bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions of hydrophilic plasticizer molecules with amorphous starch biopolymer—an investigation into the glass transition and the water activity behavior
Authors: Liu Huihua , Chaudhary Deeptangshu , Ingram Gordon , John Joseph
Published: May 2011

In this article, we demonstrated that within a hydrophilic biopolymer–plasticizer system, the molecular “activity” of the plasticizer also influenced the extent of these interactions. We demonstrated through an analysis of crystallinity and calorimetry results that the equilibrium moisture content within the starch matrix can preferentially interact with the hydrophilic plasticizers and modify the polymer recrystallization process to an extent that the commonly acknowledged relationship between the crystallinity and the glass transition behavior is disrupted. Two plasticizers, glycerol (three OH groups) and xylitol (five OH groups), were selected. The water sorption isotherm of polymer samples with 5–20 wt % (dry basis) plasticizers were examined across a water activity range from ∼0.11 to ∼0.95 and using Guggenheim‐Anderson‐de Boer analysis, we compared the molar sorption enthalpies of various starch–plasticizer mixtures. Finally, the competitive plasticization between water and plasticizer molecules at different water activities was also discussed using known glass transition models. The analyses validated the antiplasticization limit for glycerol to be ∼10–15 wt %, but for xylitol, its antiplasticization behavior did not manifest till 20 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Trifluoperazine regulation of calmodulin binding to Fas: A computational study
Authors: Pan Di , Yan Qi , Chen Yabing , McDonald Jay M. , Song Yuhua
Published: May 2011

Death‐inducing signaling complex (DISC) formation is a critical step in Fas‐mediated signaling for apoptosis. Previous experiments have demonstrated that the calmodulin (CaM) antagonist, trifluoperazine (TFP) regulates CaM‐Fas binding and affects Fas‐mediated DISC formation. In this study, we investigated the anti‐cooperative characteristics of TFP binding to CaM and the effect of TFP on the CaM‐Fas interaction from both structural and thermodynamic perspectives using combined molecular dynamics simulations and binding free energy analyses. We studied the interactions of different numbers of TFP molecules with CaM and explored the effects of the resulting conformational changes in CaM on CaM‐Fas binding. Results from these analyses showed that the number of TFP molecules bound to CaM directly influenced α‐helix formation and hydrogen bond occupancy within the α‐helices of CaM, contributing to the conformational and motion changes in CaM. These changes affected CaM binding to Fas, resulting in secondary structural changes in Fas and conformational and motion changes of Fas in CaM‐Fas complexes, potentially perturbing the recruitment of Fas‐associated death domain for DISC formation. The computational results from this study reveal the structural and molecular mechanisms that underlie the role of the CaM antagonist, TFP, in regulation of CaM‐Fas binding and Fas‐mediated DISC formation in a concentration‐dependent manner. Proteins 2011; © 2011 Wiley‐Liss, Inc.
SymmRef: A flexible refinement method for symmetric multimers
Authors: Mashiach‐Farkash Efrat , Nussinov Ruth , Wolfson Haim J.
Published: May 2011

Symmetric protein complexes are abundant in the living cell. Predicting their atomic structure can shed light on the mechanism of many important biological processes. Symmetric docking methods aim to predict the structure of these complexes given the unbound structure of a single monomer, or its model. Symmetry constraints reduce the search‐space of these methods and make the prediction easier compared to asymmetric protein‐protein docking. However, the challenge of modeling the conformational changes that the monomer might undergo is a major obstacle. In this article, we present SymmRef, a novel method for refinement and reranking of symmetric docking solutions. The method models backbone and side‐chain movements and optimizes the rigid‐body orientations of the monomers. The backbone movements are modeled by normal modes minimization and the conformations of the side‐chains are modeled by selecting optimal rotamers. Since solved structures of symmetric multimers show asymmetric side‐chain conformations, we do not use symmetry constraints in the side‐chain optimization procedure. The refined models are re‐ranked according to an energy score. We tested the method on a benchmark of unbound docking challenges. The results show that the method significantly improves the accuracy and the ranking of symmetric rigid docking solutions. SymmRef is available for download at http:// bioinfo3d.cs.tau.ac.il/SymmRef/download.html. Proteins 2011. © 2011 Wiley‐Liss, Inc.
Molecular dynamics study of small molecule inhibitors of the Bcl‐2 family
Authors: Acoca Stéphane , Cui Qizhi , Shore Gordon C. , Purisima Enrico O.
Published: May 2011

We carried out docking and molecular dynamics simulations on ABT‐737 and obatoclax, which are inhibitors of the Bcl‐2 family of proteins. We modeled the binding mode of ABT‐737 with Bcl‐xL, Bcl‐2, and Mcl‐1 and examined their dynamical behavior. We found that the binding of the chlorobiphenyl end of ABT‐737 was quite stable across all three proteins. However, the phenylpiperazine linker group was dramatically more mobile in Mcl‐1 compared to either Bcl‐xL or Bcl‐2. The S‐phenyl group at the p4 binding site was well‐anchored in Bcl‐xL and Bcl‐2 but was somewhat more mobile in Mcl‐1 although the phenyl ring itself on average stayed close to the p4 binding site in Mcl‐1. This greater mobility is likely due to the greater openness of the p3 and p4 binding sites on Mcl‐1. The calculated binding free energies were consistent with the much weaker binding affinity of ABT‐737 for Mcl‐1. Obatoclax was predicted to bind at the p1 and p2 binding sites of Mcl‐1 and the binding mode was quite stable during the molecular dynamics simulation with Mcl‐1 wrapping around the molecule. The modeled binding mode suggests that obatoclax is able to inhibit all three proteins because it makes use of the p1 and p2 binding sites alone, which is a fairly narrow groove in all three proteins unlike the p4 binding site, which is much broader in Mcl‐1. Proteins 2011. © 2011 Wiley‐Liss, Inc.
Cover and spacer insertions: Small nonhydrophobic accessories that assist protein oligomerization
Authors: Nishi Hafumi , Koike Ryotaro , Ota Motonori
Published: May 2011

We investigated fragmental sequences that were inserted into proteins during long molecular evolution and relevant to the association of homo‐oligomers. Seventeen insertions in 12 SCOP (structure classification of proteins) families were examined and were classified into large and small insertions. The large insertions are composed of interface‐like residues and effectively increase the interface area. In contrast, small insertions are composed of the residues that are not commonly found at the interfaces and have a small interface area: their roles in the oligomerization process are unclear. We found that the small insertions were located in the middle of protein sequences and therefore must involve residues with strong turn and less interface‐like propensities. From a structural viewpoint, small insertions were found to mask hydrophobic patches or act as spacers to fill cavities present at interfaces. The presence or absence of small insertions coincides with the annotated oligomeric states for homologs in the SwissProt database, and the calculation of the association scores predicts that small insertions contribute to the stability of oligomers. These results support the significant role of small, nonhydrophobic insertions in protein oligomerization. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Statistical mechanics‐based method to extract atomic distance‐dependent potentials from protein structures
Authors: Huang Sheng‐You , Zou Xiaoqin
Published: May 2011

In this study, we have developed a statistical mechanics‐based iterative method to extract statistical atomic interaction potentials from known, nonredundant protein structures. Our method circumvents the long‐standing reference state problem in deriving traditional knowledge‐based scoring functions, by using rapid iterations through a physical, global convergence function. The rapid convergence of this physics‐based method, unlike other parameter optimization methods, warrants the feasibility of deriving distance‐dependent, all‐atom statistical potentials to keep the scoring accuracy. The derived potentials, referred to as ITScore/Pro, have been validated using three diverse benchmarks: the high‐resolution decoy set, the AMBER benchmark decoy set, and the CASP8 decoy set. Significant improvement in performance has been achieved. Finally, comparisons between the potentials of our model and potentials of a knowledge‐based scoring function with a randomized reference state have revealed the reason for the better performance of our scoring function, which could provide useful insight into the development of other physical scoring functions. The potentials developed in this study are generally applicable for structural selection in protein structure prediction. © 2011 Wiley‐Liss, Inc.
Estimating the pKa values of basic and acidic side chains in ion channels using electrophysiological recordings: A robust approach to an elusive problem
Authors: Cymes Gisela D. , Grosman Claudio
Published: May 2011

As a step toward gaining a better understanding of the physicochemical bases of pKa‐value shifts in ion channels, we have previously proposed a method for estimating the proton affinities of systematically engineered ionizable side chains from the kinetic analysis of single‐channel current recordings. We reported that the open‐channel current flowing through mutants of the (cation‐selective) muscle nicotinic acetylcholine receptor (AChR) engineered to bear single basic residues in the transmembrane portion of the pore domain fluctuates between two levels of conductance. Our observations were consistent with the idea that these fluctuations track directly the alternate protonation–deprotonation of basic side chains: protonation of the introduced basic group would attenuate the single‐channel conductance, whereas its deprotonation would restore the wild‐type‐like level. Thus, analysis of the kinetics of these transitions was interpreted to yield the pKa values of the substituted side chains. However, other mechanisms can be postulated that would also be consistent with some of our findings but according to which the kinetic analysis of the fluctuations would not yield true pKas. Such mechanisms include the pH‐dependent interconversion between two conformations of the channel that, while both ion permeable, would support different cation‐conduction rates. In this article, we present experimental evidence for the notion that the fluctuations of the open‐channel current observed for the muscle AChR result from the electrostatic interaction between fixed charges and the passing cations rather than from a change in conformation. Hence, we conclude that bona fide pKa values can be obtained from single‐channel recordings. Proteins 2011; © 2011 Wiley‐Liss, Inc.
An NMR study of the N‐terminal domain of wild‐type hERG and a T65P trafficking deficient hERG mutant
Authors: Gayen Shovanlal , Li Qingxin , Chen Angela Shuyi , Nguyen Thi Hanh Thuy , Huang Qiwei , Hill Jeffrey , Kang CongBao
Published: May 2011

The human Ether‐à‐go‐go Related Gene (hERG) potassium channel plays an important role in the heart by controlling the rapid delayed rectifier current. The N‐terminal 135 residues (NTD) contain a Per‐Arnt‐Sim (PAS) domain and an N‐terminal amphipathic helix. NMR relaxation analysis and H/D exchange experiments on the NTD demonstrated that the amphipathic helix is rigid and solvent accessible. An NTD containing a T65P mutation, which causes a hERG channel trafficking deficiency, was purified from E.coli. The mutant protein did not aggregate in gel filtration analysis and the amide cross peaks of its residues disappeared in an HSQC spectrum indicating the possibility of structural changes. A carbon chemical shift comparison of the residues with cross peaks in the HSQC spectrum showed no clear difference between the purified wild‐type protein and the purified mutant. There were multiple conformations observed for the T65P mutant protein at high temperatures from HSQC experiments and a thermal stability assay showed that the T65P mutation reduced the thermal stability of NTD. This instability may affect protein folding or structural dynamics of other regions. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Quantitative use of chemical shifts for the modeling of protein complexes
Authors: Stratmann Dirk , Boelens Rolf , Bonvin Alexandre M. J. J.
Published: May 2011

Despite recent advances in the modeling of protein‐protein complexes by docking, additional information is often required to identify the best solutions. For this purpose, NMR data deliver valuable restraints that can be used in the sampling and/or the scoring stage, like in the data‐driven docking approach HADDOCK that can make use of NMR chemical shift perturbation (CSP) data to define the binding site on each protein and drive the docking. We show here that a quantitative use of chemical shifts (CS) in the scoring stage can help to resolve ambiguities. A quantitative CS‐RMSD score based on 1Hα,13Cα, and 15N chemical shifts ranks the best solutions always at the top, as demonstrated on a small benchmark of four complexes. It is implemented in a new docking protocol, CS‐HADDOCK, which combines CSP data as ambiguous interaction restraints in the sampling stage with the CS‐RMSD score in the final scoring stage. This combination of qualitative and quantitative use of chemical shifts increases the reliability of data‐driven docking for the structure determination of complexes from limited NMR data. Proteins 2011; © 2011 Wiley‐Liss, Inc.
On the development of protein pKa calculation algorithms
Authors: Carstensen Tommy , Farrell Damien , Huang Yong , Baker Nathan A. , Nielsen Jens Erik
Published: May 2011

Protein pKa calculation methods are developed partly to provide fast non‐experimental estimates of the ionization constants of protein side chains. However, the most significant reason for developing such methods is that a good pKa calculation method is presumed to provide an accurate physical model of protein electrostatics, which can be applied in methods for drug design, protein design, and other structure‐based energy calculation methods. We explore the validity of this presumption by simulating the development of a pKa calculation method using artificial experimental data derived from a human‐defined physical reality. We examine the ability of an RMSD‐guided development protocol to retrieve the correct (artificial) physical reality and find that a rugged optimization landscape and a huge parameter space prevent the identification of the correct physical reality. We examine the importance of the training set in developing pKa calculation methods and investigate the effect of experimental noise on our ability to identify the correct physical reality, and find that both effects have a significant and detrimental impact on the physical reality of the optimal model identified. Our findings are of relevance to all structure‐based methods for protein energy calculations and simulation, and have large implications for all types of current pKa calculation methods. Our analysis furthermore suggests that careful and extensive validation on many types of experimental data can go some way in making current models more realistic. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Electrostatic pKa computations in proteins: Role of internal cavities
Authors: Meyer Tim , Kieseritzky Gernot , Knapp Ernst‐Walter
Published: May 2011

The solvent accessible surface area (SASA) algorithm is conventionally used to characterize protein surfaces in electrostatic energy computations of proteins. Unfortunately, it often fails to find narrow cavities inside a protein. As a consequence pKa computations based on this algorithm perform badly. In this study a new cavity‐algorithm is introduced, which solves this problem and provides improved pKa values. The procedure is applied to 20 pKa values of titratable groups introduced as point mutations in SNase variants, where crystal structures are available. The computations of these pKas are particular challenging, since they are placed in a rather hydrophobic environment. For nine mutants, where the titratable residue is in contact with a large cavity, the RMSD between computed and measured pKa values is 2.04, which is a considerable improvement as compared to the original results obtained with Karlsberg+ (http://agknapp.chemie.fu‐berlin.de/karlsberg/) that yielded an RMSD of 8.8. However, for 11 titratable residues the agreement with experiments remains poor (RMSD = 6.01). Considering 15 pKas of SNase, which are in a more conventional less hydrophobic protein environment, the RMSD is 2.1 using the SASA‐algorithm and 1.7 using the new cavity‐algorithm. The agreement is reasonable but less good than what one would expect from the general performance of Karlsberg+ indicating that SNase belongs to the more difficult proteins with respect to pKa computations. We discuss the possible reasons for the remaining discrepancies between computed and measured pKas. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Optimisation and fabrication of a calorimetric gas sensor built up on a polyimide substrate for H2O2 monitoring
Authors: Kirchner Patrick , Oberländer Jan , Friedrich Peter , Berger Jörg , Suso Henri‐Pierre , Kupyna Andriy , Keusgen Michael , Schöning Michael J.
Published: May 2011

A calorimetric gas sensor for the detection of vapourised H2O2 in aseptic filling processes was built up on a polyimide foil instead of silicon as substrate material in order to optimise the sensor response behaviour. The sensor was catalytically activated with a dispersion of manganese(IV) oxide. The reaction mechanism of the exothermic H2O2 decomposition on the catalyst involves two pathways: an initial reaction with electron exchange between the catalyst surface and H2O2 creating free radicals, and a chain reaction of these radicals with H2O2, in which the final products, namely water and oxygen, are formed. The calorimetric gas sensor possesses a linear response behaviour with a sensitivity of 7.15 °C/(% v/v) in a H2O2 concentration range from 0 to 8% v/v.

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Calorimetric gas sensor on polyimide foil for H2O2 monitoring in sterilisation processes.
Luminescence properties of Eu3+, Bi3+ coactivated CaLaNbWO8 red phosphors under near UV and blue excitations
Authors: Thomas Mariyam , Rao Padala Prabhakar , Mahesh Sundaresan Pillai Kamalam , Kumari Leela Sandhya , Koshy Peter
Published: May 2011

Scheelite type red phosphors CaLa1–xNbWO8: xEu3+ (x = 0.01, 0.03, 0.05, 0.1, 0.15, 0.2, and 0.25) and CaLa0.8–yNbWO8: 0.2Eu3+, yBi3+(y = 0.1, 0.15, and 0.2) were prepared by conventional solid state reaction route. The crystalline structure, morphology and absorbance of these phosphors were characterized by powder X‐ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT‐IR), and UV–Visible absorption spectroscopy. Investigations on their photoluminescent properties indicated that both Eu3+ doped and Eu3+, Bi3+ coactivated samples emit strong red light at 615 nm under both near UV (394 nm) and blue (465 nm) excitations. Bi3+ codoped system showed broadened charge transfer band (CTB) and stronger excitation peaks at 394 and 465 nm. The red emission intensity of CaLa0.8NbWO8: 0.2Eu3+ phosphor is improved by a factor of 2 as 20 mol% Bi3+ is introduced into the system, and is four times stronger than that of the commercial Y2O3:Eu3+ red phosphor. These phosphors are characterized by sharp red emission with color coordinates closer to the standard red phosphors. Thus, the above phosphors could be a promising red candidate for the phosphor converted white light emitting diodes (pc‐WLEDs).
Lipid coated chitosan microparticles as protein carriers
Authors: Sommerwerk Anett , Brüßler Jana , Schäfer Jens , Baginski Leonie , Bandulik Mario , Bakowsky Udo
Published: May 2011

In this study, a novel protein‐loaded and lipid‐coated drug carrier system for pulmonary application was developed. In a first step, spherically shaped chitosan particles were produced by spray‐drying. The produced particles showed sizes between 2 μm and 3.5 µm and zeta potentials ranged between 1.4 mV and 37.9 mV. Due to the positive charge of the particles, they could easily be loaded with the model protein drug Bovine Serum Albumine (BSA) via electrostatic interaction. In a final step, the prepared BSA loaded chitosan microparticles were coated with a lipid layer to improve drug delivery via the pulmonary and nasal route. This lipid‐based surface modification changed the physico‐chemical characteristics of the drug carrier systems. While unmodified chitosan particles showed a fast burst release of the protein, the lipid coated particles released the protein over a time period of 2 days. In Conclusion, the lipid‐coated particles show characteristics which make them a promising vehicle for pulmonary administration of proteins. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective interactions of concanavalin A‐modified tetraether lipid liposomes
Authors: Ozcetin Aybike , Dayyoub Eyas , Hobler Christian , Keusgen Michael , Bakowsky Udo
Published: May 2011

For the development of site specific liposomes, high stability and long circulation properties are very promising for the improvement of drug targeting and drug delivery system as well as improvement of bioavailability of efficient bioactive drugs. Tetraether lipids (TELs) are very stabile lipids, extracted from Thermoplasma acidophilum. Because of its high chemical stability and its biocompatibility, Tetraether lipid liposomes prepared with TELs are excellent candidates for liposomal drug delivery. In this study a model protein, Concanavalin A (ConA) was chosen for a simulation of a specific adsorbtion onto mannan surface. Concanavalin A (ConA) is a lectin, extracted from Canavalia ensiformis, which interacts with sugar domains localized on inflammatory active tissues or tumors. In this study, stable TEL liposomes were prepared and characterized. Furthermore to develop side specific liposomes, tetraether lipids were activated and, ConA was covalently bond onto the surface of the prepared liposomes. Interaction of ConA conjugated liposomes with mannan‐modified surfaces was investigated by Biomolecular Interaction Analysis (BIA) via Reflectometric Interference Spectroscopy (RIfS). This provides real time observation of interactions between carbohydrate structure and TEL liposomes. Specific interaction was also visualised by AFM imaging subsequent to the RIfS measurements. According to the results, with ConA conjugated liposomes, high specific adsorption efficiency was observed. Consequently, this specific adsorption assay between ConA and mannan surface can be considered as a model for the further studies utilized with specific biomarkers for a selective active agent transfer to tumors and inflammatory active tissues. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The role of cold fronts in the onset of the monsoon season in the South Atlantic convergence zone
Authors: Nieto‐Ferreira Rosana , Rickenbach Thomas M. , Wright Emily A.
Published: May 2011

The onset of the South American monsoon season culminates with the abrupt establishment of the South American convergence zone (SACZ). The impact of cold fronts on the abrupt establishment of the SACZ is studied using an 11‐year composite analysis of the dynamic and thermodynamic structures, intensity and propagation of cold fronts that occur prior to, during, and after monsoon onset in the SACZ. A significant change in the structure and propagation of cold fronts is observed at the time of monsoon onset in the SACZ, with cold fronts suddenly stalling and becoming stationary in southeastern Brazil. It is proposed that this regime change of the structure and propagation of cold fronts causes the abrupt onset of the monsoon in the SACZ. A mechanism for this sudden change in cold front behaviour is suggested by analyzing changes in the observed upper‐level structure of midlatitude waves. Our observations show that, at the time of monsoon onset in the SACZ, midlatitude waves develop a ‘thinning trough’ behaviour, with upper‐level troughs becoming thinner, westward tilted, and sometimes forming cut‐off lows. This behaviour is characteristic of midlatitude waves that develop in the region of anticyclonic shear on the equatorward side of the upper‐level midlatitude jet. During the austral spring, the upper‐level midlatitude jet over South America migrates southward leaving subtropical South America in the equatorward, anticyclonic shear side of the jet. It is hypothesized that, as the meridional shear on the equatorward side of the upper‐level jet gradually becomes more anticyclonic, it suddenly crosses the critical threshold of horizontal shear that has been shown to produce a sudden transition to a ‘thinning trough’ midlatitude wave regime. At this time a regime change occurs whereby the character of frontal systems crossing South America changes abruptly, causing the onset of the monsoon season in the SACZ. Copyright © 2011 Royal Meteorological Society
Quantum topological molecular descriptors in QSAR analysis of organophosphorus compounds
Authors: Paukku Y. , Hill G.
Published: May 2011

A Quantitative structure–activity relationship study is performed on a set of organophosphorus compounds to reveal structural and quantum‐chemical features influencing the toxic effect. The properties derived from the topological analysis of the electron density have been used to model the toxicity data. A multiple linear regression analysis in conjunction with genetic algorithm is used in the study, followed by subsequent validation of the results. Obtained QSAR models are beneficial for virtual screening of toxicity for new compounds of interest. Because toxicity of organophosphorus compounds is dependent on conformational properties, a conformational search has been performed before optimization of geometries. All quantum‐chemical calculations are carried out at DFT/B3LYP level of theory with 6‐311++G(d,p) basis set. Frequency calculations are performed after full geometry optimization. Ab initio wave functions were obtained for further analysis and evaluation of quantum topological properties of target molecules. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
A DFT study of the enantioselective reduction of oxime ethers promoted by chiral spiroborate esters
Authors: Qu Zhibo , Chen Xiaolan , Wei Donghui , Ke Diandian , Qu Lingbo , Yuan Jinwei , Bai Yunliang , Wang Fujun , Zhao Yufen
Published: May 2011

Mechanisms of borane reduction of the (E)‐acetophenone O‐methyl oxime catalyzed by the easily prepared and stable spiroborate ester 1, derived from diphenylvalinol has been reported for the first time using density functional theory. Two reaction pathways are investigated at the B3LYP/6‐31G(d,p) level of theory. The calculated results reveal that this reaction is accomplished via four steps. All the reactants, products, transition states, and intermediates have been optimized at the B3LYP/6‐31G (d,p) level. The analysis of these results reveals that one pathway is more energetically favorable than the other, and its associated product is in good agreement with the experimental result. The solvent effect has been further considered at the B3LYP/6‐31G(d,p) level in the solvent THF using the PCM model, and the results indicate that it has no great influence on the enantioselectivity of this reduction. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Are cluster ion analysis beams good choices for hydrogen depth profiling using time‐of‐flight secondary ion mass spectrometry?
Authors: Zhu Zihua , Shutthanandan Vaithiyalingam
Published: May 2011

For more than three decades, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) has been used for elemental depth profiling. In recent years, cluster primary ion sources (principally, C60+, Bin+, and Aun+) have become widely available, and they can greatly enhance the signal intensity of molecular ions (10–1000 times). Understanding the performance of cluster ion analysis beams used in elemental depth profiling can greatly assist normal ToF‐SIMS users in choosing the optimal analysis beam for depth profiling work. Presently, however, the experimental data are lacking, and such choices are difficult to make. In this paper, hydrogen and deuterium depth profiling were studied using six different analysis beams—25 keV Bi+, Bi3+, Bi5+, 50 keV Bi32+, 10 keV C60+, and 20 keV C602+. The effort shows that cluster primary ions do enhance H− and D− yields, but the enhancement is only about 1.5–4.0 times when compared to atomic Bi+ ions. Because the currents of atomic ion analysis beams are much stronger than the currents of cluster ion analysis beams for most commercial ToF‐SIMS instruments, the atomic ion analysis beams can provide the strongest H− and D− signal intensities, and may be the best choices for hydrogen and deuterium depth profiling. In addition, two representative nuclides, 30Si and 18O, were also studied and yielded results similar to those of H− and D−. Copyright © 2011 John Wiley & Sons, Ltd.
Adhesion and friction studies of Au nanoparticle‐textured surfaces with colloidal tips
Authors: Zhang Xiaoliang , Lu Yongjuan , Zhong Xiaohua , Yi Gewen , Jia Junhong
Published: May 2011

Surface roughness plays an important role in affecting the adhesive force and friction force in microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS). One effective approach of reducing adhesion and friction of contacting interfaces is to create textured surface, which is especially beneficial for MEMS'/NEMS' production yield and product reliability. In this article, we present a convenient method to fabricate the nano‐textured surfaces by self‐assembling Au nanoparticles (NPs) on the silicon (100) surfaces. The nanoparticle‐textured surfaces (NPTS) with different packing density and texture height were prepared by controlling the assembling time and the size of Au NPs. The morphologies and chemical states of NPTS were characterized by atomic force microscope (AFM), field emission scanning electron microscope, and XPS. The adhesion and friction on the NPTS were studied by AFM with colloidal tip. The results show that the nano‐textured surfaces have effectively reduced adhesive force and friction force compared with the 3‐aminopropyl trimethoxysilane self‐assembled monolayer surfaces. The lowered adhesion and friction were attributed to the reduced real area of contact between NPTS and colloidal tip. The adhesion and friction of the NPTS are varying with the texture packing density and dependent on both the texture height and asperities spacing, which are related to the size and coverage ratio of NPs on surfaces. Copyright © 2011 John Wiley & Sons, Ltd.
Laser surface treatment of high‐speed steel: presence of TiC particles at the surface
Authors: Abdul Aleem B. J. , Hashmi M. S. J. , Yilbas B. S.
Published: May 2011

Laser treatment of a high‐speed steel surface is carried out and metallurgical and morphological changes in the laser‐treated layer are examined using SEM, EDS and XRD. A carbon film of 50 µm thickness and containing 5% TiC particles is formed at the workpiece surface prior to the laser treatment process. The carbon film formed at the surface enhances the absorption of laser irradiation and retains TiC particles at the workpiece surface. The residual stress formed at the laser‐treated surface is determined using the XRD technique while the indentation tests are carried out to measure microhardness and fracture toughness of the resulting surface. It is found that ε‐Fe3N, and ε‐Fe3 (N,C) compounds are formed at the laser‐treated surface, which are attributed to the presence of carbon film and high‐pressure nitrogen‐assisting gas. The fracture toughness of the laser‐treated surface reduces because of the increased hardness and dense layer formed at the surface vicinity. Copyright © 2011 John Wiley & Sons, Ltd.
Value creation and value capture with frictions
Authors: Chatain Olivier , Zemsky Peter
Published: May 2011

We use a formal value‐based model to study how frictions—incomplete linkages in the industry value chain that keep some parties from meeting and transacting—affect value creation and value capture. Frictions arise from search and switching costs and moderate the intensity of industry rivalry and the efficiency of the market. We find that firms with a competitive advantage prefer industries with less, but not zero, frictions. We show that rivalry interacts nontrivially with other competitive forces to affect industry attractiveness. Firm heterogeneity emerges naturally when we introduce resource development. Heterogeneity falls with frictions, but the sustainability of competitive advantage increases. Overall, we show that introducing frictions makes value‐based models very effective at integrating analyses at the industry, firm, and resource levels. Copyright © 2011 John Wiley & Sons, Ltd.
Flexible Carbon Nanotube–Cu2O Hybrid Electrodes for Li‐Ion Batteries
Authors: Goyal Anubha , Reddy Arava L. M. , Ajayan Pulickel M.
Published: May 2011

This study demonstrates the formation of a flexible and free‐standing carbon nanotube–copper oxide–poly(vinylidene fluoride) (CNT–Cu2O–PVDF) nanocomposite and its application as an electrode‐separator material for Li‐ion batteries. Binder‐free hybrid electrodes are obtained by conformally coating CNTs with Cu2O via electrodeposition and then embedding the resulting architecture into a porous poly(vinylidene fluoride‐hexafluoropropylene) PVDF‐HFP–SiO2 polymer electrolyte membrane. The synergistic presence of high‐capacity transition metal oxides and conductive CNTs results in twice the reversible areal capacity of 2.3 mAh cm−2 as compared to 1.2 mAh cm−2 for pure CNTs.
Fatigue Failure and Molecular Machine Design
Authors: Hess Henry , Dumont Emmanuel L. P.
Published: May 2011

Sophisticated molecular machines have evolved in nature, and the first synthetic molecular machines have been demonstrated. With our increasing understanding of individual operating cycles, the question of how operation can be sustained over many cycles comes to the forefront. In the design of macroscale machines, performance and lifetime are opposing goals. Similarly, the natural evolution of biological nanomachines, such as myosin motor proteins, is likely constrained by lifetime requirements. Rather than bond rupture at high forces, bond fatigue under repeated small stresses may limit the mechanical performance of molecular machines. Here, the effect of cyclic stresses using single and double bonds as simple examples are discussed. Additionally, it is demonstrated that an increase in lifetime requires a reduction in mechanical load and that molecular engineering design features, such as polyvalent bonds capable of rebinding, can extend the bond lifetime dramatically. A universal scaling law for the force output of motors is extrapolated to the molecular scale to estimate the design space for molecular machines.
Ordered, Mesoporous Metal Phosphonate Materials with Microporous Crystalline Walls for Selective Separation Techniques
Authors: Ma Tian‐Yi , Li Hui , Tang An‐Na , Yuan Zhong‐Yong
Published: May 2011

Ordered, hexagonal, mesoporous metal (Ti, Zr, V, Al)‐phosphonate materials with microporous crystalline walls are synthesized through a microwave‐assisted procedure by using triblock copolymer F127 as the template. Corresponding metal chlorides and ethylene diamine tetra(methylene phosphonic acid) are chosen as the inorganic precursors and the coupling molecule, respectively. X‐ray diffractometry, transmission electron microscopy, N2 sorption, and thermogravimetry measurements confirm that the obtained metal phosphonates possess a hierarchically porous structure with pore sizes of 7.1–7.5 nm and 1.3–1.7 nm for mesopores and micropores, respectively, and the metal phosphonate materials are thermally stable up to around 450 °C with the pore structure and hybrid framework well preserved. Magic angle spinning NMR, Fourier‐transform infrared spectroscopy, and X‐ray photoelectron spectroscopy analyses indicate that the phosphonate groups are homogenously incorporated into the hybrid framework of the obtained materials. For the first time, the mesoporous hybrid materials are employed as the stationary phase in open tubular capillary electrochromatography technique for the separation of various substances including acidic, basic, and neutral compounds. These materials show good selectivity and reproducibility for this application.
Requirement of α7 nicotinic acetylcholine receptors for amyloid beta protein‐induced depression of hippocampal long‐term potentiation in CA1 region of rats in vivo
Authors: Li Shao‐Feng , Wu Mei‐Na , Wang Xiao‐Hui , Yuan Li , Yang Dong , Qi Jin‐Shun
Published: May 2011

The high density of senile plaques with amyloid beta protein (Aβ) and the loss of cholinergic neurons in the brain are the dominated pathological characteristics of Alzheimer's disease (AD). However, the active center of Aβ, especially the cholinergic mechanism underlying the Aβ neurotoxicity, is mostly unknown. This study examined the effects of different Aβ fragments on hippocampal long‐term potentiation (LTP) and investigated its probable α7 nicotinic acetylcholine receptors (nAChRs) mechanism. The results show that: (1) intracerebroventicular injection of Aβ25–35 or Aβ31–35 significantly and similarly suppressed hippocampal LTP in CA1 region in rats; (2) choline, a selective α7 nAChR agonist, did not affect the LTP induction but enhanced LTP suppression induced by Aβ31–35; and (3) methyllycaconitine, a specific α7 nAChR antagonist, slightly suppressed hippocamal LTP but effectively prevented against Aβ31–35‐induced LTP depression in the presence of Aβ31–35. These results indicate that: (1) the amino acid sequence 31–35 of the Aβ peptide might be a shorter active sequence in the full length molecule; (2) α7 nAChRs are required for the Aβ‐induced suppression of hippocampal LTP. Thus, this study not only provides a new insight into the mechanism by which Aβ impairs synaptic plasticity but also strongly suggests that sequence 31–35 in Aβ molecule and α7 nAChRs in the brain might be potential therapeutic targets for the treatment of AD. Synapse 2011. © 2011 Wiley‐Liss, Inc.
Striatal dopamine D1 and D2 receptors: Widespread influences on methamphetamine‐induced dopamine and serotonin neurotoxicity
Authors: Gross Noah B. , Duncker Patrick C. , Marshall John F.
Published: May 2011

Methamphetamine (mAMPH) is an addictive psychostimulant drug that releases monoamines through nonexocytotic mechanisms. In animals, binge mAMPH dosing regimens deplete markers for monoamine nerve terminals, for example, dopamine and serotonin transporters (DAT and SERT), in striatum and cerebral cortex. Although the precise mechanism of mAMPH‐induced damage to monoaminergic nerve terminals is uncertain, both dopamine D1 and D2 receptors are known to be important. Systemic administration of dopamine D1 or D2 receptor antagonists to rodents prevents mAMPH‐induced damage to striatal dopamine nerve terminals. Because these studies employed systemic antagonist administration, the specific brain regions involved remain to be elucidated. The present study examined the contribution of dopamine D1 and D2 receptors in striatum to mAMPH‐induced DAT and SERT neurotoxicities. In this experiment, either the dopamine D1 antagonist, SCH23390, or the dopamine D2 receptor antagonist, sulpiride, was intrastriatally infused during a binge mAMPH regimen. Striatal DAT and cortical, hippocampal, and amygdalar SERT were assessed as markers of mAMPH‐induced neurotoxicity 1 week following binge mAMPH administration. Blockade of striatal dopamine D1 or D2 receptors during an otherwise neurotoxic binge mAMPH regimen produced widespread protection against mAMPH‐induced striatal DAT loss and cortical, hippocampal, and amygdalar SERT loss. This study demonstrates that (1) dopamine D1 and D2 receptors in striatum, like nigral D1 receptors, are needed for mAMPH‐induced striatal DAT reductions, (2) these same receptors are needed for mAMPH‐induced SERT loss, and (3) these widespread influences of striatal dopamine receptor antagonists are likely attributable to circuits connecting basal ganglia to thalamus and cortex. Synapse, 2011. © 2011 Wiley‐Liss, Inc.
Inhibition of the serotonin transporter induces microglial activation and downregulation of dopaminergic neurons in the substantia nigra
Authors: Macgillivray L. , Reynolds K.B. , Sickand M. , Rosebush P.I. , Mazurek M.F.
Published: May 2011

Drugs that selectively inhibit the serotonin transporter (SERT) are widely used in the treatment of depression and anxiety disorders. These agents are associated with a range of extrapyramidal syndromes such as akathisia, dystonia, dyskinesia and parkinsonism, suggesting an effect on dopaminergic transmission. We studied the time course of changes in dopaminergic neurons in the substantia nigra (SN) after initiation of two different SERT inhibitors, citalopram and fluoxetine. In the first experiment, groups of Sprague‐Dawley rats received daily meals of rice pudding either alone (N = 9) or mixed with citalopram 5 mg/kg/day (N = 27). Rats were sacrificed after 24 h, 7 days or 28 days of treatment. Sections of SN were processed for tyrosine hydroxylase (TH) immunohistochemistry. Citalopram induced a significant decrease in TH‐positive cell counts at 24 h (44%), 7 days (38%) and 28 days (33%). No significant differences among the citalopram treatment groups were observed in the SN. To determine whether these changes would occur with other SERT inhibitors, we conducted a second experiment, this time with a 28 day course of fluoxetine. As was observed with citalopram, fluoxetine induced a significant 21% reduction of TH cell counts in the SN. Immunoblot analysis showed that fluoxetine also induced a 45% reduction of striatal TH. To investigate a possible role for the innate immune system in mediating these changes, we also studied the microglial marker OX42 after administration of fluoxetine and noted a significant 63% increase in the SN of fluoxtine‐treated animals. These results indicate that SERT inhibition can activate microglia and alter the regulation of TH, the rate limiting enzyme for dopamine biosynthesis. These changes may play a role in mediating the extrapyramidal side effects associated with SERT inhibitors. Synapse, 2011. © 2011 Wiley‐Liss, Inc.
Impact of isoflurane anesthesia on D2 receptor occupancy by [18F]fallypride measured by microPET with a modified Logan plot
Authors: Tantawy Mohammed N. , Peterson Todd E. , Jones Carrie K. , Johnson Kari , Rook Jerri M. , Conn P. Jeffrey , Baldwin Ronald M. , Ansari M. Sib , Kessler Robert M.
Published: May 2011

In the previous work, we reported a method that utilized imaging data collected from 60 to 120 min following [18F]fallypride administration to estimate the distribution volume ratio DVR′ (DVR′ ∝ DVR; DVR = 1 + BPND, where BPND is a measure of receptor density, DA D2 in this case). In this work, we use this method to assess the effects of isoflurane anesthesia on [18F]fallypride DVR′. Methods: Rats were injected with [18F]fallypride either unconsciously under ∼1.5% isoflurane via the tail vein (Group 1) or consciously via a catheter inserted either in the jugular vein (Group 2) or the tail vein (Group 3). After about 1 h of free access to food and water the rats were anesthetized with 1.5% isoflurane and imaged in a microPET for 60 min. The rats that were injected consciously (Groups 2 and 3) were placed in a rat restrainer during [18F]fallypride injection. They were habituated in that restrainer for 3 days prior to the experiment day to minimize restraint‐related stress. For comparison, a control group of rats was imaged for 120 min simultaneously with the administration of [18F]fallypride i.v. while under 1.5% isoflurane. The DVR′ estimates from the 60 min acquisitions were compared with the DVR′ from the last 60 min of the 120 min acquisitions (after neglecting the first 60 min). In addition, the striatal time–activity curves were fit with a 2‐tissue + plasma compartment model using an arbitrary simulated plasma input function to obtain k3/k4 (≈ BPND) for the 60 and 120 min acquisitions. Results: Isoflurane anesthesia caused a significant reduction, up to 22%, in the DVR′ estimates, which were 15.7 ± 0.3 (mean ± SE) for the controls, 17.7 ± 0.3 for Group 1, 19.2 ± 0.4 for Group 2, and 18.8 ± 0.7 for Group 3. The compartmental model fit produced similar results, ∼30% reduction in k3/k4 for the 120‐min acquisitions compared with the 60‐min acquisitions (initial conscious uptake of the radiotracer). Conclusion: The results of this study demonstrate that isoflurane anesthesia significantly decreases striatal [18F]fallypride BPND in rats. Of similar importance, this work demonstrates the effectiveness of delayed scans following radiotracer injection and the implication that different types of studies can be conducted simultaneously with this method, including studies of behavioral and environmental impact on brain receptors. Synapse, 2011. © 2011 Wiley‐Liss, Inc.
Experimental treatment of bilateral fetal chylothorax using in‐utero pleurodesis
Authors: Yang Y.‐S. , Ma G.‐C. , Shih J.‐C. , Chen C.‐P. , Chou C.‐H. , Yeh K.‐T. , Kuo S.‐J. , Chen T.‐H. , Hwu W.‐L. , Lee T.‐H. , Chen M.
Published: May 2011

Objective

To assess the use and efficacy of in‐utero pleurodesis for experimental treatment of bilateral fetal chylothorax.

Methods

This was a study of 78 fetuses with bilateral pleural effusion referred to three tertiary referral centers in Taiwan between 2005 and 2009. Fetuses were karyotyped following amniocentesis and the lymphocyte ratio in the pleural effusion was determined following thoracocentesis. Forty‐nine (62.8%) fetuses had a normal karyotype and were recognized to have fetal chylothorax; of these, 45 underwent intrapleural injection of 0.1KE OK‐432 per side per treatment. We evaluated clinical (hydrops vs. no hydrops) and genetic (mutations in the reported lymphedema‐associated loci: VEGFR3, PTPN11, FOXC2, ITGA9) parameters, as well as treatment outcome. Long‐term survival was defined as survival to 1 year of age.

Results

The overall long‐term survival rate (LSR) was 35.6% (16/45); the LSR for non‐hydropic fetuses was 66.7% (12/18) and for hydropic fetuses it was 14.8% (4/27). If we included only fetuses with onset of the condition in the second trimester, excluding those with onset in the third trimester, the LSR decreased to 29.4% (10/34). Notably, 29.6% (8/27) of hydropic fetuses had mutations in three of the four loci examined.

Conclusions

OK‐432 pleurodesis appeared to be an experimental alternative to the gold‐standard technique of thoracoamniotic shunting in non‐hydropic fetal chylothorax. In hydropic fetuses, pleurodesis appeared less effective. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.