bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Supramolecular Polymer as a Self‐Assembling Polyvalent Scaffold
Authors: Müller Marion K. , Brunsveld Luc 
Published: March 2009

AbstractBinding bacteria: Discotic molecules self‐assemble into columnar supramolecular polymers that show strong polyvalent binding to bacteria by virtue of mannose ligands attached at their periphery (orange; see picture). The reversible formation of the supramolecular polymers allows simple mixing of differently substituted monomers and the optimization of bacterial aggregation.magnified image
Total Synthesis of Ouabagenin and Ouabain
Authors: Reddy Maddi Sridhar , Zhang Hongxing , Phoenix Serge , Deslongchamps Pierre 
Published: March 2009

AbstractAll done! A full account of the total synthesis of ouabagenin and ouabain has been described. The synthesis was achieved through a polyanionic cyclization strategy. Degradation studies provide an ultimate proof for a key intermediate observed in the synthesis.magnified imageA full account of the total synthesis of ouabagenin and ouabain is described. A highly stereocontrolled anionic cycloaddition for the rapid construction of the basic steroid skeleton is a pivotal conversion for the whole strategy. A careful study was needed to establish the order and the sequence of functional group manipulations. Specific conformational features of the ouabain skeleton allowed us to overcome a few stereochemical problems. Degradation studies on ouabain provided an ultimate proof for a key intermediate, which is used as a relay. Late stage butenolide formation and glycosidation yielded ouabain.
Influence of Tl+ activator ions on the luminescence characteristics of KCl0.5Br0.5:Eu2+ powder phosphors
Authors: Nagarajan S. , Sudarkodi R. 
Published: March 2009

AbstractPhotoluminescence (PL) of thallium co‐doped with KCl0.5Br0.5:Eu2+ powder phosphors display emission bands at 320 and 370 nm attributable to centres involving Tl+ ions in addition to characteristic Eu2+ emission around 420 nm. Additional PL excitation and emission bandS observed around 260 and 380 nm, respectively, were observed in the double‐doped KCl0.5Br0.5:Eu2+, Tl+ powder phosphors and are attributed to complex centres involving Tl+ and Eu2+ ions. The enhancement observed in the intensity of Eu2+ emission around 420 nm with the addition of TlBr in KCl0.5Br0.5:Eu2+ powder phosphors is attributed to the energy transfer from Tl+ → Eu2+ ions. Photostimulated luminescence (PSL) studies of γ‐irradiated KCl0.5Br0.5:Eu2+, Tl+ mixed phosphors are reported and a tentative PSL mechanism in the phosphors has been suggested. Copyright © 2009 John Wiley & Sons, Ltd.
Analytical quantification of low‐density lipoprotein using europium tetracycline indicator
Authors: De Oliveira Silva Flávia Rodrigues , Monteiro Andrea Moreira , Neto Antônio M. Figueiredo , Gidlund Magnus , Junior Nilson Dias Vieira , Courrol Lilia Coronato 
Published: March 2009

AbstractLow‐density lipoprotein (LDL) is known as ‘bad’ cholesterol. If too much LDL circulates in the blood it can be retained in the walls of the arteries, causing atherosclerosis. In this paper we showed an alternative method to quantify LDL using the europium tetracycline (EuTc) indicator. The optical properties of the EuTc complex were investigated in aqueous solutions containing LDL. An enhancement was observed of the europium luminescence in the solutions with LDL compared those without the lipoprotein. A method to quantify the amount of LDL in a sample, based on EuTc enhanced luminescence, is proposed. The enhancement mechanism is also discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Relationship between ultra‐weak bioluminescence and vigour or irradiation dose of irradiated wheat
Authors: Wang Jun , Yu Yong 
Published: March 2009

AbstractUltra‐weak luminescent analysis is a new way to detect the irradiation dose and the vigour of irradiated wheat. Wheat grain and wheat flour were used in this research for ultra‐weak luminescent analysis. The experimental data showed that the bioluminescence intensity of wheat grain sample was different with increasing storage time and increasing dose, and a similar trend appeared in the germination rates of irradiated wheat grain. It was found that the differences in bioluminescence intensities and germination rates of irradiated wheat grain at different doses and storage times were due to the effect of irraditation on the wheat embryo and self‐repair during storage. As a result, ultra‐weak luminescent analysis cannot be used to detect the irradiation dose of irradiated wheat, but it can be used to determine vigour. Experiments showed that the irradiation dose had a highly significant effect on the bioluminescence intensities of wheat flour when cane sugar was added. Copyright © 2009 John Wiley & Sons, Ltd.
A novel chemiluminescent flow injection analysis of trace amounts of rutin by its inhibition of the luminol–hydrogen peroxide reaction catalyzed by tetrasulfonated colbalt phthalocyanine
Authors: Zhu Qiyong 
Published: March 2009

AbstractBased on the inhibition effect of rutin on the luminol–hydrogen peroxide chemiluminescence (CL) system catalyzed by tetrasulfonated colbalt phthalocyanine (CoTSPc), a sensitive flow‐injection CL method has been developed for the determination of rutin. The CL reaction mechanism was carefully investigated by examining CL emission spectra, UV–visible spectra and variation of reaction conditions. It was found that there existed a linear relationship between CL intensity and the concentration of rutin in the range of 8.0 × 10−9 to 1.0 × 10−6 mol L−1, and the detection limit is 3.8 × 10−9 mol L−1. This proposed method is sensitive, convenient and simple, and has been applied to the determination of rutin in commercial rutin tablets with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.
Fluorescence sensing of nitric oxide in aqueous solution by triethanolamine‐modified CdSe quantum dots
Authors: Yan Xiao Qing , Shang Zhuo Bin , Zhang Zhao , Wang Yu , Jin Wei Jun 
Published: March 2009

AbstractThe water‐soluble luminescent CdSe quantum dots were prepared by ligand exchange with triethanolamine (TEA). Oxygen can reversibly enhance the fluorescence of the synthesized quantum dots (TEA‐CdSe‐QDs) in aqueous solution. Nitric oxide radical (NO) can react easily with dissolved oxygen in water and was found to have a significant quenching effect on the fluorescence of the TEA‐CdSe‐QDs. The fluorescence responses were concentration‐dependent and can be well described by the typical Stern–Volmer equation. A good linear relationship (R2 = 0.9963) was observed over the range 5.92 × 10−7 to 1.85 × 10−5 mol/L nitric oxide. Above this concentration was a second linear region ranging from 2.12 × 10−5 to 1.12 × 10−4 mol/L NO with a gentler slope. The detection limit, calculated following the 3σ IUPAC criteria, was 3.02 × 10−7 mol/L. The interference effect of some common interferents such as nitrite (NO2−), nitrate (NO3−), glucose and l‐ascorbic acid on the detection of NO was negligible for the proposed system, demonstrating the potential utility of this probe for the detection of NO in biological systems. The possible mechanism was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.
The effect of continuous culture on the growth and structure of tissue‐engineered cartilage
Authors: Khan Aasma A. , Suits Jocelyne M. T. , Kandel Rita A. , Waldman Stephen D. 
Published: March 2009

AbstractThe use of bioreactors for cartilage tissue engineering has become increasingly important as traditional batch‐fed culture is not optimal for in vitro tissue growth. Most tissue engineering bioreactors rely on convection as the primary means to provide mass transfer; however, convective transport can also impart potentially unwanted and/or uncontrollable mechanical stimuli to the cells resident in the construct. The reliance on diffusive transport may not necessarily be ineffectual as previous studies have observed improved cartilaginous tissue growth when the constructs were cultured in elevated volumes of media. In this study, to approximate an infinite reservoir of media, we investigated the effect of continuous culture on cartilaginous tissue growth in vitro. Isolated bovine articular chondrocytes were seeded in high density, 3D culture on Millicell™ filters. After two weeks of preculture, the constructs were cultivated with or without continuous media flow (5–10 μL/min) for a period of one week. Tissue engineered cartilage constructs grown under continuous media flow significantly accumulated more collagen and proteoglycans (increased by 50–70%). These changes were similar in magnitude to the reported effect of through‐thickness perfusion without the need for large volumetric flow rates (5–10μL/min as opposed to 240–800 μL/min). Additionally, tissues grown in the reactor displayed some evidence of the stratified morphology of native cartilage as well as containing stores of intracellular glycogen. Future studies will investigate the effect of long‐term continuous culture in terms of extracellular matrix accumulation and subsequent changes in mechanical function. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Expression of functional Candida antarctica lipase B in a cell‐free protein synthesis system derived from Escherichia coli
Authors: Park Chang‐Gil , Kim Tae‐Wan , Oh In‐Seok , Song Jae Kwang , Kim Dong‐Myung 
Published: March 2009

AbstractThis article reports the cell‐free expression of functional Lipase B from Candida antarctica (CalB) in an Escherichia coli extract. Although most of the cell‐free synthesized CalB was insoluble under conventional reaction conditions, the combined use of molecular chaperones led to the soluble expression of CalB. In addition, the functional enzyme was generated by applying the optimal redox potential. When examined using p‐nitrophenyl palmitate as a substrate, the specific activity of the cell‐free synthesized CalB was higher than that of the reference protein produced in Pichia pastoris. These results highlight the potential of cell‐free protein synthesis technology as a powerful platform for the rapid expression, screening and analysis of industrially important enzymes. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Enzymatic digestion of liquid hot water pretreated hybrid poplar
Authors: Kim Youngmi , Mosier Nathan S. , Ladisch Michael R. 
Published: March 2009

AbstractLiquid hot (LHW) water pretreatment (LHW) of lignocellulosic material enhances enzymatic conversion of cellulose to glucose by solubilizing hemicellulose fraction of the biomass, while leaving the cellulose more reactive and accessible to cellulase enzymes. Within the range of pretreatment conditions tested in this study, the optimized LHW pretreatment conditions for a 15% (wt/vol) slurry of hybrid poplar were found to be 200oC, 10 min, which resulted in the highest fermentable sugar yield with minimal formation of sugar decomposition products during the pretreatment. The LHW pretreatment solubilized 62% of hemicellulose as soluble oligomers. Hot‐washing of the pretreated poplar slurry increased the efficiency of hydrolysis by doubling the yield of glucose for a given enzyme dose. The 15% (wt/vol) slurry of hybrid poplar, pretreated at the optimal conditions and hot‐washed, resulted in 54% glucose yield by 15 FPU cellulase per gram glucan after 120 h. The hydrolysate contained 56 g/L glucose and 12 g/L xylose. The effect of cellulase loading on the enzymatic digestibility of the pretreated poplar is also reported. Total monomeric sugar yield (glucose and xylose) reached 67% after 72 h of hydrolysis when 40 FPU cellulase per gram glucan were used. An overall mass balance of the poplar‐to‐ethanol process was established based on the experimentally determined composition and hydrolysis efficiencies of the liquid hot water pretreated poplar. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Disulfide Bonds versus Trp⋅⋅⋅Trp Pairs in Irregular β‐Hairpins: NMR Structure of Vammin Loop 3‐Derived Peptides as a Case Study
Authors: Mirassou Yasmina , Santiveri Clara M. , Pérez de Vega M. Jesús , González‐Muñiz Rosario , Jiménez M. Angeles 
Published: March 2009

AbstractWhere a noncovalent interaction is better than a covalent bond: The most stabilising cross‐strand pairs were incorporated into an irregular β‐hairpin, loop 3 of vammin. 1H and 13C NMR conformational analyses of these designed peptides indicated that an edge‐to‐face Trp⋅⋅⋅Trp interaction leads to a β‐hairpin that is more stable than a disulfide bond.magnified imageStructural studies on model peptides have led to a good understanding of the rules behind the formation and stability of regular β‐hairpins. To test their applicability to the successful design of irregular β‐hairpins with long loops and/or β‐bulges at the strands, we mimicked loop 3 of vammin, a 4:6 β‐hairpin with a non‐Gly β‐bulge. The most stabilising cross‐strand pairs, disulfide bonds or/and Trp⋅⋅⋅Trp pairs, were incorporated at non‐hydrogen‐bonded sites in peptides spanning the 69–80 region of vammin. According to NMR data, these modified peptides adopt β‐hairpin conformations as intended by design. The Trp‐containing peptides reproduce even the unusual positive ϕ angle for the Gln residue, with the indole rings in the preferred edge‐to‐face orientation. For the first time the β‐hairpin‐stabilising capacities of a disulfide bond and a Trp⋅⋅⋅Trp pair are compared in the same model system. We found that the contribution to stability of the noncovalent indole–indole interaction is larger than that of the covalent disulfide bond, and that their combination gives rise to an even more stable β‐hairpin.
Localization of biogenic amines in the foregut of Aplysia californica: Catecholaminergic and serotonergic innervation
Authors: Martínez‐Rubio Clarissa , Serrano Geidy E. , Miller Mark W. 
Published: March 2009

AbstractThis study examined the catecholaminergic and serotonergic innervation of the foregut of Aplysia californica, a model system in which the control of feeding behaviors can be investigated at the cellular level. Similar numbers (15–25) of serotonin‐like‐immunoreactive (5HTli) and tyrosine hydroxylase‐like‐immunoreactive (THli) fibers were present in each (bilateral) esophageal nerve (En), the major source of pregastric neural innervation in this system. The majority of En 5HTli and THli fibers originated from the anterior branch (En2), which innervates the pharynx and the anterior esophagus. Fewer fibers were present in the posterior branch (En1), which innervates the majority of the esophagus and the crop. Backfills of the two En branches toward the central nervous system (CNS) labeled a single, centrifugally projecting serotonergic fiber, originating from the metacerebral cell (MCC). The MCC fiber projected only to En2. No central THli neurons were found to project to the En. Surveys of the pharynx and esophagus revealed major differences between their patterns of catecholaminergic (CA) and serotonergic innervation. Whereas THli fibers and cell bodies were distributed throughout the foregut, 5HTli fibers were present in restricted plexi, and no 5HTli somata were detected. Double‐labeling experiments in the periphery revealed THli neurons projecting toward the buccal ganglion via En2. Other afferents received dense perisomatic serotonergic innervation. Finally, qualitative and quantitative differences were observed between the buccal motor programs (BMPs) produced by stimulation of the two En branches. These observations increase our understanding of aminergic contributions to the pregastric regulation of Aplysia feeding behaviors. J. Comp. Neurol. 514:329–342, 2009. © 2009 Wiley‐Liss, Inc.
Postnatal development of synaptic structure proteins in pyramidal neuron axon initial segments in monkey prefrontal cortex
Authors: Cruz Dianne A. , Lovallo Emily M. , Stockton Steven , Rasband Matthew , Lewis David A. 
Published: March 2009

AbstractIn the primate prefrontal cortex (PFC), the functional maturation of the synaptic connections of certain classes of γ‐aminobutyric acid (GABA) neurons is very complex. For example, the levels of both pre‐ and postsynaptic proteins that regulate GABA neurotransmission from the chandelier class of cortical interneurons to the axon initial segment (AIS) of pyramidal neurons undergo marked changes during both the perinatal period and adolescence in the monkey PFC. In order to understand the potential molecular mechanisms associated with these developmental refinements, we quantified the relative densities, laminar distributions, and lengths of pyramidal neuron AIS immunoreactive for ankyrin‐G, βIV spectrin, or gephyrin, three proteins involved in regulating synapse structure and receptor localization, in the PFC of rhesus monkeys ranging in age from birth through adulthood. Ankyrin‐G‐ and βIV spectrin‐labeled AIS declined in density and length during the first 6 postnatal months, but then remained stable through adolescence and into adulthood. In contrast, the density of gephyrin‐labeled AIS was stable until approximately 15 months of age and then markedly declined during adolescence. Thus, molecular determinants of the structural features that define GABA inputs to pyramidal neuron AIS in monkey PFC undergo distinct developmental trajectories with different types of changes occurring during the perinatal period and adolescence. In concert with previous data, these findings reveal a two‐phase developmental process of GABAergic synaptic stability and GABA neurotransmission at chandelier cell inputs to pyramidal neurons that likely contributes to the protracted maturation of behaviors mediated by primate PFC circuitry. J. Comp. Neurol. 514:353–367, 2009. © 2009 Wiley‐Liss, Inc.
Synapse‐to‐synapse variation in mean synaptic vesicle size and its relationship with synaptic morphology and function
Authors: Qu Lei , Akbergenova Yulia , Hu Yunming , Schikorski Thomas 
Published: March 2009

AbstractSynaptic vesicle (SV) size is one parameter that controls the amount of neurotransmitter released from individual SVs and, therefore, is fundamental to our understanding of synaptic function. The recently discovered variability of mean SV size among excitatory hippocampal synapses—if actively regulated—is a potential mechanism for the regulation of transmitter release. Here, we investigated which parameters influence mean SV size. First, we revealed that synapse‐to‐synapse variability of SV size is a general phenomenon in several species and brain regions. In addition, we determined the relationship between mean SV size and synaptic morphology. In three‐dimensional reconstructions from serial ultrathin sections, we found that SV size did not correlate with the area of the postsynaptic density (a measure for synaptic size and synaptic cleft volume) nor with the total number of SVs within a bouton or bouton volume. We tested the long‐held hypothesis that a change in osmotic pressure (potentially caused by a change in neurotransmitter concentration) affects SV size. When we reduced the osmotic pressure, SVs became significantly smaller; however, an increase in osmotic pressure had no effect on SV size. Furthermore, we found that SV size does not adapt to chronic changes in activity and that the SV cycle is capable of providing constant SV size during long‐lasting, high‐frequency stimulation. J. Comp. Neurol. 514:343–352, 2009. © 2009 Wiley‐Liss, Inc.
Preparation, Characterization, and Electrocatalytic Properties of Mixed‐Valent Nickel Hexacyanoferrate/Phosphomolybdate Hybrid Film Electrodes Towards Oxidation of Ascorbic Acid and Reduction of S2O$\rm{ {_{8}^{2-}}}$
Authors: Chen Shen‐Ming , Liou Ching‐Yeoung , Balamurugan A. , Thangamuthu R. 
Published: March 2009

AbstractPolynuclear mixed‐valent nickelhexacyanoferrate/phosphomolybdate (NiHCF/PMo), nickel/phosphomolybdate (Ni/PMo) hybrid films were prepared on glassy carbon electrode by multiple scan cyclic voltammetry. Combination of individual components gave the opportunity to fabricate hybrid film with tunable electrochemical and analytical properties compared to individual components. The film growth was monitored using electrochemical quartz crystal microbalance (EQCM). The cyclic voltammogram of the nickelhexacyanoferrate/phosphomolybdate film is characterized by four redox couple whereas nickel/phosphomolybdate hybrid film exhibits three redox couples. Cyclic voltammetric features suggest that the charge transfer process in both films resembles that of surface‐confined redox species. The voltammetric response of nickelhexacyanoferrate/phosphomolybdate film electrode was found to be depending on the pH of the contacting solution. Electrocatalytic behavior of nickel/phosphomolybdate hybrid film coated electrodes toward oxidation of ascorbic acid and reduction of sulfur oxoanion, S2O$\rm{ {_{8}^{2-}}}$, was investigated using cyclic voltammetry technique. Analytical application of nickel/phosphomolybdate hybrid film electrode was tested in amperometry and flow injection analysis.
Conformational dynamics of DNA‐electrophoresis on cationic membranes
Authors: Kahl Valentin , Hennig Martin , Maier Berenike , Rädler Joachim O. 
Published: March 2009

AbstractThe conformational dynamics of DNA molecules undergoing electrophoresis on a fluid substrate‐supported cationic lipid bilayer is investigated using fluorescence microscopy. At low electrophoretic velocities, drift of 2‐D random coils is observed. In contrast, at velocities larger than 0.3 μm/s, the DNA molecules stretch out and assume branched configurations. The cross‐over scenario is explained by the observation that cationic lipids segregate underneath the adsorbed DNA and confine the DNA to its counter charge imprint on time scales shorter than the relaxation time of the imprint. The concept of a tube‐like confinement of the DNA is corroborated by the observed 1/N size dependence of the electrophoretic mobility in analogy to the biased reptation model in gels. The role of membrane defects and possible applications of membrane‐based electrophoresis in microfluidic devices are discussed.
A new method for preparation of an etched porous joint for capillary electrophoresis and its pore‐size evaluation
Authors: Guo Longhua , Qiu Bin , Chen Mingxing , Chen Guonan 
Published: March 2009

AbstractIn this work, an improved approach was developed for the construction of a hydrofluoric acid etched capillary porous joint, and the pore size of the porous joint was investigated. Several etching factors such as reagents concentration and etching temperature were optimized. Results showed that moderate temperature with low hydrofluoric acid concentration was helpful for proportional etching. Low‐range protein molecular weight marker labeled with acridinium ester was used as pore‐size reference for pore‐size evaluation of the joint. A homemade CE with chemiluminescence detection system was used for the analysis of the acridinium ester labeled protein molecular weight marker, and the results showed that only the small molecular peptides can pass through the etched porous joint and the big size proteins cannot. The penetration of protein whose molecular mass was larger than 6500 Da was a signal of over‐etching.