bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of degradation tunable poly(ε‐caprolactone) using a Sn(Oct)2/BF3 dual catalyst
Authors: Jiang G. , Jones I. A. , Rudd C. D. , Walker G. S. 
Published: September 2008

AbstractTailoring the degradation rate of poly(ε‐caprolactone) (PCL) was found to be easily accomplished by the polymerization of ε‐caprolactone using a Sn(Oct)2/BF3 dual catalyst. The resulting PCL contained BF3, which acts as a hydrolytic degradation catalyst for PCL. The degradation rate of the polymer was controlled by the concentration of BF3 in the polymer matrix. At lower BF3 concentrations (<0.002 mol dm−3), the degradation rate was linearly proportional to the BF3 concentration. At higher BF3 concentrations, the degradation rate rapidly increased, significantly deviating from the linear relationship between degradation rate and BF3 concentration. The system was found to be very versatile, producing PCL with degradation rates ranging from a half‐life of 0.9–46 weeks. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of the two novel liquid crystalline epoxy resins based on bisphenol‐s mesogen
Authors: Huo Li , Gao Jungang , Du Yonggang , Chai Zhihua 
Published: September 2008

AbstractTwo novel liquid crystalline epoxy resins (LCER) based on bisphenol‐S mesogen, 4,4′‐Bis‐(2,3‐epoxypropyloxy)‐sulfonyl bis(1,4‐phenylene) (p‐BEPSBP) and sulfonyl bis(4,1‐phenylene) bis[4‐(2,3‐epoxypropyloxy)benzoate] (p‐SBPEPB), were synthesized. Their liquid crystalline behavior and structure were characterized by Fourier transmittance infrared ray (FTIR), differential scanning calorimetry (DSC), 1HNMR, polarized optical microscopy (POM) and X‐ray diffraction (XRD). The results show that p‐BEPSBP is a kind of thermotropic liquid crystal and has a smectic mesophase with a melting point (Tm) at 165°C; the p‐SBPEPB is a kind of nematic mesophase with the temperature range of 155–302°C from the Tm to the clearing point Ti. The curing behaviors and texture of the liquid crystalline epoxy resins with 4,4′‐diaminodiphenyl ether (DDE) were also studied by DSC and some kinetic parameters were evaluated according to the Ozawa's method. The dynamic mechanical properties of curing products were also investigated by torsional braid analysis (TBA), and the results suggest that the dynamic mechanical loss peak temperature (Tp) of p‐BEPSBP/DDE and p‐SBPEPB/DDE is 120 and 130°C, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and properties of electrically‐sensitive poly(acrylic acid‐co‐acetoacetoxy ethyl methacrylate) gels
Authors: Jin Xiachao , Kang Hongmei , Huang Yongmin , Liu Honglai , Hu Ying 
Published: September 2008

AbstractA series of electric field sensitive copolymer P(AA‐co‐AAEM) gels of acrylic acid (AA) with acetoacetoxy ethyl methacrylate (AAEM) were prepared by free‐radical copolymerization, with N,N′‐methylene bisacrylamide (MBAAm) and ammounium persulfate (APS) as crosslinking agent and initiator, respectively. The structures and properties of the gels were tunable by changing the monomer feed weighty ratio (R) (R = WAAEM/(WAAEM + WAA) of AAEM and AA. The influences of the NaCl concentration and pH buffer solutions on the equilibrium swelling ratios of the gels were studied in detail. It is shown that both NaCl concentration and pH value of the buffer solution affect the swelling properties of the P(AA‐co‐AAEM) gels greatly. Moreover, the gel deswelling behavior induced by a direct current electric field was investigated and an excellent electric‐sensitivity was found. Among all the samples, the gel with monomer feed weighty ratio (R) = 0.1479 showed the best electrical contraction properties. On the basis of the experimental results, the mechanism of the electricity‐induced deswelling behavior was presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polystyrene composites containing crosslinked polystyrene‐multiwalled carbon nanotube balls
Authors: Kwon Soon‐Min , Kim Hun‐Sik , Kim Don‐Young , Yun Young Soo , Jin Hyoung‐Joon 
Published: September 2008

AbstractCrosslinked polystyrene‐multiwalled carbon nanotube (PS‐MWCNT) balls, which act as conductive microfillers, were prepared by the in situ suspension polymerization of styrene with MWCNTs and divinyl benzene (DVB) as a crosslinking agent. The diameters of the synthesized crosslinked PS‐MWCNT balls ranged from 10 to 100 μm and their electrical conductivity was about 7.7 × 10−3 S/cm. The morphology of the crosslinked PS‐MWCNT balls was observed by scanning electron microscopy and transmission electron microscopy. The change in the chemical structure of the MWCNTs was confirmed by Raman spectroscopy and Fourier transform infrared spectroscopy. The mechanical and electrical properties of the PS/crosslinked PS‐MWCNT ball composites were investigated. It was found that the tensile strength, ultimate strain, Young's modulus, and impact strength of the PS matrix were enhanced by the incorporation of the crosslinked PS‐MWCNT balls. In addition, the mechanical properties of the PS/crosslinked PS‐MWCNT ball composites were better than those of the PS/pristine MWCNT composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Natural language processing versus content‐based image analysis for medical document retrieval
Authors: Névéol Aurélie , Deserno Thomas M. , Darmoni Stéfan J. , Güld Mark Oliver , Aronson Alan R. 
Published: September 2008

AbstractOne of the most significant recent advances in health information systems has been the shift from paper to electronic documents. While research on automatic text and image processing has taken separate paths, there is a growing need for joint efforts, particularly for electronic health records and biomedical literature databases. This work aims at comparing text‐based versus image‐based access to multimodal medical documents using state‐of‐the‐art methods of processing text and image components. A collection of 180 medical documents containing an image accompanied by a short text describing it was divided into training and test sets. Content‐based image analysis and natural language processing techniques are applied individually and combined for multimodal document analysis. The evaluation consists of an indexing task and a retrieval task based on the “gold standard” codes manually assigned to corpus documents. The performance of text‐based and image‐based access, as well as combined document features, is compared. Image analysis proves more adequate for both the indexing and retrieval of the images. In the indexing task, multimodal analysis outperforms both independent image and text analysis. This experiment shows that text describing images can be usefully analyzed in the framework of a hybrid text/image retrieval system.
Protein inheritance (prions) based on parallel in‐register β‐sheet amyloid structures
Authors: Wickner Reed B. , Shewmaker Frank , Kryndushkin Dmitry , Edskes Herman K. 
Published: September 2008

AbstractMost prions (infectious proteins) are self‐propagating amyloids (filamentous protein multimers), and have been found in both mammals and fungal species. The prions [URE3] and [PSI+] of yeast are disease agents of Saccharomyces cerevisiae while [Het‐s] of Podospora anserina may serve a normal cellular function. The parallel in‐register beta‐sheet structure shown by prion amyloids makes possible a templating action at the end of filaments which explains the faithful transmission of variant differences in these molecules. This property of self‐reproduction, in turn, allows these proteins to act as de facto genes, encoding heritable information. BioEssays 30:955–964, 2008. © 2008 Wiley Periodicals, Inc.
Feedback‐mediated neuronal competition for survival cues regulates innervation of a target tissue
Authors: Li Yang , Fivaz Marc 
Published: September 2008

AbstractProper wiring of the nervous system requires tight control of the number of nerve terminals that innervate a target tissue. Recent work by Deppmann et al.,1 now suggests that this is achieved by feedback‐mediated neuronal competition for target‐derived survival cues. The authors' model is inspired by the theory for pattern formation based on self‐activation and lateral inhibition, proposed by Meinhardt and Gierer more than 30 years ago.2 BioEssays 30:929–933, 2008. © 2008 Wiley Periodicals, Inc.
Matchmaking, metrics and money: a pathway to progress in translational research
Authors: Krontiris Theodore G. , Rubenson David 
Published: September 2008

AbstractIn the 24 years since the founding of BioEssays, the level of translational research, as well as the expectations for its success, have burgeoned. Based on our analysis of current and projected US efforts to establish effective centers of translational research, our own institutional experience and discussions with academic research center leaders and institutional research executives, we have arrived at several critical conclusions about how best to foster disease‐based research on the institutional, national and international level, what summary statistics may best serve as a measurement of successful practice, roughly how much more money will be required to fund the ongoing venture in the US and how to organize and promote this vision. BioEssays 30:1025–1029, 2008. © 2008 Wiley Periodicals, Inc.
Fluorescence quenching and bonding properties of some hydroxamic acid derivatives by iron(III) and manganese(II)
Authors: Senthilnithy R. , De Costa M. D. P. , Gunawardhana H. D. 
Published: September 2008

AbstractSpectrophotometric investigations of highly fluorescent metal chelating molecules are of relevance due to their potential application in novel, selective fluorescence‐based sensors. Benzene and naphthalene chromophores are highly fluorescent while hydroxamic acids are widely used as ligands for complexation of transition metals. In order to develop fluorescence probes, several phenyl derivatives of N‐phenylbenzohydroxamic acid and an aminodihydroxamic acid linked with a naphthalene chromophore were synthesized and their selective ionophoric properties towards iron(III) and manganese(II) ions were investigated using fluorescence and absorption spectroscopy. Both methods confirm the formation of 1:1 and 1:2 complexes for iron(III) and a 1:1 complex for manganese(II). The complex that is formed depends on the concentration of the ligand and pH of the medium. The amino dihydroxamic acid exhibits a prominent selectivity towards iron(III) with a two‐step 1:1 and 1:2 quenching mechanism at pH 3 and towards manganese(II) with a 1:1 quenching mechanism at a probe concentration of 1 × 10−5 mol dm−3 at pH 9.5 The logarithm of overall formation constants of 1:1 and 1:2 complexes of iron(III) were estimated as 3.30 and 9.05, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
The effect of hydroxylamine on the activity and aggregate structure of autotrophic nitrifying bioreactor cultures
Authors: Harper Willie F. , Terada Akihiko , Poly Franck , Le Roux Xavier , Kristensen Ken , Mazher Mustafa , Smets Barth F. 
Published: September 2008

AbstractAddition of hydroxylamine (NH2OH) to autotrophic biomass in nitrifying bioreactors affected the activity, physical structure, and microbial ecology of nitrifying aggregates. When NH2OH is added to nitrifying cultures in 6‐h batch experiments, the initial NH3‐N uptake rates were physiologically accelerated by a factor of 1.4–13. NH2OH addition caused a 20–40% decrease in the median aggregate size, broadened the shape of the aggregate size distribution by up to 230%, and caused some of the microcolonies to appear slightly more dispersed. Longer term NH2OH addition in fed batch bioreactors decreased the median aggregate size, broadened the aggregate size distribution, and decreased NH3‐N removal from >90% to values ranging between 75% and 17%. This altered performance is explained by quantitative fluorescence in situ hybridization (FISH) results that show inhibition of nitrifying populations, and by qPCR results showing that the copy numbers of amoA and nxrA genes gradually decreased by up to an order‐of‐magnitude. Longer term NH2OH addition damaged the active biomass. This research clarifies the effect of NH2OH on nitrification and demonstrates the need to incorporate NH2OH‐related dynamics of the nitrifying biomass into mathematical models, accounting for both ecophysiological and structural responses. Biotechnol. Bioeng. 2009; 102: 714–724. © 2008 Wiley Periodicals, Inc.
In situ 2D fluorometry and chemometric monitoring of mammalian cell cultures
Authors: Teixeira Ana P. , Portugal Carla A.M. , Carinhas Nuno , Dias João M.L. , Crespo João P. , Alves Paula M. , Carrondo M.J.T. , Oliveira Rui 
Published: September 2008

AbstractThe main objective of the present study was to investigate the use of in situ 2D fluorometry for monitoring key bioprocess variables in mammalian cell cultures, namely the concentration of viable cells and the concentration of recombinant proteins. All studies were conducted using a recombinant Baby Hamster Kidney (BHK) cell line expressing a fusion glycoprotein IgG1‐IL2 cultured in batch and fed‐batch modes. It was observed that the intensity of fluorescence signals in the excitation/emission wavelength range of amino acids, vitamins and NAD(P)H changed along culture time, although the dynamics of single fluorophors could not be correlated with the dynamics of the target state variables. Therefore, multivariate chemometric modeling was adopted as a calibration methodology. 2D fluorometry produced large volumes of redundant spectral data, which were first filtered by principal components analysis (PCA). Then, a partial least squares (PLS) regression was applied to correlate the reduced fluorescence maps with the target state variables. Two validation strategies were used to evaluate the predictive capacity of the developed PLS models. Accurate estimations of viable cells density (r2 = 0.95; 99.2% of variance captured in the training set; r2 = 0.91; 97.7% of variance captured in the validation set) and of glycoprotein concentration (r2 = 0.99 and 99.7% of variance captured in the training set; r2 = 0.99 and 99.3% of variance captured in the validation set) were obtained over a wide range of reactor operation conditions. The results presented herein confirm that 2D fluorometry constitutes a reliable methodology for on‐line monitoring of viable cells and recombinant protein concentrations in mammalian cell cultures. Biotechnol. Bioeng. 2009;102: 1098–1106. © 2008 Wiley Periodicals, Inc.
Using FRET to measure the angle at which a protein bends DNA
Authors: Kugel Jennifer F. 
Published: September 2008

AbstractAn undergraduate biochemistry laboratory experiment that will teach the technique of fluorescence resonance energy transfer (FRET) while analyzing protein‐induced DNA bending is described. The experiment uses the protein TATA binding protein (TBP), which is a general transcription factor that recognizes and binds specific DNA sequences known as TATA boxes. When TBP binds to a TATA box, it bends the DNA. Such bending will be detected using FRET to measure the distance between two fluorophores located on the ends of the DNA. When TBP binds and bends the DNA, the fluorophores move closer together, reflected by an increase in FRET. At the completion of the experiment, three parameters will be determined: 1) the efficiency of the FRET, 2) the end‐to‐end distance between the fluorophores, and 3) the angle at which TBP bends the DNA. In performing this experiment, students will be introduced to FRET, gain experience in quantitative biophysical measurements, and appreciate how a protein can induce a dramatic change in DNA conformation.
Phosphoenolpyruvate
Authors: Behrman E. J. , Gopalan V. 
Published: September 2008

AbstractThe conversion of phosphoenolpyruvate (PEP) in glycolysis is coupled with the formation of ATP. This note discusses the origin of the energy required for ATP formation as arising from redistribution of energy in PEP when compared with its precursor, 2‐phosphoglycerate.
Teaching glycoproteins with a classical paper: Knowledge and methods in the course of an exciting discovery
Authors: Zhu Lixin 
Published: September 2008

AbstractTo integrate research into the teaching of glycoproteins, the story of discovering hydrogen‐potassium ATPase (HK‐ATPase) β subunit is presented in a way covering all the important teaching points. The interaction between the HK‐ATPase α subunit and a glycoprotein of 60–80 kDa was demonstrated to support the existence of the β subunit. On revealing the strategies and experimental designs of this discovery, the knowledge of glycoproteins is delivered. The purpose of this effort was to facilitate the teaching of scientific thinking in the science classroom, to make the biochemistry classroom a more interesting place, and to attract uncertain minds into the career of biochemistry research.
Biotinylated Bi‐ and Tetra‐antennary Glycoconjugates for Escherichia coli Detection
Authors: Hatch Duane M. , Weiss Alison A. , Kale Ramesh R. , Iyer Suri S. 
Published: September 2008

AbstractGlycans cover the surface of all mammalian cells. Several toxins and pathogens use these glycans to bind and infect the cell. Using a versatile modular synthetic strategy, we have developed biotinylated bi‐ and tetraantennary glycoconjugates to capture and detect E. coli and compared the capturing ability of these molecules to commercial polyclonal antibodies. Magnetic beads were coated with biotinylated glycoconjugate or antibody, and these beads were used to capture, isolate, and quantify bacterial recovery by using a luminescence assay. The glycoconjugate‐coated magnetic beads outperformed antibody‐coated magnetic beads in sensitivity and selectivity when compared under identical experimental conditions. Glycoconjugates could capture Escherichia coli from stagnant water, and the ability of a panel of glycoconjugates to capture a selection of pathogenic bacteria was also evaluated. To the best of our knowledge, this study represents the first comprehensive study that compares synthetic glycoconjugates and antibodies for E. coli detection. The glycoconjugates are also very stable and inexpensive. The results presented here are expected to lead to an increased interest in developing glycoconjugate‐based high affinity reagents for diagnostics.
Resin‐Bound Aminofluorescein for C‐Terminal Labeling of Peptides: High‐Affinity Polarization Probes Binding to Polyproline‐Specific GYF Domains
Authors: Uryga‐Polowy Viviane , Kosslick Daniela , Freund Christian , Rademann Jörg 
Published: September 2008

AbstractA polymer support for the solid‐phase synthesis of C‐terminally labeled carboxylic acids has been developed. Fluorophore‐labeled peptides were constructed directly on the amino group of resin‐bound aminofluorescein. Fmoc‐protected aminofluorescein was coupled onto tritylpolystyrene, and the free phenolic hydroxyl positions of the fluorescein were blocked with suitable protecting groups. The mode of attachment was analyzed and found to be selective for the phenoxy ether linkage. The conditions for peptide synthesis on the labeling resin were investigated, and a small library of C‐terminally labeled peptides was prepared. The fluorescence quantum yields of C‐terminally labeled peptides were determined and indicated the suitability of the compounds for imaging and binding experiments. The obtained peptides were therefore investigated as fluorescence polarization probes. Two different proline‐rich binding domains of the GYF family—CD2BP2 and PERQ2—were targeted by peptides labeled either C‐ or N‐terminally. Reversible binding constants were determined by fluorescence polarization measurements and were verified by competition experiments with the corresponding unlabeled peptide. As a second control, the binding constants were measured by NMR titration experiments, recording the HSQC NMR spectra of 15N‐labeled proteins in the presence of the peptide polarization probes. Ligands with higher affinities than all others known previously were identified for both GYF domains. The competition assay with the developed fluorescent probe has a high statistical reliability and can thus be used for screening of GYF domain inhibitors.
The Extended View on the Empty C2(3)‐C82 Fullerene: Isolation, Spectroscopic, Electrochemical, and Spectroelectrochemical Characterization and DFT Calculations
Authors: Zalibera Michal , Popov Alexey A. , Kalbac Martin , Rapta Peter , Dunsch Lothar 
Published: September 2008

AbstractAn extended study of the spectroscopic and redox properties of the C82 fullerene is presented. Among the nine isolated‐pentagon‐rule (IPR) isomers of the C82 fullerene the C82(3) isomer with C2 symmetry is the only stable, empty fullerene structure formed in the arc burning process that can be isolated in an isomerically pure form. Here, its formation and isolation are described and its structure is confirmed by experimental spectroscopic studies as well as time‐dependent DFT calculations. The electrochemistry of the C82(3) isomer is studied in detail by cyclic voltammetry and spectroelectrochemistry. The anionic species of C82 with the charge ranging from C82− to C824− were successively generated in o‐dichlorobenzene solution at room temperature and characterized by in situ ESR and visible/near‐infrared (Vis/NIR) spectroscopy. The data give new insights into the charged states of the C82(3) fullerene.
Comparison of the Surprising Metal‐Ion‐Binding Properties of 5‐ and 6‐Uracilmethylphosphonate (5Umpa2− and 6Umpa2−) in Aqueous Solution and Crystal Structures of the Dimethyl and Di(isopropyl) Esters of H2(6Umpa)
Authors: Freisinger Eva , Griesser Rolf , Lippert Bernhard , Moreno‐Luque Cristóbal F. , Niclós‐Gutiérrez Juan , Ochocki Justyn , Operschall Bert P. , Sigel Helmut 
Published: September 2008

Abstract5‐ and 6‐Uracilmethylphosphonate (5Umpa2− and 6Umpa2−) as acyclic nucleotide analogues are in the focus of anticancer and antiviral research. Connected metabolic reactions involve metal ions; therefore, we determined the stability constants of M(Umpa) complexes (M2+=Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Zn2+, or Cd2+). However, the coordination chemistry of these Umpa species is also of interest in its own right, for example, the phosphonate‐coordinated M2+ interacts with (C4)O to form seven‐membered chelates with 5Umpa2−, thus leading to intramolecular equilibria between open (op) and closed (cl) isomers. No such interaction occurs with 6Umpa2−. In both M(Umpa) series deprotonation of the uracil residue leads to the formation of M(Umpa−H)− complexes at higher pH values. Their stability was evaluated by taking into account the fact that the uracilate residue can bind metal ions to give M2(Umpa−H)+ species. This has led to two further important insights: 1) In M(6Umpa−H)${{{- \hfill \atop {\rm cl}\hfill}}}$ the H+ is released from (N1)H, giving rise to six‐membered chelates (degrees of formation of ca. 90 to 99.9 % with Mn2+, Co2+, Cu2+, Zn2+, or Cd2+). 2) In M(5Umpa−H)${{{- \hfill \atop {\rm cl}\hfill}}}$ the (N3)H is deprotonated, leading to a higher stability of the seven‐membered chelates involving (C4)O (even Mg2+ and Ca2+ chelates are formed up to ≈50 %). In both instances the M(Umpa−H)${{{- \hfill \atop {\rm op}\hfill}}}$ species led to the formation of M2(Umpa−H)+ complexes that have one M2+ at the phosphonate and one at the (N3)− (plus carbonyl) site; this proves that nucleotides can bind metal ions independently at the phosphate and the nucleobase residues. X‐ray structural analyses of 6Umpa derivatives show that in diesters the phosphonate group is turned away from the uracil residue, whereas in H2(6Umpa) the orientation is such that upon deprotonation in aqueous solution a strong hydrogen bond is formed between (N1)H and PO32−; replacement of the hydro gen with M2+ gives the M(6Umpa−H)${{{- \hfill \atop {\rm cl}\hfill}}}$ chelates mentioned.