bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of chloromethylated and aminated gel‐type poly(styrene‐co‐divinylbenzene) microparticles with controlled degree of functionalization
Authors: Rodrigo Raúl , Toro Claudio Andrés , Cuellar Jorge 
Published: July 2013

ABSTRACTThe possibility of adjusting the degree of hydrophilic functionalization in polymeric microparticles with a hydrophobic skeleton makes it possible to obtain adsorbents and catalyst microparticles that may show better performance. In this regard, in this study, gel‐type poly(styrene‐co‐divinyl benzene) microparticles were chloromethylated and subsequently aminated, and the quantitative effect of the chloromethylation reaction conditions on the final degree of functionalization achieved were examined. In the chloromethylation route, methylal, thionyl chloride, and a Friedel–Craft catalyst were used. From the experimental results, two models were obtained by multiple linear regression relating the chloromethylation conditions to the anion‐exchange capacity (AEC) achieved and to the replaceable chlorine content, according to which the achievement of a high degree of useful functionalization within the microparticles entailed chloromethylation with low methylal/polymer molar ratios and high thionyl chloride/polymer molar ratios, relatively high temperatures, and short reaction times; all of these values were within the ranges used in this study. Additionally, we found that the highest values of AEC could be reached with a methylal/thionyl chloride molar ratio close to unity. The models obtained could be useful for the synthesis of microparticles with required degrees of functionalization, that is, with the chosen hydrophilicity/hydrophobicity ratio. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4054–4065, 2013
Enhanced mechanical and thermal properties of biodegradable poly(butylene succinate‐co‐adipate)/graphene oxide nanocomposites via in situ polymerization
Authors: Zhou Weidong , Wang Xiaowei , Wang Pingli , Zhang Wei , Ji Junhui 
Published: July 2013

ABSTRACTPoly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites were synthesized via in situ polymerization for the first time. Atomic force microscopy demonstrated the achievement of a single layer of GO, and transmission electron microscopy proved the homogeneous distribution of GO in the PBSA matrix. Fourier transform infrared spectroscopy results showed the successful grafting of PBSA chains onto GO. With the incorporation of 1 wt % GO, the tensile strength and flexural modulus of the PBSA were enhanced by 50 and 27%, respectively. The thermal properties characterized by differential scanning calorimetry and thermogravimetric analysis showed increases in the melting temperatures, crystallization temperatures, and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4075–4080, 2013
Replenishing our defensive microbes
Authors: Ursell Luke K. , Treuren William Van , Metcalf Jessica L. , Pirrung Meg , Gewirtz Andrew , Knight Rob 
Published: July 2013

AbstractLarge‐scale characterization of the human microbiota has largely focused on Western adults, yet these populations may be uncharacteristic because of their diets and lifestyles. In particular, the rise of “Western diseases” may in part stem from reduced exposure to, or even loss of, microbes with which humans have coevolved. Here, we review beneficial microbes associated with pathogen resistance, highlighting the emerging role of complex microbial communities in protecting against disease. We discuss ways in which modern lifestyles and practices may deplete physiologically important microbiota, and explore prospects for reintroducing or encouraging the growth of beneficial microbes to promote the restoration of healthy microbial ecosystems.
HPLC fluorescence method for the determination of nizatidine in human plasma and its application to pharmacokinetic study
Authors: Çakar Mahmut B. , Ulu Sevgi T. 
Published: July 2013

ABSTRACTA sensitive high‐performance liquid chromatographic (HPLC) method was developed for the determination of nizatidine in human plasma. Nizatidine was derivatized by 4‐fluoro‐7‐nitrobenzofurazan (NBD‐F). Chromatographic separation was performed on a Inertsil C18 column (150 mm × 4.6 mm, 5 µm) using isocratic elution by a mobile phase consisting of methanol/water (55:45) at a flow rate of 1.2 mL/min. Amlodipine was used as the internal standard (IS). Fluorescence detector was used operated at 461 nm (excitation) and 517 nm (emission), respectively. The calibration curve was linear over the range of 50–2000 ng/mL. This method was successfully applied to a pharmacokinetic study after oral administration of a dose (150 mg) of nizatidine. Copyright © 2013 John Wiley & Sons, Ltd.
N‐glycosylation affects the proper folding, enzymatic characteristics and production of a fungal β‐glucosidase
Authors: Wei Wei , Chen Ling , Zou Gen , Wang Qianfu , Yan Xing , Zhang Jun , Wang Chengshu , Zhou Zhihua 
Published: July 2013

ABSTRACTHeterologous expression of β‐glucosidase is one of the approaches to enhance the efficiency of fungal cellulase preparations. It has been reported that N‐glycosylation affects the structure framework, function and stability of proteins. In this study, a β‐glucosidase from Aspergillus terreus (GenBank: XP_001216552, BglS) was heterologously expressed in Pichia pastoris and Trichoderma reesei. The four asparagine residues were all linked with high‐mannose‐type oligosaccharides in P. pastoris, whereas only N224 carried high‐mannose‐type glycan in T. reesei (the other three sites carried one N‐acetylglucosamine). The long N‐glycan chains on PpBglS weakened its substrate affinity, activity and thermostability. The moderate post‐translational and post‐secretory glycan modification in T. reesei makes it a suitable expression system for BglS. The N224 glycan played a critical role in BglS folding. The elucidation of the correlation between the different N‐glycosylation patterns of BglS and their corresponding enzymatic characteristics is an important step towards improving the activity, thermostability and even production of heterologous β‐glucosidase by glycan engineering. Biotechnol. Bioeng. 2013;110: 3075–3084. © 2013 Wiley Periodicals, Inc.
Chromate Reduction in Anaerobic Systems by Bacterial Strain Pseudomonas aeruginosa CRM100
Authors: Salamanca Diego , Strunk Niko , Engesser Karl‐Heinrich 
Published: July 2013

AbstractThe biological reduction of soluble chromate(VI) compounds by bacteria was investigated as a possible treatment for industrial wastewater. A chromate(VI) reducing bacterial strain CRM100 was isolated from a wastewater treatment plant and identified as Pseudomonas aeruginosa. Strain CRM100 using citrate as carbon source, was able to reduce 99.8 % of chromate(VI) added at a concentration of 100 mg L–1. The results demonstrated the potential applicability of CRM100 for the bioremediation of heavy metal contaminated wastewater.
Adaptive clinical trial designs to detect interaction between treatment and a dichotomous biomarker
Authors: Zhu Hongjian , Hu Feifang , Zhao Hongyu 
Published: July 2013

AbstractBiomarkers play a crucial role in the design and analysis of clinical trials for personalized medicine. One major goal of these trials is to derive an optimal treatment scheme based on each patient's biomarker level. Although completely randomized trials may be employed, a more efficient design can be attained when patients are adaptively allocated to different treatments throughout the trial using biomarker information. Therefore, we propose a new adaptive allocation method based on using multiple regression models to study treatment–biomarker interactions. We show that this perspective simplifies the derivation of optimal allocations. Moreover, when implemented in real clinical trials, our method can consolidate all the covariates which may not be related to the treatment–biomarker interaction for a joint analysis. Our general idea can be applied to diverse models to derive optimal allocations. Simulation results show that both the optimal allocation and the proposed design can lead to a more efficient trial. The Canadian Journal of Statistics 41: 525–539; 2013 © 2013 Statistical Society of Canada
Discovery of an Acyclic Nucleoside Phosphonate that Inhibits Mycobacterium tuberculosis ThyX Based on the Binding Mode of a 5‐Alkynyl Substrate Analogue
Authors: Parchina Anastasia , Froeyen Matheus , Margamuljana Lia , Rozenski Jef , De Jonghe Steven , Briers Yves , Lavigne Rob , Herdewijn Piet , Lescrinier Eveline 
Published: July 2013

AbstractThe urgent need for new antibiotics poses a challenge to target un(der)exploited vital cellular processes. Thymidylate biosynthesis is one such process due to its crucial role in DNA replication and repair. Thymidylate synthases (TS) catalyze a crucial step in the biosynthesis of thymidine 5‐triphosphate (TTP), an elementary building block required for DNA synthesis and repair. To date, TS inhibitors have only been successfully applied in anticancer therapy due to their lack of specificity for antimicrobial versus human enzymes. However, the discovery of a new family of TS enzymes (ThyX) in a range of pathogenic bacteria that is structurally and biochemically different from the “classic” TS (ThyA) has opened the possibility to develop selective ThyX inhibitors as potent antimicrobial drugs. Here, the interaction of the known inhibitor 5‐(3‐octanamidoprop‐1yn‐1yl)‐2′‐deoxyuridine‐5′‐monophosphate (1) with Mycobacterium tuberculosis ThyX enzyme is explored using molecular modeling starting from published crystal structures, with further confirmation through NMR experiments. While the deoxyuridylate (dUMP) moiety of compound 1 occupies the cavity of the natural substrate in ThyX, the rest of the ligand (the “5‐alkynyl tail”) extends to the outside of the enzyme between two of its four subunits. The hydrophobic pocket that accommodates the alkyl part of the tail is formed by displacement of Tyr 44.C, Tyr 108.A and Lys 165.A. Changes to the resonance of the Lys 165 NH3 group upon ligand binding were monitored in a titration experiment by 2D HISQC NMR. Guided by the results of the modeling and NMR studies, and inspired by the success of acyclic antiviral nucleosides, compounds where a 5‐alkynyl uracyl moiety is coupled to an acyclic nucleoside phosphonate (ANP) were synthesized and evaluated. Of the compounds evaluated, sodium (6‐(5‐(3‐octanamidoprop‐1‐yn‐1‐yl)‐2,4‐dioxo‐3,4‐dihydropyrimidin‐1(2H)‐yl)hexyl)phosphonate (3 e) exhibited 43 % of inhibitory effect on ThyX at 50 μM. While only modest activity was achieved, this is the first example of an ANP inhibiting ThyX, and these results can be used to further guide structural modifications to this class to develop more potent compounds with potential application as antibacterial agents acting through a novel mechanism of action.
α‐Dialdimine Complexes of Rhodium(I) and Iridium(I): Their Reactivity with Dioxygen and Dihydrogen
Authors: Eiβler Anna , Kläring Paul , Emmerling Franziska , Braun Thomas 
Published: July 2013

AbstractThe rhodium(I) and iridium(I) complexes [M(Cl){ArN=C(H)C(H)=NAr}(CNtBu)] (1: M = Rh, Ar = 2,6‐iPr2C6H3; 2: M = Rh, Ar = Mes; 3: M = Ir, Ar = Mes; Mes = 2,4,6‐Me3C6H2) have been prepared by the reaction of [M(μ‐Cl)(coe)2]2 (M = Rh, Ir; coe = cyclooctene) with the α‐dialdimines ArN=C(H)C(H)=NAr (Ar = 2,6‐iPr2C6H3, Mes) in thf, followed by the addition of CNtBu. XANES spectra and DFT calculations on 2 and 3 suggest an oxidation state +I at the metal centers. Treatment of the complexes 2 and 3 with O2 or 18O2 gave the peroxido complexes [M(Cl)(O2){MesN=C(H)C(H)=NMes}(CNtBu)] (4a: M = Rh; 5a: M = Ir) and [M(Cl)(18O2){MesN=C(H)C(H)=NMes}(CNtBu)] (4b: M = Rh; 5b: M = Ir). The reaction of 3 with dihydrogen resulted in the formation of the iridium dihydrido complex [Ir(Cl)(H)2{MesN=C(H)C(H)=NMes}(CNtBu)] (6a). Two isomeric α‐imine‐amine complexes [Ir(Cl)(H)2{MesN(H)CH2C(H)=NMe}(CNtBu)] (7/7′) were obtained after prolonged reaction under H2. All of the complexes were characterized by NMR and IR spectroscopy. In addition, complexes 2, 3,and 7 were characterized by X‐ray crystallography.
Investigating the Ritter Type Reaction of α‐Methylene‐β‐hydroxy Esters in Acidic Medium: Evidence for the Intermediacy of an Allylic Cation
Authors: Sá Marcus M. , Ferreira Misael , Caramori Giovanni F. , Zaramello Laize , Bortoluzzi Adailton J. , Faggion Deonildo , Domingos Josiel B. 
Published: July 2013

AbstractThe acid‐mediated solvolytic transformation of α‐methylene‐β‐hydroxy esters in acetonitrile was investigated. The reaction was shown to involve nucleophilic attack either at the terminal methylene or at the benzylic carbon. Kinetic and theoretical studies were performed to elucidate the possible pathways involved in the formation of the acetamide products, i.e., through an addition‐elimination mechanism, a concerted process (SN2 and SN2′), or involving an allylic cation (SN1 and SN1′). The results of the kinetic analysis, including the isotope effect, Hammett plot, and Eyring plot, are in agreement with a proton transfer equilibrium prior to the formation of a benzylic carbenium ion intermediate, which is consistent with a unimolecular stepwise mechanism. Theoretical examination at the DFT level of theory corroborated these findings, with the lowest activation energy being associated with the SN1′‐type mechanism.
One‐Pot Enantioselective Synthesis of 3‐Nitro‐2H‐chromenes Catalyzed by a Simple 4‐Hydroxyprolinamide with 4‐Nitrophenol as Cocatalyst
Authors: Yin Guohui , Zhang Richeng , Li Lei , Tian Jun , Chen Ligong 
Published: July 2013

AbstractThe asymmetric domino oxa‐Michael–Henry reaction of salicylaldehyde derivatives with trans‐β‐nitro olefins catalyzed by a readily available trans‐4‐hydroxy‐L‐prolinamide with 4‐nitrophenol as an effective cocatalyst is presented. The corresponding 3‐nitro‐2H‐chromenes were obtained in moderate to excellent yields (up to 99 %) and with up to 90 % ee under mild conditions. In addition, a preliminary study shows that this organocatalytic system is able to promote the domino aza‐Michael–Henry reaction of 2‐formylpyrrole derivatives with trans‐β‐nitro olefins to give chiral 2‐nitro‐3H‐pyrrolizines.
Sulfonation and Trifluoromethylation of Enol Acetates with Sulfonyl Chlorides Using Visible‐Light Photoredox Catalysis
Authors: Jiang Heng , Cheng Yuanzheng , Zhang Yan , Yu Shouyun 
Published: July 2013

AbstractA mild, practical method to prepare α‐sulfonyl and α‐trifluoromethyl ketones from readily available enol acetates and sulfonyl chlorides has been developed using visible‐light photoredox catalysis. The method could be used with a wide range of enol acetates and sulfonyl chlorides, and gave the desired products in satisfactory to excellent yields.
PVC‐Based Ion‐Selective Electrodes with Enhanced Biocompatibility by Surface Modification with “Click” Chemistry
Authors: Pawlak M. , Grygolowicz‐Pawlak E. , Crespo G. A. , Mistlberger G. , Bakker E. 
Published: July 2013

AbstractWe report here on plasticized ion‐selective poly(vinyl chloride) membranes with increased biocompatibility by means of a copper(I)‐catalyzed azide‐alkyne cycloaddition (‘click chemistry’) on the surface of finished membranes. We aimed for increasing the hydrophilicity of the surface and the application of NO releasing molecules. Employing the first principle, sodium selective membranes based on azide‐substituted PVC were modified with different length poly(ethylene glycol) (PEG) chains. For the second, cysteine groups were used as a nitrous oxide releasing substance. Surface modification was confirmed by Electrochemical Impedance Spectroscopy (EIS). Potentiometric measurements in undiluted whole blood showed an increased sensor stability in comparison to unmodified PVC. Membrane surfaces after 18 h contact with blood were analyzed with Scanning Electron Microscopy (SEM) and revealed a reduced level of blood cell adsorption on membranes modified with tetraethylene glycol (TEG) and PEGs. In contrast, cysteine modified membranes did not exhibit improved fouling resistance, suggesting that nitric oxide release by itself is not a sufficiently efficient mechanism.
Vanadium bioavailability and toxicity to soil microorganisms and plants
Authors: Larsson Maja A. , Baken Stijn , Gustafsson Jon Petter , Hadialhejazi Golshid , Smolders Erik 
Published: July 2013

Abstract

Vanadium, V, is a redox-sensitive metal that in solution, under aerobic conditions, prevails as the oxyanion vanadate(V). There is little known regarding vanadium toxicity to soil biota, and the present study was set up to determine the toxicity of added vanadate to soil organisms and to investigate the relationship between toxicity and vanadium sorption in soils. Five soils with contrasting properties were spiked with 7 different doses (3.2–3200 mg V kg−1) of dissolved vanadate, and toxicity was measured with 2 microbial and 3 plant assays. The median effective concentration (EC50) thresholds of the microbial assays ranged from 28 mg added V kg−1 to 690 mg added V kg−1, and the EC50s in the plant assays ranged from 18 mg added V kg−1 to 510 mg added V kg−1. The lower thresholds were in the concentration range of the background vanadium in the untreated control soils (15–58 mg V kg−1). The vanadium toxicity to plants decreased with a stronger soil vanadium sorption strength. The EC50 values for plants expressed on a soil solution basis ranged from 0.8 mg V L−1 to 15 mg V L−1 and were less variable among soils than corresponding values based on total vanadium in soil. It is concluded that sorption decreases the toxicity of added vanadate and that soil solution vanadium is a more robust measure to determine critical vanadium concentrations across soils. Environ Toxicol Chem 2013;32:2266–2273. © 2013 SETAC
VAAST 2.0: Improved Variant Classification and Disease‐Gene Identification Using a Conservation‐Controlled Amino Acid Substitution Matrix
Authors: Hu Hao , Huff Chad D. , Moore Barry , Flygare Steven , Reese Martin G. , Yandell Mark 
Published: July 2013

ABSTRACTThe need for improved algorithmic support for variant prioritization and disease‐gene identification in personal genomes data is widely acknowledged. We previously presented the Variant Annotation, Analysis, and Search Tool (VAAST), which employs an aggregative variant association test that combines both amino acid substitution (AAS) and allele frequencies. Here we describe and benchmark VAAST 2.0, which uses a novel conservation‐controlled AAS matrix (CASM), to incorporate information about phylogenetic conservation. We show that the CASM approach improves VAAST's variant prioritization accuracy compared to its previous implementation, and compared to SIFT, PolyPhen‐2, and MutationTaster. We also show that VAAST 2.0 outperforms KBAC, WSS, SKAT, and variable threshold (VT) using published case‐control datasets for Crohn disease (NOD2), hypertriglyceridemia (LPL), and breast cancer (CHEK2). VAAST 2.0 also improves search accuracy on simulated datasets across a wide range of allele frequencies, population‐attributable disease risks, and allelic heterogeneity, factors that compromise the accuracies of other aggregative variant association tests. We also demonstrate that, although most aggregative variant association tests are designed for common genetic diseases, these tests can be easily adopted as rare Mendelian disease‐gene finders with a simple ranking‐by‐statistical‐significance protocol, and the performance compares very favorably to state‐of‐art filtering approaches. The latter, despite their popularity, have suboptimal performance especially with the increasing case sample size.
The Value of Statistical or Bioinformatics Annotation for Rare Variant Association With Quantitative Trait
Authors: Byrnes Andrea E. , Wu Michael C. , Wright Fred A. , Li Mingyao , Li Yun 
Published: July 2013

ABSTRACTIn the past few years, a plethora of methods for rare variant association with phenotype have been proposed. These methods aggregate information from multiple rare variants across genomic region(s), but there is little consensus as to which method is most effective. The weighting scheme adopted when aggregating information across variants is one of the primary determinants of effectiveness. Here we present a systematic evaluation of multiple weighting schemes through a series of simulations intended to mimic large sequencing studies of a quantitative trait. We evaluate existing phenotype‐independent and phenotype‐dependent methods, as well as weights estimated by penalized regression approaches including Lasso, Elastic Net, and SCAD. We find that the difference in power between phenotype‐dependent schemes is negligible when high‐quality functional annotations are available. When functional annotations are unavailable or incomplete, all methods suffer from power loss; however, the variable selection methods outperform the others at the cost of increased computational time. Therefore, in the absence of good annotation, we recommend variable selection methods (which can be viewed as “statistical annotation”) on top of regions implicated by a phenotype‐independent weighting scheme. Further, once a region is implicated, variable selection can help to identify potential causal single nucleotide polymorphisms for biological validation. These findings are supported by an analysis of a high coverage targeted sequencing study of 1,898 individuals.
Basin‐scale CO2 storage capacity assessment of deep saline aquifers in the Songliao Basin, northeast China
Authors: Su Xiaosi , Xu Wei , Du Shanghai 
Published: July 2013

AbstractGeological storage of CO2 in deep saline aquifers has become one of the most important methods of reducing the emission of anthropogenic greenhouse gas into the atmosphere. The assessment of potential CO2 storage capacity is an important part of geological storage design. In this study, the potential CO2 storage capacity in the deep saline aquifers of the Songliao Basin – a large sedimentary basin in northeastern China – was assessed on a basin scale. The study results showed that: (1) deep saline aquifers suitable for geological CO2 storage occur mainly in the Cretaceous layers. Six deep saline aquifers were identified as potential storage formations, all with good reservoir‐caprock properties. (2) The residual gas trapping storage capacity and solubility trapping storage capacity of CO2 were considered for theoretical storage capacity estimation and the total CO2 storage capacity is 160030.00 × 106 t in the deep saline aquifers. The effective storage capacity was 19983.89 × 106 t, 78368.16 × 106 t and 215512.40 × 106 t with the storage efficiency factors of 0.0051, 0.02 and 0.055, respectively, and the average value is 104621.50 × 106 t. Storage intensity is defined as the effectiveness of unit area storage capability and the value of each tectonic unit ranges from 0.21 to 1.10 × 106 t/km2, with an average storage intensity for the whole Songliao Basin of 0.63 × 106 t/km2. The saline formations could be used to store CO2 for at least 55 years with a great CO2 emission annual growth rate of 10%, and for about 980 years with the CO2 emission annual growth rate of 1%. (3) Comparative analysis of the deep saline storage capacities in the basin showed that the Northern Plunge area and Central Downwarp area have the highest potential for CO2 storage in saline aquifer. These results could be used as important guidelines for the selection and design of CO2 storage fields in the Songliao Basin, China.