bluuebunny/crossref_metadata_2025_split huggingface dataset:
Responsive Polymers at the Biology/Materials Science Interface
Authors: Alexander C. , Shakesheff K. M. 
Published: November 2006

AbstractSynthetic polymers can be prepared with features that combine many of the advantageous properties of natural materials, including environmental response. This Research News article considers the different types of response that can be ‘programmed in' to polymers and the applications that are developing as a consequence of the designed responses. In particular, we focus on two key applications at the biology/materials science interface: responsive drug delivery systems and ‘smart' surfaces for cell culture and regenerative medicine.
A Cautionary Note on Design Implications when the Primary Analysis is a Stratified Analysis of a Binary Endpoint
Authors: Chuang‐Stein Christy 
Published: November 2006

AbstractWhen the primary analysis is a stratified analysis of a binary endpoint, the commonly used CMH procedure could produce results that are quite different from those obtained by ignoring the stratification factor altogether. This means that when designing a trial with a primary endpoint that is binary, it is important that one keep in mind how the data will be analyzed. Only when design and analysis are considered in tandem will the study possess the desired properties. The discussion in this paper is illustrated by a hypothetical example, which nevertheless resembles the findings from a confirmatory trial involving the evaluation of a biologic for severe sepsis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microtiter Plate‐Based Screening for the Optimization of DNA–Protein Conjugate Synthesis by Means of Expressed Protein Ligation
Authors: Lovrinovic Marina , Niemeyer Christof M. 
Published: November 2006

AbstractWe report a rapid microtiter plate screening assay for the optimization of the synthesis of covalent DNA–protein conjugates by means of expressed protein ligation (EPL). The EPL method allows for the site‐specific coupling of cysteine‐modified DNA oligomers with recombinant intein‐fusion proteins, the latter containing a C‐terminal thioester that enables a mild and highly specific reaction with N‐terminal cysteine compounds. To screen for optimal reaction conditions, we developed a microtiter plate‐based assay that utilizes DNA‐directed immobilization of the products formed in the ligation reaction of cysteine‐modified DNA oligonucleotides with the model protein thioester of the maltose‐binding protein (MBP), recombinantly expressed as an intein‐fusion protein in E. coli. The screening assay allowed the rapid quantitative monitoring of various reaction parameters, such as the ratio of the reactants, reaction times, pH and ion strength of the buffer, the influence of various thiol additives and the nature of the chemical linker within the cysteine‐bearing DNA oligonucleotide. As the consequence of the assay‐based optimization, the ligation of MBP with the oligonucleotide was improved to near quantitative yields.
Shape Dependence in the Formation of Condensed Phases Exhibited by Disubstituted Sucrose Esters
Authors: Molinier Valérie , Kouwer Paul J. J. , Fitremann Juliette , Bouchu Alain , Mackenzie Grahame , Queneau Yves , Goodby John W. 
Published: November 2006

AbstractWe report on the self‐organizing properties of sucrose esters that are di‐(1′,6′, 1′,6, and 6,6′)‐substituted with aliphatic chains of identical or different chain lengths and levels of saturation. For the materials possessing two saturated aliphatic chains, the compounds exhibited thermotropic lamellar smectic A phases. A remarkable new phase transition was observed for the di‐octadecanoyl homologue in which one smectic A phase transformed into another with a continuous change in layer spacing, but with a discontinuous change in the correlation length. The incorporation of long cis‐unsaturated chains led to increased cross‐sectional areas of the chains relative to the sucrose head groups and, hence, columnar phases were observed.
Unexpected Conformational Properties of 1‐Trifluoromethyl‐1‐Silacyclohexane, C5H10SiHCF3: Gas Electron Diffraction, Low‐Temperature NMR Spectropic Studies, and Quantum Chemical Calculations
Authors: Girichev Georgiy V. , Giricheva Nina I. , Bodi Andras , Gudnason Palmar I. , Jonsdottir Sigridur , Kvaran Agust , Arnason Ingvar , Oberhammer Heinz 
Published: November 2006

AbstractThe molecular structure of axial and equatorial conformers of 1‐trifluoromethyl‐1‐silacyclohexane, (C5H10SiHCF3), as well as the thermodynamic equilibrium between these species was investigated by means of gas electron diffraction (GED), dynamic nuclear magnetic resonance (DNMR) spectroscopy, and quantum chemical calculations (B3LYP, MP2, and CBS‐QB3). According to GED, the compound exists as a mixture of two Cs symmetry conformers possessing the chair conformation of the six‐membered ring and differing in the axial or equatorial position of the CF3 group (axial=58(12) mol %/equatorial=42(12) mol %) at T=293 K. This result is in a good agreement with the theoretical prediction. This is, however, in sharp contrast to the conformational properties of the cyclohexane analogue. The main structural feature for both conformers is the unusually long exocyclic bond length SiC 1.934(10) Å. A low‐temperature 19F NMR experiment results in an axial/equatorial ratio of 17(2) mol %:83(2) mol % at 113 K and a ΔG ≠ of 5.5(2) kcal mol−1. CBS‐QB3 calculations in the gas‐phase and solvation effect calculations using the PCM(B3LYP/6‐311G*) and IPCM(B3LYP/6‐311G*) models were applied to estimate the axial/equatorial ratio in the 100–300 K temperature range, which showed excellent agreement with the experimental results. The minimum energy pathways for the chair‐to‐chair inversion of trifluoromethylsilacyclohexane and methylsilacyclohexane were also calculated using the STQN(Path) method.
Metal‐Ion‐Coordinating Properties of the Dinucleotide 2′‐Deoxyguanylyl(5′→3′)‐2′‐deoxy‐5′‐guanylate (d(pGpG)3−): Isomeric Equilibria Including Macrochelated Complexes Relevant for Nucleic Acids
Authors: Knobloch Bernd , Sigel Helmut , Okruszek Andrzej , Sigel Roland K. O. 
Published: November 2006

AbstractThe interaction between divalent metal ions and nucleic acids is well known, yet knowledge about the strength of binding of labile metal ions at the various sites is very scarce. We have therefore studied the stabilities of complexes formed between the nucleic acid model d(pGpG) and the essential metal ions Mg2+ and Zn2+ as well as with the generally toxic ions Cd2+ and Pb2+ by potentiometric pH titrations; all four ions are of relevance in ribozyme chemistry. A comparison of the present results with earlier data obtained for M(pUpU)− complexes allows the conclusion that phosphate‐bound Mg2+ and Cd2+ form macrochelates by interaction with N7, whereas the also phosphate‐coordinated Pb2+ forms a 10‐membered chelate with the neighboring phosphate diester bridge. Zn2+ forms both types of chelates with formation degrees of about 91 % and 2.4 % for Zn[d(pGpG)]${{{- \hfill \atop {\rm cl}/{\rm N7}\hfill}}}$ and Zn[d(pGpG)]${{{- \hfill \atop {\rm cl}/{\rm PO}\hfill}}}$, respectively; the open form with Zn2+ bound only to the terminal phosphate group, Zn[d(pGpG)]${{{- \hfill \atop {\rm op}\hfill}}}$, amounts to about 6.8 %. The various intramolecular equilibria have also been quantified for the other metal ions. Zn2+, Cu2+, and Cd2+ also form macrochelates in the monoprotonated M[H;d(pGpG)] species (the proton being at the terminal phosphate group), that is, the metal ion at N7 interacts to some extent with the P(O)2(OH)− group. Thus, this study demonstrates that the coordinating properties of the various metal ions toward a pGpG unit in a nucleic acid differ: Mg2+, Zn2+, and Cd2+ have a significant tendency to bridge the distance between N7 and the phosphate group of a (d)GMP unit, although to various extents, whereas Pb2+ (and possibly Ca2+) prefer a pure phosphate coordination.
[40]Nonaphyrin(1.1.1.1.1.1.1.1.1) and Its Heterometallic Complexes with Palladium–Carbon Bonds
Authors: Kamimura Yiho , Shimizu Soji , Osuka Atsuhiro 
Published: November 2006

Abstractmeso‐Pentafluorophenyl‐ substituted [40]nonaphyrin(1.1.1.1.1.1.1.1.1) 3 has been prepared by using a stepwise ring‐size‐selective synthesis, and has been reduced with NaBH4 to [42]nonaphyrin(1.1.1.1.1.1.1.1.1) 5. Structurally, 3 is characterized by a figure‐of‐eight shape, consisting of a porphyrin‐like tetrapyrrolic segment and a hexaphyrin‐like hexapyrrolic segment, whereas 5 has been found to adopt a distorted nonplanar butterfly‐like shape. In the mono‐metal complexes 6 and 7, a ZnII or CuII ion is bound by the porphyrin‐like tetrapyrrolic segment, maintaining the overall structure of 3. Similarly to 3, complexes 6 and 7 are interconvertible with the corresponding complexes 9 and 10 through two‐electron reduction with NaBH4 and oxidation with DDQ. The metal‐free hexaphyrin‐like segments of 6 and 7 have been shown to serve as a suitable platform for the complexation of two palladium ions, providing hetero‐trinuclear metal complexes 11 (ZnII–PdII–PdII) and 13 (CuII–PdII–PdII) in high yields, in which the Zn or Cu ion resides at the same porphyrin‐like segment, and one Pd ion is bound in an NNCC fashion through double CH bond activation while the other is bound in an NNC fashion with single CH bond activation. Multi‐metal complexes 11, 12, and 13 exhibit small electrochemical HOMO–LUMO gaps (<0.6 eV), despite their nonplanar conformations.
Hyperfine Coupling Tensors of the Benzosemiquinone Radical Anion from Car–Parrinello Molecular Dynamics
Authors: Asher James R. , Kaupp Martin 
Published: November 2006

AbstractBased on Car–Parrinello ab initio molecular dynamics simulations of the benzosemiquinone radical anion in both aqueous solution and the gas phase, density functional calculations provide the currently most refined EPR hyperfine coupling (HFC) tensors of semiquinone nuclei and solvent protons. For snapshots taken at regular intervals from the molecular dynamics trajectories, cluster models with different criteria for inclusion of water molecules and an additional continuum solvent model are used to analyse the HFCs. These models provide a detailed picture of the effects of dynamics and of different intermolecular interactions on the spin‐density distribution and HFC tensors. Comparison with static calculations allows an assessment of the importance of dynamical effects, and of error compensation in static DFT calculations. Solvent proton HFCs depend characteristically on the position relative to the semiquinone radical anion. A point‐dipolar model works well for in‐plane hydrogen‐bonded protons but deviates from the quantum chemical values for out‐of‐plane hydrogen bonding.
On the Origin of Red and Blue Shifts of XH and CH Stretching Vibrations in Formic Acid (Formate Ion) and Proton Donor Complexes
Authors: Tâme Parreira Renato Luis , Galembeck Sérgio Emanuel , Hobza Pavel 
Published: November 2006

AbstractComplexes between formic acid or formate anion and various proton donors (HF, H2O, NH3, and CH4) are studied by the MP2 and B3LYP methods with the 6‐311++G(3df,3pd) basis set. Formation of a complex is characterized by electron‐density transfer from electron donor to ligands. This transfer is much larger with the formate anion, for which it exceeds 0.1 e. Electron‐density transfer from electron lone pairs of the electron donor is directed into σ* antibonding orbitals of XH bonds of the electron acceptor and leads to elongation of the bond and a red shift of the XH stretching frequency (standard H‐bonding). However, pronounced electron‐density transfer from electron lone pairs of the electron donor also leads to reorganization of the electron density in the electron donor, which results in changes in geometry and vibrational frequency. These changes are largest for the CH bonds of formic acid and formate anion, which do not participate in H‐bonding. The resulting blue shift of this stretching frequency is substantial and amounts to almost 35 and 170 cm−1, respectively.
pH Sensitivity of SiC Linked Organic Monolayers on Crystalline Silicon Surfaces
Authors: Faber Erik J. , Sparreboom Wouter , Groeneveld Wilrike , de Smet Louis C. P. M. , Bomer Johan , Olthuis Wouter , Zuilhof Han , Sudhölter Ernst J. R. , Bergveld Piet , van den Berg Albert 
Published: November 2006

AbstractThe electrochemical behavior of SiC linked organic monolayers is studied in electrolyte–insulator–Si devices, under conditions normally encountered in potentiometric biosensors, to gain fundamental knowledge on the behavior of such Si electrodes under practical conditions. This is done via titration experiments, Mott–Schottky data analysis, and data fitting using a site‐binding model. The results are compared with those of native SiO2 layers and native SiO2 layers modified with hexamethyldisilazane. All samples display pH sensitivity. The number of SiOH groups on the alkylated samples is calculated to be less than 0.7 % of that of a pure SiO2 insulator, which still causes a pH sensitivity of ≈25 mV per pH unit in the pH range: 4–7. The alkylated samples hardly suffer from response changes during up‐ and down‐going titrations, which indicates that very little oxide is additionally formed during the measurements. The pKa values of all samples with monolayers (4.0–4.4) are lower than that of native SiO2 (6.0). The long‐term drift (of approximately 1 mV h−1) is moderate. The results indicate that biosensors composed of alkylated Si substrates are feasible if a cross‐sensitivity towards pH in the sensor signal is taken into account.
Synthesis and Anion‐Selective Complexation of Homobenzylic Tripodal Thiourea Derivatives
Authors: Hisaki Ichiro , Sasaki Shin‐ichi , Hirose Keiji , Tobe Yoshito 
Published: November 2006

AbstractCryptand‐ and tripod‐type thiourea derivatives 4b and 5a–d, which have binding functionalities at the homobenzylic positions, were synthesized as possible neutral receptors toward anions with an expectation that the three binding sites work cooperatively to bind an anion selectively. 1H NMR spectroscopic monitoring of the titration of cryptand 4b with CH3CO2–, Cl–, and F– in CDCl2CDCl2 at 100 °C showed that the binding constants were considerably smaller than those of tripodal thiourea 5a, presumably owing to the presence of strong intramolecular hydrogen bonding in 4b. Complexation constants of tripodal receptors 5a–d with H2PO4–, CH3CO2–, Cl–, and Br– anions were evaluated by 1H NMR and/or UV/Vis spectroscopic analysis of the titration in DMSO. Though tripodal receptors 5a,b undergo complexation with phosphate anion in a 1:1 stoichiometry, their association constants were not as large as simple reference compound 14 probably because of the steric hindrance around the binding sites and the large entropy cost for cooperative binding. Receptor 5c exhibits complexation in a 1:2 stoichiometry with H2PO4– and CH3CO2–, whereas it forms 1:1 complexes with chloride and bromide anions because of the subtle balance between the steric hindrance and the binding ability. However, by increasing the acidity of the thiourea functionality, receptor 5d exhibited remarkably enhanced binding ability and selectivity toward H2PO4– compared to those of reference compound 15 presumably through cooperative complexation of the three binding sites to the guest anion. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Push‐Pull Oligomers with 2,2‐Dicyanovinyl Groups as Electron Acceptors
Authors: Meier Herbert , Mühling Bastian , Gerold Jürgen , Jacob Dominic , Oehlhof Annette 
Published: November 2006

AbstractThree conjugated oligomer series with terminal donor–acceptor substitution were studied: oligo(1,4‐phenylenevinylene)s DAOPVs 4a–d (n = 1–4), oligo(1,4‐phenyleneethynylene)s DAOPEs 6a–d (n = 1–4) and oligo(2,5‐thienyleneethynylene)s DAOTEs 8a–e (n = 1–5). Dialkylamino or methoxy groups served as electron donors and 2,2‐dicyanovinyl groups as strong electron acceptors. The push‐pull effect polarizes the molecular chains – an effect which is documented by the splitting of the 13C chemical shifts of two carbon atoms of the double or triple bonds in the chain. For higher oligomers (n ≥ 3), the effect is mainly localized at the chain ends. The long‐wavelength absorption results in a charge‐transfer band which loses gradually its CT character since the intramolecular charge transfer (ICT) declines with increasing numbers n of repeat units (increasing chromophore extension, increasing distance D–A). As a consequence, theDAOPVs 4a–d and the DAOPEs 6a–d represent hypsochromic series, for which the λmax values decrease steadily from n = 1 to n = 4. This is also true for the DAOTE series 8a–e, but contrary to 4a–d and 6a–d the decrease is very small in the beginning [λmax(1) – λmax(2) = 1 nm] and grows with increasing n to λmax(4) – λmax(5) = 29 nm. Thus, series 8a–e represents an until now unknown type of conjugated push‐pull oligomers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Alternative method to locate centre of rigidity in asymmetric buildings
Authors: Basu Dhiman , Jain Sudhir K. 
Published: November 2006

AbstractResponse of asymmetric buildup under earthquake excitation often involves lateral vibration coupled with torsional vibration. Floor slab is, in general, assumed as rigid along the in‐plane direction. Building code provisions to account for the torsional effect in static force procedure are based on centre of rigidity or shear centre of the building. A convenient procedure is developed here to locate the centre of rigidity or shear centre, which can be implemented, using any standard building analysis software. The procedure is applicable for orthogonal as well as non‐orthogonal building systems and accounts for all possible definitions of static eccentricity to compute the design response. An irregular building is analysed to illustrate the proposed methodology. Significant variation in member force resultants is observed due to different definitions of static eccentricity. Finally, a mathematical proof is presented to substantiate the applicability of the proposed procedure to a non‐orthogonal building. Copyright © 2006 John Wiley & Sons, Ltd.
Deficiency of tenascin‐C attenuates liver fibrosis in immune‐mediated chronic hepatitis in mice
Authors: El‐Karef A , Yoshida T , Gabazza EC , Nishioka T , Inada H , Sakakura T , Imanaka‐Yoshida K 
Published: November 2006

AbstractTenascin‐C (TNC), an extracellular matrix glycoprotein, is upregulated in chronic liver disease. Here, we investigated the contribution of TNC to liver fibrogenesis by comparing immune‐mediated hepatitis in wild‐type (WT) and TNC‐null (TNKO) mice. Eight‐week‐old BALB/c mice received weekly intravenous injections of concanavalin A to induce hepatitis, and were sacrificed one week after the 3rd, 6th, 9th, and 12th injections. In WT livers, immunohistochemical staining revealed a gradual increase in TNC deposition. TNC mRNA levels also increased sequentially and peaked after the 9th injection. Collagen deposition, stained with picrosirius red, was significantly less intense in TNKO mice than in WT mice, and procollagen I and III transcripts were significantly upregulated in WT mice compared with TNKO mice. Inflammatory infiltrates were most prominent after the 3rd‐6th injections in both groups and were less intense in TNKO mice than in WT mice. Interferon‐γ, tumour necrosis factor‐α, and interleukin‐4 mRNA levels were significantly higher in WT mice than in TNKO mice, while activated hepatic stellate cells (HSCs) and myofibroblasts, a cellular source of TNC and procollagens, were more common in WT livers. Transforming growth factor (TGF)‐β1 mRNA expression was significantly upregulated in WT mice, but not in TNKO mice. In conclusion, TNC can promote liver fibrogenesis through enhancement of inflammatory response with cytokine upregulation, HSC recruitment, and TGF‐β expression during progression of hepatitis to fibrosis. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
The CADEUS study: methods and logistics
Authors: Depont F. , Fourrier A. , Merlière Y. , Droz C. , Amouretti M. , Bégaud B. , Bénichou J. , Moride Y. , Blin P. , Moore N. 
Published: November 2006

AbstractPurposeAt the request of the French Health authorities, a study called CADEUS (COX‐2 inhibitors and NSAIDs: description of users) aimed to describe the users of cyclo‐oxygenase (COX)‐2 inhibitors and traditional non‐selective non‐steroidal anti‐inflammatory drugs (tNSAIDs). We report here the methodology, logistics and study design performances.MethodsCADEUS is a cohort study designed to include 40 000 patients randomly sampled monthly in the French National Healthcare Insurance database, who received at least one dispensation of celecoxib, rofecoxib or tNSAIDs (1:1:2), from September 2003 to August 2004. Patients and prescribers were asked to fill a questionnaire on indication, medical history, risk factors and hospitalizations since drug acquisition. There was no reminder. For each respondent, healthcare resources used for the 6 months before and after inclusion were extracted from the database. Response rate, response delay, responders and non‐responders characteristics were assessed.ResultsOf the 222 879 patients and their prescribers contacted, 20.8% patients and 32.6% prescribers responded. Median response delay was 16 days for patients and 17 days for physicians. Factors associated with patient response were age, cohort, type of prescriber and period of inclusion.ConclusionThis is the first study of this design in France, combining data from a claims database and direct patient and prescriber questionnaires. Copyright © 2006 John Wiley & Sons, Ltd.
Kinetics of the pH‐independent hydrolyses of 4‐nitrophenyl chloroformate and 4‐nitrophenyl heptafluorobutyrate in water‐acetonitrile mixtures: consequences of solvent composition and ester hydrophobicity
Authors: El Seoud Omar A. , Siviero Fábio 
Published: November 2006

AbstractThe pH‐independent hydrolyses of 4‐nitrophenyl chloroformate, NPCF and 4‐nitrophenyl heptafluorobutyrate, NPFB in aqueous acetonitrile were studied spectrophotometrically from 15 to 45 °C. The binary solvent composition covers water concentrations from 2.349 to 53.207 and from 2.745 to 53.333 mol L−1 for NPCF and NPFB, respectively. For both esters, the dependence of log (kobs), the observed rate constant, on log [water] is sigmoidal. The approximate kinetic orders with respect to water were found to be 2 and 3 for NPCF and NPFB, respectively. ΔG≠ gradually decreases as a function of increasing [water], due to a complex, quasi‐mirror image compensation of ΔH≠ and ΔS≠; both parameters increase. The structures of the transition states were probed by a proton inventory study, carried out in the presence of L2O mole fractions (L = H or D) of 0.190, 0.540, 0.890 and 0.180, 0.529, 0.890, for NPCF and NPFB, respectively. Plots of observed rate constants versus the atom fraction of deuterium in the solvent curve downward. Cyclic transition state models were fitted to the kinetic data; these models contain the ester and two water molecules (NPCF) or three water molecules (NPFB). Thus, the sigmoidal dependences of log (kobs) on log [water] are not due to a change in the number of water molecules in the transition states as a function of increasing [water]. The binary solvent mixture is micro‐heterogeneous; there exists two “micro‐domains,” one consists predominantly of coordinated water molecules, the other consists mostly of acetonitrile hydrogen‐bonded to water molecules. NPCF is 232 times more soluble in water than NPFB. That is, the former ester is dissolved in the outer, more polar periphery of these micro‐domains whereas the more hydrophobic NPFB is dissolved in their inner, less polar interiors. This conclusion is corroborated by comparing the dependence on log [water] of log [kobs], and of ET, the empirical solvent polarity parameter, as measured by solvatochromic probes of increasing hydrophobicity. Copyright © 2006 John Wiley & Sons, Ltd.