CpCo(S2C2B10H8){(MeO2C)CCH(CO2Me)}2] (9 S) and [CpCo(S2C2B10H8){(MeO2C)CHC(CO2Me)}{(MeO2C)CCH(CO2Me)}] (10 S). Compound 9 S is a 16e complex with two olefinic units in E/E configurations, whereas 10 S is an 18e species containing both an olefinic substituent and an alkyl BCH unit. The reaction of 7 S with methyl acetylenemonocarboxylate at ambient temperature leads to the sole 16e compound [CpCo(S2C2B10H8){CHCH(CO2Me)}{(MeO2C)CCH(CO2Me)}] (11 S). In contrast, 6 Se does not rearrange. All new complexes 2 S–4 S, 5 Se, 6 Se, and 7 S–11 S were characterized by NMR spectroscopy (1H, 11B, 13C) and X‐ray structural analyses were performed for 2 S–4 S, 5 Se, 6 Se, and 7 S–9 S.
ChemInform Abstract: Stochastic Search of the Quantum Conformational Sapce of Small Lithium and Bimetallic Lithium—Sodium Clusters
Authors: Perez Jhon F. , Florez Elizabeth , Hadad Cacier Z. , Fuentealba Patricio , Restrepo Albeiro 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Vanadium Oxide Compounds with Quantum Monte Carlo
Authors: Bande Annika , Luechow Arne 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Silver(I) Chalcogenide Halides Ag19Te6Br7, Ag19Te6Br5.4I1.6, and Ag19Te5SeBr7.
Authors: Nilges Tom , Messel Julia , Bawohl Melanie , Lange Stefan 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Origins of Superstructure Ordering and Incommensurability in Stuffed CoSn‐Type Phases.
Authors: Fredrickson Daniel C. , Lidin Sven , Venturini Gerard , Malaman Bernard , Christensen Jeppe 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: The Crystal Structure of LiMgAlD6 from Combined Neutron and Synchroton X‐Ray Powder Diffraction.
Authors: Grove Hilde , Brinks Hendrik W. , Loevvik Ole M. , Heyn Richard H. , Hauback Bjoern C. 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Crystal Structure and Electronic Properties of New Uranium Intermetallic Compound UGa1.85Zr0.15.
Authors: Havela L. , Andreev A. V. , Goncalves A. P. , Sebek J. , Sechovsky V. , Popov Y. F. 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Neutron Powder Diffraction and Solid‐State Deuterium NMR Studies of Ca2RuD6 and the Stability of Transition Metal Hexahydride Salts.
Authors: Moyer Ralph O. Jr. , Antao Sytle M. , Toby Brian H. , Morin Frederick G. , Gilson Denis F. R. 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Optimization of Pr3+, Tb3+, and Sm3+ Co‐Doped (Y0.65Gd0.35) BO3:Eu0.053+ VUV Phosphors Through Combinatorial Approach.
Authors: Chen Lei , Fu Yibing , Zhang Guobin , Bao Jun , Gao Chen 
Published: September 2008

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.