bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous crosslinking of poly(1,5‐dioxepan‐2‐one) originating from ether bond fragmentation
Authors: Höglund Anders , Albertsson Ann‐Christine 
Published: September 2008

AbstractThe spontaneous reaction of unsaturated double bonds induced by the fragmentation of ether bonds is presented as a method to obtain a crosslinked polymer material. Poly(1,5‐dioxepan‐2‐one) (PDXO) was synthesized using three different polymerization techniques to investigate the influence of the synthesis conditions on the ether bond fragmentation. It was found that thermal fragmentation of the ether bonds in the polymer main chain occurred when the synthesis temperature was 140 °C or higher. The double bonds produced reacted spontaneously to form crosslinks between the polymer chains. The formation of a network structure was confirmed by Fourier transform infrared spectrometry and differential scanning calorimetry. In addition, the low molar mass species released during hydrolysis of the DXO polymers were monitored by ESI‐MS and MALDI‐TOF‐MS. Ether bond fragmentation also occurred during the ionization in the electrospray instrument, but predominantly in the lower mass region. No fragmentation took place during MALDI ionization, but it was possible to detect water‐soluble DXO oligomers with a molar mass up to approximately 5000 g/mol. The results show that ether bond fragmentation can be used to form a network structure of PDXO. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7258–7267, 2008
Influence of multiwall carbon nanotubes on morphology and electrical conductivity of PP/ABS blends
Authors: Khare Rupesh A. , Bhattacharyya Arup R. , Kulkarni Ajit R. , Saroop Madhumita , Biswas Amit 
Published: September 2008

AbstractPolypropylene (PP) and acrylonitrile‐butadiene‐styrene (ABS) blends with multiwall carbon nanotubes (MWNT) were prepared by melt mixing. PP/ABS blends without MWNT revealed coarse co continuous structures on varying the ABS content from 40 to 70 wt %. Bulk electrical conductivity of the blends showed lower percolation threshold (0.4–0.5 wt %) in the 45/55 co continuous blends whereas the percolation threshold was between 2 and 3 wt % in matrix‐particle dispersed morphology of 80/20 blends. Interestingly, droplet size was observed to decrease with addition of MWNT above percolation threshold in 80/20 blends. Further, the bulk electrical conductivity was found to be dependent on the melt flow index of PP. The non‐polar or weakly polar nature of blends constituents resulted in the temperature independent dielectric constant, dielectric loss, and DC electrical conductivity. Rheological analysis revealed the formation of 3D network‐like structure in 80/20 PP/ABS blends at 3 wt % MWNT. An attempt was made to understand the relationship between rheology, morphology, and electrical conductivity of these blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2286–2295, 2008
Saccharide‐structure effects on poly N‐isopropylacrylamide phase transition in aqueous media; Reflections on protein stability
Authors: Shpigelman Avi , Portnaya Irina , Ramon Ory , Livney Yoav D. 
Published: September 2008

AbstractProtein stability in aqueous solutions is important in numerous fields, particularly biotechnology and food‐science. To shed new light on the protective effect of carbohydrates on proteins, we studied saccharide‐structure effects in aqueous solutions on the coil‐to‐globule transition occurring at the lower critical solution temperature (LCST) of poly‐N‐isopropylacrylamide (PNIPA), an isomer of polyleucine, as a simple model representing certain key behaviors of proteins (e.g., denaturation/renaturation). We systematically selected sugars and polyols to relate structural and physical characteristics of these carbohydrates to their effect on PNIPA solutions. Using isothermal titration‐microcalorimetry, we showed that no significant binding of saccharides to the polymer occurs. Using micro‐DSC, we studied the decreasing polymer LCST temperature with rising carbohydrate concentration. Beyond the expected observation that steric exclusion is important, we observed previously‐unreported significant differences among the effects of isomeric aldohexoses and also among the effects of isomeric diglucoses on PNIPA LCST. We found good correlation between the sugar hydration number and its effect on LCST. We conclude that the larger and denser the hydrated cluster a carbohydrate forms, the worse a cosolvent is for the polymer, and the stronger it's lowering effect of the coil‐to‐globule transition. Such favoring of the compact globule state provides a protective effect against denaturation of globular proteins. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2307–2318, 2008
Rheological studies of the interactions in cellulose/ethylene diamine/salt systems
Authors: Xiao Min , Frey Margaret W. 
Published: September 2008

AbstractDegree of polymerization (DP) of cellulose was measured to confirm that aging time and salt concentration did not cause cellulose degradation. Dynamic rheological studies of cellulose solutions were carried out to probe the evolving interactions between cellulose and ethylene diamine (EDA)/salt solvent system. Potassium thiocyanate (KSCN) was used as the salt in these studies. Steady shear studies indicated that all solutions exhibited shear‐thinning behavior. The empirical Cox‐Merz rule did not hold true for the cellulose system with weak gel microstructure. The shear viscosities at the shear rates explored decreased with aging time. The zero‐shear viscosity, however, increased with increasing salt concentration. Oscillatory shear studies were investigated and the time temperature superposition (TTS) method was used to extend the experimental frequency range of the instrument. The results showed that the average relaxation time of the cellulose system decreased as the sample aged and increased with increasing salt concentration, indicative of dynamic interactions between cellulose and the solvent system in solution. The conformations of cellulose chains were constantly changing over time. The system gelled when the salt concentration was increased to a critical point. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2326–2334, 2008
Blast Impulse at Very Near Distance
Authors: Held Manfred 
Published: September 2008

AbstractSteel cubes and steel spheres were propelled in radial directions by a detonating cylindrical high explosive charge at scaled distances of 0.05–0.25 m kg−1/3. The analysed velocities can be simply transferred to momenta, to energies and analysed impulse densities. A little surprising result is that the cubes with the larger area mass achieved remarkably higher velocities compared to the spheres. This is definitely a result caused by different air drag coefficients.
Structural heterogeneity and protein composition of exosome‐like vesicles (prostasomes) in human semen
Authors: Poliakov Anton , Spilman Michael , Dokland Terje , Amling Christopher L. , Mobley James A. 
Published: September 2008

AbstractBACKGROUNDHuman seminal fluid contains small exosome‐like vesicles called prostasomes. Prostasomes have been reported previously to play an important role in the process of fertilization by boosting survivability and motility of spermatozoa, in addition to modulating acrosomal reactivity. Prostasomes have also been reported to present with sizes varying from 50 to 500 nm and to have multilayered lipid membranes; however, the fine morphology of prostasomes has never been studied in detail.METHODSSucrose gradient‐purified prostasomes were visualized by cryo‐electron microscopy (EM). Protein composition was studied by trypsin in‐gel digestion and liquid chromatography/mass spectrometry.RESULTSHere we report for the first time the detailed structure of seminal prostasomes by cryo‐EM. There are at least three distinct dominant structural types of vesicles present. In parallel with the structural analysis, we have carried out a detailed proteomic analysis of prostasomes, which led to the identification of 440 proteins. This is nearly triple the number of proteins identified to date for these unique particles and a number of the proteins identified previously were cross‐validated in our study.CONCLUSIONFrom the data reported herein, we hypothesize that the structural heterogeneity of the exosome‐like particles in human semen reflects their functional diversity. Our detailed proteomic analysis provided a list of candidate proteins for future structural and functional studies. Prostate 69: 159–167, 2009. © 2008 Wiley–Liss, Inc.
RETRACTED: Interleukin‐4 activates androgen receptor through CBP/p300
Authors: Lee Soo Ok , Chun Jae Yeon , Nadiminty Nagalakshmi , Lou Wei , Feng Siting , Gao Allen C. 
Published: September 2008

AbstractBACKGROUNDAberrant activation of androgen receptor (AR) plays an important role in the progression of castration resistant prostate cancer. Interleukin‐4 (IL‐4) enhances AR activation in the absence of androgen and stimulates castration resistant growth of androgen‐sensitive prostate cancer cells. However, the mechanism of IL‐4 mediated AR activation has not yet been revealed.METHODSThe effect of IL‐4 on CBP/p300 expression was examined by Western blot analysis. The effect of IL‐4 on the interactions of AR and CBP/p300 was examined by co‐immunoprecipitation and ChIP assays. CBP/p300 siRNA was used to knockdown CBP/p300 expression to examine the role of CBP/p300 expression on IL‐4 mediated AR activation.RESULTSWe found that IL‐4 increases CBP/p300 protein expression and enhances interaction of AR with CBP/p300 proteins through an increase in the recruitment of CBP/p300 protein to the androgen responsive elements in the promoters of androgen responsive genes. Down regulation of CBP/p300 expression using CBP/p300 specific siRNA abolished IL‐4 mediated AR activation, suggesting that CBP/p300 is responsible for AR activation induced by IL‐4. Furthermore, AR activation can be enhanced by AR acetylation induced by IL‐4 in prostate cancer cells. The IL‐4 mediated AR acetylation can be blocked by knocking down CBP/p300 expression using CBP/p300 specific siRNA.CONCLUSIONThese results suggest that IL‐4 activates AR through enhanced expression of CBP/p300 and its histone acetyltransferase activity. Prostate 69: 126–132, 2009. © 2008 Wiley–Liss, Inc.
Evaluating the absolute quality of a single protein model using structural features and support vector machines
Authors: Wang Zheng , Tegge Allison N. , Cheng Jianlin 
Published: September 2008

AbstractKnowing the quality of a protein structure model is important for its appropriate usage. We developed a model evaluation method to assess the absolute quality of a single protein model using only structural features with support vector machine regression. The method assigns an absolute quantitative score (i.e. GDT‐TS) to a model by comparing its secondary structure, relative solvent accessibility, contact map, and beta sheet structure with their counterparts predicted from its primary sequence. We trained and tested the method on the CASP6 dataset using cross‐validation. The correlation between predicted and true scores is 0.82. On the independent CASP7 dataset, the correlation averaged over 95 protein targets is 0.76; the average correlation for template‐based and ab initio targets is 0.82 and 0.50, respectively. Furthermore, the predicted absolute quality scores can be used to rank models effectively. The average difference (or loss) between the scores of the top‐ranked models and the best models is 5.70 on the CASP7 targets. This method performs favorably when compared with the other methods used on the same dataset. Moreover, the predicted absolute quality scores are comparable across models for different proteins. These features make the method a valuable tool for model quality assurance and ranking. Proteins 2009. © 2008 Wiley‐Liss, Inc.
The effect of Asp54 phosphorylation on the energetics and dynamics in the response regulator protein Spo0F studied by molecular dynamics
Authors: Peters Günther H. 
Published: September 2008

AbstractThe response regulator protein Spo0F acts as an intermediate phospho‐messenger in the signal transduction pathway that controls initiation of the differentiation process of sporculation in the bacterium Bacillus subtilis. The regulatory domain of Spo0F contains a triad of three conserved aspartate residues, whereof one aspartate (Asp54) is phosphorylated. Using molecular dynamics simulations, we have studied the changes in flexibility induced by phosphorylation and estimated the free energy cost of introducing a phosphate group at this position using alchemical free energy calculations. The deduced conformational flexibility compares well with experimental NMR results. We find that the apo‐conformation of the protein explores a rough energy landscape resulting in a broad population of conformational substates. Phosphorylation of Spo0F reduces protein flexibility, and in particular, the so‐called anchor and recognition regions exhibit lower mobility relative to the apo‐conformation. Phosphorylation of Asp54 (P‐Asp54), in which the apo‐structure coordinates to the magnesium ion, results in extension of the sidechain, and depending on which carboxylate oxygen is phosphorylated, distinct interactions between P‐Asp54 and magnesium ion as well as residues in its proximity are established. However, phosphorylation does not affect the coordination number of the magnesium ion yielding, within the statistical uncertainties, the same free energy change. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Structural basis for the complete loss of GSK3β catalytic activity due to R96 mutation investigated by molecular dynamics study
Authors: Zhang Na , Jiang Yongjun , Zou Jianwei , Yu Qingsen , Zhao Wenna 
Published: September 2008

AbstractMany Ser/Thr protein kinases, to be fully activated, are obligated to introduce a phospho‐Ser/Thr in their activation loop. Presently, the similarity of activation loop between two crystal complexes, i.e. glycogen synthase kinase 3β (GSK3β)‐AMPNP and GSK3β‐sulfate ion complex, indicates that the activation segment of GSK3β is preformed requiring neither a phosphorylation event nor conformational changes. GSK3β, when participated in glycogen synthesis and Wnt signaling pathways, possesses a unique feature with the preference of such substrate with a priming phosphate. Experimental mutagenesis proved that the residue arginine at amino acid 96 mutations to lysine (R96K) or alanine (R96A) selectively abolish activity on the substrates involved in glycogen synthesis signaling pathway. Based on two solved crystal structures, wild type (WT) and two mutants (R96K and R96A) GSK3β‐ATP‐phospho‐Serine (pSer) complexes were modeled. Molecular dynamics simulations and energy analysis were employed to investigate the effect of pSer involvement on the GSK3β structure in WT, and the mechanisms of GSK3β deactivation due to R96K and R96A mutations. The results indicate that the introduction of pSer to WT GSK3β generates a slight lobe closure on GSK3β without any remarkable changes, which may illuminate the experimental conclusion, whereas the conformations of GSK3β and ATP undergo significant changes in two mutants. As to GSK3β, the affected positions distribute over activation loop, α‐helix, and glycine‐rich loop. Based on coupling among the mentioned positions, the allosteric mechanisms for distorted ATP were proposed. Energy decomposition on the residues of activation loop identified the important residues Arg96 and Arg180 in anchoring the phosphate group. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Stability of carbon nanotubes to laser irradiation probed by Raman spectroscopy
Authors: Olevik D. , Soldatov A. V. , Dossot M. , Vigolo B. , Humbert B. , McRae E. 
Published: September 2008

AbstractWe report on a systematic study of the influence of laser irradiation on the Raman spectra of HiPco‐produced single‐wall CNTs. Specifically, we have examined the Raman response of bundled CNTs to: i) laser power density; ii) exposure time and iii) photon energy (1.96 and 2.33 eV). Our results show that irreversible destruction of CNTs in the bundles can occur at even low laser power density (0.15 kW/cm2). The tubes with smaller diameters are influenced first and the rate of CNT destruction increases with photon energy. Finally, we determined that when investigating destruction of CNT bundles, the use of a low laser power density is required because changes in the structure of the bundles can lead to sample temperature changes for otherwise identical measurement parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (b) 245/10
Authors: Thomsen Christian , Dinse Peter , Kuzmany Hans , Roth Siegmar 
Published: September 2008

AbstractThe 22nd Winterschool on Electronic Properties of Novel Materials (IWEPNM 2008) took place from 1 March to 8 March 2008. It continued the tradition of winterschools of this type in Kirchberg/Tirol in its well‐known atmosphere of collegiality and emphasis on scientific exchange between young and experienced scientists.The sessions at the IWEPNM 2008 focused on carbon nanostructure synthesis, purification and separation, the characterization and properties of carbon nanostructures, graphene, fullerenes, endohedrals, fullerides, double‐walled nanotubes, graphite, non‐carbonaceous nanostructures, nanotube optics, molecular electronics, quantum interactions, nanotube devices, electron and heat transport in carbon nanostructures, composites with carbon nanotubes, and on theory and applications of these materials.The program of the Winterschool was composed of invited oral presentations, poster presentations and mini‐workshops. The oral presentations were scheduled in the morning and evening sessions, the mini‐workshops took place during the afternoons, and the posters were presented and discussed in two late‐evening sessions.In 2008 the Winterschool took place again at the Hotel Sonnenalp, a hotel ideally suited for the close interactions of the international participants from many countries. We are grateful to the manager of Hotel Sonnenalp, Frau Edith Mayer, and her staff for the local arrangements as well as her patience for many special requests during the meeting. We owe special thanks to the hotel staff for their careful organization of all events.The Winterschool benefited substantially from support of the Verein zur Förderung der Winterschulen in Kirchberg, of the Verein zur Durchführung der Internationalen Winterschool of Electronic Properties of Novel Materials, as well as from numerous industrial sponsors. We greatly appreciate their financial contribution without which the meeting would have hardly become possible.Finally, special acknowledgments go to all contri‐ butors of the IWEPNM 2008 and to the authors of this volume, the proceedings of the Winterschool. Viera Skákalová was instrumental in compiling and editing the proceedings.The next Winterschool in this series will take place from 7 March to 14 March 2009, in Kirchberg/Tirol, and will be organized again by Christian Thomsen from Berlin.Berlin, Darmstadt, Wien, Stuttgart, 2008
Bayesian fitting of a logistic dose–response curve with numerically derived priors
Authors: Huson L. W. , Kinnersley N. 
Published: September 2008

AbstractIn this report we describe the Bayesian analysis of a logistic dose–response curve in a Phase I study, and we present two simple and intuitive numerical approaches to construction of prior probability distributions for the model parameters. We combine these priors with the expert prior opinion and compare the results of the analyses with those obtained from the use of alternative prior formulations. Copyright © 2008 John Wiley & Sons, Ltd.
A Combined Use of Quantum Chemical Parameters Hydrophobic and Geometrical Descriptors to Establish QSARs of Allylamine Antimycotics
Authors: Hecht Peter , Vyplel Hermann , Nussbaumer Peter , Berner Heinz 
Published: September 2008

AbstractAntifungal activities of a series of allylamines (Figure 1) were correlated with physicochemical parameters describing structural properties, such as lipophilicity, electronic distribution and steric requirements. A large number of physicochemical descriptors were calculated on the basis of a “possible” common conformation for all compounds studied. This conformation was deduced by crystallographic and theoretical studies. By an iteratively used, stepwise, multiple regression analysis (st‐MLR), the initial set of 27 descriptrs could be reduced to a number of 8–9 with only minimal loss of information content. Hence, three highly significant regression equations were established, indcating distinct requirements for the antimycotic activity against three different families of fungi.
Computer Modeling and NMR Studies of Interactions Between Phospholipids and Benzylamines
Authors: Coats Eugene A. , Wiese Michael , Chi Han‐Lin , Cordes Hans P. , Seydel Joachim K. 
Published: September 2008

AbstractAn interactive receptor docking program has been implemented to facilitate computer modeling of the observed binding between N‐alkylbenzylamines and phospholipid vesicles.The computer modeling studies indicate that the aromatic portion of the benzylamines lies in close proximity to the phospholipid ester alkyl chains while the N‐alkyl groups may either project into the region occupied by the phospholipid head groups or fold back into the more hydrophobic environment. In this orientation, the interaction energies arising from a change in conformation with increasing N‐alkyl hydrophobicity correlate very well with experimental observations. This hypothesis was validated by NMR experiments in which two‐dimensional transferred nuclear Overhauser effects demonstrated that benzylamine N‐alkyl chains longer than five carbons bind in a folded conformation.
A new Method for the Calculation of Partition Coefficients from Experimental Data for Both Mixtures and Pure Compounds
Authors: Barnett Spencer P. , Hill Alan P. , Livingstone David J. , Wood John 
Published: September 2008

AbstractA new method for estimating partition coefficients from data collected using the filter probe extractor (or similar equipment) is described.The method was developed to analyse the data from a two‐component mixture, which cannot be dealt with using the conventional form of data analysis. It is suggested that not only is this method suitable for mixtures but that it also offers advantages for pure compounds.
pH‐Metric log P. Part 1. Difference Plots for Determining Ion‐Pair Octanol‐Water Partition Coefficients of Multiprotic Substances
Authors: Avdeef Alex 
Published: September 2008

AbstractNew potentiometrically‐based octanol‐water partition coefficient (log P) equations for di‐, tri‐ and tetraprotic weak acids are derived. These equations are valid when one or more species partition into the octanol phase as neutral or ion‐paired substances. Citric and phthalic acids were selected to demonstrate the log Pderivation procedure experimentally. Citric acid appears to participate in weak ion‐pair partitioning. Addition of tetra‐n‐butylammonium bromide to the solutions containing the weak acids, induces the hydrogen phthalate anion, the dihydrogen citrate anion and the hydrogen citrate dianinn to partition into octanol, presumably as ion‐pairs with the lipophilic cation. Extensive use is made of difference titration curves. The graphically derived models were refined by a general weighted nonlinear least squares procedure.