bluuebunny/crossref_metadata_2025 huggingface dataset:
Base‐Mediated Direct Arylation of Pyrrole Derivatives
Authors: Vakuliuk Olena , Koszarna Beata , Gryko Daniel T.
Published: April 2011

It appears that transition metal catalysts are not necessary to perform the direct arylation of electron‐rich heterocycles with aryl iodides and bromides. Lithium tert‐butoxide in DMF promotes this reaction for a variety of N‐alkyl‐ and N‐arylpyrroles as well as for benzofuran and some other electron‐rich aromatic compounds and provides the desired products in moderate to high yields. In contrast to all previous reports on the Pd‐catalyzed direct arylation of indolizine, the reaction mediated by lithium tert‐butoxide proceeds selectively at position 5.
Kinetic Resolution of α‐Bromoamides: Experimental and Theoretical Investigation of Highly Enantioselective Reactions Catalyzed by Haloalkane Dehalogenases
Authors: Westerbeek Alja , Szymański Wiktor , Wijma Hein J. , Marrink Siewert J. , Feringa Ben L. , Janssen Dick B.
Published: April 2011

Haloalkane dehalogenases from five sources were heterologously expressed in Escherichia coli, isolated, and tested for their ability to achieve kinetic resolution of racemic α‐bromoamides, which are important intermediates used in the preparation of bioactive compounds. To explore the substrate scope, fourteen α‐bromoamides, with different Cα‐ and N‐substituents, were synthesized. Catalytic activity towards eight substrates was found, and for five of these compounds the conversion proceeded with a high enantioselectivity (E value >200). In all cases, the (R)‐α‐bromoamide is the preferred substrate. Conversions on a preparative scale with a catalytic amount of enzyme (enzyme:substrate ratio less 1:50 w/w) were all completed within 17–46 h and optically pure α‐bromoamides and α‐hydroxyamides were isolated with good yields (31–50%). Substrate docking followed by molecular dynamics simulations indicated that the high enantioselectivity results from differences in the percentage of the time in which the substrate enantiomers are bound favourably for catalysis. For the preferred (R)‐substrates, the angle between the attacking aspartate oxygen atom of the enzyme, the attacked carbon atom of the substrate, and the displaced halogen atom, is more often in the optimal range (>157°) for reactivity. This can explain the observed enantioselectivity of LinB dehalogenase in a kinetic resolution experiment.
Silver Hexafluoroantimonate‐Catalyzed Three‐Component [2+2+1] Cycloadditions of Allenoates, Dual Activated Olefins, and Isocyanides
Authors: Li Jian , Liu Yuejin , Li Chunju , Jia Xueshun
Published: April 2011

The intermolecular [2+2+1] multicomponent cycloadditions from readily available allenoates, dual activated olefins and isocyanides catalyzed by silver hexafluoroantimonate were studied. This protocol allowed the syntheses of highly functionalized five‐membered carbocycles with exclusive regioselectivity and stereoselectivity in an efficient and atom‐economical manner.
Intramolecular Palladium‐Catalyzed Aminocarboxylation of Olefins as a Direct Route to Bicyclic Oxazolidinones
Authors: Borsini Elena , Broggini Gianluigi , Fasana Andrea , Galli Simona , Khansaa Maisaa , Piarulli Umberto , Rigamonti Micol
Published: April 2011

An efficient, direct synthesis of oxazolidinones fused to six‐membered heterocyclic rings starting from carbamate‐protected aminoalkenes has been developed. This procedure is based on an oxidative palladium(II)‐catalyzed reaction performed in the presence of stoichiometric copper chloride, which is determinant to promote the formation of the bicyclic product and prevent the isolation of the monocyclic amination product. Oxazolidinone compounds arise from a domino aminocarboxylation process through the direct intervention of the carbamate oxygen after the initial palladium‐promoted transfer of the nitrogen atom on the CC double bond.
Pyrazinium Salts as Efficient Organocatalysts of Mild Oxidations with Hydrogen Peroxide
Authors: Ménová Petra , Kafka František , Dvořáková Hana , Gunnoo Smita , Šanda Miloslav , Cibulka Radek
Published: April 2011

A series of 3‐substituted pyrazinium tetrafluoroborates was prepared as simple analogues of flavinium salts which are efficient organocatalysts for oxidations with hydrogen peroxide. It was shown that pyrazinium derivatives with an electron‐withdrawing substituent catalyze mild oxidations of sulfides to sulfoxides and Baeyer–Villiger oxidations in a similar way to flavinium catalysts. The most reactive catalyst, 3‐cyanopyrazinium tetrafluoroborate, was efficiently employed in preparative sulfoxidations of aromatic and aliphatic sulfides as well as in Baeyer–Villiger oxidations of cyclobutanones. A proposed mechanism for the catalysis is based on the formation of pyrazine hydroperoxide which is the agent oxidizing the substrate.
Hafnium Triflate as an Efficient Catalyst for Direct Friedel–Crafts Reactions of Chromene Hemiacetals
Authors: Wu Yan‐Chao , Li Hui‐Jing , Liu Li , Demoulin Nicolas , Liu Zhe , Wang Dong , Chen Yong‐Jun
Published: April 2011

The direct Friedel–Crafts reaction of chromene hemiacetals with indoles, furans and sterically hindered anilines has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of hafnium triflate [Hf(OTf)4, 0.1 mol%, 0–40 °C]. The mild conditions tolerate various sensitive functional and protecting groups, and the products were confirmed unambiguously from their spectra and by single‐crystal X‐ray analysis. This direct Friedel–Crafts reaction of chromene hemiacetals should inspire and encourage the consideration of hafnium triflate in the development of mild reaction conditions for the efficient derivatization of hemiacetal‐containing compounds.
Development of a General and Practical Iron Nitrate/TEMPO‐Catalyzed Aerobic Oxidation of Alcohols to Aldehydes/Ketones: Catalysis with Table Salt
Authors: Ma Shengming , Liu Jinxian , Li Suhua , Chen Bo , Cheng Jiajia , Kuang Jinqiang , Liu Yu , Wan Baoqiang , Wang Yuli , Ye Juntao , Yu Qiong , Yuan Weiming , Yu Shichao
Published: April 2011

Oxidation of alcohols is a fundamental transformation related to our daily life. Traditional approaches with at least one stoichiometric amount of oxidants are expensive and cause serious environmental burdens. There are many reports on the aerobic oxidation of simple alcohols such as alkyl or phenyl carbinols and allylic alcohols, which used oxygen or air as the environmentally benign oxidant forming water as the only by‐product. However, no such protocol has been reported for allenols and propargylic alcohols. Thus, it still highly desirable to develop efficient room temperature oxidations of alcohols with a wide scope including allenols and propargylic alcohols. In this paper, an efficient and clean aerobic oxidation of so far the widest spectrum of alcohols using 1 atm of oxygen or air, producing aldehydes/ketones at room temperature in fairly high isolated yields mostly within a couple of hours is described. It is interesting to observe that the reaction has been efficiently expedited by a catalytic amount of sodium chloride in easily recoverable 1,2‐dichloroethane. A mechanism involving NO and NO2 has been proposed based on the results of the control experiments and GC‐MS studies of the in‐situ formed gas phase of the reaction mixture.
An Easy Entry to Optically Active Spiroindolinones: Chiral Brønsted Acid‐Catalysed Pictet–Spengler Reactions of Isatins
Authors: Duce Sara , Pesciaioli Fabio , Gramigna Lucia , Bernardi Luca , Mazzanti Andrea , Ricci Alfredo , Bartoli Giuseppe , Bencivenni Giorgio
Published: April 2011

The first catalytic asymmetric Pictet–Spengler reaction of isatins is presented. BINOL‐derived phosphoric acids were found to be competent catalysts for this transformation, giving challenging spirooxindole structures bearing a quaternary stereocentre with generally good results. The 1,2,3,4‐tetrahydro‐β‐carboline products (spiroindolinones) are the core of some newly discovered anti‐malarial agents.
Improved nonlinear process monitoring using KPCA with sample vector selection and combined index
Authors: Sumana C. , Bhushan Mani , Venkateswarlu Ch. , Gudi Ravindra D.
Published: April 2011

Kernel principal component analysis (KPCA) has been found to be one of the promising methods for nonlinear process monitoring in recent years. It effectively captures the data nonlinearities by transforming the original data using nonlinear kernel functions and then performs linear PCA in high‐dimensional feature space F. However, KPCA is computationally intense, as it needs the solution of the eigenvalue decomposition problem involving a high‐dimensional kernel matrix. The present work addresses this issue by adopting a sample vector selection (SVS) scheme that facilitates the analysis in a lower dimensional kernel space formed by a set of optimally selected transformed samples in F. These sample vectors are selected through an iterative sequential forward selection procedure based on a geometric consideration. Furthermore, the efficiency of the KPCA methodology is improved by proposing a combined index‐based process monitoring in the reduced kernel space. The performance of the proposed methodology is evaluated by applying it to a complex nonlinear Tennessee Eastman process. The results demonstrate the better fault detection ability of the proposed methodology in terms of lower computational effort and reduced false alarm and missed detection rates. Copyright © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.
Preparation of core–shell microcapsules using nanodispersed fibroin
Authors: Kim Eun Jong , Lee Shin Young , Hur Won
Published: April 2011

An elaborate control of fibroin self‐assembly is critical in determining the size, structure, and release properties of a microcapsule. This report describes the preparation of microspheres in the submicron range using an aqueous fibroin solution nanoemulsified in decane with a mixed detergent solution of Tween 80 and Span 80. Nanodispersed water droplets containing fibroin molecules were dried under vacuum to facilitate the coalescence of fibroin and then transformed to suspended particles in the range of 200–1200 nm in diameter. The method was also applied to encapsulate dextran and fluorescein isothiocyanate‐dextran (FITC‐dextran), producing core–shell structured microcapsules as identified by scanning electron microscopy and confocal scanning laser microscopy. The microcapsule yield was in the range of 82–85% per fibroin consumed. The encapsulation efficiency was 64% for the microcapsules fabricated from a nanoemulsion containing 0.1 mg of FITC‐dextran per mg fibroin. Approximately 70.5% of the core material was released within 2 weeks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Influence of morphology effects on electrical properties in XLPE
Authors: Nilsson S. , Hjertberg T. , Smedberg A. , Sonerud B.
Published: April 2011

This study elucidates the influence of differences in crosslink structure and crosslink density on water tree growth, electrical tree growth, and electrical breakdown strength. One reference LDPE was compared with a LDPE containing a higher number of vinyl groups, introduced via the copolymerisation with a diene. Because of the chemical difference, the initially formed crosslink structure will be different for the materials. A range of various crosslink densities was considered for the two materials. It was found that along with a noticeable change in morphology after crosslinking, significant changes in particularly water tree growth, electrical tree growth, and electrical breakdown strength could be observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Improvement of impact properties of polypropylene by modification with very low‐density polyethylene
Authors: Kim Eung Soo , Shim Jae Hun , Woo Ji Yoon , Lee Keun Young , Yoon Jin‐San
Published: April 2011

Very low‐density polyethylene (VLDPE) was compounded with polypropylene (PP) to improve its impact strength. VLDPE was modified by grafting 3‐(trimethoxysilyl) propyl methacrylate silane (MS) to VLDPE to prepare mVLDPE. PP was melt‐mixed either with VLDPE or mVLDPE together with Cloisite®20A (C20A). The composites exhibited a phase‐separated morphology, irrespective of whether the VLDPE had been modified with the silane compounds or not. Incorporation of C20A decreased the domain size of the dispersed phases of both PP/VLDPE and PP/mVLDPE blends. The tensile strength and elongation at break of PP/VLDPE and PP/mVLDPE were improved by the addition of C20A. In contrast, their impact strengths were reduced by the clay. However, the decrease in impact strength was less significant in PP/mVLDPE/C20A than in PP/VLDPE/C20A. The superior mechanical properties of PP/mVLDPE/C20A over PP/VLDPE/C20A were attributed to enhanced interfacial interactions originating from chemical reactions between silane residues on mVLDPE and the silanol groups of C20A. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermal properties of polyurethane binder with 2‐(ferrocenylpropyl)dimethylsilane‐grafted hydroxyl‐terminated polybutadiene
Authors: Cho Bong‐Sang , Noh Si‐Tae
Published: April 2011

We synthesized a ferrocene‐based burning rate catalyst, 2‐(ferrocenylpropyl) dimethylsilane (FPDS). FPDS‐grafted hydroxyl‐terminated polybutadiene (FPDS‐g‐HTPB) was synthesized using hydrosilylation with a Pt catalyst. The structures of FPDS and FPDS‐g‐HTPB were investigated by Fourier transform infrared spectroscopy and nuclear magnetic resonance. HTPB‐based polyurethanes were prepared from HTPB, 6‐hexamethylenediisocyanate (HDI), and HDI‐trimer. Polyurethane network was prepared with an (NCO)/(OH) ratio of 1.05 and an [isocyanate trimer]/[total NCO] ratio of 0.3 then subjected to accelerated aging at 80°C. The thermal behaviors of the polyurethane network were compared using differential scanning calorimetry and thermal gravity analysis. The glass transition temperatures (Tg) of HTPB and FPDS‐g‐HTPB were −76°C and −47°C, respectively. The value of Tg for the networked polyurethane was not influenced by HDI‐trimer content but by FPDS content. The decomposition temperature of the neat HTPB‐based polyurethane network was lower than that of the FPDS‐g‐HTPB‐based polyurethane networks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Chemorheology and thermomechanical characteristics of benzoxazine‐urethane copolymers
Authors: Rimdusit Sarawut , Bangsen Wanchat , Kasemsiri Pornnapa
Published: April 2011

In this research, processability and some important thermomechanical properties of polybenzoxazine (BA‐a) modified with a highly flexible urethane elastomer (PU) are discussed. This copolymer has been reported to show synergy in its glass transition temperature and some mechanical properties thus provides a fascinating group of high temperature polymers with enhanced flexibility. The results reveal that a processing window of the BA‐a/PU mixtures is widened with the increasing urethane prepolymer fraction, that is, the liquefying temperature is lowered and the gel point shifted to higher temperature with the amount of the PU. Synergism in glass transition temperature (Tg) of this copolymer was clearly confirmed, i.e., Tg's of the BA‐a/PU alloys were significantly greater than those of the parent resins, i.e., BA‐a (Tg = 166°C) and PU (Tg = − 70°C). In addition, flexural modulus was found to systemically decrease from 5.4 GPa of the neat polybenzoxazine to 2.1 GPa at 40% by weight of the PU. Flexural strength of the alloys also shows a synergistic behavior at the BA‐a/PU ratio of 90/10. Coefficient of thermal expansion of the polymer alloys were also found to show a minimum value at BA‐a/PU = 90/10. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Design of an ammonium dinitramide compatible polymer matrix
Authors: Rahm Martin , Malmström Eva , Eldsäter Carina
Published: April 2011

To enable future environmentally friendly access to space by means of solid rocket propulsion a viable replacement to the toxic ammonium perchlorate (AP) oxidizer is needed. Ammonium dinitramide (ADN) holds great promise as a green replacement. Unfortunately compatibility issues with many polymer binder systems have hampered the development of ADN‐based formulations. Herein we present proof‐of‐concept of a polymer cure system based on hyperbranched copolymers of 3‐ethyl‐3‐(hydroxymethyl)oxetane (TMPO) and tetrahydrofuran (THF). The partly alkyne‐functionalized macromolecules were synthesized in a one‐pot procedure. TMPO and THF are found to polymerize in exact ratios, indicating a kinetically controlled buildup of nonrandom composition copolymers. Several of the materials show excellent compatibility with ADN, and rapid curing of the energetic polyglycidyl azide polymer (GAP) have been demonstrated through 1,3‐dipolar cycloaddition at 75°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Mechanical properties of (poly(L‐lactide‐co‐glycolide))‐based fibers coated with hydroxyapatite layer
Authors: Buczynska Joanna , Pamula Elzbieta , Blazewicz Stanislaw
Published: April 2011

This article presents the results of the experimental study on manufacturing and mechanical evaluation of poly(L‐lactide‐co‐glycolide) (PLGA)‐based fibers modified with ceramic nanoparticles. Study was conducted to establish the effect of biomimetic formation of apatite layers on polymeric fibers on their mechanical properties. The tensile tests were performed to determine the influence of polymer crystallinity and the presence of hydroxyapatite nanoparticles (nanoHAp) on mechanical properties of PLGA fibers coated with hydroxyapatite (HAp) layer. HAp deposits on the surfaces of the fibers precipitated from simulated body fluid (SBF). Three types of fibers coated with HAp layers were compared in mechanical tests. The results indicated that by using a biomimetic fiber coating method the mechanical properties of the fibers are affected by their crystallinity. The nanoHAp modified polymer fibers after incubation in SBF were found to have a continuous HAp layer. The layer affected the mechanical behavior (force–strain function) of the fibers from nonlinear to linear, typical of ceramic materials. The tensile modulus of the fibers with a continuous layer was found to increase with the apatite layer thickness, whereas the tensile strength decreases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
No evidence for IL1RAPL1 involvement in selected high‐risk autism pedigrees from the AGRE data set
Authors: Allen‐Brady Kristina , Cai Guiqing , Cannon Dale , Robison Reid , McMahon William M. , Coon Hilary , Buxbaum Joseph D.
Published: April 2011

Finding predisposition genes for Autism Spectrum Disorder (ASD) has proven challenging, and new methods are needed to aid the process. Using pedigree structure as a strategy to identify ASD predisposition genes, we previously performed a genome‐wide linkage scan of 86 selected families from the Autism Resource Exchange (AGRE) that appeared to inherit ASD in a dominant manner. We identified a suggestive linkage peak on chromosome Xp22.11‐p21.2 that encompasses the IL1RAPL1 gene, a strong candidate gene for ASD. In this follow‐up study, we sequenced the coding regions of the IL1RAPL1 gene in 14 male cases representing one case from each pedigree that showed at least nominal linkage evidence on per pedigree basis to the chromosome X region. We observed no deleterious mutations or deletions in the IL1RAPL1 gene in these 14 ASD cases. A SNP was identified in exon 2 in five cases and a variant of unknown significance was identified in intron 6 in a single case. In conclusion, coding changes of the IL1RAPL1 gene do not appear to be associated with ASD in selected AGRE families with linkage evidence to the chromosome Xp22.11‐p21.2 region. Autism Res 2011,4:293–296. © 2011 International Society for Autism Research, Wiley Periodicals, Inc.
Glyoxalase I polymorphism rs2736654 causing the Ala111Glu substitution modulates enzyme activity—implications for autism
Authors: Barua Madhabi , Jenkins Edmund C. , Chen Wenqiang , Kuizon Salomon , Pullarkat Raju K. , Junaid Mohammed A.
Published: April 2011

Autism is a pervasive, heterogeneous, neurodevelopmental disability characterized by impairments in verbal communications, reciprocal social interactions, and restricted repetitive stereotyped behaviors. Evidence suggests the involvement of multiple genetic factors in the etiology of autism, and extensive genome‐wide association studies have revealed several candidate genes that bear single nucleotide polymorphisms (SNPs) in non‐coding and coding regions. We have shown that a non‐conservative, non‐synonymous SNP in the glyoxalase I gene, GLOI, may be an autism susceptibility factor. The GLOI rs2736654 SNP is a C→A change that causes an Ala111Glu change in the Glo1 enzyme. To identify the significance of the SNP, we have conducted functional assays for Glo1. We now present evidence that the presence of the A‐allele at rs2736654 results in reduced enzyme activity. Glo1 activity is decreased in lymphoblastoid cells that are homozygous for the A allele. The Glu‐isoform of Glo1 in these cells is hyperphosphorylated. Direct HPLC measurements of the glyoxalase I substrate, methylglyoxal (MG), show an increase in MG in these cells. Western blot analysis revealed elevated levels of the receptor for advanced glycation end products (RAGEs). We also show that MG is toxic to the developing neuronal cells. We suggest that accumulation of MG results in the formation of AGEs, which induce expression of the RAGE that during crucial neuronal development may be a factor in the pathology of autism. Autism Res 2011,4:262–270. © 2011 International Society for Autism Research, Wiley Periodicals, Inc.
Measuring the persistence length of MCF7 cell microtubules in vitro
Authors: Feizabadi Mitra Shojania , Mutafopulos Kiryako S. , Behr Adam
Published: April 2011

The dynamic and mechanical properties of mammalian neural microtubules have been widely studied; however, similar knowledge about these properties is limited for non‐neural microtubules, which, unlike neural microtubules, consist of different β‐tubulin isotypes. In this study, we report, for the first time, an estimated value for the persistence length of a single non‐neural microtubule polymerized from purified tubulin from human breast cancer cell lines (MCF7 tubulin). The method of measurement is based on an analysis of the local curvature of a microtubule as a result of thermal fluctuations. In parallel, we measured the persistence length of a single bovine brain microtubule under similar conditions. The results of our measurements indicate a higher value for the persistence length of MCF7 microtubules in vitro as compared to the persistence length of a neural microtubule. The difference can be associated with different β‐tubulin isotypes in the structure of MCF7 microtubules.
Ternary Cobalt–Iron Phosphide Nanocrystals with Controlled Compositions, Properties, and Morphologies from Nanorods and Nanorice to Split Nanostructures
Authors: Ye Enyi , Zhang Shuang‐Yuan , Lim Suo Hon , Bosman Michel , Zhang Zhihua , Win Khin Yin , Han Ming‐Yong
Published: April 2011

Structural phase‐controlled formation of binary Co2P and CoP nanocrystals is achieved by reacting cobalt(II) oleate with trioctylphosphine. In the absence of oleylamine, Co2P nanowires are formed at both 290 and 320 °C. In the presence of oleylamine, Co2P nanorods are formed at 290 °C, and CoP nanorods are formed at 320 °C. With the simultaneous reaction of iron(III) oleate and cobalt(II) oleate with trioctylphosphine in the presence of oleylamine, ternary Co2P‐type cobalt–iron phosphide nanostructures are produced at both 290 and 320 °C, corresponding to rice‐shaped Co1.5Fe0.5P nanorods and split Co1.7Fe0.3P nanostructures, respectively. The controlled incorporation of iron into cobalt phosphide can alter the magnetic properties from paramagnetic binary Co2P to ferromagnetic Co2P‐type ternary cobalt–iron phosphide nanostructures. Meanwhile, the time‐dependent morphological evolution from small nanodots/nanorods, through seeded growth to unique split nanostructures is demonstrated in one‐pot reaction at 320 °C.
Identification of retinotectal projection pathway in the deep tectal laminae in the chick
Authors: Omi Minoru , Harada Hidekiyo , Nakamura Harukazu
Published: April 2011

The optic tectum is a visual center of nonmammalian vertebrates that receives retinal fibers in a retinotopic manner. It has been accepted that retinal fibers project to some superficial laminae of the tectum, but do not go through lamina g of stratum griseum et fibrosum superficiale (SGFS). By a novel fiber‐tracing method, we found a novel pathway of retinal fibers that run through deep laminae of the tectum. The retinal fibers that would run through the newly identified pathway first run caudally along the medial edge after invading the tectum, turn laterally, and extend toward the lateral side through the deep pathway. The deep pathway runs through stratum album centrale and stratum fibrosum periventriculare. The fibers that run through the deep pathway do not enter the stratum opticum, where the conventional retinal fibers run. As development proceeds, these fibers decrease and disappear by the adult stage. By the new method, we found that some of the conventional retinal fibers transiently run through lamina g of SGFS and invade laminae h/i. In conclusion, we found distinct but transient retinal fiber pathway in the deep tectal laminae, which have not been thought to be retinorecipient. J. Comp. Neurol. 519:2615–2621, 2011. © 2011 Wiley‐Liss, Inc.
Phenotypic changes in calbindin D28K immunoreactivity in the hippocampus of Fmr1 knockout mice
Authors: Real M. Angeles , Simón M. Pilar , Heredia Raúl , de Diego Yolanda , Guirado Salvador
Published: April 2011

Fragile X syndrome (FXS), the most prevalent form of inherited mental retardation, is caused by the lack of FMRP (fragile mental retardation protein) as a result of the transcriptional silencing of the FMR1 gene. Here we analyze the immunohistochemical expression of the calbindin D28K protein in the hippocampus of Fmr1 knockout (KO) mice and compare it with that of their wildtype (WT) littermates. The spatial distribution pattern of calbindin‐immunoreactive cells in the hippocampus was similar in WT and KO mice but for each age studied (ranging from 3.5–8 months) the dentate gyrus of Fmr1‐KO mice showed a significant reduction in calbindin‐immunoreactive granule cells. Also, the number of calbindin‐immunoreactive cells was reduced in the CA1 pyramidal layer in KO mice compared to their WT littermates. In addition, Frm1‐KO mice showed a group of calbindin‐immunoreactive cells located only in the left CA3b subregion that was only sometimes observed in WT mice. Overall, the absence of FMRP results in a dysregulation of the calbindin protein expression in the hippocampus. This dysregulation is cell type‐ and time‐dependent and as a consequence key elements of the hippocampal trisynaptic circuitry may lack calbindin in critical periods for normal memory/learning abilities to be achieved and may explain some of the FXS symptoms observed in the Fmr1‐KO mouse model. J. Comp. Neurol. 519:2622–2636, 2011. © 2011 Wiley‐Liss, Inc.
The Evolution of Bonding and Thermodynamic Properties of Boron‐Doped Small Carbon Clusters: An Ab Initio Study
Authors: Saloni Julia , Kadłubański Paweł , Roszak Szczepan , Majumdar D. , Hill Glake , Leszczynski Jerzy
Published: April 2011

Theoretical studies on BCn (n=1–6) clusters are carried out using density functional theory, Møller–Plesset second‐order perturbation theory (MP2), coupled‐cluster calculations including up to triple excitations (CCSD(T)), and higher‐level approaches. All possible isomers depending on the positions of the boron atom are generated and the lowest‐energy isomers are determined for doublet and quartet electronic states. The three potential evolution paths of the clusters are determined as a function of their size. The energetic and electronic consequences for the increased size of structures differ significantly, which leads to representatives of the ground electronic state from different structural groups. The ab initio calculated thermal functions allow enhancements to the available atomization energies and improve the agreement between the calculated and experimental heat content.
Effect of the Chirality of Residues and γ‐Turns on the Electronic Excitation Spectra, Excited‐State Reaction Paths and Conical Intersections of Capped Phenylalanine–Alanine Dipeptides
Authors: Shemesh Dorit , Domcke Wolfgang
Published: April 2011

The capped dipeptides Ac‐L‐Phe‐Xxx‐NH2, Xxx=L‐Ala, D‐Ala, Aib, where Aib (aminoisobutyric acid) is a non‐chiral amino acid, have been investigated by means of UV/IR double‐resonance spectroscopy in supersonic jets and density functional theory calculations by Gloaguen et al. [Phys. Chem. Chem. Phys. 2007, 9, 4491]. The UV and IR spectra of five different species were observed and their structures assigned by comparison with calculated vibrational frequencies in the NH‐stretching region. The peptides with two chiral residues can form homochiral or heterochiral species. In addition, γ‐turns exist as two helical forms (γD, γL) of opposite handedness. Herein, we explore the excited‐state potential‐energy surfaces of these dipeptides with ab initio calculations. Vertical and adiabatic excitation energies, excited‐state reaction paths and conical intersections are characterized with the ADC(2) propagator method. It is shown that electron/proton transfer along the hydrogen bond of the γ‐turn gives rise to efficient radiationless deactivation of the 1ππ* state of the chromophore via several conical intersections. While the homo/hetero chirality of the residues appears to have a negligible effect on the photophysical dynamics, we found evidence that the γL conformers may have shorter excited‐state lifetimes (and thus higher photostability) than the γD conformers.
Granulomatous interstitial nephritis in a patient with Crohn's disease
Authors: Hall Amanda K. , Kohan Donald E. , Lowichik Amy , Sikora Magdalena B.
Published: April 2011

Granulomatous interstitial nephritis (GIN) is an uncommon disorder, previously documented in the literature in asso‐ciation with sarcoidosis, multiple medications, and infection. The coexistence of GIN and Crohn's disease has rarely been reported, and its true incidence is unknown. We describe a young female with Crohn's disease who was found to have an elevated serum creatinine with a normal urinalysis and autoimmune work‐up. Kidney biopsy revealed granulomatous interstitial nephritis. She was treated with corticosteroids, cyclophosphamide, and mycophenolate mofetil. Her kidney function remains stable 2 years after diagnosis. This case report highlights the diagnosis and explores a novel treatment regimen.
Expression of metanephric nephron‐patterning genes in differentiating mesonephric tubules
Authors: Georgas K.M. , Chiu H.S. , Lesieur E. , Rumballe B.A. , Little Melissa H.
Published: April 2011

The metanephros is the functional organ in adult amniotes while the mesonephros degenerates. However, parallel tubulogenetic events are thought to exist between mesonephros and metanephros. Mesonephric tubules are retained in males and differentiate into efferent ducts of the male reproductive tract. By examining the murine mesonephric expression of markers of distinct stages and regions of metanephric nephrons during tubule formation and patterning, we provide further evidence to support this common morphogenetic mechanism. Renal vesicle, early proximal and distal tubule, loop of Henle, and renal corpuscle genes were expressed by mesonephric tubules. Vip, Slc6a20b, and Slc18a1 were male‐specific. In contrast, mining of the GUDMAP database identified candidate late mesonephros‐specific genes, 10 of which were restricted to the male. Among the male‐specific genes are candidates for regulating ion/fluid balance within the efferent ducts, thereby regulating sperm maturation and genes marking tubule‐associated neurons potentially critical for normal male reproductive tract function. Developmental Dynamics 240:1600–1612, 2011. © 2011 Wiley‐Liss, Inc.
New doxycycline‐inducible transgenic lines in Xenopus
Authors: Rankin Scott A. , Zorn Aaron M. , Buchholz Daniel R.
Published: April 2011

We have characterized two new transgenic Xenopus lines enabling transgene expression using the Tet‐On inducible system. An inducer line expresses the doxycycline‐ (Dox‐) activated transcription factor rtTA under control of the ubiquitous promoter CMV. A responder line enables Dox‐inducible expression of a dominant positive thyroid hormone receptor via a tetracycline responsive transgenic promoter (TRE). Dox‐induced expression of transgenic GFP mRNA was detectable after 3 hr and increased up to 10‐ to 50‐fold by 2 days depending on dose of Dox. Induced GFP mRNA expression returned to uninduced levels within 3 days upon Dox removal. Treatment of rtTA inducer and TRE responder double transgenic animals with Dox caused acceleration of metamorphic changes in thyroid hormone‐response gene expression and morphology. These transgenic lines will be made available through the new Xenopus Stock Center and will serve as valuable tools for genetic analysis of development and metamorphosis. Developmental Dynamics 240:1467–1474, 2011. © 2011 Wiley‐Liss, Inc.
C4‐Symmetric Alkoxyresorcin[4]arene Triflates: The Use of Palladium‐Catalyzed Reactions in the Synthesis of Axially Chiral Derivatives with Amino‐ and/or Alkoxy‐Substituents
Authors: Page Philip C. Bulman , Bygrave Terence R. , Chan Yohan , Heaney Harry , McKee Vickie
Published: April 2011

The conversion of axially chiral tetraalkoxyresorcin[4]arenes (cyclochiral resorcinarenes) into the related tetrakis(triflates) in high yields is described; this provides an efficient source of chiral materials for use in palladium‐catalyzed transformations, including the reductive removal of triflate groups and the synthesis of compounds that are formally derived from 3‐aminophenol, providing axially chiral derivatives that are nitrogen‐substituted on the upper rim.
Gold Nanoparticles and Hydrophobic Ionic Liquid Applied on the Development of a Voltammetric Biosensor for Polyphenol Determination
Authors: Zapp Eduardo , Brondani Daniela , Vieira Iolanda Cruz , Dupont Jairton , Scheeren Carla Weber
Published: April 2011

A novel biosensor based on gold nanoparticles dispersed in ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (Au‐BMI.PF6) and polyphenol oxidase (PPO) from garlic (Allium sativum L.) immobilized in clay was developed for determination of polyphenol by square‐wave voltammetry. Under optimized conditions, the analytical curve showed a linear range for esculetin concentrations from 0.40 to 9.86 µM (R=0.9997), with a limit of detection (LOD) of 0.11 µM. This biosensor demonstrated good repeatability and reproducibility, with relative standard deviations of 3.5 % and 4.6 %, respectively. The method was successfully applied to the determination of esculetin content in black tea samples.
Computer models for estimating the breakdown voltage of air in uniform and non‐uniform fields at 30 kHz
Authors: Rodriguez Doeg , Gorur Ravi S. , Hansen Peder
Published: April 2011

This paper reports on the development of models to estimate the breakdown voltage of air in uniform and non‐uniform gap configurations for the very low frequency (VLF) and low‐frequency (LF) bands. The breakdown voltage of air at VLF/LF is considerably lower and has a larger dependency on ambient humidity than at 60 Hz. Both characteristics have been explained by increased space charge formation at the higher frequencies. The models are shown to be useful for predicting breakdown voltages at VLF/LF for uniform field gap spacings up to 125 mm and non‐uniform field gap spacings up to 4 m. Copyright © 2011 John Wiley & Sons, Ltd.
ErbB signaling has a role in radial sorting independent of Schwann cell number
Authors: Raphael Alya R. , Lyons David A. , Talbot William S.
Published: April 2011

In the peripheral nervous system, Schwann cells make myelin, a specialized sheath that is essential for rapid axonal conduction of action potentials. Immature Schwann cells initially interact with many axons, but, through a process termed radial sorting, eventually interact with one segment of a single axon as promyelinating Schwann cells. Previous studies have identified genes that are required for Schwann cell process extension and proliferation during radial sorting. Previous analyses also show that ErbB signaling is required for Schwann cell proliferation, myelination, radial sorting, and the proper formation of unmyelinated Remak bundles. Because ErbB signaling and Schwann cell proliferation are both required during radial sorting, we sought to determine if the primary function of ErbB signaling in this process is to regulate Schwann cell proliferation or if ErbB signaling also controls other aspects of radial sorting. To address this question, we applied small molecule inhibitors in vivo in zebrafish to independently block ErbB signaling and proliferation. Ultrastructural analysis of treated animals revealed that both ErbB signaling and Schwann cell proliferation are required for radial sorting in vivo. ErbB signaling, however, is required for Schwann cell process extension, while Schwann cell proliferation is not. These results provide in vivo evidence that ErbB signaling plays a direct role in process extension during radial sorting, in addition to its role in regulating Schwann cell proliferation. © 2011 Wiley‐Liss, Inc
Nitrophorins: Nitrite disproportionation reaction and other novel functionalities of insect heme‐based nitric oxide transport proteins
Authors: Knipp Markus , He Chunmao
Published: April 2011

Nitrophorins (NPs) comprise a unique class of heme proteins used by the blood‐sucking insect Rhodnius prolixus to deliver the signaling gas molecule NO into the blood vessel of a host during feeding. Upon NO release, histamine can be scavenged by coordination to the heme iron. Although the protein is of similar size as the mammalian globin monomers and shares the same cofactor and proximal histidine coordination, nitrophorin structure, in contrast, is almost entirely composed of a β‐barrel. Comparison of the NO and histamine association constants with the concentrations of both compounds invivo raises concerns about the very simple ligand release model in case of at least some of the NPs. Therefore, novel functionalities of the NPs were sought. As a result, catalysis of the nitrite disproportionation reaction was found, which leads to the formation of NO with nitrite as the sole substrate. This is the first example of a ferriheme protein that can perform this reaction. Furthermore, although NPs stabilize the ferriheme state, a peroxidase reactivity of the cofactor involving the higher oxidation state iron (Compound I/II) was studied with the potential to catalyze the oxidation of histamine and norepinephrine. In contrast to many other heme proteins including the globins, the ferroheme state was found to be extremely sensitive to O2, which is a consequence of the much lower reduction potential of the NPs, so that the 1‐electron reduction of O2 to O becomes a thermodynamically favored process. Altogether, the detailed study of the NPs gives insight into the structure‐function relationships required for the targeted delivery of diatomic gas molecules in biology. Moreover, the comparison of the structure‐function relationships of the NPs (NO transporters) with those of the globins (O2 transporters) will help to elucidate the architectural requirement for the respective tasks. © 2011 IUBMB IUBMB Life, 63(5): 304–312, 2011
Recombinant functional multidomain hemoglobin from the gastropod Biomphalaria glabrata
Authors: Moeller Vanessa , Dürr Ralf , Sarraf‐Zadeh Ladan , Keller Sabrina , Heinz Stefanie , Hellmann Nadja , Moeller Arne , Lieb Bernhard , Markl Jürgen
Published: April 2011

The extracellular hemoglobin multimer of the planorbid snail Biomphalaria glabrata, intermediate host of the human parasite Schistosoma mansoni, is presumed to be a 1.44 MDa complex of six 240 kDa polypeptide subunits, arranged as three disulfide‐bridged dimers. The complete amino acid sequence of two subunit types (BgHb1 and BgHb2), and the partial sequence of a third type (BgHb3) are known. Each subunit encompasses 13 paralogus heme domains, and N‐terminally a smaller plug domain responsible for subunit dimerization. We report here the recombinant expression of different functional fragments of BgHb2 in Escherichia coli, and of the complete functional subunits BgHb1 and BgHb2 in insect cells; BgHb1 was also expressed as disulfide‐bridged dimer (480 kDa). Oxygen‐binding measurements of the recombinant products show a P50 of about 7 mmHg and the absence of a significant cooperativity or Bohr effect. The covalently linked dimer of BgHb1, but not the monomer, is capable to form aggregates closely resembling native BgHb molecules in the electron microscope. © 2011 IUBMB IUBMB Life, 63(5): 323–328, 2011
1,3‐Dipolar cycloaddition of unstabilized N‐methyl azomethine ylide to nitrobenzene annelated with azoles
Authors: Starosotnikov Alexey M. , Bastrakov Maxim A. , Pechenkin Sergey Yu. , Leontieva Margarita A. , Kachala Vadim V. , Shevelev Svyatoslav A.
Published: April 2011

The 1,3‐dipolar cycloaddition of unstabilized N‐methyl azomethine ylide to mononitro benzazoles was studied. Depending on the nature of substituents and annelated azoles, the reaction affords previously unknown isoindole fused heterocyclic systems. The reactivity of the cycloadducts was examined. J. Heterocyclic Chem., (2011).
A simple procedure for the preparation of 2‐cyano‐4‐chloropyridines
Authors: Veerareddy Arava , Surendrareddy Gogireddy , Dubey P. K.
Published: April 2011

4‐Nitro‐pyridine‐N‐oxides are reacted with ethylchloroformate and trimethylsilyl cyanide to give 4‐chloro‐2‐cyanopyridine. J. Heterocyclic Chem., (2011).
Chromatographic evaluation using basic solutes of the silanol activity of stationary phases based on poly(methyloctylsiloxane) immobilized onto silica
Authors: Borges Endler M. , Collins Carol H.
Published: April 2011

The chromatographic behaviors of some basic solutes were evaluated on stationary phases based on poly(methyloctylsiloxane) immobilized onto silica (PMOS‐SiO2). The test solutes present both hydrophobic and hydrophilic properties. Evaluations of the pH effect used 80:20 v/v methanol/buffered mobile phase over the pH range of 5–11.5 with inorganic buffers such as borate, carbonate and phosphate and with organic buffers such as citrate, tricine and triethylamine. Evaluations in acidic mobile phases used 50:50 v/v and 30:70 v/v methanol/buffer (pH 2.5; 20 mmol/L) mobile phases. The buffer concentration effect used 65:35 v/v methanol/phosphate (pH 7; 20 and 100 mmol/L) mobile phases. The results are compared with those obtained with two chemically bonded stationary phases. The immobilized phases show greater contributions from an ion‐exchange mechanism than do the commercial phases. The results indicate that the silanol activity of PMOS‐SiO2 stationary phases can be adequately evaluated by using appropriate basic probes and mobile phases having different pH, using different buffers.
Determination of azoles in sewage sludge from Spanish wastewater treatment plants by liquid chromatography‐tandem mass spectrometry
Authors: García‐Valcárcel Ana I. , Tadeo José L.
Published: April 2011

A simple and rapid analytical method for the determination of 16 azoles in sewage sludge has been developed and validated. The method was based on ultrasound‐assisted extraction followed by dispersive solid‐phase extraction cleanup and liquid chromatography‐electrospray tandem mass spectrometric detection. The azoles were selected by their intensive usage as biocides (tebuconazole, propiconazole, cyproconazole and thiabendazole), antimycotic pharmaceuticals (ketoconazole, econazole, fluconazole and clotrimazole) or fungicides in agriculture (difenoconazole, flusilazole, hexaconazole, prochloraz, bromuconazole, epoxiconazole and triticonazole). The recoveries of these compounds through the method were between 71.9 and 115.8%, with relative standard deviations lower than 20%. Detection limits were in the range of 0.5–5.0 ng/g. The developed method was applied to the analysis of azoles in sewage sludge samples collected from 19 Spanish wastewater treatment plants. Although azoles used as biocides or agriculture fungicides were present in a few sludge samples, the pharmaceuticals ketoconazole, econazole and clotrimazole were present in all of the analyzed sludge samples, being ketoconazole the one found at the highest level, representing the 68.6% of the total azole content found in the 19 sludge samples studied.
Numerical model for the investigation of countercurrent chromatography
Authors: Yang Zhao‐Hui , Wang Bing , Liang Yi‐Zeng , Xie Gui‐Xiang , Ren Xiao‐Mei
Published: April 2011

A numerical model is developed to describe the separation process of countercurrent chromatography (CCC) in this work. The theory of countercurrent extraction table (TCCET) is first proposed to calculate concentration distributions of chemical components in the CCC, which is essential for a numerical model to describe the dynamic equilibrium of mass transfer. According to the theory of countercurrent extraction, the concentration in chromatography obeys binomial distribution, while the outflow from the n‐th stage is a negative binomial distribution. As a result of the central limit theorem, they will obey normal distribution for sufficiently large n. Row‐stage ratio (RRS) is then defined to determine the K value or retention time because it has a linear relationship to K value and retention time. The stage for a certain K value can be subsequently obtained with a very simple form, $n_k=1/(2\pi q_kX^2_{k,\ \rm {max}})$, which can be calculated from the peak height obtained from experiments. Finally, the actual stage for a separation chromatogram can be acquired with using this simple expression. The agreement between theoretic and experimental results is quite satisfactory in the normal‐phase and reversed‐phase elution mode.
Quantitative plasma analysis using automated online solid‐phase extraction with column switching LC‐MS/MS for characterising cytochrome P450 2D6 and 2C19 metabolism
Authors: Dodgen Tyren M. , Cromarty A. Duncan , Pepper Michael S.
Published: April 2011

In this study an easy and efficient assay for simultaneous quantitation of plasma concentrations of probe drugs and their metabolically relevant metabolites for the phenotypic analysis of cytochrome P450 2D6 and 2C19, respectively, has been established. This sensitive method makes use of a simple initial sample preparation, followed by a 6‐min automated analysis that includes online solid‐phase extraction (SPE), column switching and tandem mass spectrometry. Validation over a concentration range of 1.3–2500 ng/mL for dextromethorphan, omeprazole, dextrorphan and 5′‐hydroxyomeprazole was performed with LOQ between 215 and 1145 pg/mL. Intra‐ and inter‐day precision and accuracy over the calibration ranges were within 15% for all analytes with recoveries of greater than 85%. Advantages are small sample volumes required, a robust, sensitive and highly selective method suitable for pre‐prescription metabolic screening. This method could compliment or offer an alternative to DNA mutation analysis for determining appropriate dosage regimens for personalised medicine.