bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation on different reducing power of cocatalysts on the Ziegler–Natta catalyst containing alkoxide species for ethylene polymerization
Authors: Hongmanee Goond , Sripothongnak Saovalak , Jongsomjit Bunjerd , Praserthdam Piyasan 
Published: May 2014

ABSTRACTIn this work, the effects of three types of cocatalyst having different alkyl groups, such as triethylaluminium (TEA), triisobutylaluminum (TiBA), and trioctylaluminium (TnOA), and their concentrations on the catalytic activity and polymer properties were investigated for the Ziegler–Natta catalyst containing alkoxide species. The drastic escalation of catalytic activity was observed when the ratio of Al/Ti was increased only for TEA because of its good diffusivity as proven by the electron spin resonance technique. Moreover, it was found that the characteristic of the alkyl group in cocatalyst affected on the chain transfer ability. The chain transfer ability of TnOA was found to be equal to the TiBA in spite of its concentration was higher. By the way, the cocatalyst types and their concentrations did not affect on the variety of active sites as seen in molecular weight distribution of polymer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40884.
Adaptive Control Design for a Class of Uncertain High‐Order Nonlinear Systems with Time Delay
Authors: Sun Zong‐Yao , Liu Yun‐Gang 
Published: May 2014

AbstractThis paper is concerned with adaptive stabilization for a class of uncertain high‐order nonlinear systems with time delays. To the authors' knowledge, there has been no analogous result. Hence during investigation, the conditions on delay effect and the control design framework should be established for the first time. In this paper, under somewhat necessary restrictions on the system nonlinearities, by the method of adding a power integrator and the related adaptive technique, a procedure is developed to design the continuous adaptive state‐feedback controller without overparametrization. Moreover, the uniform stability and convergence of the resulting closed‐loop system are rigorously proven, with the aid of a suitable Lyapunov‐Krasovskii functional. Finally, a numerical example is provided to illustrate the effectiveness of the theoretical result.
Comparative studies on the interactions of dihydroartemisinin and artemisinin with bovine serum albumin using spectroscopic methods
Authors: Liu Rong , Cheng Zhengjun , Jiang Xiaohui 
Published: May 2014

ABSTRACTThe interactions of dihydroartemisinin (DHA) and artemisinin (ART) with bovine serum albumin (BSA) have been investigated using fluorescence, UV/vis absorption and Fourier transform infrared (FTIR) spectra under simulated physiological conditions. The binding characteristics of DHA/ART and BSA were determined by fluorescence emission and resonance light scattering (RLS) spectra. The quenching mechanism between BSA and DHA/ART is static. The binding constants and binding sites of DHA/ART–BSA systems were calculated at different temperatures (293, 298, 304 and 310 K). According to Förster non‐radiative energy transfer theory, the binding distance of BSA to DHA/ART was calculated to be 1.54/1.65 nm. The effect of DHA/ART on the secondary structure of BSA was analyzed using UV/vis absorption, FTIR, synchronous fluorescence and 3D fluorescence spectra. In addition, the effects of common ions on the binding constants of BSA–DHA and BSA–ART systems were also discussed. Copyright © 2014 John Wiley & Sons, Ltd.
Detachably assembled microfluidic device for perfusion culture and post‐culture analysis of a spheroid array
Authors: Sakai Yusuke , Hattori Koji , Yanagawa Fumiki , Sugiura Shinji , Kanamori Toshiyuki , Nakazawa Kohji 
Published: May 2014

AbstractMicrofluidic devices permit perfusion culture of three‐dimensional (3D) tissue, mimicking the flow of blood in vascularized 3D tissue in our body. Here, we report a microfluidic device composed of a two‐part microfluidic chamber chip and multi‐microwell array chip able to be disassembled at the culture endpoint. Within the microfluidic chamber, an array of 3D tissue aggregates (spheroids) can be formed and cultured under perfusion. Subsequently, detailed post‐culture analysis of the spheroids collected from the disassembled device can be performed. This device facilitates uniform spheroid formation, growth analysis in a high‐throughput format, controlled proliferation via perfusion flow rate, and post‐culture analysis of spheroids. We used the device to culture spheroids of human hepatocellular carcinoma (HepG2) cells under two controlled perfusion flow rates. HepG2 spheroids exhibited greater cell growth at higher perfusion flow rates than at lower perfusion flow rates, and exhibited different metabolic activity and mRNA and protein expression under the different flow rate conditions. These results show the potential of perfusion culture to precisely control the culture environment in microfluidic devices. The construction of spheroid array chambers allows multiple culture conditions to be tested simultaneously, with potential applications in toxicity and drug screening.
A serum‐free medium developed for in vitro expansion of murine intestinal stem cells
Authors: Mohamed Mahmoud S. , Chen Yun , Yao Chao‐Ling 
Published: May 2014

AbstractIntestinal stem cells (ISCs) are located at the base of the intestinal crypts and have the ability to self‐renew as well as to differentiate into mature epithelial cells. Recently, ISCs have received much attention for the treatment of many intestinal diseases. However, many challenges face those studying ISCs because insufficient ISCs are available. Therefore, the development of a culture medium for ISC expansion is an important necessity for basic research and clinical application. In this study, we described the technique used to develop a serum‐free medium for expanding ISCs in vitro. Furthermore, five serum substitutes were selected and optimized in order to maintain the long‐term proliferation and enteroid‐forming ability of ISCs: (i) ethanolamine; (ii) ascorbic acid phosphate; (iii) transferrin; (iv) glutathione; and (v) sodium selenite. Analysis of gene expression of Lgr5, Bmi1, Msi1 and PTEN demonstrated that our serum‐free medium sustained the expression of genes involved in ISC‐related functions in the expanded ISCs. Additionally, the expression intensity of surface markers, including Lgr5, CD24 and CD44, on serum‐free expanded cells in crypts was greatly increased. Taken together, our results demonstrate that the number of ISCs can be expanded and their functionality maintained in our serum‐free medium, indicating the suitability of this serum‐free expansion medium for increasing the numbers of ICSs available for basic research and clinical applications in the future.
PEGylation of lysine residues improves the proteolytic stability of fibronectin while retaining biological activity
Authors: Zhang Chen , Desai Raj , Perez‐Luna Victor , Karuri Nancy 
Published: May 2014

AbstractExcessive proteolysis of fibronectin (FN) impairs tissue repair in chronic wounds. Since FN is essential in wound healing, our goal is to improve its proteolytic stability and at the same time preserve its biological activity. We have previously shown that reduced FN conjugated with polyethylene glycol (PEG) at cysteine residues is more proteolytically stable than native FN. Cysteine‐PEGylated FN supported cell adhesion and migration to the same extent as native FN. However, unlike native FN, cysteine‐PEGylated FN was not assembled into an extracellular matrix (ECM) when immobilized. Here, we present an alternative approach in which FN is preferentially PEGylated at lysine residues using different molecular weight PEGs. We show that lysine PEGylation does not perturb FN secondary structure. PEG molecular weight, from 2 to 10 kDa, positively correlates with FN–PEG proteolytic stability. Cell adhesion, cell spreading, and gelatin binding decrease with increasing molecular weight of PEG. The 2‐kDa FN–PEG conjugate shows comparable cell adhesion to native FN and binds gelatin. Moreover, immobilized FN–PEG is assembled into ECM fibrils. In summary, lysine PEGylation of FN can be used to stabilize FN against proteolytic degradation with minimal perturbation to FN structure and retained biological activity.
Ligand‐Assisted Dual‐Site Click Labeling of EGFR on Living Cells
Authors: Yang Yi , Lin Shixian , Lin Wei , Chen Peng R. 
Published: May 2014

AbstractWe have developed a dual‐site click labeling strategy for the simultaneous installation of a FRET donor–acceptor pair onto the extracellular domains of epidermal growth factor receptor (EGFR) on living cells. Our method integrates the genetic code expansion strategy, enzyme‐mediated protein labeling, and ligand‐assisted CuI‐catalyzed azide–alkyne cycloaddition (CuAAC) into a tri‐step labeling procedure. This enabled cis‐membrane FRET imaging of EGFR under living conditions. This procedure might be generally applicable for dual‐site labeling and cis‐membrane FRET analysis of the domain–domain dynamics of important mammalian cell‐surface receptors.
Plant‐based biopharming of recombinant human lactoferrin
Authors: Yemets Alla I. , Tanasienko Iryna V. , Krasylenko Yuliya A. , Blume Yaroslav B. 
Published: May 2014

AbstractRecombinant proteins are currently recognized as pharmaceuticals, enzymes, food constituents, nutritional additives, antibodies and other valuable products for industry, healthcare, research, and everyday life. Lactoferrin (Lf), one of the promising human milk proteins, occupies the expanding biotechnological food market niche due to its important versatile properties. Lf shows antiviral, antimicrobial, antiprotozoal and antioxidant activities, modulates cell growth rate, binds glycosaminoglycans and lipopolysaccharides, and also inputs into the innate/specific immune responses. Development of highly efficient human recombinant Lf expression systems employing yeasts, filamentous fungi and undoubtedly higher plants as bioreactors for the large‐scale Lf production is a biotechnological challenge. This review highlights the advantages and disadvantages of the existing non‐animal Lf expression systems from the standpoint of protein yield and its biological activity. Special emphasis is put on the benefits of monocot plant system for Lf expression and the biosafety aspects of the transgenic Lf‐expressing plants.
Cardiomyocyte cytokinesis score: a potential method for cardiomyocyte proliferation
Authors: Hua Kun , Nie Yu , Hou Jianfeng , Zheng Zhe , Hu Shengshou 
Published: May 2014

AbstractOne of the most important indicators of myocardial regeneration is cardiomyocyte proliferation. However, it is difficult to distinguish cardiomyocytes in the regenerating stage from binucleated or multinucleated myocytes by conventional morphometric techniques. As cell cycle progression (CCP) scores have been successfully applied to the evaluation of the proliferation of cancer cells, we sought to establish a multi‐gene score to evaluate cardiomyocyte proliferation in this study. Given the disturbances of nuclear division without cell division that occurs in cardiomyocytes, ten cytokinesis‐correlated genes (Anln, Aurkb, Cenpa, Kif4, Kif23, Prc1, RhoA, Spin1, TACC2, and CDC42) were chosen to establish the cardiomyocyte cytokinesis score (CC‐Score). The expression levels of these genes in H9C2 rat cardiomyoblast cells, the proliferation of which were stimulated or inhibited, were detected using qRT‐PCR. To confirm the feasibility of the CC‐Score system, four conventional methods for evaluating cardiomyocyte proliferation, including the MTT assay, BrdU assay, immunofluorescence, and flow cytometry analysis, were used in each group. The results of the CC‐Score in the assessment of the proliferation of H9C2 cells were consistent with those of four commonly used proliferative assay methods. We conclude that the CC‐Score can be used to assess the proliferation status of H9C2 cells, and suggest that the CC‐Score may be a potential method for the assessment of cardiomyocyte proliferation in myocardial regeneration. However, validation studies utilizing primary cultured rat cardiomyocytes and heart tissue are warranted.
Delineating cellular interactions between ciliates and fish by co‐culturing Tetrahymena thermophila with fish cells
Authors: Pinheiro Marcel D.O. , Bols Niels C. 
Published: May 2014

AbstractAlthough several species of Tetrahymena are often described as histophagous and opportunistic pathogens of fish, little is known about ciliate/fish cell interactions, but one approach for studying these is in vitro with cell lines. In this study, T. thermophila, B1975 (wild type) and NP1 (temperature sensitive mutant for phagocytosis) were cultured on monolayers of 3 fish epithelial cell lines, CHSE‐214, RTgill‐W1, and ZEB2J, and the rabbit kidney epithelial cell line, RK‐13. Generally the ciliates flourished, whereas the monolayers died, being completely consumed over several days. The destruction of monolayers required that the ciliates could make contact with the animal cells through swimming, which appeared to dislodge or loosen cells so that they could be phagocytosed. The ciliates internalized into food vacuoles ZEB2J from cell monolayers as well as from cell suspensions. Phagocytosis was essential for monolayer destruction as monolayers remained intact under conditions where phagocytosis was impeded, such as 37°C for NP1 and 4°C for B1975. Monolayers of fish cells supported the proliferation of ciliates. Thus T. thermophila can ‘eat’ animal cells or be histophagous in vitro, with the potential to be histophagous in vivo.
Syngas Production Process Development and Economic Evaluation for Gas‐to‐Liquid Applications
Authors: Maqbool Wahab , Lee Euy Soo 
Published: May 2014

AbstractThe range of syngas composition produced by autothermal reforming of natural gas makes it suitable and in compliance with the gas‐to‐liquid technology for subsequent conversion to synthetic crude oil. A modified and improvised design for this reforming technique is proposed in which oxygen consumption is reduced as compared to the conventional process. Simulative optimization helps in optimal designing of the new process subject to a set of constraints applied to both the processes for uniform and homogeneous comparison. Aspen HYSYS is used for simulation and optimization of the process and the economics are evaluated by an Aspen Process Economic Analyzer.
Determination of the Metastable Zone Width by a Simple Optical Probe
Authors: Chaitanya Koduru K. , Sarkar Debasis 
Published: May 2014

AbstractThe metastable zone width (MSZW) defines an operating boundary for a crystallization process; thus, it is important to determine the MSZW for a given crystallization process. The application of a simple optical probe consisting of a line laser source, a light‐dependent resistor, and a simple processing circuit in the determination of the MSZW of an anti‐solvent crystallization process is presented. The optical probe detects the point of nucleation as a sharp change in output voltage upon the onset of nucleation. The isothermal crystallization of glycine from a glycine/water solution using ethanol as anti‐solvent was used here to assess the performance of the proposed measurement system. The effects of various operating parameters on the MSZW of glycine were also investigated. The kinetic parameters of nucleation were estimated from the data obtained.
New Insights into Glycopeptide Antibiotic Binding to Cell Wall Precursors using SPR and NMR Spectroscopy
Authors: Treviño Juan , Bayón Carlos , Ardá Ana , Marinelli Flavia , Gandolfi Raffaella , Molinari Francesco , Jimenez‐Barbero Jesús , Hernáiz María J. 
Published: May 2014

AbstractGlycopeptide antibiotics, such as vancomycin and teicoplanin, are used to treat life‐threatening infections caused by multidrug‐resistant Gram‐positive pathogens. They inhibit bacterial cell wall biosynthesis by binding to the D‐Ala‐D‐Ala C‐terminus of peptidoglycan precursors. Vancomycin‐resistant bacteria replace the dipeptide with the D‐Ala‐D‐Lac depsipeptide, thus reducing the binding affinity of the antibiotics with their molecular targets. Herein, studies of the interaction of teicoplanin, teicoplanin‐like A40926, and of their semisynthetic derivatives (mideplanin, MDL63,246, dalbavancin) with peptide analogues of cell‐wall precursors by NMR spectroscopy and surface plasmon resonance (SPR) are reported. NMR spectroscopy revealed the existence of two different complexes in solution, when the different glycopeptides interact with Ac2KdAlaDAlaOH. Despite the NMR experimental conditions, which are different from those employed for the SPR measurements, the NMR spectroscopy results parallel those deduced in the chip with respect to the drastic binding difference existing between the D‐Ala and the D‐Lac terminating analogues, confirming that all these antibiotics share the same primary molecular mechanism of action and resistance. Kinetic analysis of the interaction between the glycopeptide antibiotics and immobilized AcKdAlaDAlaOH by SPR suggest a dimerization process that was not observed by NMR spectroscopy in DMSO solution. Moreover, in SPR, all glycopeptides with a hydrophobic acyl chain present stronger binding with a hydrophobic surface than vancomycin, indicating that additional interactions through the employed surface are involved. In conclusion, SPR provides a tool to differentiate between vancomycin and other glycopeptides, and the calculated binding affinities at the surface seem to be more relevant to in vitro antimicrobial activity than the estimations from NMR spectroscopy analysis.
Analysis of High and Selective Uptake of CO2 in an Oxamide‐Containing {Cu2(OOCR)4}‐Based Metal–Organic Framework
Authors: Alsmail Nada H. , Suyetin Mikhail , Yan Yong , Cabot Rafel , Krap Cristina P. , Lü Jian , Easun Timothy L. , Bichoutskaia Elena , Lewis William , Blake Alexander J. , Schröder Martin 
Published: May 2014

AbstractThe porous framework [Cu2(H2O)2L]⋅4 H2O⋅2 DMA (H4L=oxalylbis(azanediyl)diisophthalic acid; DMA=N,N‐dimethylacetamide), denoted NOTT‐125, is formed by connection of {Cu2(RCOO)4} paddlewheels with the isophthalate linkers in L4−. A single crystal structure determination reveals that NOTT‐125 crystallises in monoclinic unit cell with a=27.9161(6), b=18.6627(4) and c=32.3643(8) Å, β=112.655(3)°, space group P21/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three‐dimensional space. Cage A is constructed from twelve {Cu2(OOCR)4} paddlewheels and six linkers to form an ellipsoid‐shaped cavity approximately 24.0 Å along its long axis and 9.6 Å across its central diameter. Cage B consists of six {Cu2(OOCR)4} units and twelve linkers and has a spherical diameter of 12.7 Å taking into account the van der Waals radii of the atoms. NOTT‐125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT‐125a, is responsible for excellent CO2 uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO2 over CH4 or N2. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO2 and CH4 with the linkers in NOTT‐125 reveals a set of strong interactions between CO2 and the oxamide motif that are not possible with a single amide.
Aromatic Nitrogen Mustard‐Based Prodrugs: Activity, Selectivity, and the Mechanism of DNA Cross‐Linking
Authors: Chen Wenbing , Han Yanyan , Peng Xiaohua 
Published: May 2014

AbstractThree novel H2O2‐activated aromatic nitrogen mustard prodrugs (6–8) are reported. These compounds contain a DNA alkylating agent connected to a H2O2‐responsive trigger by different electron‐withdrawing linkers so that they are inactive towards DNA but can be triggered by H2O2 to release active species. The activity and selectivity of these compounds towards DNA were investigated by measuring DNA interstrand cross‐link (ICL) formation in the presence or absence of H2O2. An electron‐withdrawing linker unit, such as a quaternary ammonia salt (6), a carboxyamide (7), and a carbonate group (8), is sufficient to deactivate the aromatic nitrogen mustard resulting in less than 1.5 % cross‐linking formation. However, H2O2 can restore the activity of the effectors by converting a withdrawing group to a donating group, therefore increasing the cross‐linking efficiency (>20 %). The stability and reaction sites of the ICL products were determined, which revealed that alkylation induced by 7 and 8 not only occurred at the purine sites but also at the pyrimidine site. For the first time, we isolated and characterized the monomer adducts formed between the canonical nucleosides and the aromatic nitrogen mustard (15) which supported that nitrogen mustards reacted with dG, dA, and dC. The activation mechanism was studied by NMR spectroscopic analysis. An in vitro cytotoxicity assay demonstrated that compound 7 with a carboxyamide linker dramatically inhibited the growth of various cancer cells with a GI50 of less than 1 μM, whereas compound 6 with a charged linker did not show any obvious toxicity in all cell lines tested. These data indicated that a neutral carboxyamide linker is preferable for developing nitrogen mustard prodrugs. Our results showed that 7 is a potent anticancer prodrug that can serve as a model compound for further development. We believe these novel aromatic nitrogen mustards will inspire further and effective applications.
A Rare Example of the Formation of Polystyrene‐Grafted Aliphatic Polyester in One‐Pot by Radical Polymerization
Authors: Shi Yinfeng , Zheng Zhicheng , Agarwal Seema 
Published: May 2014

AbstractThe radical copolymerization of cyclic ester β‐propiolactone (β‐PL) with styrene (St) at 120 °C, with a complete range of monomer ratios, is a rare example of a system providing graft copolymers (PSt‐g‐β‐PL) in one pot. The structure of the resulting β‐PL–St copolymers was proven by using a combination of different characterization techniques, such as 1D and 2D NMR spectroscopy and gel permeation chromatography (GPC), before and after alkaline hydrolysis of the polymers. The number of grafting points increased with an increasing amount of β‐PL in the feed. A significant difference in the reactivity of St and β‐PL and radical chain‐transfer reactions at the polystyrene (PSt) backbone, followed by combination with the active growing poly(β‐PL) chains, led to the formation of graft copolymers by a grafting‐onto mechanism.
gem‐Difluoroolefination of Diaryl Ketones and Enolizable Aldehydes with Difluoromethyl 2‐Pyridyl Sulfone: New Insights into the Julia–Kocienski Reaction
Authors: Gao Bing , Zhao Yanchuan , Hu Mingyou , Ni Chuanfa , Hu Jinbo 
Published: May 2014

AbstractThe direct conversion of diaryl ketones and enolizable aliphatic aldehydes into gem‐difluoroalkenes has been a long‐standing challenge in organofluorine chemistry. Herein, we report efficient strategies to tackle this problem by using difluoromethyl 2‐pyridyl sulfone as a general gem‐difluoroolefination reagent. The gem‐difluoroolefination of diaryl ketones proceeds by acid‐promoted Smiles rearrangement of the carbinol intermediate; the gem‐difluoroolefination is otherwise difficult to achieve through a conventional Julia–Kocienski olefination protocol under basic conditions due to the retro‐aldol type decomposition of the key intermediate. Efficient gem‐difluoroolefination of aliphatic aldehydes was achieved by the use of an amide base generated in situ (from CsF and tris(trimethylsilyl)amine), which diminishes the undesired enolization of aliphatic aldehydes and provides a powerful synthetic method for chemoselective gem‐difluoroolefination of multi‐carbonyl compounds. Our results provide new insights into the mechanistic understanding of the classical Julia–Kocienski reaction.