bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and characterization of molecular targets of natural products by mass spectrometry
Authors: Cheng Ka‐Wing , Wong Chi‐Chun , Wang Mingfu , He Qing‐Yu , Chen Feng 
Published: March 2009

AbstractNatural products, and their derivatives and mimics, have contributed to the development of important therapeutics to combat diseases such as infections and cancers over the past decades. The value of natural products to modern drug discovery is still considerable. However, its development is hampered by a lack of a mechanistic understanding of their molecular action, as opposed to the emerging molecule‐targeted therapeutics that are tailored to a specific protein target(s). Recent advances in the mass spectrometry‐based proteomic approaches have the potential to offer unprecedented insights into the molecular action of natural products. Chemical proteomics is established as an invaluable tool for the identification of protein targets of natural products. Small‐molecule affinity selection combined with mass spectrometry is a successful strategy to “fish” cellular targets from the entire proteome. Mass spectrometry‐based profiling of protein expression is also routinely employed to elucidate molecular pathways involved in the therapeutic and possible toxicological responses upon treatment with natural products. In addition, mass spectrometry is increasingly utilized to probe structural aspects of natural products–protein interactions. Limited proteolysis, photoaffinity labeling, and hydrogen/deuterium exchange in conjunction with mass spectrometry are sensitive and high‐throughput strategies that provide low‐resolution structural information of non‐covalent natural product–protein complexes. In this review, we provide an overview on the applications of mass spectrometry‐based techniques in the identification and characterization of natural product–protein interactions, and we describe how these applications might revolutionize natural product‐based drug discovery. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:126–155, 2010
Improved half RF slice selectivity in the presence of eddy currents with out‐of‐slice saturation
Authors: Josan Sonal , Kaye Elena , Pauly John M. , Daniel Bruce L. , Pauly Kim Butts 
Published: March 2009

AbstractUltrashort echo time imaging with half RF pulse excitation is sensitive to eddy currents induced by the slice‐select gradient that distorts the half pulse slice profile. This work demonstrates improvements in the half pulse profile by using spatial saturation on both sides of the imaged slice to suppress the out‐of‐slice magnetization. This effectively improves the selectivity of the half pulse excitation profile. A quadratic phase RF pulse with high bandwidth and selectivity was used to achieve a wide saturation band with sharp edges. Experimental results demonstrate substantially improved slice selectivity and R quantitation accuracy obtained with the out‐of‐slice saturation. This approach is effective in making short T2 imaging and quantitation with half pulses less sensitive to eddy currents. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Ghost magnetic resonance angiography
Authors: Koktzoglou Ioannis , Edelman Robert R. 
Published: March 2009

AbstractTraditional methods for magnetic resonance angiography (MRA) involve the radiofrequency excitation of vascular spins within a selected region of tissue, followed by gradient localization and imaging of those spins within that same region. Signals that unfaithfully localize within the imaging volume, so‐called “ghost artifacts”, have historically been considered undesirable since they degrade image quality and every effort is made to suppress them. To the contrary, we hypothesized that these ghost artifacts could be manipulated to create detailed angiograms of the human body. In this initial demonstration of the method, which we call “Ghost MRA,” we show that the human arterial system can be depicted with exquisite anatomic detail and near total suppression of background signal. Moreover, unlike alternative unenhanced methods, Ghost MRA can be acquired without the need for cardiac synchronization. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
3D single‐shot VASO using a maxwell gradient compensated GRASE sequence
Authors: Poser Benedikt A. , Norris David G. 
Published: March 2009

AbstractThe vascular space occupancy (VASO) method was recently proposed as a functional MRI (fMRI) method that is capable of detecting activation‐related changes in blood volume (CBV), without the need for a blood‐pool contrast agent. In the present work we introduce a new whole‐brain VASO technique that is based on a parallel‐accelerated single‐shot 3D GRASE (gradient and spin echo) readout. The GRASE VASO sequence employs a flow‐compensated correction scheme for concomitant Maxwell gradients which is necessary to avoid smearing artifacts that may occur due to violation of the Carr–Purcell–Meiboom–Gill (CPMG) condition for off‐resonance excitation. Experiments with 6 min of visual‐motor stimulation were performed on eight subjects. At P < 0.01, average percent signal change and t‐score for visual stimulation were −3.11% and −8.42, respectively; activation in left and right motor cortices and supplementary motor area was detected with −2.75% and −6.70, respectively. Sensitivity and signal changes are comparable to those of echo‐planar imaging (EPI)‐based single‐slice VASO, as indicated by additional visual‐task experiments (−3.39% and −6.93). The method makes it possible to perform whole‐brain cognitive activation studies based on CBV contrast. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol
Authors: You Bo , Wen Nangeng , Cao Yichen , Zhou Shuxue , Wu Limin 
Published: March 2009

AbstractBACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability.RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed.CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry
Grafting of polystyrene on carbon nanofibers by introducing a methacrylate unit
Authors: Hou Jingqiang , Zhou Xiaodong , Sui Zhijun , Zhou Xinggui 
Published: March 2009

AbstractBACKGROUND: To overcome the self‐agglomeration of carbon nanofibers (CNFs), a number of studies have dealt with surface modification of CNFs to improve their wettability. In this work, a novel, simple and practical approach based on the introduction of methacrylate units to graft polymers onto the surface of CNFs is proposed.RESULTS: The functionalized CNF samples were characterized using Fourier transform infrared and Raman spectroscopy, thermal gravimetric analysis and transmission electron microscopy. The molecular weight of grafted polystyrene (PS) is influenced by the monomer feed ratio. The stabilities of various CNF dispersions were measured using an optical analyzer. When the content of grafted PS is 34.2%, the functionalized CNFs attain a stable dispersion in xylene.CONCLUSION: In the presence of methacrylate units, PS has been successfully grafted onto the surface of CNFs via an in situ polymerization. Moreover, the introduction of methacrylate units opens the functionalization of CNFs to other routes. Copyright © 2009 Society of Chemical Industry
Nonadditive effects of mixed crowding on protein stability
Authors: Batra Jyotica , Xu Ke , Zhou Huan‐Xiang 
Published: March 2009

AbstractThe crowded environments inside cells can have significant effects on the folding stability and other biophysical properties of proteins. In this study on how macromolecular crowding affects protein folding, we took a significant step toward realistically mimicking intracellular environments by using a mixture of two crowding agents, Ficoll and dextran. We found that the mixed crowding exerts a greater stabilizing effect than the sum of the two individual crowding agents. Therefore, the composition of crowders, not just the total concentration, has a significant influence on the effects of crowding on protein folding. Since the composition of intracellular macromolecules varies within the lifetime of a cell, our finding may provide an explanation for age being an important risk factor for protein aggregation‐related diseases such as Alzheimer's disease and Parkinson's disease. Proteins 2009. © 2009 Wiley‐Liss, Inc.
A dramatic conformational rearrangement is necessary for the activation of DNR from Pseudomonas aeruginosa. Crystal structure of wild‐type DNR
Authors: Giardina Giorgio , Rinaldo Serena , Castiglione Nicoletta , Caruso Manuela , Cutruzzolà Francesca 
Published: March 2009

AbstractThe opportunistic pathogen Pseudomonas aeruginosa can grow in low oxygen, because it is capable of anaerobic respiration using nitrate as a terminal electron acceptor (denitrification). An intermediate of the denitrification pathway is nitric oxide, a compound that may become cytotoxic at high concentration. The intracellular levels of nitric oxide are tightly controlled by regulating the expression of the enzymes responsible for its synthesis and degradation (nitrite and nitric oxide reductases). In this article, we present the crystallographic structure of the wild‐type dissimilative nitrate respiration regulator (DNR), a master regulator controlling expression of the denitrification machinery and a putative target for new therapeutic strategies. Comparison with other structures among the CRP‐FNR class of regulators reveals that DNR has crystallized in a conformation that has never been observed before. In particular, the sensing domain of DNR has undergone a rotation of more than 50° with respect to the other structures. This suggests that DNR may undergo an unexpected and very large conformational rearrangement on activation. Proteins 2009. © 2009 Wiley‐Liss, Inc.
A novel method for predicting and using distance constraints of high accuracy for refining protein structure prediction
Authors: Liu Tianyun , Horst Jeremy A. , Samudrala Ram 
Published: March 2009

AbstractThe principal bottleneck in protein structure prediction is the refinement of models from lower accuracies to the resolution observed by experiment. We developed a novel constraints‐based refinement method that identifies a high number of accurate input constraints from initial models and rebuilds them using restrained torsion angle dynamics (rTAD). We previously created a Bayesian statistics‐based residue‐specific all‐atom probability discriminatory function (RAPDF) to discriminate native‐like models by measuring the probability of accuracy for atom type distances within a given model. Here, we exploit RAPDF to score (i.e., filter) constraints from initial predictions that may or may not be close to a native‐like state, obtain consensus of top scoring constraints amongst five initial models, and compile sets with no redundant residue pair constraints. We find that this method consistently produces a large and highly accurate set of distance constraints from which to build refinement models. We further optimize the balance between accuracy and coverage of constraints by producing multiple structure sets using different constraint distance cutoffs, and note that the cutoff governs spatially near versus distant effects in model generation. This complete procedure of deriving distance constraints for rTAD simulations improves the quality of initial predictions significantly in all cases evaluated by us. Our procedure represents a significant step in solving the protein structure prediction and refinement problem, by enabling the use of consensus constraints, RAPDF, and rTAD for protein structure modeling and refinement. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Prion protein region 23–32 interacts with tubulin and inhibits microtubule assembly
Authors: Osiecka Katarzyna M. , Nieznanska Hanna , Skowronek Krzysztof J. , Karolczak Justyna , Schneider Gabriela , Nieznanski Krzysztof 
Published: March 2009

AbstractIn previous studies we have demonstrated that prion protein (PrP) binds directly to tubulin and this interaction leads to the inhibition of microtubule formation by inducement of tubulin oligomerization. This report is aimed at mapping the regions of PrP and tubulin involved in the interaction and identification of PrP domains responsible for tubulin oligomerization. Preliminary studies focused our attention to the N‐terminal flexible part of PrP encompassing residues 23–110. Using a panel of deletion mutants of PrP, we identified two microtubule‐binding motifs at both ends of this part of the molecule. We found that residues 23–32 constitute a major site of interaction, whereas residues 101–110 represent a weak binding site. The crucial role of the 23–32 sequence in the interaction with tubulin was confirmed employing chymotryptic fragments of PrP. Surprisingly, the octarepeat region linking the above motifs plays only a supporting role in the interaction. The binding of Cu2+ to PrP did not affect the interaction. We also demonstrate that PrP deletion mutants lacking residues 23–32 exhibit very low efficiency in the inducement of tubulin oligomerization. Moreover, a synthetic peptide corresponding to this sequence, but not that identical with fragment 101–110, mimics the effects of the full‐length protein on tubulin oligomerization and microtubule assembly. At the cellular level, peptide composed of the PrP motive 23–30 and signal sequence (1–22) disrupted the microtubular cytoskeleton. Using tryptic and chymotryptic fragments of α‐ and β‐tubulin, we mapped the docking sites for PrP within the C‐terminal domains constituting the outer surface of microtubule. Proteins 2009. © 2009 Wiley‐Liss, Inc.
Synthesis and antifungal activity of 2‐azetidinonyl‐5‐(2‐benzoylphenoxy)methyl‐1,3,4‐oxadiazoles against seed‐borne pathogens of Eleusine coracana (L.) Gaertn
Authors: Khanum Shaukath A , Shashikanth Sheena , Sathyanarayana Syagadadu Giriyanna , Lokesh Siddalingaiah , Deepak Saligrama A 
Published: March 2009

AbstractBACKGROUND: Finger millet is a major food crop as well as feed and fodder for livestock, especially in regions of southern India. A sturdy crop to fluctuating environmental conditions, it can be cultivated in all seasons of the year. Leaf, neck and finger blast caused by Pyricularia grisea Sacc. and Bipolaris setariae (Saw.) Shoem, as well as leaf spot disease, Bipolaris nodulosa (Berk & M.A.Curtis) Shoem, are major production constraints in southern India. Apart from environmental conditions, the use of harvested seeds by farmers is a major reason for disease prevalence. Benzophenone analogues have been investigated for controlling phytopathogenic fungi. In addition, the most important applications of azetidin‐2‐ones are as antibiotics. Based on this information, the present study was conducted to explore the antifungal activity of integrated 2‐azetidinonyl and 1,3,4‐oxadiazoles moieties into a benzophenone framework.RESULTS: A simple high‐yielding method for the integration of heterocyclic rings, namely 2‐azetidinonyl, at the benzophenone nucleus has been achieved, starting from substituted 2‐hydroxybenzophenones under mild conditions on a wet solid surface using microwave irradiation. In the present study, an array of newly synthesised compounds, 2‐azetidinonyl‐5‐(2‐benzoylphenoxy)methyl‐1,3,4‐oxadiazoles, were screened for their antifungal property against blast and leaf spot causing fungi associated with the seeds of finger millet, cv. Indof‐9.CONCLUSION: Two of the newly synthesised compounds showed promising effects in depleting the incidence of seed‐borne pathogenic fungi of finger millet. The suppression of Pyricularia grisea and Bipolaris setariae resulted in enhanced seed germination and seedling growth. Copyright © 2009 Society of Chemical Industry
Magnetotransport through a magnetic semiconductor single electron transistor
Authors: Lebedeva N. , Kuivalainen P. 
Published: March 2009

AbstractThe magnetic version of the Anderson model is applied to transport through a single electron transistor (SET), where the central region consists of a magnetic semiconductor weakly coupled to two nonmagnetic source and drain leads and a nonmagnetic gate electrode. We study theoretically magnetoresistance in a magnetic SET at various temperatures around the Curie temperature. The exchange interaction between the magnetic ions and the spins of the charge carriers causes spin disorder scattering, which results in temperature and magnetic field dependent level broadening in the central region of the SET. Consequently, a large magnetoresistance effect, whose sign and magnitude can be controlled by the gate voltage of the SET, appears at low temperatures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence of dimer lead centers in aluminium perovskites and garnets
Authors: Babin V. , Bichevin V. , Gorbenko V. , Makhov A. , Mihokova E. , Nikl M. , Vedda A. , Zazubovich S. , Zorenko Yu. 
Published: March 2009

AbstractSteady‐state emission and excitation spectra and luminescence decay kinetics were studied at 80–300 K under excitation in the 2.5–6.0 eV energy range for undoped and Ce3+‐doped aluminium garnet (Lu3Al5O12, Y3Al5O12) and aluminium perovskite (LuAlO3, YAlO3) single crystalline films (SCF) grown by Liquid Phase Epitaxy method from the PbO‐based flux. The aim of the work was to identify spectral bands, arising from lead‐induced centers of different types, and to clarify their influence on scintillation characteristics of Ce3+ centers. It was found that in the perovskite SCF studied, the concentration of single Pb2+‐based centers is comparatively small. In the SCF of garnets, in YAG SCF their concentration is considerably smaller than in LuAG SCF. The lead‐induced emission at about 3.1–3.2 eV excited around 3.9 eV was observed in all the SCF studied and ascribed to the dimer lead centers of the type of {Pb2+ – oxygen vacancy – Pb2+}. In Ce3+‐doped perovskite SCF, due to a strong overlap of the excitation band of the dimer centers and the emission band of Ce3+ centers, a considerable influence of dimer lead centers on the scintillation characteristics of these materials is expected. In the SCF of garnets, the influence of dimer lead centers on the characteristics of Ce3+ centers is negligible. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ecological niche and potential geographic distribution of the invasive fruit flyBactrocera invadens(Diptera, Tephritidae)
Authors: De Meyer M. , Robertson M.P. , Mansell M.W. , Ekesi S. , Tsuruta K. , Mwaiko W. , Vayssières J-F , Peterson A.T. 
Published: March 2009

AbstractTwo correlative approaches to the challenge of ecological niche modeling (genetic algorithm, maximum entropy) were used to estimate the potential global distribution of the invasive fruit fly,Bactrocera invadens, based on associations between known occurrence records and a set of environmental predictor variables. The two models yielded similar estimates, largely corresponding to Equatorial climate classes with high levels of precipitation. The maximum entropy approach was somewhat more conservative in its evaluation of suitability, depending on thresholds for presence/absence that are selected, largely excluding areas with distinct dry seasons; the genetic algorithm models, in contrast, indicate that climate class as partly suitable. Predictive tests based on independent distributional data indicate that model predictions are quite robust. Field observations in Benin and Tanzania confirm relationships between seasonal occurrences of this species and humidity and temperature.
The Impact of Market Forces on Child Care Provision: Insights from the 2005 Child Care Act in the Netherlands
Authors: NOAILLY JOËLLE , VISSER SABINE 
Published: March 2009

AbstractThis article examines the impact of the introduction of market forces on child care provision in the Netherlands. In January 2005, the Dutch government introduced the Child Care Act, replacing the former financing system, which had elements of both supply- and demand-financing, with a fully demand-financing system. As a result, the provision of child care is now driven by market forces. Using data on the geographical location of child care facilities, this article compares the factors affecting the provision of child care in the Netherlands before and after the introduction of the Child Care Act. The results suggest that after the regulatory reform the provision of child care has shifted towards wealthy urbanised areas, characterised by high demand and high purchasing power. This shift has largely benefited for-profit providers particularly active in these markets. In parallel, the results indicate an important drop in child care provision by non-profit organisations, most pronounced in less wealthy rural areas. These findings suggest that the introduction of demand-financing may have implications for the accessibility of child care.