bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractGranulomatous 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

AbstractThe 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

AbstractWe 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

AbstractThe 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

AbstractA 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

SUMMARYThis 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

AbstractIn 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

AbstractNitrophorins (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

AbstractThe 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

AbstractThe 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

Abstract4‐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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractIn 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.
Studies on the performance of different coiled column configurations for compact type‐I countercurrent chromatography
Authors: Yang Yi , Gu Dongyu , Aisa Haji Akber , Ito Yoichiro 
Published: April 2011

AbstractThree types of novel coiled column configurations, i.e. a triangular coiled column and elliptical coiled columns I and II, were designed for type‐I countercurrent chromatography and their performances were evaluated with two solvent systems each with suitable test samples. Three dinitrophenyl (DNP) amino acids (DNP‐DL‐glu, DNP‐β‐ala and DNP‐L‐ala) were separated with a moderately hydrophobic two‐phase solvent system composed of hexane–ethyl acetate–metanol–0.1 M hydrochloric acid (1:1:1:1, v/v), while two dipeptides (tryptophyl‐tyrosine and valyl‐tyrosine) were separated with a polar solvent system composed of 1‐butanol–acetic acid–water (4.75:0.25:5, v/v). The overall results indicated that the performance of compact type‐I countercurrent chromatography was improved by elliptical coiled column I which was mounted with its maximum coil diameter perpendicular to the surface of the column holder. Hydrodynamic effects involved in these separations were discussed.
Synthesis and application of a novel molecularly imprinted polymer‐coated stir bar for microextraction of triazole fungicides in soil
Authors: Hu Yuling , Li Jiawei , Li Gongke 
Published: April 2011

AbstractThe preparation, characteristics and application of a sorptive stir bar coated with molecularly imprinted polymer (MIP) using triadimefon as the template molecule are described here. Raw glass capillary was coated with MIP through chemical bonding. The synthesis method was effective and reproducible with the batch‐to‐batch RSD within 7.8%. Scanning electron micrographs of the stir bar revealed a highly porous coating with average thickness of 15 μm. The synthesized stir bar was proved to be highly stable in most of the solvent for use. Extraction performance showed the fabricated stir bar has excellent molecular recognition abilities for triadimefon and the structure‐related compounds, such as triadimenol, diniconazole, flutriafol, hexaconazole, tebuconazole, paclobutrazol and uniconazole, and thus can be applied for simultaneous determination of these triazole fungicides from complex samples by coupling with high‐performance liquid chromatography. The variables that influence extraction were optimized with 10.0 μg/L standard solutions of triazole fungicides, and the analytical method was established for the determination of triazole fungicides in soil. The detection limits were in the range of 0.14–0.34 μg/L, and the recoveries were from 86.7 to 114.6% for spiked soil sample.
EPR Spectroscopy Provides a Molecular View on Thermoresponsive Dendronized Polymers Below the Critical Temperature
Authors: Junk Matthias J. N. , Li Wen , Schlüter A. Dieter , Wegner Gerhard , Spiess Hans W. , Zhang Afang , Hinderberger Dariush 
Published: April 2011

AbstractThe nanoscopic structure of thermoresponsive dendronized polymers below the critical aggregation temperature (TC) is revealed by CW EPR spectroscopy. At temperatures far below TC, the water‐swollen polymers start to dehydrate and hydrophobic cavities are formed. Two different dehydration processes can be discerned, the more effective of which is observed within 4 K below TC. The dehydration predominantly takes place at the peripheral dendritic shell, rendering it increasingly hydrophobic and eventually triggering an interchain aggregation and the formation of mesoglobules at the critical temperature. While the polymer aggregation is mainly dependent on the dendron periphery, the efficiency of the dehydration below TC is closely related to the hydrophobicity of the dendritic core. magnified image
The Influence of Blend Morphology (Co‐Continuous or Sub‐Micrometer Droplets Dispersions) on the Nucleation and Crystallization Kinetics of Double Crystalline Polyethylene/Polyamide Blends Prepared by Reactive Extrusion
Authors: Córdova Miguel E. , Lorenzo Arnaldo T. , Müller Alejandro J. , Gani Léa , Tencé‐Girault Sylvie , Leibler Ludwik 
Published: April 2011

AbstractReactive blending of functionalized polyethylenes (PE) and polyamides (PA) is performed by carefully choosing extrusion conditions and polymeric materials in order to obtain two types of stable morphologies. The first blend type yields a co‐continuous morphology and the second type a dispersion of sub‐micron droplets of the PA phase in a PE matrix. The crystallization kinetics of the PA change from a sigmoidal classical type (for the co‐continuous blend) to first‐order kinetics in the case of the sub‐micron PA droplets. The results demonstrate an intimate relationship between blend morphology and nucleation and crystallization kinetics of the blend components. magnified image