bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bisphosphine‐Functionalized Cyclic Decapeptides Based on the Natural Product Gramicidin S: A Potential Scaffold for Transition‐Metal Coordination
Authors: Burck Sebastian , van Assema Sander G. A. , Lastdrager Bas , Slootweg J. Chris , Ehlers Andreas W. , Otero José M. , Dacunha‐Marinho Bruno , Llamas‐Saiz Antonio L. , Overhand Mark , van Raaij Mark J. , Lammertsma Koop 
Published: July 2009

AbstractThe natural product Gramicidin S is a promising scaffold for novel oligopeptide‐based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine‐containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the α‐carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single‐crystal X‐ray structure analysis. By detaching the template, enantiopure L‐phosphine amino acids resulted enabling the solid‐phase, stepwise construction of a linear sequence of the phosphine‐modified oligopeptides. On cyclization three bisphosphine‐substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands.
Self‐assembly and chiral recognition of quartz crystal microbalance chiral sensor
Authors: Luo Miao Li , Zhang Wei Guang , Zhang Sheng , Fan Jun , Su Wen Cui , Yin Xia 
Published: July 2009

AbstractA novel chiral sensor based on the self‐assembled monolayer of (6A‐ω‐mercaptoethylureado‐6A‐deoxy)heptakis(2,3‐di‐o‐phenylcarbamoyl)‐6B, 6C, 6D, 6E, 6F, 6G‐ hexa‐o‐phenylcarbamoyl‐β‐cyclodextrin (Ph‐β‐CD‐SH) on a quartz crystal transducer for chiral recognition was set up. (R,S)‐(±)‐(3‐Methoxyphenyl)ethylamine were recognized by this QCM chiral sensor with a QCM chiral discrimination factor of 1.33. Furthermore, UV spectroscopy was used to investigate the mechanism of host‐guest interactions between (6A‐azido‐6A‐deoxy)heptakis(2,3‐di‐o‐phenylcarbamoyl)‐6B, 6C, 6D, 6E, 6F, 6G‐hexa‐o‐phenylcarbamoyl‐β‐cyclodextrin (Ph‐β‐CD) and (R,S)‐(±)‐(3‐methoxyphenyl) ethylamine. The UV discrimination factor was determined to be 0.066. Chirality, 2010. © 2009 Wiley‐Liss, Inc.
Ultrasound‐mediated synthesis of camphoric acid‐based chiral salens for the enantioselective trimethylsilylcyanation of aldehydes
Authors: Serra Maria E. Silva , Murtinho Dina , Goth Albertino , Rocha Gonsalves António M. D'A. , Abreu Paulo E. , Pais Alberto A. C. C. 
Published: July 2009

AbstractNew chiral salen ligands were prepared by the ultrasound‐irradiated condensation of optically active (1R, 3S)‐1,2,2‐trimethyl‐1,3‐diaminocyclopentane with aromatic 1‐hydroxyaldehydes. The ultrasound‐mediated process is more convenient due to shorter reaction times, energy economy, and easier isolation of the products. The in situ formed Ti(IV)(salen) complexes, evaluated as catalysts in the enantioselective trimethylsilylcyanation of benzaldehyde, were found to be efficient for this process, originating the corresponding product in high yields (72–99%) and selectivities of up to 79%. The lowest energy transition states were determined by computational studies. These results were in qualitative agreement with the experimentally observed ones. Chirality, 2010. © 2009 Wiley‐Liss, Inc.
The search for meaning—Symptoms and transvaginal sonography screening for ovarian cancer
Authors: Pavlik Edward J. , Saunders Brook A. , Doran Stacey , McHugh Katherine W. , Ueland Frederick R. , DeSimone Christopher P. , DePriest Paul D. , Ware Rachel A. , Kryscio Richard J. , van Nagell John R. 
Published: July 2009

AbstractBACKGROUND:The mortality rate of ovarian cancer is greater than that of all other major gynecologic malignancies. Detecting ovarian cancer at an early and curable stage long has been an objective of oncologists. Recently, it was reported that certain symptom patterns are informative for the presence of ovarian malignancy. In this article, the authors report on how symptoms and ultrasound predict ovarian malignancy.METHODS:Two hundred seventy‐two women who were participating in annual transvaginal sonography (TVS) screening were selected from among 31,748 women who were enrolled. Symptom results were correlated with ultrasound and surgical pathology findings.RESULTS:TVS performed better than symptoms analysis for detecting malignancies (sensitivity, 73.3% vs 20%), and symptoms analysis performed better for distinguishing benign tumors (specificity, 91.3% vs 74.4%). The use of TVS and symptoms analysis in series resulted in poorer identification of malignancy (sensitivity, 16.7%) but improved the ability to distinguish benign tumors (specificity, 97.9%). Decisions using either symptoms or TVS combined in parallel had small increases in sensitivity (+3.3%) and had coordinated, small decreases in specificity (−5.8%).CONCLUSIONS:Symptoms did identify ovarian malignancies, but not as well as TVS. The current findings indicated that: 1) tumors that are negative by both ultrasound and a symptoms index are likely to be benign (specificity, >97%), and 2) adding symptoms information that has weight equal to the weight of ultrasound only slightly improves the discrimination of malignancy (sensitivity increase, +3.3%). Thus, a major benefit in discriminating malignancy was achieved through ultrasound, whereas the absence of symptoms in conjunction with an abnormal ultrasound (characterized by a low morphology index) indicated that the mass was benign and that surgery may not be required. Finally, informative symptoms can be expected to be absent in 80% of patients with ovarian malignancies. Cancer 2009. © 2009 American Cancer Society.
Analysis of epigenetic alterations to chromatin during development
Authors: Minard Meghan E. , Jain Abhinav K. , Barton Michelle Craig 
Published: July 2009

AbstractEach cell within a multicellular organism has distinguishable characteristics established by its unique patterns of gene expression. This individual identity is determined by the expression of genes in a time and place‐dependent manner, and it is becoming increasingly clear that chromatin plays a fundamental role in the control of gene transcription in multicellular organisms. Therefore, understanding the regulation of chromatin and how the distinct identity of a cell is passed to daughter cells during development is paramount. Techniques with which to study chromatin have advanced rapidly over the past decade. Development of high throughput techniques and their proper applications has provided us essential tools to understand the regulation of epigenetic phenomena and its effect on gene expression. Understanding the changes that occur in chromatin during the course of development will not only contribute to our knowledge of normal gene expression, but will also add to our knowledge of how gene expression goes awry during disease. This review opens with an introduction to some of the key premises of epigenetic regulation of gene expression. A discussion of experimental techniques with which one can study epigenetic alterations to chromatin during development follows, emphasizing recent breakthroughs in this area. We then present examples of epigenetic mechanisms exploited in the control of developmental cell fate and regulation of tissue‐specific gene expression. Finally, we discuss some of the frontiers and challenges in this area of research. genesis 47:559–572, 2009. © 2009 Wiley‐Liss, Inc.
A mouse model for visualization of GABAB receptors
Authors: Casanova Emilio , Guetg Nicole , Vigot Réjan , Seddik Riad , Julio‐Pieper Marcela , Hyland Niall P. , Cryan John F. , Gassmann Martin , Bettler Bernhard 
Published: July 2009

AbstractGABAB receptors are the G‐protein‐coupled receptors for the neurotransmitter γ‐aminobutyric acid (GABA). Receptor subtypes are based on the subunit isoforms GABAB1a and GABAB1b, which combine with GABAB2 subunits to form heteromeric receptors. Here, we used a modified bacterial artificial chromosome (BAC) containing the GABAB1 gene to generate transgenic mice expressing GABAB1a and GABAB1b subunits fused to the enhanced green fluorescence protein (eGFP). We demonstrate that the GABAB1‐eGFP fusion proteins reproduce the cellular expression patterns of endogenous GABAB1 proteins in the brain and in peripheral tissue. Crossing the GABAB1‐eGFP BAC transgene into the GABAB1−/− background restores pre and postsynaptic GABAB functions, showing that the GABAB1‐eGFP fusion proteins substitute for the lack of endogenous GABAB1 proteins. Finally, we demonstrate that the GABAB1‐eGFP fusion proteins replicate the temporal expression patterns of native GABAB receptors in cultured neurons. These transgenic mice therefore provide a validated tool for direct visualization of native GABAB receptors. genesis 47:595–602, 2009. © 2009 Wiley‐Liss, Inc.
Cell adhesive affinity does not dictate primitive endoderm segregation and positioning during murine embryoid body formation
Authors: Moore Robert , Cai Kathy Q. , Escudero Diogo O. , Xu Xiang‐Xi 
Published: July 2009

AbstractThe classical cell sorting experiments undertaken by Townes and Holtfreter described the intrinsic propensity of dissociated embryonic cells to self‐organize and reconcile into their original embryonic germ layers with characteristic histotypic positioning. Steinberg presented the differential adhesion hypothesis to explain these patterning phenomena. Here, we have reappraised these issues by implementing embryoid bodies to model the patterning of epiblast and primitive endoderm layers. We have used combinations of embryonic stem (ES) cells and their derivatives differentiated by retinoic acid treatment to model epiblast and endoderm cells, and wild‐type or E‐cadherin null cells to represent strongly or weakly adherent cells, respectively. One cell type was fluorescently labeled and reconstituted with another heterotypically to generate chimeric embryoid bodies, and cell sorting was tracked by time‐lapse video microscopy and confirmed by immunostaining. When undifferentiated wild‐type and E‐cadherin null ES cells were mixed, the resulting cell aggregates consisted of a core of wild‐type cells surrounded by loosely associated E‐cadherin null cells, consistent with the differential adhesion hypothesis. However, when mixed with undifferentiated ES cells, the differentiated primitive endoderm‐like cells sorted to the surface to form a primitive endoderm layer irrespective of cell‐adhesive strength, contradicting the differential adhesion hypothesis. We propose that the primitive endoderm cells reach the surface by random movement, and subsequently the cells generate an apical/basal polarity that prevents reentry. Thus, the ability to generate epithelial polarity, rather than adhesive affinity, determines the surface positioning of the primitive endoderm cells. genesis 47:579–589, 2009. © 2009 Wiley‐Liss, Inc.
Misexpression of Gbx2 throughout the mesencephalon by a conditional gain‐of‐function transgene leads to deletion of the midbrain and cerebellum in mice
Authors: Sunmonu N. Abimbola , Chen Li , Li James Y.H. 
Published: July 2009

AbstractThe mouse homeobox gene, Gbx2, is expressed in discreet domains in the neural tube and plays a key role in forebrain and hindbrain development. Previous studies have demonstrated that mutual inhibition between Gbx2 and Otx2, which are respectively expressed in the anterior and posterior parts of the neural plate, positions the prospective midbrain–hindbrain junction. We describe here a conditional Gbx2 gain‐of‐function transgenic mouse line, Gbx2‐GOF, which expresses Gbx2 and red fluorescence protein, mCherry, upon Cre‐mediated recombination. In the absence of Cre, β‐galactosidase is broadly expressed in mouse embryos and adult brains carrying the transgene. By combining Gbx2‐GOF and En1Cre knock‐in allele, we activated expression of Gbx2 and mCherry throughout the mesencephalon (mes) and rhombomere 1 (r1). The ectopic expression of Gbx2 causes an anterior shift of the mes/r1 junction at embryonic day 10.5. Interestingly, we found that persistent expression of Gbx2 throughout the mes/r1 region largely abolishes expression of the isthmic organizer gene Fgf8, leading to deletion of the midbrain and cerebellum at later stages. Our data suggest that the juxtaposition of the expression domains of Gbx2 and Otx2 within the mes/r1 area is essential for the maintenance of Fgf8 expression. Furthermore, the Gbx2‐GOF transgenic line is suitable for functional study of Gbx2 during development. genesis 47:667–673, 2009. © 2009 Wiley‐Liss, Inc.
Capn8 promoter directs the expression of Cre recombinase in gastric pit cells of transgenic mice
Authors: Zhao Zengming , Sun Yanxun , Hou Ning , Teng Yan , Wang Youliang , Yang Xiao 
Published: July 2009

AbstractGastric pit cells are high‐turnover epithelial cells of the gastric mucosa. They secrete mucus to protect the gastric epithelium from acid and pepsin. To investigate the genetic mechanisms underlying the physiological functions of gastric pit cells, we generated a transgenic mouse line, namely, Capn8‐Cre, in which the expression of Cre recombinase was controlled by the promoter of the intracellular Ca2+‐regulated cysteine protease calpain‐8. To test the tissue distribution and excision activity of Cre recombinase, the Capn8‐Cre transgenic mice were bred with the ROSA26 reporter strain and a mouse strain that carries Smad4 conditional alleles (Smad4Co/Co). Multiple‐tissue PCR and LacZ staining demonstrated that Capn8‐Cre transgenic mouse expressed Cre recombinase in the gastric pit cells. Cre recombinase activity was also detected in the liver and skin tissues. These data suggest that the Capn8‐Cre mouse line described here could be used to dissect gene function in gastric pit cells. genesis 47:674–679, 2009. © 2009 Wiley‐Liss, Inc.
Synthesis of Zinc Glycerolate Microstacks from a ZnO Nanorod Sacrificial Template
Authors: Rémiás Róbert , Kukovecz Ákos , Darányi Mária , Kozma Gábor , Varga Szilvia , Kónya Zoltán , Kiricsi Imre 
Published: July 2009

AbstractWe synthesized zinc glycerolate (ZnGly) microstacks bytreating ZnO with glycerol at 100 °C under reflux. We observed that the morphology of the ZnO source has a pronounced effect on the appearance of the ZnGly product. In the absence of structure‐directing effects the product ZnGly is obtained as a random heap of hexagonal prisms with an average diameter and thickness of ca. 2.5 μm and ca. 350 nm, respectively. However, bundles of nanorod‐shaped ZnO obtained by the thermal decomposition of zinc oxalate nanorods could readily be transformed into 2–4 μm long zinc glycerolate microstacks in which 6–12 hexagonal prisms are aligned face‐to‐face. We present evidence that the ZnGly plates in the microstacks are bound together by forces strong enough to withstand mechanical deformation exercised by a contacting AFM tip. The ZnGly microstacks appear to emerge from the ZnO nanorod bundles in an approx. 1:1 ratio in the reactive template synthesis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Alkyl‐Bridged Bis‐5‐azidotetrazoles: A Safe Way of Preparation
Authors: Klapötke Thomas M. , Sproll Stefan M. 
Published: July 2009

AbstractThe general, high‐yielding synthesis of extremely dangerous alkylated bis‐5‐azidotetrazoles is presented. The preparation using 5‐bromotetrazoles for the generation of tetrazolyl hydrazines, which are then converted into the corresponding bis‐5‐azidotetrazoles, presents a safe, large‐scale preparation of alkylated bis‐5‐azidotetrazoles. In this work, 1,2‐bis(5‐azido‐1H‐tetrazol‐1‐yl)ethane, 1,2‐bis(5‐azido‐1H‐tetrazol‐1‐yl)‐1‐methylethane, and 1,4‐bis(5‐azido‐1H‐tetrazol‐1‐yl)butane were synthesized and characterized by 1H, 13C, and 15N NMR spectroscopy, vibrational spectroscopy (IR), and mass spectrometry. The crystal structure of 1,2‐bis(5‐azido‐1H‐tetrazol‐1‐yl)ethane was determined by single‐crystal X‐ray diffraction. In addition, the thermal behavior of the bis‐5‐azidotetrazoles was investigated by differential scanning calorimetry and their sensitivity towards friction and impact were determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Morita–Baylis–Hillman Reactions Between Conjugated Nitroalkenes or Nitrodienes and Carbonyl Compounds
Authors: Deb Indubhusan , Shanbhag Pramod , Mobin Shaikh M. , Namboothiri Irishi N. N. 
Published: July 2009

AbstractMorita–Baylis–Hillman (MBH) reactions between conjugated nitroalkenes or nitrodienes and various carbonyl compounds such as glyoxylate, trifluoropyruvate, pyruvaldehyde, oxomalonate, ninhydrin, and formaldehyde have been extensively investigated. The reactions proceeded smoothly in the presence of DMAP (40–100 mol‐%) in acetonitrile and in some cases also in that of imidazole (100 mol‐%) in CHCl3 or THF, to provide the multifunctional adducts in good to excellent yields. The reactions catalyzed by DMAP in acetonitrile were superior to the imidazole‐catalyzed reactions both in terms of the rate of reaction and in terms of the isolated yields of the MBH adducts. The catalytic roles played by DMAP and imidazole in these reactions, vis‐à‐vis other MBH catalysts such as DABCO, are attributed primarily to resonance stabilization of the initial zwitterionic intermediates. Whereas the E isomers are the major or exclusive products in the cases of glyoxylate, pyruvaldehyde, and formaldehyde, the Z isomers predominate in the cases of trifluoropyruvate and ninhydrin. Interestingly, oxomalonate forms E isomers with aromatic nitroalkenes and Z isomers with aliphatic ones. These selectivities and the formation of unusual deconjugated products in the case of certain β‐alkyl‐nitroethylenes have been explained.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Quantifying Primary Silver Ions Contents in Poly(vinyl chloride) and Poly(n‐butyl acrylate) Ion‐Selective Membranes
Authors: Michalska Agata , Wojciechowski Marcin , Bulska Ewa , Maksymiuk Krzysztof 
Published: July 2009

AbstractOn a model example of silver selective, poly(vinyl chloride) (PVC) or poly(n‐butyl acrylate) based plastic membranes, a method of primary ions quantification has been proposed. For this purpose the inductively coupled plasma mass spectrometry with laser ablation (LA ICP MS) was used. Significant differences of the ions distribution between examined membranes materials were observed. For both kinds of membranes the influence of the concentration of AgNO3 in conditioning solution was noticed. Conditioning in 0.1 M solution resulted in a few times higher silver levels compared to expected for 100 mol% membrane saturation (relative to lipohilic salt content). This points to pronounced co‐extraction of quite lipophilic nitrate anions. In the case of poly(n‐butyl acrylate) based membranes, silver was accumulated mainly in the surface domain of the membrane, due to low mobility of silver ions in this material. This was experimentally proved by concentration profiles of silver across the poly(n‐butyl acrylate) membrane, showing a lower contents inside the membrane, being in contrast to uniform distribution in PVC based matrix. The obtained silver contents in the membranes correlates well with potentiometric characteristic, low contents of silver corresponds to super‐Nernstian responses in low Ag+ activities range, for about 75% of saturation the detection limit close to 10−8 M is obtained, 100% saturation or even higher silver contents results in micromolar detection limits.
Metrological Aspects of Glucose Measurements by Biosensors
Authors: Wunderli Samuel , Andres Hanspeter 
Published: July 2009

AbstractIn a chronoamperometric measurement the chemical activity of glucose is directly determined using a glucose sensitive biosensor based on glucose oxidase and an efficient mediator. Within the physiological range of 2 mmol kg−1 and 10 mmol kg−1 glucose in aqueous solutions behaves almost ideally and the chemical activity equals the glucose molality, the amount of glucose per unit mass of water, within the estimated measurement uncertainty. In physiological samples the equality between chemical activity and glucose molality is destroyed and has to be corrected for. Gravimetrically prepared mixtures of high purity glucose in buffered aqueous solutions are used as standards for calibration of the chronoamperometric measurement setup. Based on the model equation for the measurand aqueous or physiological sample, all significant sources of uncertainty are identified, their magnitude estimated from published and experimental data and finally combined to give the uncertainty in the reported value of the glucose molality. It is found, that the combined uncertainty of the glucose molality comprises mainly uncertainty contributions from the nonideal behavior, the chronoamperometric measurement setup, from the purity of glucose used and from the chemical composition of the test sample. The expanded uncertainty is below 2% rel., the glucose content determined by the bioelectrochemical measurements thus competes well with today's considered most accurate reference method Isotope Dilution Mass Spectrometry. Advantageous of the presented electroanalytical method is the direct measure of the glucose molality without prior sample preparation and dilution.
Calixarene/Nafion‐Modified Bismuth‐Film Electrodes for Adsorptive Stripping Voltammetric Determination of Lead
Authors: Torma Ferenc , Grün Alajos , Bitter Isván , Tóth Klára 
Published: July 2009

AbstractThis paper presents an enhanced adsorptive stripping voltammetric procedure (AdSV) for the determination of Pb2+, which relies on the accumulation of the metals at a calixarene‐based chemically modified bismuth‐film electrode on glassy carbon substrate. Following the accumulation of the target metals at open circuit and a medium exchange, both the square wave anodic stripping detection of the metal ions and the in situ bismuth‐film formation was performed simultaneously in a Bi3+ containing supporting electrolyte. The analysis of Pb2+ under optimized conditions resulted in stripping responses with good linearity (in the range 0.05–0.6 μM) and precision (RSD=1.12% at 0.2 μM Pb2+; n=10) and low detection limit (0.02 μg/L at 10 min preconcentration). The determination of Pb2+ (0.4 μM) at 100‐fold excess of interfering ions (Cd2+, Cu2+ and Zn2+) yielded well resolved lead signal. The analytical utility of the method elaborated was tested in the analysis of trace Pb2+ in environmental water samples.
Lower Rim Substituted p‐tert‐Butyl‐Calix[4]arene. Part 15. Pb(II)‐Ion‐Selective Electrodes Based on p‐tert‐Butyl‐calix[4]arene Thioamides
Authors: Bocheńska Maria , Guziński Marcin , Kulesza Joanna 
Published: July 2009

AbstractTetrasubstituted p‐tert‐butylcalix[4]arene‐thioamides (1–5) were applied as ionophores in ion‐selective membrane electrodes (ISE) and were tested towards Pb‐selectivity. The selectivity coefficients of the electrodes were determined. The tertiary calix[4]thioamides (1, 2) show remarkable selectivity for Pb(II) cations when compared with respectable calix[4]amides. The electrode membranes with those ligands are stable, the Pb‐characteristics are close to nernstian within a wide linear range (−log c=6–1). Compounds 3–5, the secondary calix[4]thioamides form less stable electrode membranes. Complex formation constants of the ligands 1, 2, 3 and 5 with Pb(II) and some most interfering ions were determined.