bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological, electrokinetic, and morphological characterization of alginate–bentonite biocomposites
Authors: Benli B. , Boylu F. , Can M. F. , Karakaş F. , Çinku K. , Ersever G.
Published: April 2011

We prepared biocomposite gel dispersions involving sodium alginate (Na‐Alg) and calcium bentonite (Ca‐B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel–Bulkley model. The ζ‐potential results were examined in the light of different characterization methods (X‐ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate–bentonite composite gel, known as the egg‐box model, is proposed. The presence of Ca ions in the Ca‐B partially crosslinked Na‐Alg may be regarded as an excellent example of a self‐assembling process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
Effect of diblock copolymer surfactant on the microstructure and EM properties of CNT nanocomposites
Authors: Travaglia P. , Nanni F. , Hojati‐Talemi P. , Simon G. P
Published: April 2011

Carbon nanotubes (CNTs) were chosen due to their excellent electrical properties. As delivered, CNTs are highly agglomerated, and to exploit their high aspect ratio is then necessary to disagglomerate them as much as possible. A diblock copolymer surfactant was used to aid CNT disagglomeration. Disagglomeration in solvent was assessed by TEM, whereas composite microstructure was observed by scanning electron microscopy. X‐band waveguide measurements were carried out to assess complex permittivity and absorbing performance. On a same weight percent of filler basis, samples produced with the aid of surfactant show higher real permittivity than samples produced without. An equivalent circuit analogy is suggested to explain the results and relates composite microstructure with macroscopic permittivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Incorporating MATLAB® modules in reinforced concrete design instruction
Authors: Urgessa Girum S.
Published: April 2011

The Civil Engineering Department at George Mason University offered a structural design course that combines reinforced concrete and structural steel prior to Fall 2009. With recent re‐designing of course offerings, the course is split into two separate design courses: reinforced concrete design and structural steel design. The new teaching format allows instructors to incorporate additional instruction methods in design classes that supplement traditional teaching. This article discusses the development and implementation of computational MATLAB design modules that are incorporated in the first and second offering of the new reinforced concrete design course. The main objective of the modules is to improve students' computational skills for solving routine design calculations without compromising the theoretical understanding of the subject matter. The graphical user interface driven modules are designed to include program descriptions, user‐friendly field inputs, and a detailed results summary with step‐by‐step design verifications. A classroom survey was conducted on the use of the design modules and results of the survey are presented. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:209–215, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.20547
Substituent Size Effects in Lewis Base Induced Reductions in Organolanthanide Chemistry
Authors: Bojer Daniel , Neumann Beate , Stammler Hans‐Georg , Mitzel Norbert W.
Published: April 2011

The reaction of the tripodal 1,3,5‐trialkyl‐1,3,5‐triazacyclohexanes (L=cyclo‐[N(R)CH2]3, R=Et, iPr, tBu), with [Sm(AlMe4)3] resulted in the formation of divalent samarium complexes of the constitution [{LnSm(AlMe4)2}m] (n, m=1,2) under ethane extrusion. These compounds were characterised by single‐crystal X‐ray diffraction and elemental analyses. Simultaneous occurrence of Lewis base induced reduction and CH‐activation reactions is observed. The ratio of products depends on the bulkiness of the N‐alkyl substituent R. The reaction of [Sm(AlMe4)3] with 1,3,5‐triisopropyl‐1,3,5‐triazacyclohexane (TiPTAC) in benzene afforded the inversion‐symmetric dimer [{(TiPTAC)(η3‐AlMe4)Sm}2(μ2‐AlMe4)2], whereas in toluene the pseudo‐samarocene [(TiPTAC)2Sm(η1‐AlMe4)2] was obtained. The trisaluminate [(TiPTAC)Sm{(μ2‐Me)(Me2Al)}2(μ3‐CH2)2AlMe2)] was found to be the CH‐activation product. In the case of the particular bulky 1,3,5‐tri‐tert‐butyl‐1,3,5‐triazacyclohexane (TtBuTAC), the reaction led to the formation of the dimeric [{(TtBuTAC)(η3‐AlMe4)Sm}2(μ2‐AlMe4)2] even in toluene in comparably high yields. The decrease of the steric demand to ethyl groups in 1,3,5‐triethyl‐1,3,5‐triazacyclohexane (TETAC) afforded the samarocene‐like [(TETAC)2Sm(η1‐AlMe4)2] in lower yields. The resulting divalent samarium compounds are found to be stable with respect to reagents like dinitrogen, conjugated olefins and polycyclic aromatic systems.
Gold‐ and Copper‐Catalyzed Cycloisomerizations towards the Synthesis of Thujopsanone‐Like Compounds
Authors: Fehr Charles , Vuagnoux Magali , Buzas Andrea , Arpagaus Jeremy , Sommer Horst
Published: April 2011

In the search for a new access to thujopsanone related compounds by cycloisomerization reactions of unsaturated propargylic alcohols and acetates, we found several interesting reaction types and demonstrated the complementarity of Au, Pt, and Cu catalysts. Thus, 6‐en‐1‐yn‐3‐ol 10 a underwent clean cyclization/ether formation to 16, in particular using Au catalysts (76–98 %) or a newly prepared CuI‐ triflimidate‐catalyst (94 %). The corresponding acetate 11 a underwent either the cycloisomerization with concomitant [1,2]‐acyl shift (to 12: 78 % using AuCl3) or an unprecedented rearrangement‐cycloaddition leading to 20 (43 % using [(tBuXPhos)AuNTf2]), a strained fused tricyclic ring system containing a [2.2.0] bicyclic subunit.
Design and Characterization of Endosomal‐pH‐Responsive Coiled Coils for Constructing an Artificial Membrane Fusion System
Authors: Kashiwada Ayumi , Tsuboi Mana , Takamura Naohide , Brandenburg Enrico , Matsuda Kiyomi , Koksch Beate
Published: April 2011

A weakly acidic pH‐responsive polypeptide is believed to have the potential for an endosome escape function in a polypeptide‐triggered delivery system. For constructing a membrane fusion device with pH‐responsiveness, we have designed novel polypeptides that are capable of forming an α2 coiled coil structure. Circular dichroism spectroscopy reveals that a polypeptide, AP‐LZ(EH5), with a Glu and His salt‐bridge pair at a staggered position in the hydrophobic core forms a stable coiled coil structure only at endosomal pH values (pH 5.0 to 5.5). On the basis of their endosomal‐pH responsiveness, a boronic acid/polypeptide conjugate (BA‐H5‐St) was also designed as a pilot molecule to construct a pH‐responsive, one‐way membrane fusion system with a sugarlike compound (phosphatidylinositol: PI)‐containing liposome as a target. Membrane fusion behavior was characterized by lipid‐mixing, inner‐leaflet lipid‐mixing, and contents‐mixing assays. These studies reveal that membrane fusion is clearly observed when the pH of the experimental system is changed from 7.4 (physiological condition) to 5.0 (endosomal condition).
Cycloheptatrienyl Zirconium Sandwich Complexes with Lewis Basic Phospholyl Ligands (Phosphatrozircenes): Synthesis, Structure, Bonding and Coordination Chemistry
Authors: Glöckner Andreas , Bannenberg Thomas , Büschel Susanne , Daniliuc Constantin G. , Jones Peter G. , Tamm Matthias
Published: April 2011

The transmetalation reaction between [(η7‐C7H7)ZrCl(tmeda)] (1; tmeda=N,N,N′,N′‐tetramethylethylenediamine) and various phospholide anions leads to a new class of mixed sandwich complexes: [(η7‐C7H7)Zr(η5‐C4PMe4)] (2), [(η7‐C7H7)Zr(η5‐C4PH2Me2)] (3) and [(η7‐C7H7)Zr(η5‐C4PPhHMe2)] (4). The presence of Lewis basic phosphorus atoms and Lewis acidic zirconium atoms allows ambiphilic behaviour to be observed, and X‐ray diffraction analysis reveals dimeric arrangements for 2 and 3 with long intermolecular ZrP bonds, whereas 4 remains monomeric in the solid state. DFT calculations indicate that the metal–phosphorus interaction is weak, and accordingly, complexes 2–4 act as monodentate ligands upon reaction with [W(CO)5(thf)]. The resulting complexes [W(CO)5(L)] 5–7 (L=2–4) were studied by IR spectroscopy and compared with the [W(CO)5] complex 9, containing the phosphane‐functionalised trozircene [(η7‐C7H7)Zr(η5‐C5H4PPh2)] (8). They all show a close resemblance to simple phosphanes, such as PMe3, although molecular orbital analysis of 2 reveals that the free electron pair in the phosphatrozircenes is not the HOMO. Four equivalents of 2 can replace 1,4‐cyclooctadiene (COD) in [Ni(cod)2] to form the homoleptic, distorted tetrahedral complex [Ni{2}4] (10).
Generating optimal CUDA sparse matrix–vector product implementations for evolving GPU hardware
Authors: El Zein Ahmed H. , Rendell Alistair P.
Published: April 2011

The CUDA model for graphics processing units (GPUs) presents the programmer with a plethora of different programming options. These includes different memory types, different memory access methods and different data types. Identifying which options to use and when is a non‐trivial exercise. This paper explores the effect of these different options on the performance of a routine that evaluates sparse matrix–vector products (SpMV) across three different generations of NVIDIA GPU hardware. A process for analysing performance and selecting the subset of implementations that perform best is proposed. The potential for mapping sparse matrix attributes to optimal CUDA SpMV implementations is discussed. Copyright © 2011 John Wiley & Sons, Ltd.
Isolation and live imaging of enteric progenitors based on Sox10‐Histone2BVenus transgene expression
Authors: Corpening Jennifer C. , Deal Karen K. , Cantrell V. Ashley , Skelton Stephanie B. , Buehler Dennis P. , Southard‐Smith E. Michelle
Published: April 2011

To facilitate dynamic imaging of neural crest (NC) lineages and discrimination of individual cells in the enteric nervous system (ENS) where close juxtaposition often complicates viewing, we generated a mouse BAC transgenic line that drives a Histone2BVenus (H2BVenus) reporter from Sox10 regulatory regions. This strategy does not alter the endogenous Sox10 locus and thus facilitates analysis of normal NC development. Our Sox10‐H2BVenus BAC transgene exhibits temporal, spatial, and cell‐type specific expression that reflects endogenous Sox10 patterns. Individual cells exhibiting nuclear‐localized fluorescence of the H2BVenus reporter are readily visualized in both fixed and living tissue and are amenable to isolation by fluorescence activated cell sorting (FACS). FACS‐isolated H2BVenus+ enteric NC‐derived progenitors (ENPs) exhibit multipotency, readily form neurospheres, self‐renew in vitro and express a variety of stem cell genes. Dynamic live imaging as H2BVenus+ ENPs migrate down the fetal gut reveals cell fragmentation suggesting that apoptosis occurs at a low frequency during normal development of the ENS. Confocal imaging both during population of the fetal intestine and in postnatal gut muscle strips revealed differential expression between individual cells consistent with down‐regulation of the transgene as progression towards non‐glial fates occurs. The expression of the Sox10‐H2BVenus transgene in multiple regions of the peripheral nervous system will facilitate future studies of NC lineage segregation as this tool is expressed in early NC progenitors and maintained in enteric glia. genesis 49:599–618, 2011. © 2011 Wiley‐Liss, Inc.
An in vivo map of bone morphogenetic protein 2 post‐transcriptional repression in the heart
Authors: Kruithof Boudewijn P. T. , Xu Junwang , Fritz David T. , Cabral Carolina S. , Gaussin Vinciane , Rogers Melissa B.
Published: April 2011

The Bmp2 3′untranslated region (UTR) sequence bears a sequence conserved between mammals and fishes that can post‐transcriptionally activate or repress protein synthesis. We developed a map of embryonic cells in the mouse where this potent Bmp2 regulatory sequence functions by using a lacZ reporter transgene with a 3′UTR bearing two loxP sites flanking the ultra‐conserved sequence. Cre‐recombinase‐mediated deletion of the ultra‐conserved sequence caused strong ectopic expression in proepicardium, epicardium and epicardium‐derived cells (EPDC) and in tissues with known epicardial contributions (coronary vessels and valves). Transient transfections of reporters in the epicardial/mesothelial cell (EMC) line confirmed this repression. Ectopic expression of the recombined transgene also occurred in the aorta, outlet septum, posterior cardiac plexus, cardiac and extracardiac nerves and neural ganglia. Bmp2 is dynamically regulated in the developing heart. 3′UTR‐mediated mechanisms that restrain BMP2 synthesis may be relevant to congenital heart and vasculature malformations and to adult diseases involving aberrant BMP2 synthesis. genesis 49:841–850, 2011. © 2011 Wiley‐Periodicals, Inc.
A mouse reporter line to conditionally mark nuclei and cell membranes for in vivo live‐imaging
Authors: Shioi Go , Kiyonari Hiroshi , Abe Takaya , Nakao Kazuki , Fujimori Toshihiko , Jang Chuan‐Wei , Huang Cheng‐Chiu , Akiyama Haruhiko , Behringer Richard R. , Aizawa Shinichi
Published: April 2011

Live‐imaging is an essential tool to visualize live cells and monitor their behaviors during development. This technology demands a variety of mouse reporter lines, each uniquely expressing a fluorescent protein. Here, we developed an R26R‐RG reporter mouse line that conditionally and simultaneously expresses mCherry and EGFP in nuclei and plasma membranes, respectively, from the Rosa26 locus. The intensity and resolution of mCherry nuclear localization and EGFP membrane localization were demonstrated to be sufficient for live‐imaging with embryos that express RG (mCherry and EGFP) ubiquitously and specifically in fetal Sertoli cells. The conditional R26R‐RG reporter mouse line should be a useful tool for labeling nuclei and membranes simultaneously in distinct cell populations. genesis 49:570–578, 2011. © 2011 Wiley‐Liss, Inc.
Theoretical Study of Phosphorescence of Iridium Complexes with Fluorine‐Substituted Phenylpyridine Ligands
Authors: Li Xin , Minaev Boris , Ågren Hans , Tian He
Published: April 2011

Time‐dependent density functional theory (TD‐DFT) with linear and quadratic response approaches was applied to calculate absorption and luminescence spectra of a number of facial and meridional iridium complexes with fluorine‐substituted phenylpyridine (Fnppy) ligands. The absorption and luminescence spectra were studied to simulate the photophysical properties of electroluminescent devices fabricated on the basis of these iridium complexes used to increase spin–orbit coupling and the triplet‐state blue emission of the corresponding organic light‐emitting diodes (OLEDs). By using the quadratic response technique, the phosphorescence radiative rate constant and lifetime of the studied iridium complexes were calculated through spin–orbit coupling perturbation and compared with the measured data in experiments. A satisfactory agreement between these data permits us to guide improvements in the design of phosphorescence‐based OLEDs by predicting the structure–property relationships through quantum chemical calculations.
Syntheses and Evaluation of Simplified Pretubulysin Analogues
Authors: Burkhart Jens L. , Müller Rolf , Kazmaier Uli
Published: April 2011

The syntheses of new tubulysin analogues are described, in which the central amino acid, tubuvaline, is replaced by the rather simple building blocks phenyltubuvaline and phenoxytubuvaline. These analogues can be obtained in only two to three steps from easily accessible starting materials. Although the new derivatives are less active than the tubulysins, their activities towards U‐2 OS tumor cells are still in the nanomolar range.
Enantioselective Total Synthesis of (+)‐Stachyflin: A Potential Anti‐Influenza A Virus Agent Isolated from a Microorganism
Authors: Sakurai Junji , Kikuchi Takuya , Takahashi Ohgi , Watanabe Kazuhiro , Katoh Tadashi
Published: April 2011

A novel and potent hemagglutinin inhibitor, (+)‐stachyflin, was efficiently synthesized in an enantioselective manner starting from the (+)‐5‐methyl‐Wieland–Miescher ketone. The synthetic method features a BF3·Et2O‐induced cascade epoxide‐opening/rearrangement/cyclization reaction tostereoselectively construct the requisite pentacyclic ring system in one step. In order to rationalize the mechanism of the cascade reaction, quantum chemical calculations of the possible intermediary carbocations and transition states in the model synthesis were carried out. An alternative approach to synthesize (+)‐stachyflin by employing a similar cascade reaction was also described.
Micellar electrokinetic chromatography profiles of human high‐density lipoprotein phospholipids
Authors: Chong Chin‐Pong , Lin Ting‐Yu , Chang Chia‐Liang , Yang Ying‐Ling , Tsai Ming‐Hua , Yu Yu‐Shan , Liu Mine‐Yine
Published: April 2011

A simple and fast micellar electrokinetic chromatography (MEKC) method was developed to investigate phospholipids isolated from human high‐density lipoproteins (HDL). To optimize the MEKC conditions, several factors including bile salt concentration and organic modifier concentration in the separation buffer as well as temperature have been examined. The optimal separation buffer chosen was a mixture of 50 mM bile salts, 30% v/v 1‐propanol and 10 mM sodium phosphate (pH 8.5). The applied voltage and temperature selected were 25 kV and 40°C, respectively. Meanwhile, high‐salt stacking has been performed for sample pre‐concentration to enhance peak sensitivity. Several factors including organic modifier concentration and salt concentration in the sample matrix as well as sample injection time have been optimized. The optimal sample buffer selected was a mixture of 100 mM NaCl and 20% 1‐propanol, and the optimal sample injection time selected was 32 s under a pressure of 0.5 psi. Several phospholipid standards including lysophosphatidyl choline, phosphatidyl choline (PC), sphingomyelin, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl serine and phosphatidic acid have been studied using the optimal MEKC method. The MEKC profile of the mixed phospholipid standards showed good separation and reproducibility. The linear ranges for PC and sphingomyelin were 0.025–1.2 and 0.025–2.0 mg/mL, respectively. The concentration limits of detection of PC and sphingomyelin were 0.0156 and 0.0199 mg/mL, respectively. Using phosphatidic acid as an internal standard, precision and accuracy have been measured for PC and sphingomyelin. The intraday and interday quantitative analysis showed good results. The new MEKC method has been used to characterize native, in vitro oxidized and glycated human HDL phospholipids within 16 min. At absorbance 200 nm, two similar peaks were observed for native and oxidized HDL phospholipids, but three peaks were observed for glycated HDL phospholipids. Interestingly, at absorbance 234 nm, distinctively different MEKC profiles were observed for the three HDL phospholipids.
Hydroxyethylcellulose‐graft‐poly(2‐(dimethylamino)ethyl methacrylate) as physically adsorbed coating for protein separation by CE
Authors: Cao Fuhu , Luo Zhaofeng , Zhou Dan , Zeng Rongju , Wang Yanmei
Published: April 2011

In this work, a novel graft copolymer, hydroxyethylcellulose‐graft‐poly(2‐(dimethylamino)ethyl methacrylate) (HEC‐g‐PDMAEMA), used as physical coatings of the bare fused‐silica capillaries, was synthesized by using ceric ammonium nitrate initiator in aqueous nitric acid solution. EOF measurement results showed that the synthesized HEC‐g‐PDMAEMA graft copolymer‐coated capillary in this paper could suppress EOF effectively compared to the bare fused‐silica capillary, and efficient separations of basic proteins were also achieved. The electrical charge of the coated capillary wall could be modulated by varying not only the pH of the running buffer, but also the grafting ratio of poly(2‐(dimethylamino)ethyl methacrylate) grafts, which makes possible the analysis of basic and acidic proteins in the same capillary. The effects of poly(2‐(dimethylamino)ethyl methacrylate) grafting ratio in HEC‐g‐PDMAEMA and buffer pH on the separation of basic proteins for capillary electrophoresis were investigated in detail. Furthermore, egg white proteins and milk powder samples were separated by the HEC‐g‐PDMAEMA‐coated capillary. The results demonstrated that the HEC‐g‐PDMAEMA copolymer coatings have great potential in the field of diagnosis and proteomics.
Hydrophobic labeling of amino acids: Transient trapping–capillary/microchip electrophoresis
Authors: Sueyoshi Kenji , Hashiba Kota , Kawai Takayuki , Kitagawa Fumihiko , Otsuka Koji
Published: April 2011

Transient trapping (tr‐trapping) was developed as one of the on‐line sample preconcentration techniques to improve a low concentration‐sensitivity in microchip electrophoresis (MCE), providing highly effective preconcentration and separation based on the trap‐and‐release mechanism. However, a poor performance to hydrophilic analytes limited the applicability of tr‐trapping. To overcome this drawback, tr‐trapping was combined with a sample labeling using a hydrophobic reagent in CE. Three commercially available fluorescent dyes, fluorescein isothiocyanate, succinimidyl esters of Alexa Fluor 488 and BODIPY FL‐X, were tested as derivatization reagents to increase the hydrophobicity of amino acids (AAs) that were undetectable due to no fluorescence/UV‐absorbance. As a result, it was confirmed that BODIPY labeling allowed various AAs to be analyzed in tr‐trapping–micellar electrokinetic chromatography (tr‐trapping–MEKC) by the increase in the hydrophobicity. In tr‐trapping–MEKC, both the improvement of the resolution and 106–125‐fold enhancements of the detectability of labeled AAs were achieved relative to the conventional capillary zone electrophoresis. The limit of detection of labeled phenylalanine was improved from 800 to 5 pM by applying tr‐trapping–MEKC. In tr‐trapping–microchip MEKC, furthermore, an 80–160‐fold enhancement of the peak intensity and a baseline separation was also achieved within 30 s. These results clearly demonstrate that the tr‐trapping technique with hydrophobic labeling will make CE/MCE more sensitive for various analytes.
Mass spectrometry detection as an innovative and advantageous tool in ligand exchange capillary electrophoresis
Authors: Giuffrida Alessandro , Contino Annalinda , Maccarrone Giuseppe , Messina Marianna , Cucinotta Vincenzo
Published: April 2011

The copper(II) complex of a modified cyclodextrin, namely 6‐mono‐deoxy‐6‐[4‐(2‐aminoethyl)imidazolyl]‐β‐CD (CDmh), previously synthesized and characterized in our laboratory and already used as chiral selector for ligand exchange capillary electrophoresis (LECE) with optical detection, is investigated here in LECE using electrospray‐mass spectrometry (ESI‐MS) as the detection device. The potential of this hyphenated method is compared with the results previously obtained with optical detection by studying the chiral resolution of tryptophan racemate. Chiral separation conditions compatible with LECE‐ESI‐MS could be achieved based on the figures of merit obtained by LECE‐UV. Interestingly, the values of LOD obtained by LECE‐ESI‐MS were significantly better than those obtained by LECE‐UV and thus, ESI‐MS detection seems to open new perspectives in chiral separations by LECE.
Free‐solution electrophoretic separations of DNA–drag‐tag conjugates on glass microchips with no polymer network and no loss of resolution at increased electric field strength
Authors: Albrecht Jennifer Coyne , Kerby Matthew B. , Niedringhaus Thomas P. , Lin Jennifer S. , Wang Xiaoxiao , Barron Annelise E.
Published: April 2011

Here, we demonstrate the potential for high‐resolution electrophoretic separations of ssDNA–protein conjugates in borosilicate glass microfluidic chips, with no sieving media and excellent repeatability. Using polynucleotides of two different lengths conjugated to moderately cationic protein polymer drag‐tags, we measured separation efficiency as a function of applied electric field. In excellent agreement with prior theoretical predictions of Slater et al., resolution is found to remain constant as applied field is increased up to 700 V/cm, the highest field we were able to apply. This remarkable result illustrates the fundamentally different physical limitations of free‐solution conjugate electrophoresis (FSCE)‐based DNA separations relative to matrix‐based DNA electrophoresis. ssDNA separations in “gels” have always shown rapidly declining resolution as the field strength is increased; this is especially true for ssDNA > 400 bases in length. FSCE's ability to decouple DNA peak resolution from applied electric field suggests the future possibility of ultra‐rapid FSCE sequencing on chips. We investigated sources of peak broadening for FSCE separations on borosilicate glass microchips, using six different protein polymer drag‐tags. For drag‐tags with four or more positive charges, electrostatic and adsorptive interactions with poly(N‐hydroxyethylacrylamide)‐coated microchannel walls led to appreciable band‐broadening, while much sharper peaks were seen for bioconjugates with nearly charge‐neutral protein drag‐tags.
Electrokinetic supercharging with a system‐induced terminator and an optimized capillary versus electrode configuration for parts‐per‐trillion detection of rare‐earth elements in CZE
Authors: Xu Zhongqi , Kawahito Kouji , Ye Xiaoxue , Timerbaev Andrei R. , Hirokawa Takeshi
Published: April 2011

A further improvement of electrokinetic supercharging (EKS) methodology has been proposed, with the objective to enhance the sensitivity of the conventional CZE‐UV method down to a single‐digit part per trillion (ppt) level. The advanced EKS procedure is based on a novel phenomenon displaying the formation of a zone with an increased concentration of the hydrogen ion, capable to perform the function of a terminator, behind the sample zone upon electrokinetic injection. In combination with a visualizing co‐ion of BGE, protonated 4‐methylbenzylamine, acting as the leading ion, such system‐induced terminator a effected the transient ITP state to efficiently concentrate cationic analytes prior to CZE. Furthermore, to amass more analyte ions within the effective electric field at the injection stage, a standard sample vial was replaced with an elongated vial that allowed the sample volume to be increased from 500 to 900 μL. Alongside, this replacement made the upright distance between the electrode and the capillary tips prolonged to 40.0 mm to achieve high‐efficiency electrokinetic injection. The computer simulation was used for profiling analyte concentration, pH, and field strength in order to delineate formation of the terminator during sample injection. The proposed preconcentration strategy afforded an enrichment factor of 80 000 and thereby the LODs of rare‐earth metal ions at the ppt level, e.g. 0.04 nM (6.7 ng/L) for erbium(III).
Optimization of separation of heavy metals by capillary electrophoresis with contactless conductivity detection
Authors: Lau Hiu Fung , Quek Ngee Mian , Law Wai Siang , Zhao Jian Hong , Hauser Peter C. , Li Sam Fong Yau
Published: April 2011

The separation of four toxic metal ions (Cr3+, Pb2+, Hg2+, Ni2+) was achieved by optimizing the composition of the histidine/tartaric acid background electrolyte. An on‐column preconcentration technique, viz. field amplified sample injection, was performed to improve the sensitivity. This method afforded an enhancement factor of up to 91 800 fold with the LODs ranging from 0.005 to 2.32 μg/L, which were well below the maximum contaminant levels set by the United States Environmental Protection Agency. The robustness of this method was demonstrated with its application to the analysis of real samples including tap water, drain water, and reservoir water with recoveries between 90 and 120%.
Rapid and simple pretreatment of human body fluids using electromembrane extraction across supported liquid membrane for capillary electrophoretic determination of lithium
Authors: Strieglerová Lenka , Kubáň Pavel , Boček Petr
Published: April 2011

Electromembrane extraction was used for simultaneous sample cleanup and preconcentration of lithium from untreated human body fluids. The sample of a body fluid was diluted 100 times with 0.5 mM Tris solution and lithium was extracted by electromigration through a supported liquid membrane composed of 1‐octanol into 100 mM acetic acid acceptor solution. Matrix compounds, such as proteins, red blood cells, and other high‐molecular‐weight compounds were efficiently retained on the supported liquid membrane. The liquid membrane was anchored in pores of a short segment of a polypropylene hollow fiber, which represented a low cost, single use, disposable extraction unit and was discarded after each use. Acceptor solutions were analyzed using capillary electrophoresis with capacitively coupled contactless conductivity detection (CE‐C4D) and baseline separation of lithium was achieved in a background electrolyte solution consisting of 18 mM L‐histidine and 40 mM acetic acid at pH 4.6. Repeatability of the electromembrane extraction‐CE‐C4D method was evaluated for the determination of lithium in standard solutions and real samples and was better than 0.6 and 8.2% for migration times and peak areas, respectively. The concentration limit of detection of 9 nM was achieved. The developed method was applied to the determination of lithium in urine, blood serum, blood plasma, and whole blood at both endogenous and therapeutic concentration levels.
Nanoparticle‐based pseudostationary phases in CEC: A breakthrough in protein analysis?
Authors: Nilsson Christian , Birnbaum Staffan , Nilsson Staffan
Published: April 2011

This review focuses on major trends in nanoparticle‐based pseudostationary phase (PSP) CEC since the publication of our previous reviews within nanoparticle‐based CEC [Nilsson, C., et al., Electrophoresis 2006, 27, 76‐83; Nilsson, C., et al., J. Chromatogr. A 2007, 1168, 212‐224.]. Special attention is given to the development toward protein analysis, which is driven by the strong emergence of protein drug development in the pharmaceutical industry. Furthermore, we discuss the development in coupling different detection techniques with nanoparticle‐based PSP CEC, which were originally predicted to be particularly cumbersome. However, at present, direct UV, LIF and ESI‐MS have been used without any severe complications. Different types of nanoparticles used as PSP during the period include gold nanoparticles, carbon nanostructures and lipid‐based nanoparticles. New materials (for example, different types of carbon nanostructures and self assembled lipid‐based nanostructures) are a strong driving force for development in separation science. Finally, future trends in nanoparticles‐based CEC are envisioned.
Capillary electrophoresis immunoassays with conjugated quantum dots
Authors: Klepárník Karel , Voráčová Ivona , Lišková Marcela , Přikryl Jan , Hezinová Věra , Foret František
Published: April 2011

Water‐soluble CdTe quantum dots (QDs) and their conjugates with antibodies and antigenes were prepared by optimized procedures for applications in CE immunoassays. The QD size of 3.5 nm, excitation spectrum in the range of 300–500 nm, the maximum wavelength of the emission spectrum at 610 nm, quantum yield of 0.25 and luminescence lifetimes in the range of 3.6–43 ns were determined. The 0.1 M solution of TRIS/TAPS (pH 8.3) was found to be the optimum buffer for the separation of the antiovalbumin–ovalbumin immunocomplex from the free conjugates of QDs.
Determination of acrylamide in potato crisps by capillary electrophoresis with quantum dot‐mediated LIF detection
Authors: Chen Qidan , Zhao Wenfeng , Fung Yingsing
Published: April 2011

Acrylamide or 2‐propenamide (AAM), a water‐soluble toxic contaminant, has recently caused health concern after it was found in food products made by high‐temperature cooking. Due to its weak UV absorption and electrochemically inactive state, common analytical methods do not have sufficient sensitivity to meet the World Health Organization requirement. A LIF detection method mediated by water‐soluble CdTe quantum dots capped with mercaptopropyl acid (MPA) is thus developed for AAM quantitation. The optimized conditions are as follows: 30 mmol/L SDS, 0.1 mmol/L quantum dot, and 40 mmol/L phosphate buffer solution at pH 8.0 under 18 kV run voltage with LIF detection at 473 nm excitation and 568 nm fluorescence. The linear quantitation range for AAM was found to vary from 1.0 to 100 mg/kg and a detection limit (S/N=2) at 0.1 mg/kg, showing sufficient sensitivity to meet the maximum AAM specified by the Joint Food and Agriculture Organization/World Health Organization Expert Committee for potato crisps. Recoveries for potato crisps sample spiked with 10, 20, and 100 mg/kg AAM were found to vary between 90 and 95% with RSD <5.7% (n=3).
Molecular modelling and models in the study of sweet and umami taste receptors. A review.
Authors: Morini Gabriella , Bassoli Angela , Borgonovo Gigliola
Published: April 2011

The mechanism of action of tastants has been under investigation for many years. For the sweet taste several models have been developed to describe the nature and topological arrangement of the glucophores of ideal sweet compounds and/or the recognition sites of the sweet taste receptor. In less than a decade our knowledge about the mechanism of sweet taste chemoreception has grown enormously, following the identification and cloning of T1Rs. The observation that receptor cells co‐expressing T1R2 and T1R3 respond to a great variety of sweet compounds has been generally interpreted as an inference that there is a single heterodimeric receptor for sweet taste. The three‐dimensional structure of the receptor is not known and alternative methodologies are required to model the binding of sweet compounds. Therefore homology modelling and molecular modelling become indispensable tools to suggest point mutations which further define the binding regions. Only their cooperative effect allowed researchers to determine several molecular mechanisms of the sweet taste receptors, including the modality of action of blockers and positive allosteric modulators. For umami taste, despite the general appreciation of the meaty, mouth filling and rich taste found in many foods (and the great interest of the food industry thereof), the existence of an umami receptor has been accepted only after its cloning. Probably because of this, no umami taste receptor models have been developed, while the molecular mechanism for its synergism has been unravelled before that of the sweet taste receptor. Copyright © 2011 John Wiley & Sons, Ltd.
Oligocene–Miocene thrusting in central Aegean: insights from the Cycladic island of Amorgos
Authors: Chatzaras V. , Xypolias P. , Kokkalas S. , Koukouvelas I.
Published: April 2011

In the central Aegean, the Cycladic island of Amorgos consists of two high‐pressure (HP) units, the marble‐rich Amorgos unit, which is correlated to the Mesozoic ‘cover’ sequence of the Menderes Massif, and the Cycladic Blueschist unit. New structural data show that the deformation history of the Amorgos HP‐rocks was principally governed by early Oligocene (or late Eocene)–early Miocene ductile to brittle thrusting (D1–D3) followed by middle–late Miocene oblique contractional movements (D4–D5). The D1 phase caused syn‐blueschist‐facies ductile thrusting of the Cycladic Blueschist unit over the Amorgos unit, with ambiguous kinematics. Progressive deformation under continuous NW–SE compression produced a sequence of imbricate NW‐directed thrusts (D2/3) characterized by a stratification of fault‐related rocks, with mylonitic zones (D2) giving way downwards to cataclastic zones (D3). Ductile D2 thrusting synchronous to greenschist‐facies retrogression, was accompanied by mega‐sheath folding during constrictional and general shear deformation. Brittle D3 thrusting was associated with NW‐verging F3 folds trending at a high‐angle to the transport direction. Orthogonal contraction gave way to transpression during which the compression orientation changed from NW–SE (D4) to NE–SW (D5). Back‐arc related NW–SE pure extension (D6) seems to have been established in post‐late Miocene times and related high‐angle normal faulting affected HP‐rocks only after they had already reached the uppermost crustal levels. Oligocene–early Miocene deformation history is interpreted to indicate syn‐compressional exhumation of HP‐rocks possibly in an extrusion wedge. In this case, Amorgos HP‐rocks should have occupied the base of the extrusion wedge. Copyright © 2011 John Wiley & Sons, Ltd.
Parental income and child health in Germany
Authors: Reinhold Steffen , Jürges Hendrik
Published: April 2011

Using newly available data from Germany, we study the relationship between parental income and child health. We find a strong gradient between parental income and subjective child health as has been documented earlier in the United States, Canada, and the United Kingdom. The relationship in Germany is about as strong as in the United States and stronger than in the United Kingdom. However, in contrast to US results, we do not find consistent evidence that the disadvantages associated with low parental income accumulate as the child ages, nor that children from low socioeconomic background are more likely to suffer from doctor‐diagnosed conditions. There is some evidence, however, that high‐income children are better able to cope with the adverse consequences of chronic conditions. Investigating potential diagnosis bias, we find only weak evidence for health disadvantages for low‐income children when using objective health measures, but some evidence for under‐utilization of health services among low‐income families. Copyright © 2011 John Wiley & Sons, Ltd.
Krüppel-like factor 15 activates hepatitis B virus gene expression and replication
Authors: Zhou Jie , Tan Thomas , Tian Yongjun , Zheng Bojian , James Ou J.-H. , Huang Eric J. , Yen Benedict T.S.
Published: April 2011

Abstract:

Hepatitis B virus (HBV) is a small DNA virus that requires cellular transcription factors for the expression of its genes. To understand the molecular mechanisms that regulate HBV gene expression, we conducted a yeast one-hybrid screen to identify novel cellular transcription factors that may control HBV gene expression. Here, we demonstrate that Krüppel-like factor 15 (KLF15), a liver-enriched transcription factor, can robustly activate HBV surface and core promoters. Mutations in the putative KLF15 binding site in the HBV core promoter abolished the ability of KLF15 to activate the core promoter in luciferase assays. Furthermore, the overexpression of KLF15 stimulated the expression of HBV surface antigen (HBsAg) and the core protein and enhanced viral replication. Conversely, small interfering RNA knockdown of the endogenous KLF15 in Huh7 cells resulted in a reduction in HBV surface- and core-promoter activities. In electrophoretic mobility shift and chromatin immunoprecipitation assays, KLF15 binds to DNA probes derived from the core promoter and the surface promoter. Introduction of an expression vector for KLF15 short hairpin RNA, together with the HBV genome into the mouse liver using hydrodynamic injection, resulted in a significant reduction in viral gene expression and DNA replication. Additionally, mutations in the KLF15 response element in the HBV core promoter significantly reduced viral DNA levels in the mouse serum. Conclusion: KLF15 is a novel transcriptional activator for HBV core and surface promoters. It is possible that KLF15 may serve as a potential therapeutic target to reduce HBV gene expression and viral replication. (HEPATOLOGY 2011;)
Emergence of hepatitis B virus S gene mutants in patients experiencing hepatitis B surface antigen seroconversion after peginterferon therapy
Authors: Hsu Chao-Wei , Yeh Chau-Ting
Published: April 2011

Abstract:

With anti–hepatitis B virus (anti-HBV) therapy using peginterferon, the seroconversion of hepatitis B surface antigen (HBsAg), which is considered a cure of the disease, can be achieved in a small percentage of patients. Eight of 245 consecutive patients (3.27%) with chronic hepatitis B who received peginterferon therapy at our center achieved HBsAg seroclearance. Surprisingly, two of the eight patients remained viremic according to standard HBV DNA assays. The coding regions of the HBV pre-S/S gene, which were derived from serial serum samples, were analyzed. Site-directed mutagenesis experimentation was performed to verify the phenotypic alterations in Huh-7 cells. In patient 1, an sT125A mutant developed during the HBsAg-negative stage and constituted 11.2% of the viral population. The HBV DNA level was 2.73 × 104 IU/mL at the time of detection. This mutant was not detectable in the HBsAg-positive stages. A phenotypic study of Huh-7 cells showed a significant reduction of antigenicity. In patient 2, an sW74* truncation mutation was found during the HBsAg-negative stage and constituted 83.1% of the viral population. The HBV DNA level was 4.12 × 104 IU/mL at the time of detection. A phenotypic study of Huh-7 cells showed a complete loss of antigenicity. Patient 2 subsequently experienced an episode of hepatitis relapse 7 months after the end of treatment and was negative for HBsAg throughout the hepatitis flare. Conclusion: During antiviral therapy with peginterferon, the achievement of HBsAg seroconversion does not necessarily indicate viral eradication. The emergence of S gene mutants is another possibility, and a relapse with HBsAg-negative hepatitis can occur. (Hepatology 2011;)
Liver-specific loss of glucose-regulated protein 78 perturbs the unfolded protein response and exacerbates a spectrum of liver diseases in mice
Authors: Ji Cheng , Kaplowitz Neil , Lau Mo Yin , Kao Eddy , Petrovic Lydia M. , Lee Amy S.
Published: April 2011

Abstract:

The endoplasmic reticulum (ER) chaperone protein glucose-regulated protein 78 (GRP78)/binding immunoglobulin protein is a master regulator of ER homeostasis and stress responses, which have been implicated in the pathogenesis of metabolic disorders. By applying the locus of X-over P1–cyclization recombination strategy, we generated mice with liver-specific GRP78 loss. Our studies using this novel mouse model revealed that liver GRP78 was required for neonatal survival, and a loss of GRP78 in the adult liver greater than 50% caused an ER stress response and dilation of the ER compartment, which was accompanied by the onset of apoptosis. This suggested the critical involvement of GRP78 in maintaining hepatocyte ER homeostasis and viability. Furthermore, these mice exhibited elevations of serum alanine aminotransferase and fat accumulation in the liver, and they were sensitized to a variety of acute and chronic hepatic disorders by alcohol, a high-fat diet, drugs, and toxins. These disorders were alleviated by the simultaneous administration of the molecular chaperone 4-phenylbutyrate. A microarray analysis and a two-dimensional protein profile revealed major perturbations of unfolded protein response targets, common enzymes/factors in lipogenesis, and new factors possibly contributing to liver steatosis or fibrosis under ER stress (e.g., major urinary proteins in the liver, fatty acid binding proteins, adipose differentiation-related protein, cysteine-rich with epidermal growth factor–like domains 2, nuclear protein 1, and growth differentiation factor 15). Conclusion: Our findings underscore the importance of GRP78 in managing the physiological client protein load and suppressing apoptosis in hepatocytes, and they support the pathological role of ER stress in the evolution of fatty liver disease under adverse conditions (i.e., drugs, diet, toxins, and alcohol). (HEPATOLOGY 2011;)
How strong is the case for dollarization in Central America? An empirical analysis of business cycles, credit market imperfections and the exchange rate
Authors: Lindenberg Nannette , Westermann Frank
Published: April 2011

In this paper, we contrast two different views in the debate on official dollarization. The Mundell framework of optimum currency areas and a model on boom–bust cycles, by Schneider and Tornell, who take account of credit market imperfections prevalent in middle income countries. We highlight that the role of the exchange rate is strikingly different in the two models. Although in the Mundell framework, the exchange rate is expected to smooth the business cycle, the other model predicts that the exchange rate plays an amplifying role. We empirically evaluate both models for eight highly dollarized Central American economies. We document the existence of credit market imperfections and find that shocks from the exchange rate indeed amplify business cycles in these countries. Using a new method of Cubadda, we furthermore test for cyclical comovement and reject the hypothesis that the countries form an optimum currency area with the United States according to the Mundell definition. Copyright © 2011 John Wiley & Sons, Ltd.
Mechanical and acid neutralizing properties and bacteria inhibition of amorphous calcium phosphate dental nanocomposite
Authors: Moreau Jennifer L. , Sun Limin , Chow Laurence C. , Xu Hockin H. K.
Published: April 2011

Dental composites do not hinder bacteria colonization and plaque formation. Caries at the restoration margins is a frequent reason for replacement of existing restorations, which accounts for 50 to 70% of all restorations. The objectives of this study were to examine the filler level effect on nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and investigate the load‐bearing and acid‐neutralizing properties and bacteria inhibition. NACP with 116‐nm particle size were synthesized via a spray‐drying technique and incorporated into a resin. Flexural strength of nanocomposite with 10 to 30% NACP fillers matched the strength of a commercial hybrid composite (p > 0.1). Nanocomposite with 40% NACP matched the strength of a microfill composite, which was 2‐fold that of a resin‐modified glass ionomer. Nanocomposite with 40% NACP neutralized a lactic acid solution of pH 4 by rapidly increasing the pH to 5.69 in 10 min. In contrast, the commercial controls had pH staying at near 4. Using Streptoccocus mutans, an agar disk‐diffusion test showed no inhibition zone for commercial controls. In contrast, the inhibition zone was (2.5 ± 0.7) mm for nanocomposite with 40% NACP. Crystal violet staining showed that S. mutans coverage on nanocomposite was 1/4 that on commercial composite. In conclusion, novel calcium–phosphate nanocomposite matched the mechanical properties of commercial composite and rapidly neutralized lactic acid of pH 4. The nanocomposite appeared to moderately reduce the S. mutans growth, and further study is needed to obtain strong antimicrobial properties. The new nanocomposite may have potential to reduce secondary caries and restoration fracture, two main challenges facing tooth cavity restorations. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.