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Different Series (different + series)
Selected AbstractsOligohis-tags: mechanisms of binding to Ni2+ -NTA surfacesJOURNAL OF MOLECULAR RECOGNITION, Issue 4 2009Steven Knecht Abstract Since immobilized metal ion affinity chromatography (IMAC) was first reported, several modifications have been developed. Among them, Ni2+ immobilized by chelation with nitrilotriacetic acid (NTA) bound to a solid support has become the most common method for the purification of proteins carrying either a C - or N -terminal histidine (His) tag. Despite its broad application in protein purification, only little is known about the binding properties of the His-tag, and therefore almost no thermodynamic and kinetic data are available. In this study, we investigated the binding mechanism of His-tags to Ni2+ -NTA. Different series of oligohistidines and mixed oligohistidines/oligoalanines were synthesized using automated solid-phase peptide synthesis (SPPS). Binding to Ni2+ -NTA was analyzed both qualitatively and quantitatively with surface plasmon resonance (SPR) using commercially available NTA sensor chips from Biacore. The hexahistidine tag shows an apparent equilibrium dissociation constant (KD) of 14,±,1,nM and thus the highest affinity of the peptides synthesized in this study. Furthermore, we could demonstrate that two His separated by either one or four residues are the preferred binding motifs within hexahis tag. Finally, elongation of these referred motifs decreased affinity, probably due to increased entropy costs upon binding. Copyright © 2009 John Wiley & Sons, Ltd. [source] Symbolic dynamics for identifying similarity between rhythms of ecological time seriesECOLOGY LETTERS, Issue 9 2004Bernard Cazelles Abstract Explaining the associations between animal populations or between population and environmental signals is an important challenge. The time series that quantify animal populations are often complex, nonlinear, noisy and non-stationary. These characteristics may make it inappropriate to use traditional techniques when analysing these time series and their mutual dependencies. Here I propose to use symbolic dynamics and techniques from Information Theory to evaluate the degree of dynamic cohesion between time series fluctuations. The main idea is to check whether two (or more) signals tend to oscillate simultaneously, rising and falling together with the same rhythm. Based on synthetic and real time series, I demonstrate that this method is robust to the presence of noise and to the short length of the analysed time series and gives relevant information about the weak relationships between different series. Furthermore, this method appears as simple as classical cross-correlation and outperforms it in the analysed examples. [source] Polystyrene nanocomposite materials by in situ polymerization into montmorillonite,vinyl monomer interlayersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Ahmed Akelah Abstract A different series of new polystyrene,clay nanocomposites have been prepared by grafting polymerization of styrene with vinyl-montmorillonite (MMT) clay. The synthesis was achieved through two steps. The first step is the modification of clay with the vinyl monomers, such as N,N -dimethyl- n -octadecyl-4-vinylbenzyl-ammonium chloride, n -octadecyl-4-vinylbenzyl-ammonium chloride, triphenyl-4-vinylbenzyl-phosphonium chloride, and tri- n -butyl-4-vinylbenzyl-phosphonium chloride. The second step is the polymerization of styrene with different ratios of vinyl-MMT clay. The materials produced were characterized by different physical and chemical methods: (1) IR spectra, confirming the intercalation of the vinyl-cation within the clay interlayers; (2) thermogravimetric analysis (TGA), showing higher thermal stability for PS,nanocomposites than polystyrene (PS) and higher thermal stability of nanocomposites with of phosphonium moieties than nanocomposites with ammonium moieties; (3) swelling measurements in different organic solvents, showing that the swelling degree in hydrophobic solvents increases as the clay ratio decreases; (4) X-ray diffraction (XRD), illustrating that the nanocomposites were exfoliated at up to a 25 wt % of organoclay content; and (5) scanning electron microscopy (SEM), showing a complete dispersion of PS into clay galleries. Also, transmission electron microscopy (TEM) showed nanosize spherical particles of , 150,400 nm appearing in the images. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3739,3750, 2007 [source] Combining inflation density forecastsJOURNAL OF FORECASTING, Issue 1-2 2010Christian Kascha Abstract In this paper, we empirically evaluate competing approaches for combining inflation density forecasts in terms of Kullback,Leibler divergence. In particular, we apply a similar suite of models to four different datasets and aim at identifying combination methods that perform well throughout different series and variations of the model suite. We pool individual densities using linear and logarithmic combination methods. The suite consists of linear forecasting models with moving estimation windows to account for structural change. We find that combining densities is a much better strategy than selecting a particular model ex ante. While combinations do not always perform better than the best individual model, combinations always yield accurate forecasts and, as we show analytically, provide insurance against selecting inappropriate models. Logarithmic combinations can be advantageous, in particular if symmetric densities are preferred. Copyright © 2010 John Wiley & Sons, Ltd. [source] Cellulose Acetate- graft -Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer CompositionMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2004Yoshikuni Teramoto Abstract Summary: Several different series of cellulose acetate- graft -poly(hydroxyalkanoate)s (CA- g -PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L -lactide, (R,S)- , -butyrolactone, , -valerolactone and , -caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA- g -PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi-empirical equations available for polymer blends or comb-like polymers. In particular, the composition dependence of the Tgs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb-like polymers, when CAs of acetyl DS ,2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification. [source] Study of prelocalized graphite/styrene acrylonitrile conducting composites for device applicationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2006V. K. Sachdev Abstract Conductive polymer composites were prepared by compression molding of prelocalized graphite on to styrene acrylonitrile (SAN) particles. The electrical conductivity is found to be strongly dependent on the graphite content. Three different series were prepared for different processing and material parameters. A low percolation threshold has been noticed when only 1 wt% of graphite is incorporated. Resistivity as low as ,14 , cm has been achieved in a composite with SAN resin particles of 180,212 µm size and graphite 10,20 µm at 90 °C, 105 MPa and 15 min. An electrically conducting network of graphite channels has been observed using scanning electron microscopy. V,I characteristic reveals that at a lower percentage of graphite the increase in current with increase in electric field is due to the hopping/tunneling of electrons, while for higher percentages of graphite ohmic behavior similar to metals has been observed. The data has been analyzed using percolation model. The value of the exponent t that determines the increase in electrical conductivity above the percolation threshold is found to be close to the values given in the literature. The theoretically calculated values of conductivity are found to be in satisfactory agreement with the experimental ones. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screening for Wound-induced Oxylipins in Arabidopsis thaliana by Differential HPLC-APCI/MS Profiling of Crude Leaf Extracts and Subsequent Characterisation by Capillary-scale NMRPHYTOCHEMICAL ANALYSIS, Issue 3 2008Aly Thiocone Abstract A simple non-targeted differential HPLC-APCI/MS approach has been developed in order to survey metabolome modifications that occur in the leaves of Arabidopsis thaliana following wound-induced stress. The wound-induced accumulation of metabolites, particularly oxylipins, was evaluated by HPLC-MS analysis of crude leaf extracts. A generic, rapid and reproducible pressure liquid extraction procedure was developed for the analysis of restricted leaf samples without the need for specific sample preparation. The presence of various oxylipins was determined by head-to-head comparison of the HPLC-MS data, filtered with a component detection algorithm, and automatically compared with the aid of software searching for small differences in similar HPLC-MS profiles. Repeatability was verified in several specimens belonging to different series. Wound-inducible jasmonates were efficiently highlighted by this non-targeted approach without the need for complex sample preparation as is the case for the ,oxylipin signature' procedure based on GC-MS. Furthermore this HPLC-MS screening technique allowed the isolation of induced compounds for further characterisation by capillary-scale NMR (CapNMRTM) after HPLC scale-up. In this paper, the screening method is described and applied to illustrate its potential for monitoring polar and non-polar stress-induced constituents as well as its use in combination with CapNMR for the structural assignment of wound-induced compounds of interest. Copyright © 2008 John Wiley & Sons, Ltd. [source] Particle size effect on the film-forming process of PS/PBA composite latexesPOLYMER COMPOSITES, Issue 9 2010aziye U In this work, the effect of hard particle size and blend ratio on the film formation behavior of hard polystyrene (PS) and soft poly(n -butyl acrylate) (PBA) latex blends was studied by means of steady-state fluorescence and UV,visible techniques in conjunction with atomic force microscopy. Three different sets of latexes were synthesized: PBA latex (diameter 97 nm), pyrene (P)-labeled large PS (LgPS; diameter 900 nm), and small PS (SmPS; diameter 320 nm). Two different series of latex blends (LgPS/PBA and SmPS/PBA) were prepared with varying blend composition at room temperature separately. Films were then annealed at elevated temperatures above glass transition (Tg) temperature of PS. Fluorescence intensity (IP) from P and photon transmission intensity (Itr) were measured after each annealing step to monitor the stages of film formation. The results showed that a significant change occurred in IP and Itr at a certain critical weight fraction (Rc) of PBA. Below Rc, two distinct film formation stages, which are named as void closure and interdiffusion, were seen. However, at PBA concentrations nearer to or above Rc, no film formation can be achieved. Comparing to the LgPS/PBA, the sintering process of SmPS/PBA particles occurred at much lower temperatures. Film formation stages for R < Rc were modeled, and related activation energies were calculated. Void closure (,H) and interdiffusion (,E) activation energies for SmPS/PBA were also found smaller in comparing with LgPS/PBA series. However, ,H and ,E values were not changed much with the blend composition for both series. POLYM. COMPOS., 31:1637,1652, 2010. © 2009 Society of Plastics Engineers [source] An Approach towards the Quantitative Structure,Activity Relationships of Caffeic Acid and its DerivativesCHEMBIOCHEM, Issue 9 2004Rajeshwar P. Verma Dr. Abstract Caffeic acid and its derivatives are already known to possess a wide range of biological activities. We have developed quantitative structure,activity relationships (QSARs) for different series of caffeic acid derivatives (including caffeic acid) in order to understand the chemical,biological interactions governing antitumor activity against six different tumor cell lines, nitric oxide production, anti-HIV and enzymatic activities, and binding affinity to the lck domain. QSAR results have shown that the different activities of caffeic acid and its derivatives are largely dependent on their hydrophobicity or molar refractivity, with a bilinear correlation being the most important. [source] Ni Catalyst Coating on Fecralloy® Microchanneled Foils and Testing for Methane Steam ReformingCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010N. de Miguel Abstract The procedure following the washcoating of three different Ni catalyst systems (MgO, Al2O3, and CeO2/Al2O3 supported) on pretreated Fecralloy® microchanneled foils under controlled milling times and viscosities of the slurries is described. The activity of the prepared coatings is also presented. Four different series of coated foils were prepared: one per each catalyst system, keeping constant the average particle size on 5 ,m, and one extra series to study the effect of reducing the average particle size of the MgO-supported catalyst system to 3 ,m. For each coating, scanning electron microscopy pictures were taken and specific surface areas and average densities of the catalyst layers were estimated. Finally, each series of coated foils was stacked and tested in a microreactor for the methane steam reforming (MSR) reaction under different conditions. [source] BRAF mutations in an Italian cohort of thyroid cancersCLINICAL ENDOCRINOLOGY, Issue 2 2004Laura Fugazzola Summary objective, Recently, a somatic point mutation of the BRAF gene (V599E) has been identified as the most common genetic event in papillary thyroid carcinoma (PTC) with a variable frequency (about 25,70%) in different series from USA, Japan, Portugal and Ukraine. design, In the present study, the genetic analysis of BRAF in an Italian cohort of 65 thyroid tumours with corresponding normal tissues and 21 thyroid benign disorders is reported. methods, For BRAF analysis, the somatic DNA was PCR amplified by means of specific intronic primers and PCR products were directly sequenced. Statistical analyses were obtained by means of Fisher's exact test. results, All mutations detected involved a T > A transversion at 1796 (V599E) and were heterozygous. Overall, BRAFV599E mutation was found in 18/56 (32·1%) PTCs. According to the histological type of the tumour, the mutation was present in 38·3% of cases of conventional PTC (18/47), in 0/6 follicular variant of PTC, in 0/3 oncocytic variant of PTC. No BRAF mutations were detected either in five follicular carcinomas, or in four poorly differentiated or undifferentiated cancers or in benign thyroid disorders. No statistically significant correlation of BRAF mutation with patient age and gender, with multicentricity of the tumour, with the lymphocytic infiltration of the tissue, with the stage and with the recurrence rate, was found. BRAFV599E tended to be associated, although not significantly, with a greater volume and extension of the tumour and with lymph-nodal metastases at surgery. conclusions, In conclusion, the present study on the first Italian series of thyroid cancers shows a frequency of 38·3% of BRAFV599E in the classical variant of PTC, confirming the key role of this mutation in promoting tumourigenesis. [source] | |||||||||||||