bluuebunny/crossref_metadata_2025_split huggingface dataset:
The major toxin from the Australian Common Brown Snake is a hexamer with unusual gas‐phase dissociation properties
Authors: Aquilina J. Andrew 
Published: September 2008

AbstractAsymmetric dissociation of multiply charged protein assemblies has been frequently reported. This phenomenon, which relies on the dissociation of one or more highly charged monomers, has been shown to provide insights into the structure and organization of large monodisperse and polydisperse assemblies. Here, the process of asymmetric dissociation is investigated using the multisubunit protein, textilotoxin, which has unusually high structural constraints on its monomers due to multiple disulfide linkages. Initially, it is shown that, contrary to previous reports, textilotoxin is made up of six, rather than five subunits. Furthermore, the hexamer exists as two isoforms, one of which is substantially more glycosylated. Gas‐phase dissociation studies on the hexamers reveal the subunit stoichiometry of each isoform to be (A/B)2C2D2a and (A/B)CD2aD2b, where A and B are subunits of very similar mass and D2a, D2b refer to differentially glycosylated dimers of the D subunit. The mechanism of dissociation was unusual, as rather than one subunit being largely removed before sequential dissociation of a second, the process was predominantly concurrent for the two smallest subunits. Furthermore, a small proportion of the dissociated species was observed to be a noncovalently associated dimer. A comparison of dissociation pathways for two neighboring charge states of the same textilotoxin isoform demonstrates that, in agreement with previous reports, variations in quaternary structure are responsible for the distinct charge states of a protein. Proteins 2009. © 2008 Wiley‐Liss, Inc.
Computational determination of effects of electric fields upon “trigger linkages” of prototypical energetic molecules
Authors: Politzer Peter , Murray Jane S. , Lane Pat 
Published: September 2008

AbstractFor five prototypical energetic molecules (nitrobenzene, methyl azide, methyl nitrate, nitromethane, and dimethylnitramine), we examine computationally the effects of external electric fields upon their “trigger linkage” bonds, the breaking of which is believed to play a key role in detonation initiation. The bonds are, respectively, CNO2, NN2, ONO2, CNO2, and NNO2. The calculations are at the B3PW91/6–31G** level. We find that fields along these bonds that reinforce the molecules' intrinsic polarities also lower their energies and increase the bonds' stretching vibration frequencies. This suggests a strengthening of the bonds. Fields in the opposite direction do the reverse. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Density functional study of aurophilic interaction in Cl(AuPH3) and in its dimerization
Authors: Fang Hua , Wang Shu‐Guang , Zhang Xiao‐Gang 
Published: September 2008

AbstractWith the help of quantum mechanical calculations, the geometric structures and electronic structures of the closed‐shell systems Cl(AuPH3) and [Cl(AuPH3)]2 have been determined by DFT and MP2 methods. Experimental structure parameters of the title compounds were reproduced at Xα level. The Mulliken population and HOMO–LUMO gaps were examined. The intermolecular aurophilic interactions in [Cl(AuPH3)]2 were analyzed and decomposed. A positive BE value (no bonding) was calculated. When 2PC was added, each pair Au… Au interaction energy was about 83 kJ/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Nonadditivity of methyl group in single‐electron hydrogen bond of methyl radical‐water complex
Authors: Li Qingzhong , Zhu Hongjie , An Xiulin , Gong Baoan , Cheng Jianbo 
Published: September 2008

AbstractThe nonadditivity of methyl group in the single‐electron hydrogen bond of the methyl radical‐water complex has been studied with quantum chemical calculations at the UMP2/6‐311++G(2df,2p) level. The bond lengths and interaction energies have been calculated in the four complexes: CH3H2O, CH3CH2H2O, (CH3)2CHH2O, and (CH3)3CH2O. With regard to the radicals, tert‐butyl radical forms the strongest hydrogen bond, followed by iso‐propyl radical and then ethyl radical; methyl radical forms the weakest hydrogen bond. These properties exhibit an indication of nonadditivity of the methyl group in the single‐electron hydrogen bond. The degree of nonadditivity of the methyl group is generally proportional to the number of methyl group in the radical. The shortening of the C···H distance and increase of the binding energy in the (CH3)2CHH2O and (CH3)3CH2O complexes are less two and three times as much as those in the CH3CH2H2O complex, respectively. The result suggests that the nonadditivity among methyl groups is negative. Natural bond orbital (NBO) and atom in molecules (AIM) analyses also support such conclusions. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Evaluation of molecular integral of Cartesian Gaussian type basis function with complex‐valued center coordinates and exponent via the McMurchie–Davidson recursion formula, and its application to electron dynamics
Authors: Kuchitsu T. , Okuda J. , Tachikawa M. 
Published: September 2008

AbstractMcMurchie–Davidson recursion formula is extended to derive the ab initio molecular integrals with higher angular quantum number complex Gaussian type basis function which has complex‐valued center coordinates and a complex‐valued exponent. Using the analytical recursion formulae, some calculations of electronic dynamics after beta decay of tritium hydride molecular ion HT+ are performed by a quantum wave packet method with thawed Gaussian basis functions of s‐ and p‐type. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Theoretical estimates of the IR spectrum of water intercalated into kaolinite
Authors: Campos Renan Borsoi , Wypych Fernando , Martins Filho Harley Paiva 
Published: September 2008

AbstractCalculations at AM1, PM3, and HF/6‐31G levels of part of the IR spectrum of the water–kaolinite intercalated system based on a 96‐atom cluster of kaolinite with one water molecule are reported. Only the water molecule conformation is optimized. Frequencies and intensities for just the water vibrations and stretchings of four cluster hydroxyls were calculated through partial Hessian matrices and polar tensors obtained by numerical differentiation of energy gradients and dipole moment. The water molecule was found to attach to the cluster mainly through a double hydrogen bond to the siloxane inner surface, partially entering the siloxane ring hexagonal hole. Though the theoretical results predict that the water OH stretching frequencies decrease from the gas‐phase state to the intercalated state, they are still higher than expected with respect to the observed spectrum. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Theory of chemical bonds in metalloenzymes XI: Full geometry optimization and vibration analysis of porphyrin iron‐oxo species
Authors: Shoji Mitsuo , Isobe Hiroshi , Saito Toru , Kitagawa Yasutaka , Yamanaka Shusuke , Kawakami Takashi , Okumura Mitsutaka , Yamaguchi Kizashi 
Published: September 2008

AbstractPhysiochemical properties of compound I and II intermediate states for heme enzymes (catalase, peroxidase, P450) and inorganic models are investigated by hybrid density functional theory. Used theoretical models are composed of an oxoferryl porphyrin and an axial ligand, which are cresol, methylimidazole, methylthiol, and chloride for catalase, peroxidase, P450, and inorganic models, respectively. The oxoferryl bonds are characterized in terms of bond lengths and vibration frequencies. It is found that the oxoferryl bond lengths (the stretching frequency) are shorter (higher) than those of the X‐ray crystal structures of enzymes, on the other hand for inorganic models, they are comparable with the experimental values. Spin density distributions showed that radical state at the compound I can be classified into two types: (1) porphyrin radical state and (2) axial ligand radical state. Peroxidase and inorganic model are in the former case and Catalase and P450 are in the later case at the present calculation models. Magnetic interactions between oxoferryl and ligand radical moieties are analyzed by the natural orbital analysis and it is showed that the effective exchange integral (J) values are strongly related to the radical spin density distributions: axial ligand radical tends to increase the antiferromagnetic interaction. Mössbauer shift parameters are also evaluated and it is shown that iron charge states are similar for these models. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Comparison of polarization consistent and correlation consistent basis sets for noncovalent interactions
Authors: ElSohly Adel M. , Tschumper Gregory S. 
Published: September 2008

AbstractThe convergence of the polarization consistent family of basis sets to the MP2 complete basis set (CBS) limit has been examined for the dissociation energies of five weakly bound clusters: (HF)2, (HF)3, (H2O)2, (H2O)3, and (C2H2)2. MP2 results obtained with two series of polarization consistent basis sets and the analogous series of Dunning's correlation consistent basis sets are compared to the CBS limits obtained with the explicitly correlated MP2‐R12 method. Although the polarization consistent basis sets do converge systematically to the CBS limit, the correlation consistent basis sets with diffuse functions on nonhydrogen atoms (i.e., cc‐pVXZ for H and aug‐cc‐pVXZ otherwise) consistently produced the smallest errors. Counterpoise corrections for basis set superposition error did not improve the performance of either the polarization or correlation consistent basis sets. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Nature of science as depicted in Turkish biology textbooks
Authors: Irez Serhat 
Published: September 2008

AbstractGiven the impact of textbooks on learning, this study assesses the five most frequently used secondary school biology textbooks in Turkey to examine the nature and the quality of treatment given to the nature of science. A qualitative oriented approach was employed and ethnographic content analysis was used as the methodological framework for this particular research. Data were analyzed by means of cognitive maps. The investigation revealed a number of serious problems with the way nature of science is portrayed in the textbooks. Science was generally portrayed as collection of facts, not as a dynamic process of generating and testing alternative explanations about nature. The authors of the textbooks often appeared not to understand the processes well enough to explain them to students and therefore presented various misleading and inadequate descriptions regarding scientific enterprise, similar to those revealed by research on science teachers' and students' understandings of science. Furthermore, some important aspects of science were found to be neglected by textbooks. The study discusses the future success of scientific literacy movement in Turkey and has implications for science education, science curriculum, and science teacher education in Turkey and other developing countries. © 2008 Wiley Periodicals, Inc. Sci Ed 93: 422–447, 2009
Physical characteristics of Saccharomyces cerevisiae
Authors: Bui V. C. , Kim Y. U. , Choi S. S. 
Published: September 2008

AbstractWe examined the physical properties of the surrounding yeast cell walls by using atomic force microscopy (AFM). The yeast cells were prepared on a cleaned glass substrate for confocal microscopy (CM) observation and were mechanically trapped into a porous membrane for AFM measurement. The confocal image of the yeast cells was measured in air, meanwhile the AFM topography images of the cells were measured in both deionized (DI) water (pH = 6.9) and phosphate‐buffered saline (PBS) solution (pH = 7.4). No significant differences between the AFM topography images of the yeast cells measured in DI water and in PBS solution could be inferred. In order to get the quantitative information on the sample elasticity, the force curves between an AFM tip and the yeast cell have been measured. These curves were measured in both DI water and in PBS solution on the same yeast cell using the same AFM cantilever to get the reliable result. The contact region of the force curve in approach mode was then converted into force versus indentation curve, which would be fitted with Hertz–Sneddon model for the calculation of the elasticity. Analysis of the curves indicates that there is a difference of the Young's modulus values of the yeast cell in various environments. These data show that the salt buffer solution increases the rigidity of the biological system. Copyright © 2008 John Wiley & Sons, Ltd.
Differentiating calcium carbonate polymorphs by surface analysis techniques—an XPS and TOF‐SIMS study
Authors: Ni Ming , Ratner Buddy D. 
Published: September 2008

AbstractCalcium carbonate has evoked interest owing to its use as a biomaterial, and for its potential in biomineralization. Three polymorphs of calcium carbonate, i.e. calcite, aragonite, and vaterite were synthesized. Three conventional bulk analysis techniques, Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and SEM, were used to confirm the crystal phase of each polymorphic calcium carbonate. Two surface analysis techniques, X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS), were used to differentiate the surfaces of these three polymorphs of calcium carbonate. XPS results clearly demonstrate that the surfaces of these three polymorphs are different as seen in the Ca(2p) and O(1s) core‐level spectra. The different atomic arrangement in the crystal lattice, which provides for a different chemical environment, can explain this surface difference. Principal component analysis (PCA) was used to analyze the TOF‐SIMS data. Three polymorphs of calcium carbonate cluster into three different groups by PCA scores. This suggests that surface analysis techniques are as powerful as conventional bulk analysis to discriminate calcium carbonate polymorphs. Copyright © 2008 John Wiley & Sons, Ltd.
Efficiency enhancement of solid‐state dye sensitized solar cell by in situ deposition of CuI
Authors: Han Jing , Chen Jin Mao , Zhou Xiao Wen , Lin Yuan , Zhang Jing Bo , Jia Jian Guang , Sankapal Babasaheb Raghunath 
Published: September 2008

AbstractSolid‐state dye‐sensitized solar cells based on nanocrystalline TiO2 thin film with the structures TiO2/dye/CuI/Pt and TiO2/dye/In situ CuI/CuI/Pt were developed in order to compare the use of In situ deposited CuI (In situ CuI). Porosity of the screen‐printed nanoporous TiO2 thin film was enhanced by the addition of polystyrene balls. Evidence of decrease in interfacial resistance was observed by electrochemical impedance measurement for the device with In situ deposited CuI as compared to that without In situ deposited CuI as hole conductor. This was attributed to good interfacial contacts and better charge transfer between CuI and dye‐sensitized TiO2 nanoparticles, which resulted in the enhancement of power conversion efficiency from 0.058 to 1.01%. Copyright © 2008 John Wiley & Sons, Ltd.
Einsparpotentiale bei Tragkonstruktionen von Offshore‐Windenergieanlagen
Authors: Scharff Rüdiger , Siems Michael , Ummenhofer Thomas 
Published: September 2008

AbstractAufgrund der hohen dynamischen Lastanteile aus Wind‐ und Wellenbeanspruchungen bei Offshore‐Windenergieanlagen erweist sich der Nachweis der Betriebsfestigkeit in vielen Fällen als bestimmender Faktor für die Auslegung der Tragstrukturen. Hierdurch wird in der aktuellen Bemessungspraxis insbesondere die Nutzung wirtschaftlicher Vorteile aus der Anwendung höherfester Stähle behindert. Gerade unter dem Aspekt der Serienfertigung ist jedoch die wirtschaftliche Optimierung der Bauteile für die Firmen ein wesentlicher Wettbewerbsvorteil. In diesem Beitrag werden verschiedene Möglichkeiten für Einsparungen bei Entwurf und Bemessung von Offshore‐Gründungsstrukturen aufgezeigt und am Beispiel der Übergangskonstruktion für eine Jacket‐Struktur dargestellt. Die Einsparpotentiale werden durch optimale Formgebung der Konstruktion, richtungsabhängige Last‐ermittlung, eine verfeinerte Nachweismethodik sowie durch moderne Verfahren der Schweißnahtnachbehandlung ermöglicht.
Bewertung der Ermüdungsfestigkeit von Baustrukturen in Offshore‐Windenergie‐Anlagen
Authors: Thöns Sebastian , Rohrmann Rolf G. , Rücker Werner , Faber Michael H. 
Published: September 2008

AbstractDas Bauwerk einer Windenergieanlage dient der Sicherstellung der Energieproduktion. Eine entsprechende Zuverlässigkeit der Struktur und deren permanente Bewertung und Unterhaltung ist dazu notwendig. In diesem Beitrag werden Möglichkeiten der Bewertung des für die Struktur wichtigen Schädigungsmechanismus Ermüdung sowie dessen Überwachung in Zusammenhang mit Schädigungsindikatoren aufgezeigt. Dabei wird auf strukturmechanische, werkstoffmechanische und probabilistische Modelle sowie auf Messdaten eines Prototyps einer OWEA zurückgegriffen. Ausgehend von der gesamtdynamischen Berechnung wird die Zuverlässigkeit gemäß der Auslegung für den Schädigungsmechanismus Ermüdung durch ein Wöhlerlinienmodell berechnet. Damit werden ermüdungssensible Komponenten der Struktur identifiziert. Schädigungsindikatoren zur Überwachung der Ermüdungsfestigkeit werden auf Grundlage schädigungs‐äquivalenter Dehnungen vorgestellt.
Grout‐Verbindungen von Monopile‐Gründungsstrukturen – Trag‐ und Ermüdungsverhalten
Authors: Schaumann Peter , Wilke Fabian , Lochte‐Holtgreven Stephan 
Published: September 2008

AbstractIn dem Beitrag wird der aktuelle Stand der Technik für Grout‐Strukturen von Offshore‐Windenergieanlagen (OWEA) vorgestellt sowie über die Ergebnisse von experimentellen und numerischen Untersuchungen an klein‐ und großmaßstäblichen Grout‐Verbindungen berichtet, die im Rahmen des ForWind‐Projektes “TPV: Lebensdauerprognose für die Tragstruktur von Offshore‐Windenergieanlagen” am Institut für Stahlbau der Leibniz Universität Hannover durchgeführt wurden. Auf Grundlage der Erkenntnisse aus Versuch und Numerik werden anhand einer Referenzstruktur in der Ostsee mit einer Anlagengröße von 3MW repräsentative Berechnungen von Grouted‐Joint‐Verbindungen unter vorwiegender Biegebeanspruchung mit Hilfe von numerischen Modellen vorgestellt. Neben der Betrachtung von Grouted‐Joint‐Verbindungen mit glatten Stahlrohroberflächen werden die Möglichkeiten von Grout‐Strukturen unter Ansatz von versteifenden Schubrippen (Shear Keys) im Grenzzustand der Tragfähigkeit und Ermüdung vorgestellt. Neben der Betrachtung der Gesamtstruktur einer Grout‐Verbindung unter Ermüdungsbeanspruchungen werden lokale Konzepte für Degradationsberechnungen im Bereich der Shear Keys durchgeführt und eine Einstufung in Kerbfallklassen vorgenommen.
Temperature Related Structural Changes in Wheat and Corn Starch Granules and Their Effects on Gels and Dry Foam
Authors: Glenn Gregory M. , Klamczynski Artur , Chiou Bor‐Sen. , Orts William J. , Imam Syed H. , Wood Delilah F. 
Published: September 2008

AbstractThe effect of processing temperature on structural changes in wheat, corn, and high amylose corn starch granules was investigated and related to the mechanical properties of gels and microcellular foam (MCF). Scanning electron micrographs (SEM) showed that wheat starch granules form ghosts with thicker walls than dent corn granules. The granule wall was permeable to water and appeared to be at least partially permeable to the solubilized contents of the granule. The ghost walls became visibly porous after heating at 95ºC for 60 min and were completely solubilized by heating to 120ºC. High‐amylose corn starch (HACS) granules were completely dissolved by heating to 140ºC. Gels made with wheat starch had higher gel strength and dynamic modulus compared to dent corn starch gels. The density, compressive strength and modulus of MCF were lower in samples cooked for 60 min. The density of dent corn MCF was higher than that of wheat starch which may have accounted for higher compressive strength and modulus in the corn sample. MCF made from HACS had higher surface area and lower density, compressive strength, and modulus than the other starches tested. There were no significant differences in pore volume or surface area due to extended cooking times.
Influence of aroclor 1254 on benzo(a)pyrene‐induced DNA breakage, oxidative DNA damage, and cytochrome P4501A activity in human hepatoma cell line
Authors: Yuan Jing , Lu Wen‐Qing , Zou Ya‐Lin , Wei Wei , Zhang Chi , Xie Hong , Chen Xue‐Min 
Published: September 2008

AbstractBoth polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) are important environmental pollutants. They coexist widely in the environment at very low levels. Numerous studies indicated that aroclor1254 (one of PCBs mixture) is the inducer of cytochrome P450 1A enzyme acitivity. Benzo(a)pyrene (BaP) can cause a variety of toxicities in vitro, such as oxidative DNA damage and genotoxicity. In the present study, HepG2 cells were treated with either BaP (50 μM) or aroclor1254 at concentrations of 11.5 (low), 23.0 (medium), and 46.0 μM (high) alone, or pretreated the cells with aroclor1254 (11.5, 23.0, and 46.0 μM), followed by BaP (50 μM). It was found that 7‐ethoxyresorufin‐O‐deetylase (EROD) activities of HepG2 cells exposed to either BaP or aroclor 1254 increased. DNA damage measured by DNA migration and the formation of 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG) also increased in cells exposed to BaP, but not in cells exposed to aroclor1254. Under the Aroclor 1254 pretreatment condition, BaP‐induced EROD activities was enhanced in cells exposed to the medium and high concentrations of aroclor1254 (P < 0.01 for both), whereas in all pretreatment groups aroclor1254 significantly increased BaP‐induced DNA migration (P < 0.01 for all) and the 8‐OHdG formation (P < 0.05 for all). In addition, there was positive correlation between the EROD induction activity and Olive tail moment (r2 = 0.958, P < 0.01) or the levels of 8‐OHdG (r2 = 0.992, P < 0.01). The findings suggest that under the experimental conditions aroclor1254 may enhance BaP‐induced DNA migration and oxidative DNA damage in HepG2, due to inducing CYP1A enzyme activity. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Effect of short‐time exposures to nickel and lead on brain monoamine oxidase fromDanio rerioandPoecilia reticulata
Authors: Senatori Ornella , Setini Andrea , Scirocco Annunziata , Nicotra Antonietta 
Published: September 2008

AbstractThe aim of this work was to verify, in two small size freshwater teleostsDanio rerioandPoecilia reticulata, the effects of short‐time exposures (24 and 72 h) to a sublethal dose (500 μg/L) of nickel and lead, on brain monoamine oxidase (MAO), an important neural enzyme. The 24‐h treatment using both metals caused a strong reduction of MAO activity inD. reriobrain, whereas causing a slight MAO activity stimulation inP. reticulatabrain. The same treatment in both species did not affect the brain MAO mRNA production as showed by RT‐PCR. Extending the duration of treatment as far as 72 h, partly (D. rerio) or completely (P. reticulata) reversed the metal effects on brain MAO activity suggesting that mechanisms to neutralize the metals had been activated. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.