bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers by combining ATRP and RAFT polymerizations
Authors: Petruczok Christy D. , Barlow Richard F. , Shipp Devon A.
Published: September 2008

The synthesis of poly(tert‐butyl acrylate‐block‐vinyl acetate) copolymers using a combination of two living radical polymerization techniques, atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization, is reported. The use of two methods is due to the disparity in reactivity of the two monomers, viz. vinyl acetate is difficult to polymerize via ATRP, and a suitable RAFT agent that can control the polymerization of vinyl acetate is typically unable to control the polymerization of tert‐butyl acrylate. Thus, ATRP was performed to make poly(tert‐butyl acrylate) containing a bromine end group. This end group was subsequently substituted with a xanthate moiety. Various spectroscopic methods were used to confirm the substitution. The poly(tert‐butyl acrylate) macro‐RAFT agent was then used to produce (tert‐butyl acrylate‐block‐vinyl acetate). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7200–7206, 2008
Glycopolymers resulting from ethylene–vinyl alcohol copolymers: Synthetic approach, characterization, and interactions with lectins
Authors: Ruiz C. , Sánchez‐Chaves M. , Cerrada M. L. , Fernández‐García M.
Published: September 2008

Ethylene–vinyl alcohol copolymers, EVOH, with two different vinyl alcohol compositions have been functionalized with carboxylic acid groups by reaction with phthalic anhydride. Later on, the coupling reaction of three aminosaccharides (D‐(+)‐glucosamine, D‐(+)‐galactosamine, and D‐(+)‐mannosamine) to functionalized EVOH copolymers has been carried out in dimethyl sulfoxide at 70 °C to achieve water soluble glycopolymers. The structure of the resulting functionalized copolymers and the new glycopolymers was confirmed by 1H and 13C NMR. Likewise, the thermal behavior of glycopolymers has been performed by differential scanning calorimetry and thermal gravimetric analysis. In addition, their affinity to lectins, specifically to Concanavalin A and Ricinus Communis Agglutinin, has been evaluated. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7238–7248, 2008
Spontaneous crosslinking of poly(1,5‐dioxepan‐2‐one) originating from ether bond fragmentation
Authors: Höglund Anders , Albertsson Ann‐Christine
Published: September 2008

The 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

Polypropylene (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

Protein 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

Degree 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

Steel 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

BACKGROUND

Human 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.

METHODS

Sucrose gradient‐purified prostasomes were visualized by cryo‐electron microscopy (EM). Protein composition was studied by trypsin in‐gel digestion and liquid chromatography/mass spectrometry.

RESULTS

Here 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.

CONCLUSION

From 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

BACKGROUND

Aberrant 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.

METHODS

The 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.

RESULTS

We 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.

CONCLUSION

These 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

Knowing 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

The 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

Many 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

We 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

The 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

In 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

Antifungal 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

An 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

A 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

New 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.
Rapid‐resolution liquid chromatography/mass spectrometry for determination and quantitation of polyphenols in grape berries
Authors: Cavaliere Chiara , Foglia Patrizia , Gubbiotti Riccardo , Sacchetti Paolo , Samperi Roberto , Laganà Aldo
Published: September 2008

A rapid‐resolution liquid chromatography/mass spectrometric (RRLC/MS) method for detection and quantitation of polyphenols in grape berry skins and seeds has been developed. Pulp‐free berry skins were treated with liquid nitrogen and ground; seeds were also ground. Then, 3 g of samples were extracted with 30 mL of a mixture of methanol/water/formic acid 70:30:1 (v/v/v) under sonication and 1 µL of the final extract was injected into two 100 × 2.1 mm i.d., 1.8 µm Zorbax Eclipse plus C18 columns connected in series. Compounds were fractionated using a gradient elution of acidified acetonitrile/methanol 50:50 (v/v)/water. Columns were thermostatted at 70°C. MS was carried out on an Agilent 6410 QqQ instrument equipped with an electrospray ionization source. Positive and negative MS/MS product ion scans were used for compound identification, whereas positive full scan MS in the m/z range 200–1400 was used for quantitation. By means of mass spectra comparison, various flavonols, flavan‐3‐ols, anthocyanins and stilbenes were identified. Quantitation was performed by external calibration, and concentration values were corrected for matrix effect that was evaluated in separate experiments. Semi‐quantitative estimation was performed for compounds for which standards were not commercially available. Recoveries ranged from 90–102% with relative standard deviation (RSD) <5%, whereas the between samples RSD was in the range 4–12%. Two surrogate standards were used for quality control. The developed method was applied to analyze the polyphenol content of three Vitis vinifera table cultivars at physiological maturity and after proper preservation for 6 weeks. Results demonstrated that during preservation about half of the polyphenol content was lost. Copyright © 2008 John Wiley & Sons, Ltd.
A gas chromatography/combustion/isotope ratio mass spectrometry system for high‐precision δ13C measurements of atmospheric methane extracted from ice core samples
Authors: Behrens Melanie , Schmitt Jochen , Richter Klaus‐Uwe , Bock Michael , Richter Ulrike C. , Levin Ingeborg , Fischer Hubertus
Published: September 2008

Past atmospheric composition can be reconstructed by the analysis of air enclosures in polar ice cores which archive ancient air in decadal to centennial resolution. Due to the different carbon isotopic signatures of different methane sources high‐precision measurements of δ13CH4 in ice cores provide clues about the global methane cycle in the past. We developed a highly automated (continuous‐flow) gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) technique for ice core samples of ∼200 g. The methane is melt‐extracted using a purge‐and‐trap method, then separated from the main air constituents, combusted and measured as CO2 by a conventional isotope ratio mass spectrometer. One CO2 working standard, one CH4 and two air reference gases are used to identify potential sources of isotope fractionation within the entire sample preparation process and to enhance the stability, reproducibility and accuracy of the measurement. After correction for gravitational fractionation, pre‐industrial air samples from Greenland ice (1831 ± 40 years) show a δ13CVPDB of −49.54 ± 0.13‰ and Antarctic samples (1530 ± 25 years) show a δ13CVPDB of −48.00 ± 0.12‰ in good agreement with published data. Copyright © 2008 John Wiley & Sons, Ltd.
Structural modifications of serum transthyretin in rats during protein‐energy malnutrition
Authors: Henze Andrea , Rohn Sascha , Gericke Beate , Raila Jens , Schweigert Florian J.
Published: September 2008

Transthyretin (TTR) is a sensitive marker of protein‐energy malnutrition and changes in serum and expression levels during protein and energy deficiency are well described. However, little is known about structural modifications of TTR during protein and/or energy deprivation. Therefore, the aim of this study was to determine the effects of protein inadequacies on post‐translational modifications of TTR. For this purpose, male Wistar rats were fed a diet with either casein or gelatine as sole protein source subsequent to a protein wash‐out period. Changes in TTR serum levels as well as other markers of nutritional status as body weight, food consumption, total serum protein and serum RBP4 levels as well as antioxidative capacity were determined. Post‐translational modifications of TTR were examined by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS) analysis. The rats from the gelatine group revealed a marked change in the post‐translational modification pattern of TTR which was reflected by a significant elevation of sulfonated TTR and which was inversely correlated to the antioxidative capacity. Additionally, the elevation of sulfonated TTR was accompanied by a decrease in body weight and food consumption, low antioxidative capacity as well as a deprivation of serum TTR, RBP4 and total serum protein levels in the animals of the gelatine group. Protein‐energy malnutrition leads therefore next to changes in TTR serum concentration, also to changes in the post‐translational modification pattern of TTR. Such changes are probably induced by protein‐energy malnutrition‐driven oxidative stress and might be linked to alterations in protein function and stability. Copyright © 2008 John Wiley & Sons, Ltd.
Development of a validated liquid chromatography/tandem mass spectrometry method for the distinction of thyronine and thyronamine constitutional isomers and for the identification of new deiodinase substrates
Authors: Piehl Susanne , Heberer Thomas , Balizs Gabor , Scanlan Thomas S. , Köhrle Josef
Published: September 2008

Thyronines (THs) and thyronamines (TAMs) are two groups of endogenous iodine‐containing signaling molecules whose representatives differ from each other only regarding the number and/or the position of the iodine atoms. Both groups of compounds are substrates of three deiodinase isozymes, which catalyze the sequential reductive removal of iodine from the respective precursor molecule. In this study, a novel analytical method applying liquid chromatography/tandem mass spectrometry (LC‐MS/MS) was developed. This method permitted the unequivocal, simultaneous identification and quantification of all THs and TAMs in the same biological sample. Furthermore, a liquid‐liquid extraction procedure permitting the concurrent isolation of all THs and TAMs from biological matrices, namely deiodinase (Dio) reaction mixtures, was established. Method validation experiments with extracted TH and TAM analytes demonstrated that the method was selective, devoid of matrix effects, sensitive, linear over a wide range of analyte concentrations and robust in terms of reproducible recoveries, process efficiencies as well as intra‐assay and inter‐assay stability parameters. The method was applied to study the deiodination reactions of iodinated THs catalyzed by the three deiodinase isozymes. With the HPLC protocol developed herein, sufficient chromatographic separation of all constitutional TH and TAM isomers was achieved. Accordingly, the position of each iodine atom removed from a TH substrate in a Dio‐catalyzed reaction was backtracked unequivocally. While several established deiodination reactions were verified, two as yet unknown reactions, namely the phenolic ring deiodination of 3′,5′‐diiodothyronine (3′,5′‐T2) by Dio2 and the tyrosyl ring deiodination of 3‐monoiodothyronine (3‐T1) by Dio3, were newly identified. Copyright © 2008 John Wiley & Sons, Ltd.
A high‐resolution scanning microprobe matrix‐assisted laser desorption/ionization ion source for imaging analysis on an ion trap/Fourier transform ion cyclotron resonance mass spectrometer
Authors: Koestler Martin , Kirsch Dieter , Hester Alfons , Leisner Arne , Guenther Sabine , Spengler Bernhard
Published: September 2008

A new scanning microprobe matrix‐assisted laser desorption/ionization (SMALDI) ion source for high spatial resolution has been developed for linear ion trap and Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). The source is fully compatible with commercial ion trap flanges (such as the LTQ series, Thermo Fisher Scientific). The source is designed for atmospheric pressure (AP) operation but is also suitable for mid‐pressure operation. The AP mode is especially useful for investigating volatile compounds. The source can be interchanged with other ion sources within a minute when operated in the AP mode. Combining high‐lateral resolution MALDI imaging with high mass resolution and high mass accuracy mass spectrometry, available in the FT‐ICR mode, provides a new quality of analytical information, e.g. from biological samples. First results obtained with the new ion source demonstrate a maximum lateral resolution of 0.6 by 0.5 µm. Depending on the limit of detection of the chosen mass analyzer, however, the size of the focus had to be enlarged to a diameter of up to 8 µm in the FT‐ICR mode, in order to create enough ions for detection. Mass spectra acquired for analytical imaging were obtained from single laser pulses per pixel in all the experiments. This mode allows us to investigate biological thin sections with desorption focus diameters in the micrometer range, known to cause complete evaporation of material under the laser focus with a very limited number of laser pulses. As a first example, peptide samples deposited in microstructures were investigated with the new setup. A high quality and validity of the acquired images were obtained in the ion trap mode due to the low limit of detection. High mass resolution and accuracy but poorer image quality were obtained in the ICR mode due to the lower detection sensitivity of the ICR detector. Copyright © 2008 John Wiley & Sons, Ltd.
Securing reactive routing protocols in MANETs using PKI (PKI‐DSR)
Authors: Kadri Benamar , Feham Mohammed , M'hamed Abdallah
Published: September 2008

Mobile Ad hoc Networks (MANETs) are deployed in many new domestic and public applications, contributing to new requirements in terms of performance and efficiency. However due to their nature, some usual network services such as routing and security are not carried out as well as expected. Securing routing protocols is one of these challenging tasks, since security is not natively implemented in ad hoc routing, and the extensions given in the literature are complex and vulnerable against several attacks. Therefore in this paper, we propose an implementation of public key infrastructure (PKI) exploiting the route discovery and route reply mechanisms of reactive routing protocols to publish self‐issued certificates in a distributed fashion. These certificates are used by mobile nodes to secure communications, ensure authentication, integrity, confidentiality, and detect attacks in mobile ad hoc networks. Our proposed scheme is simple and utilizes the underlying protocol as a support for certificate publishing; therefore it does not affect the performance of the network. In addition, all the operations in our scheme are performed in the network layer making it useful for heterogeneous networks since it has no additional relation with other network layers such as MAC and PHY. Copyright © 2008 John Wiley & Sons, Ltd.
Epitaxial Integration of Nanowires in Microsystems by Local Micrometer‐Scale Vapor‐Phase Epitaxy
Authors: Mølhave Kristian , Wacaser Brent A. , Petersen Dirch Hjorth , Wagner Jakob B. , Samuelson Lars , Bøggild Peter
Published: September 2008

Free‐standing epitaxially grown nanowires provide a controlled growth system and an optimal interface to the underlying substrate for advanced optical, electrical, and mechanical nanowire device connections. Nanowires can be grown by vapor‐phase epitaxy (VPE) methods such as chemical vapor deposition (CVD) or metal organic VPE (MOVPE). However, VPE of semiconducting nanowires is not compatible with several microfabrication processes due to the high synthesis temperatures and issues such as cross‐contamination interfering with the intended microsystem or the VPE process. By selectively heating a small microfabricated heater, growth of nanowires can be achieved locally without heating the entire microsystem, thereby reducing the compatibility problems. The first demonstration of epitaxial growth of silicon nanowires by this method is presented and shows that the microsystem can be used for rapid optimization of VPE conditions. The important issue of the cross‐contamination of other parts of the microsystem caused by the local growth of nanowires is also investigated by growth of GaN near previously grown silicon nanowires. The design of the cantilever heaters makes it possible to study the grown nanowires with a transmission electron microscope without sample preparation.
A Novel Flow‐Cytometry‐Based Assay for Cellular Uptake Studies of Polyelectrolyte Microcapsules
Authors: Semmling Maximilian , Kreft Oliver , Muñoz Javier Almudena , Sukhorukov Gleb B. , Käs Josef , Parak Wolfgang J.
Published: September 2008

A flow‐cytometry‐based assay is presented with which the uptake of polyelectrolyte capsules can be quantified. The cavity of the capsules is loaded with the pH‐sensitive dye SNARF, which emits in the red and green in alkaline and acidic environments, respectively. By recording the fluorescence intensities in the red and green channels, the localization of capsules associated with cells can be determined. Capsules adherent to the outer cell membrane fluoresce in the red due to the alkaline pH of the cell medium, whereas capsules internalized by cells fluoresce in the green due to the acidic pH in the endosomal/lysosomal/phagosomal compartments in which incorporated capsules are located. Adding the SNARF readout to the scattering signal typically derived with flow cytometry analysis allows for a more detailed quantitative analysis of particle uptake, which can also distinguish between adherent and ingested particles.
A Polydiacetylene Microchip Based on a Biotin–Streptavidin Interaction for the Diagnosis of Pathogen Infections
Authors: Jung Yun Kyung , Kim Tae Won , Jung Cheulhee , Cho Dae‐Yeon , Park Hyun Gyu
Published: September 2008

A micropatterned polydiacetylene (PDA) chip, utilizing the unique fluorogenic property of PDA and a specific biotin–streptavidin (STA) interaction, is constructed to detect pathogen infections. To construct the PDA chip, biotin‐modified diacetylene liposomes are immobilized on aldehyde glass and conjugated with STA, followed by UV irradiation to polymerize the STA‐functionalized diacetylene liposomes. Genomic DNA of a model pathogen, Chlamydia trachomatis, is isolated from human samples and biotin‐labeled target DNA is obtained through PCR amplification using biotin‐11‐dUTP. Owing to the stimulus caused by the biotin–STA interaction, the biotinylated DNA induces an intense fluorescence signal on the immobilized PDA. By using this strategy, it is possible to diagnose Chlamydia infections by applying DNA samples from several nonhealthy humans to a single PDA chip. The results of this study serve as the basis for a new strategy for fluorogenic PDA microarray‐based diagnosis of pathogen infections.
Lysosomal membrane response of earthworm, Eisenia fetida, to arsenic contamination in soils
Authors: Lee Byung‐Tae , Kim Kyoung‐Woong
Published: September 2008

Earthworm (Eisenia fetida) were exposed to sandy soils contaminated with arsenate (0.01–0.3 μmol g−1) for 28 days. Lysosomal membrane stability was used as a biomarker to determine the applicability of neutral‐red retention times (NRRTs) for arsenic (As) toxicity to earthworm in soils. Total As and As speciation were analyzed to evaluate dose–response relationship between As accumulation and NRRTs and to observe the role of As metabolism in earthworms on a subcellular level toxicity. Significant decrease of NRRTs was found with the increasing As concentration in soils (ANOVA, P < 0.05). Adverse effects on earthworm survival and growth did not occur when exposed to 0.1 and 0.05 μmol g−1 at 14 and 28 days, respectively, whereas NRRTs showed significant reduction from the control, as was readily bioconcentrated in the reduced form of As(III) in earthworms and clear dose–response relationships were found for As body burden and NRRTs. Therefore, it is possible to conclude that As has an adverse effect on lysosomal membrane of coelomocytes, and NRRT assay is a potentially applicable method to assess As toxicity as an early warning tool. Also, sequestered As in the form of As(III)‐thiol complex can be expected to cause an adverse effect on lysosomal membrane stability. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Synthesis and Characterization of an Enantiomerically Pure Lutetium Benzyl Complex
Authors: Meyer Nils , Roesky Peter W.
Published: September 2008

The synthesis and the single‐crystal X‐ray structure of the enantiopure ligand (S,S)‐H2{(iPrATI)2diph} are reported. Reaction of (S,S)‐H2{(iPrATI)2diph} with the lutetium benzyl complex [Lu(CH2Ph)3(THF)3] resulted in the mono benzyl complex [(S,S)‐{(iPrATI)2diph}Lu(CH2Ph)(THF)], which is the first chiral benzyl compound of the lanthanides.
BaN3Cl: Synthese, Kristallstruktur, Schwingungsspektren und thermischer Abbau von Barium‐Azid‐Chlorid
Authors: Blaschkowski Björn , Balzer Harald , Keller Hans‐Lothar , Schleid Thomas
Published: September 2008

BaN3Cl: Synthesis, Crystal Structure, Vibrational Spectra and Thermal Decomposition of Barium Azide Chloride

BaN3Cl was yielded as colourless, lath‐shaped and oftenly intergrown single crystals from concentrated aqueous solutions of equimolar quantities of BaCl2 and NaN3. This first example of a ternary metal(II) azide chloride crystallizes monoclinically in space group P 21/m (no. 11) with the lattice constants a = 557.46(5) pm, b = 452.07(4) pm, c = 780.81(7) pm and β = 101.835(6)° (Z = 2). Its crystal structure contains Ba2+ cations in a ninefold monocapped tetragonal antiprismatic environment of five triatomic azide dumbbells (N3−) together with four chloride anions. The Cl− anions themselves are surrounded by four Ba2+ cations tetrahedrally (d(Cl–Ba) = 311–316 pm), whereas N3− shows a fivefold distorted pyramidal Ba2+ coordination (d(N–Ba) = 295–297 pm). The participating ions are stacked in layers along the c‐axis forming cationic $^{2}_{\infty}\rm \{[ClBa_{4/4}]^{+}\}$ sheets of which every rectangular face of four Ba2+ cations is capped with one N3− dumbbell. This arrangement of the involved ions corresponds to a monoclinically distorted variation of the matlockite‐type structure of PbFCl and is therefore viewed as homeotypic. The azide dumbbell in barium azide chloride is strictly linear (∢(N–N–N) = 179.9(6)° and exhibits N–N bond lengths of 117 – 118 pm. The infrared and Raman spectra show vibration frequencies typical for a slightly asymmetric N3− unit (i. e. νas = 2070 cm−1, νs = 1352 cm−1 and δ = 644/634 cm−1). Thermal analyses revealed BaN3Cl to be stable up to 230 °C, before it decomposes to an amorphous solid under evolution of elemental nitrogen (N2).
Formation of Calcium Carbonate Superstructures by Rapid Temperature Change
Authors: Nebel H. , Epple M.
Published: September 2008

Calcium carbonate was crystallized in a tubular reactor with crystallization times of the order of seconds from aqueous solutions of calcium chloride and sodium carbonate without additives. By a rapid temperature change during this time, both the morphology and the phase composition (calcite, aragonite, vaterite) changed dramatically. Superstructures consisting of smaller nanoparticles and recrystallization phenomena that otherwise require the presence of additives were formed.
Asymptotic solution for a micropolar flow in a curvilinear channel
Authors: Dupuy D. , Panasenko G.P. , Stavre R.
Published: September 2008

This paper is concerned with an asymptotic approach for a micropolar flow through a thin curvilinear channel. A priori estimates (which we obtain together with the existence and the uniqueness of the solution) are used to establish the error between the exact solution and the asymptotic one and to justify the asymptotic analysis. We obtain the expression of an expansion of order K and we study the general problems for the boundary layer functions. Under some additional assumptions on the data we obtain satisfactory error estimates.
A numerical method with properties of consistency in the energy domain for a class of dissipative nonlinear wave equations with applications to a Dirichlet boundary‐value problem
Authors: Macías‐Díaz J.E. , Puri A.
Published: September 2008

In this work, we present a conditionally stable finite‐difference scheme that consistently approximates the solution of a general class of (3+1)‐dimensional nonlinear equations that generalizes in various ways the quantitative model governing discrete arrays consisting of coupled harmonic oscillators. Associated with this method, there exists a discrete scheme of energy that consistently approximates its continuous counterpart. The method has the properties that the associated rate of change of the discrete energy consistently approximates its continuous counterpart, and it approximates both a fully continuous medium and a spatially discretized system. Conditional stability of the numerical technique is established, and applications are provided to the existence of the process of nonlinear supratransmission in generalized Klein‐Gordon systems and the propagation of binary signals in semi‐unbounded, three‐dimensional arrays of harmonic oscillators coupled through springs and perturbed harmonically at the boundaries, where the basic model is a modified sine‐Gordon equation; our results show that a perfect transmission is achieved via the modulation of the driving amplitude at the boundary. Additionally, we present an example of a nonlinear system with a forbidden band‐gap which does not present supratransmission, thus establishing that the existence of a forbidden band‐gap in the linear dispersion relation of a nonlinear system is not a sufficient condition for the system to present supratransmission.