bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of surrounding point charges on the density functional calculations of NixOx clusters (x = 4–12)
Authors: Kadossov Evgueni B. , Gaskell Karen J. , Langell Marjorie A. 
Published: February 2007

AbstractEmbedded NixOx clusters (x = 4–12) have been studied by the density‐functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed NiO lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed and measured bulk physical parameters. The optimum point charge value depends on the cluster size, but in all cases is significantly less than ±2.0, the formal oxidation state typically employed in cluster modeling of NiO bulk and surface properties. The electronic structure calculated with the optimized point charge magnitude is in general agreement with literature photoemission and XPS data and agrees with the presently accepted picture of the valence band as containing charge‐transfer insulator characteristics. The orbital population near the Fermi level does not depend on the cluster size and is characterized by hybridized Ni 3d and O 2p orbitals with relative oxygen contribution of about 70%. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Agonist‐induced calcium entry correlates with STIM1 translocation
Authors: Ross Kehinde , Whitaker Michael , Reynolds Nick J. 
Published: February 2007

AbstractThe mechanisms of agonist‐induced calcium entry (ACE) following depletion of intracellular calcium stores have not been fully established. We report here that calcium‐independent phospholipase A (iPLA2) is required for robust Ca2+ entry in HaCaT keratinocytes following ATP or UTP stimulation. Lysophosphatidic acid (LPA), an unrelated agonist, evoked Ca2+ release without inducing robust Ca2+ entry. Both LPA and UTP induced the redistribution of STIM1 into puncta which localized to regions near or at the plasma membrane, as well as within the cytoplasm. Plasma membrane‐associated STIM1 remained high for up to 10 min after UTP stimulation, whereas it had returned almost to baseline by that time point in LPA‐stimulated cells. This correlated with faster reloading of the endoplasmic reticulum Ca2+ stores in LPA treated cells. Thus by differentially regulating store‐refilling after agonist‐mediated depletion, LPA and UTP may exert distinct effects on the duration of STIM1 localization at the plasma membrane, and thus, on the magnitude and duration of ACE. J. Cell. Physiol. 211: 569–576, 2007. © 2007 Wiley‐Liss, Inc.
Development of the osteocranium in the suckermouth armored catfish Ancistrus cf. triradiatus (Loricariidae, siluriformes)
Authors: Geerinckx Tom , Brunain Marleen , Adriaens Dominique 
Published: February 2007

AbstractThe development of the osteocranium of the suckermouth armored catfish Ancistrus cf. triradiatus is described based on specimens ranging from prehatching stages to juvenile stages where the osteocranium is more or less fully formed. The first bony elements that arise are the opercle, jaws, and lateralmost branchiostegal rays, as well as the basioccipital and parasphenoid in the skull floor. The supracleithrum and the membranous and perichondral pterotic components form one large, double‐layered skull bone during ontogeny, without clear evidence of the involvement of a supratemporal. The Baudelot's ligament ossifies from two sides, i.e., from the basioccipital medially and the supracleithrum laterally. The lower jaw consists of a dentary, mentomeckelian, and angulo‐articular, which all soon fuse. The parurohyal, formed by the fusion of a ventral sesamoid bone and a dorsal cartilage element associated with the first basibranchial, is pierced by a vein, unlike in some other siluriforms. The interhyal cartilage disappears during ontogeny; medially of it, a small sesamoid bone appears in a ligament. The largest, canal‐bearing cheek plate is not homologous to the interopercle. The results of the present research, with emphasis on bone formations and homologies, are compared with studies on related catfishes. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Complexes between some lysine‐containing peptides and crown ethers—electrospray ionization mass spectrometric study
Authors: Frański Rafał , Schroeder Grzegorz , Kamysz Wojciech , Niedzialkowski Pawel , Ossowski Tadeusz 
Published: February 2007

AbstractThe complexes between lysine‐containing peptides (M) and crown ethers (CEs, 18C6, 15C5, 12C4) have been studied by the electrospray ionization (ESI) mass spectrometry. The maximum number of CEs attached has been found to be the same as that of the alkyl‐amino side chains of lysine and as that of the protons attached. Examination of the breakdown plots of the abundances of the ions observed against the cone voltage (CV) has shown that mass spectrometric fragmentation pathways of [M + nH + (CE)n]+n may involve a loss of a neutral CE molecule as well as protonated one. The decrease in the CE cavity (the use of 12C4 or 15C5 instead of 18C6) leads to a dramatic lowering in the stability of the complexes in the gas phase but not in solution. Attachment of a CE to peptides increases their hydrophobicity, and therefore proceeds with lower efficiency in water than in methanol. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of a putative Xylella fastidiosa diffusible signal factor by HRGC‐EI‐MS
Authors: Colnaghi Simionato Ana Valéria , da Silva Denise Santos , Lambais Marcio Rodrigues , Carrilho Emanuel 
Published: February 2007

AbstractXylella fastidiosa (X.f.) is a plant pathogen with high levels of genomic similarity to Xanthomonas campestris pv. campestris (X.c.c.). It has been shown that X. fastidiosa synthesizes a putative diffusible signal factor (X.f.‐DSF) that activates regulation of pathogenicity factor (rpf) genes in a X.c.c. reporter system, which might be involved in the regulation of pathogenesis associated genes as in X.c.c., as well as in quorum‐sensing. The nature of the X.f.‐DSF is not known, whereas the X.c.c.‐DSF has been identified as cis‐11‐methyl‐2‐dodecenoic acid. In this work, the chemical nature of a putative X.f.‐DSF molecule, able to restore endoglucanase activity in a X.c.c. rpfF mutant, was investigated as if it was a fatty acid derivative. Bioassays with X.c.c. reporter bacterium and X.f. culture extracts, based on endoglucanase restoration activity, were also carried out in order to confirm the DSFs molecules similarities. For this reason, a gas chromatography–mass spectrometry method was developed with standard fatty acids methyl esters mixtures. The retention time, as well as the fragmentation patterns, of each standard was used to identify the DSF molecule synthesized by X.f. in the culture medium. Typical ester fragmentation patterns (the derivatized analyte) were observed, such as: McLafferty rearrangement and migration of the Hδ followed by 1,4‐hydrogen shift and cleavage of the bond CβCγ, confirming the nature of this molecule. This confirmation was corroborated by the common peaks in both spectra. Besides, the observed retention time reinforces our conclusion since it corresponds to a methyl ester with 15 carbons. Since the X.f.‐DSF molecule was tentatively identified as 12‐methyl‐tetradecanoic acid (by mass spectra library comparison), this standard compound was also analyzed, strongly suggesting that this is the identification of such a molecule. To our knowledge, this is the first time a DSF produced by X.f. has been characterized. Copyright © 2007 John Wiley & Sons, Ltd.
Enantiomeric separation of chiral pesticides by high performance liquid chromatography on cellulose tris‐3,5‐dimethyl carbamate stationary phase under reversed phase conditions
Authors: Tian Qin , Lv Chunguang , Wang Peng , Ren Liping , Qiu Jing , Li Li , Zhou Zhiqiang 
Published: February 2007

AbstractTwenty chiral pesticides were tested, of which seven samples were directly separated by HPLC using cellulose tris‐3,5‐dimethyl carbamate (CDMPC) chiral stationary phase under RP conditions. The influence of mobile phase composition and column temperatures from 0°C to 40°C on the separations were investigated. The mobile phases were methanol/water or ACN/water at a flow rate of 0.8 mL/min with UV detection at 230 or 210 nm. Epoxiconazole, terallethrin, benalaxyl, and diclofop‐methyl were observed to obtain the baseline separation under suitable conditions and other pesticides pyriproxyfen, lactofen, and quizalofop‐ethyl were separated partially. The retention factors (k) and selectivity factor (α) for the enantiomers of most investigated pesticides decreased upon increasing the temperature except for the selectivity factors (α) of pyriproxyfen in methanol/water. The ln α–1/T plots for racemic chiral pesticides were linear at the range of 0–40 except for that of pyriproxyfen enantiomers in methanol/water and the chiral separations were controlled by enthalpy. Better separations were not always at low temperature. The elution orders of the eluting enantiomers were determined by a circular dichroism (CD) detector.
Palladium(II) chelate of tetradentate Schiff base as mixed stationary phase for gas chromatography
Authors: Laghari Abdul J. , Khuhawar Muhammad Y. , Ali Zeenat M. 
Published: February 2007

AbstractBis(acetylacetone)ethylenediiminepalladium(II) (PdAA2en) was examined as a mixed stationary phase with OV‐1 on Chromosorb G/NAW 60–80 mesh size for the GC separation of aromatic hydrocarbons, heteroaromatics, alcohols, aldehydes, ketones, esters, and nitro compounds. Forty‐two compounds were examined and the GC results were compared with those obtained with 3% OV‐1 on Chromosorb G/NAW 60–80 mesh size under similar operating conditions. Improved resolution, peak asymmetry, theoretical plate numbers, and Kovats indices were obtained on the mixed stationary phase of 3% OV‐1 + 5% PdAA2en compared to 3% OV‐1 column. The stability constant (Km), enthalpies (ΔH), entropies (ΔS), and Gibbs free energies (ΔG) of the GC elution on the column (2 m×3 mm id) packed with 3% OV‐1 + 5% PdAA2en on Chromosorb G/NAW 60–80 mesh size have been calculated. Donor‐acceptor complexation in the gas phase is indicated by negative values of enthalpy (–ΔH) within 5.81 to 10.89 kcal/mol and Gibbs free energy (–ΔG) from 1.34 to 4.08 kcal/mol. The retention time transformations on both the phases were calculated and the ratios obtained from the stationary phases 3% OV‐1 and 3% OV‐1 + 5% PdAA2en were plotted on the x‐axis and the y‐axis, respectively, and the coefficients of determination for alkanes, aromatic and heteroaromatics, ketones, and alcohols were observed to lie within 0.5253 to 0.9742, indicative of some different kinds of interaction of the two stationary phases with the solutes.
Compositional changes induced by UV‐B radiation treatment of common bean and soybean seedlings monitored by capillary electrophoresis with diode array detection
Authors: Dinelli Giovanni , Aloisio Irene , Bonetti Alessandra , Marotti Ilaria , Cifuentes Alejandro 
Published: February 2007

AbstractIn this work, a new CE method with diode array detection (DAD) was developed for the monitoring and quantitation of flavonoids in different beans treated and untreated with UV‐B radiation. Flavonoid concentration was monitored in UV‐B‐treated and untreated sprouts of three common beans (Zolfino ecotype, cv. Verdone, cv. Lingua di Fuoco) and one soybean (cv. Pacific). After acid hydrolysis of extracts, the CE‐DAD method provides reproducible quantitative determinations of daidzein, glycitein, genistein, and kaempferol at ppm level in these natural matrices within a relatively short time (less than 16 min). Total flavonoid content determined by CE‐DAD was 159 ± 8, 26 ± 2, 13 ± 1, and 1.3 ± 0.3 μg/g fresh weight for untreated sprouts of Pacific soybean, Verdone bean, Zolfino bean, and Lingua di Fuoco bean, respectively. UV‐B treatment caused no significant quantitative effect on Pacific soybean sprouts, whereas it enhanced the total isoflavone content by 1.5, 1.8, and 3.2‐fold in Verdone, Zolfino, and Lingua di Fuoco beans, respectively. The proposed method shows (i) the potentialities of bean sprouts as a natural source of bioactive compounds (antioxidants); (ii) the technological role of UV‐B treatment for sprout isoflavone enrichment; and (iii) the good capabilities of CE‐DAD to monitor this process.
Antioxidant compounds of propolis determined by capillary electrophoresis–mass spectrometry
Authors: Gómez‐Romero María , Arráez‐Román David , Moreno‐Torres Rosario , García‐Salas Patricia , Segura‐Carretero Antonio , Fernández‐Gutiérrez Alberto 
Published: February 2007

AbstractPropolis is a resinous hive product rich in antioxidant compounds. Capillary electrophoresis coupled to mass spectrometric detection can provide selective information about the analytes present in complex extracts of propolis and has turned out to be an attractive alternative to HPLC methods. Therefore, a CE‐ESI‐MS method has been developed for the analysis of antioxidant compounds obtained from propolis. For this purpose, different electrophoretic parameters such as the nature, pH, and concentration of the separation buffer, as well as electrospray parameters (dry gas temperature and flow, nebulising gas pressure, and make‐up flow) have been carefully optimised. Different phenolic compounds (e. g. pinobanksin 3‐acetate, naringenin, pinocembrin, chrysin, daidzein, quercetin 3′,7‐dimethyl ether, apigenin, and kaempferid) could be detected. To confirm the identity of the phenolic compounds in propolis extracts, accurate mass data of the molecular ions were obtained by TOF MS. Limits of detection ranging from 6 mg/100 g of raw propolis for chrysin to 58 mg/100 g of raw propolis for luteolin, were obtained.
Comparison of comprehensive two‐dimensional gas chromatography‐time‐of‐flight mass spectrometry and gas chromatography‐mass spectrometry for the qualitative characterisation of roasted barley by solid‐phase microextraction
Authors: Bianchi Federica , Careri Maria , Conti Chiara , Musci Marilena , Vreuls Renè 
Published: February 2007

AbstractVolatile compounds of roasted barley used in the production of barley coffee, the most common coffee substitute, were analysed by using solid‐phase microextraction (SPME) followed by GC‐MS and comprehensive GC×GC‐TOF‐MS, respectively. The optimised SPME extraction conditions in terms of selection of the fibre coating, extraction time and extraction temperature allowed to obtain the highest GC response, thus enhancing the identification capabilities of the developed method. As for the SPME‐GC×GC‐TOF‐MS analysis, 64 compounds with similarity, reverse and probability values above 800, 900 and 6000, respectively, were identified, by using a polar×apolar column set combination; in contrast, GC‐MS was able to identify a lower number of compounds, i. e. 40 volatiles.
Template‐Directed Control of Crystal Morphologies
Authors: Meldrum Fiona C. , Ludwigs Sabine 
Published: February 2007

AbstractBiominerals are characterised by unique morphologies, and it is a long‐term synthetic goal to reproduce these synthetically. We here apply a range of templating routes to investigate whether a fascinating category of biominerals, the single crystals with complex forms, can be produced using simple synthetic methods. Macroporous crystals with sponge‐like morphologies identical to that of sea urchin skeletal plates were produced on templating with a sponge‐like polymer membrane. Similarly, patterning of individual crystal faces was achieved from the micrometer to nanometer scale through crystallisation on colloidal particle monolayers and patterned polymer thin films. These experiments demonstrate the versatility of a templating approach to producing single crystals with unique morphologies.magnified image
Spider Silk and Amyloid Fibrils: A Structural Comparison
Authors: Slotta Ute , Hess Simone , Spieß Kristina , Stromer Thusnelda , Serpell Louise , Scheibel Thomas 
Published: February 2007

AbstractAlthough spider silks have been studied for decades, the assembly properties of the underlying silk proteins have still not been unravelled. Previously, the detection of amyloid‐like nanofibrils in the spider's silk gland suggested their involvement in the assembly process.Recombinantly produced spider silk also self‐assembles into nanofibrils. In order to investigate the structural properties of such silk nanofibrils in more detail, they have been compared to amyloid‐like fibrils to highlight structural similarities.magnified image
Bioinspired Mineralization of Inorganics from Aqueous Media Controlled by Synthetic Polymers
Authors: Gorna Katarzyna , Muñoz‐Espí Rafael , Gröhn Franziska , Wegner Gerhard 
Published: February 2007

AbstractThe formation of inorganic structures in nature is commonly controlled by biogenic macromolecules. The understanding of mineralization phenomena and the nucleation and growth mechanisms involved is still a challenge in science but also of great industrial interest. This article focuses on the formation and mineralization of two archetypical inorganic materials: zinc oxide and amorphous calcium carbonate (ACC). Zinc oxide is selected as a model compound to investigate the role that polymers play in mineralization. Most of the effort has been devoted to the investigation of the effects of double‐hydrophilic block and graft copolymers. Recent work has demonstrated that latex particles synthesized by miniemulsion polymerization, properly functionalized by various chemical groups, have similar effects to conventional block copolymers and are excellently suited for morphology control of ZnO crystals. Latex particles might serve as analogues of natural proteins in biomineralization. The second example presented, ACC, addresses the issue of whether this amorphous phase is an intermediate in the biomineralization of calcite, vaterite, or aragonite. Conditions under which amorphous calcium carbonate can be obtained as nanometer‐sized spheres as a consequence of a liquid–liquid phase segregation are presented. Addition of specific block copolymers allows control of the particle size from the micrometer to the submicrometer length scale. The physical properties of novel materials synthesized from concentrated solution and their potential applications as a filler of polymers are also discussed.magnified image
Potential of Various Archae‐ and Eubacterial Strains as Industrial Polyhydroxyalkanoate Producers from Whey
Authors: Koller Martin , Hesse Paula , Bona Rodolfo , Kutschera Christoph , Atlić Aid , Braunegg Gerhart 
Published: February 2007

AbstractThree different microbial wild‐type strains are compared with respect to their potential as industrial scale polyhydroxyalkanoate (PHA) producers from the feed stock whey lactose. The halophilic archaeon Haloferax mediterranei as well as two eubacterial strains (Pseudomonas hydrogenovora and Hydrogenophaga pseudoflava) are investigated. H. mediterranei accumulated 50 wt.‐% of poly‐3‐(hydroxybutyrate‐co‐8%‐hydroxyvalerate) from hydrolyzed whey without addition of 3‐hydroxyvalerate (3HV) precursors (specific productivity qp: 9.1 mg · g−1 · h−1). Using P. hydrogenovora, the final percentage of poly‐3‐hydroxybutyrate (PHB) amounted to 12 wt.‐% (qp: 2.9 mg · g−1 · h−1). With H. pseudoflava, it was possible to reach 40 wt.‐% P‐3(HB‐co‐5%‐HV) on non‐hydrolyzed whey lactose plus addition of valeric acid as 3HV precursor (qp: 12.5 mg · g−1 · h−1). A detailed characterization of the isolated biopolyesters and an evaluation with regard to the economic feasibility completes the study.magnified image
Suberin: A Biopolyester of Plants' Skin
Authors: Graça José , Santos Sara 
Published: February 2007

AbstractSuberin is a biopolymer that acts as a barrier between plants and the environment. It is known to be a complex polyester based on glycerol and long‐chain α,ω‐diacids and ω‐hydroxyacids. How these monomeric units are assembled at a macromolecular level remains mostly unknown. The knowledge gathered in the last 10 years has opened new insights into suberin structure. Suberin oligomeric blocks have been obtained after the partial depolymerization of the biopolymer, and in‐situ studies by solid‐state 13C NMR spectroscopy have shown different molecular domains and how they are spatially related. Based on these latter developments, a model is proposed for the suberin macromolecular structure. The uniqueness of the suberin polyester opens perspectives for its use as a source of bio‐based materials.magnified image
Bio‐Refinery as the Bio‐Inspired Process to Bulk Chemicals
Authors: Sanders Johan , Scott Elinor , Weusthuis Ruud , Mooibroek Hans 
Published: February 2007

AbstractThis paper describes several examples of knowledge‐intensive technologies for the production of chemicals from biomass, which take advantage of the biomass structure in a more efficient way than the production of fuels or electricity alone. The depletion in fossil feedstocks, increasing oil prices, and the ecological problems associated with CO2 emissions are forcing the development of alternative resources for energy, transport fuels, and chemicals, such as the replacement of fossil resources with CO2 neutral biomass. Allied with this is the conversion of crude oil products utilizes primary products (ethylene, etc.) and their conversion into either materials or (functional) chemicals with the aid of co‐reagents such as ammonia, by various process steps to introduce functionalities such as ‐NH2 into the simple structures of the primary products. Conversely, many products found in biomass often contain functionalities. Therefore, it is attractive to exploit this in order to by‐pass the use, and preparation of, co‐reagents as well as to eliminate various process steps by utilizing suitable biomass‐based precursors for the production of chemicals.magnified image
Functional, Hierarchically Structured Poly(diacetylene)s via Supramolecular Self‐Assembly
Authors: Jahnke Eike , Millerioux Anne‐Sophie , Severin Nikolai , Rabe Jürgen P. , Frauenrath Holger 
Published: February 2007

AbstractThe supramolecular self‐assembly of macromonomers may serve as a first step to prepare well‐defined, highly functionalized, hierarchically structured, conjugated polymers. Functional diacetylene macromonomers equipped with an oligopeptide segment designed to promote self‐assembly into parallel β‐sheet type structures and a polydisperse, aliphatic coil segment to prevent global ordering give rise to supramolecular polymers with a tubular double‐helical quarternary structure in organic solution. These supramolecular polymers may then be converted into the corresponding poly(diacetylene)s by UV irradiation under retention of their hierarchical structure.