bluuebunny/crossref_metadata_2025_split huggingface dataset:
Engineering a β‐Helical d,l‐Peptide for Folding in Polar Media
Authors: Kulp John L. , Clark Thomas D. 
Published: September 2009

Abstractβ Helices—helices formed by alternating d,l‐peptides and stabilized by β‐sheet hydrogen bonding—are found naturally in only a handful of highly hydrophobic peptides. This paper explores the scope of β‐helical structure by presenting the first design and biophysical characterization of a hydrophilic d,l‐peptide, 1, that forms a β helix in methanol. The design of 1 is based on the β‐hairpin/β helix—a new supersecondary that had been characterized previously only for hydrophobic peptides in nonpolar solvents. Incorporating polar residues in 1 provided solubility in methanol, in which the peptide adopts the expected β‐hairpin/β‐helical structure, as evidenced by CD, analytical ultracentrifugation (AUC), NMR spectroscopy, and NMR‐based structure calculations. Upon titration with water (at constant peptide concentration), the structure in methanol (1 m) transitions cooperatively to an extended conformation (1 w) resembling a cyclic β‐hairpin; observation of an isodichroic point in the solvent‐dependent CD spectra indicates that this transition is a two‐state process. In contrast, neither 1 m nor 1 w show cooperative thermal melting; instead, their structures appear intact at temperatures as high as 65 °C; this observation suggests that steric constraint is dominant in stabilizing these structures. Finally, the 1H NMR CαH spectroscopic resonances of 1 m are downfield‐shifted with respect to random‐coil values, a hitherto unreported property for β helices that appears to be a general feature of these structures. These results show for the first time that an appropriately designed β‐helical peptide can fold stably in a polar solvent; furthermore, the structural and spectroscopic data reported should prove useful in the future design and characterization of water‐soluble β helices.
A Simple Chemical Tuning of the Effective Concentration: Selection of Single‐, Double‐, and Triple‐Stranded Binuclear Lanthanide Helicates
Authors: Terazzi Emmanuel , Guénée Laure , Bocquet Bernard , Lemonnier Jean‐François , Dalla Favera Natalia , Piguet Claude 
Published: September 2009

AbstractThe replacement of terminal 2‐benzimidazol‐6‐carboxypyridine (two internal rotational degrees of freedom) with 2‐benzimidazol‐8‐hydroxyquinoline (one internal rotational degree of freedom) into segmental bis‐tridentate ligands in going from L2 and [L3‐2 H]2− to [L12 b‐2 H]2− does not significantly affect the structures of the resulting binuclear lanthanide triple‐stranded helical complexes [Ln2(L2)3]6+, [Ln2(L3‐2 H)3], and [Ln2(L12 b‐2 H)3] (palindromic helices, intermetallic contact distance≈9 Å, helical pitch≈1.4 nm per turn). However, their thermodynamic assemblies are completely different in solution, as evidenced by the spectacular decrease of the effective concentrations by two orders of magnitude for [L12 b‐2 H]2−. This key parameter in the [Ln2(L12 b‐2 H)n] (n=2, 3) complexes is further abruptly modulated along the lanthanide series (Ln=La to Lu), which provides an unprecedented tool for 1) tuning the number of ligand strands in the final helicates, 2) selectively coordinating lanthanides in the various complexes, and 3) controlling the ratio of lanthanide‐containing polymers over discrete assemblies.
Visualization of the Local Catalytic Activity of Electrodeposited Pt–Ag Catalysts for Oxygen Reduction by means of SECM
Authors: Nagaiah Tharamani C. , Maljusch Artjom , Chen Xingxing , Bron Michael , Schuhmann Wolfgang 
Published: September 2009

AbstractPt–Ag nanoparticle co‐deposits with different Pt–Ag ratios were prepared on a glassy carbon (GC) surface by pulsed electrodeposition and investigated for their catalytic activity in electrocatalytic oxygen reduction by using cyclic voltammetry (CV), rotating disc electrode (RDE) and scanning electrochemical microscopy (SECM) in 0.1 M phosphate buffer (pH 7.0). The atomic composition of the Pt–Ag co‐deposits was studied by means of energy‐dispersive X‐ray analysis (EDAX). In combination with X‐ray diffraction (XRD), the presence of partly alloyed Pt and Ag on the GC surface was confirmed. Scanning electron microscopy (SEM) images indicate that the prepared Pt–Ag catalyst particles are homogenously dispersed over the GC surface. Their size and morphology depend on their composition. The electrocatalytic activity of Pt–Ag deposits with high Pt content was the highest, exceeding even that of electrodeposited Pt as evaluated by quantitative RDE analysis. The redox competition mode of scanning electrochemical microscopy (RC‐SECM) was successfully used to visualize the local catalytic activity of the deposited Pt–Ag particles. Semi‐quantitative assessment of the SECM results confirmed the same order of activity of the different catalysts as the RDE investigations.
Novel straight and circular road driving control of electric power assisted wheelchair based on fuzzy algorithm
Authors: Seki Hirokazu , Tadakuma Susumu 
Published: September 2009

AbstractThis paper describes a novel straight and circular road driving control scheme for electric power‐assisted wheelchairs. “Electric power‐assisted wheelchair” which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people, however, the performance of straight and circular road driving must be further improved because the two wheels drive independently. This paper proposes a novel driving control scheme based on fuzzy algorithm to realize stable and reliable driving on straight and circular roads. The suitable assisted torque of the right and left wheels is determined by fuzzy algorithm based on the posture angular velocity of the wheelchair and the human input torque proportion of the right and left wheels. Some experiments on the practical roads show the effectiveness of the proposed control system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 36–44, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20846
Balancing control for dispersed generators considering torsional torque suppression and AVR performance for synchronous generators
Authors: Senjyu Tomonobu , Omine Eitaro , Hayashi Daisuke , Muhando Endusa Billy , Yona Atsushi , Funabashi Toshihisa 
Published: September 2009

AbstractElectric utility deregulation enabled PPSs (Power Producers and Suppliers) to enter the electricity market. PPSs are supposed to achieve 30‐minute balancing control for stable power supply of electric power. In addition, load rejection and instantaneous voltage drops greatly affect turbine shafting, that is, torsional torque oscillation. Therefore, PPSs must consider a reduction of torsional torque in order to prevent generator shaft damage. This paper proposes a control system which allows the achievement of both 30‐minute balancing control and reduction of torsional torque by using an H∞ controller. The effectiveness of the proposed controller is validated by using MATLAB. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 16–25, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20868
Sequential Mannich‐Aza‐Michael Reactions for the Stereodivergent Synthesis of Highly Substituted Pyrrolidines
Authors: Enkisch Charlotte , Schneider Christoph 
Published: September 2009

AbstractA stereodivergent synthesis of 2,3,5‐trisubstituted pyrrolidines by an organocatalytic Mannich/aza‐Michael addition sequence has been developed. Depending upon the choice of the base used in the intramolecular aza‐Michael additions, 2,5‐trans‐ or 2,5‐cis‐configured pyrrolidines were obtained in high yields and excellent diastereomeric ratios. Selective deprotection of the amino group and the side‐chain hydroxy group proceeded without loss of diastereomeric purity. The stereodivergent outcome of the key aza‐Michael reactions is the result of thermodynamically versus kinetically controlled cyclization.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Diastereo‐ and Enantioselective Synthesis of Functionalized β‐Lactams from Oxiranecarbaldimines and Lithium Ester Enolates
Authors: Michel Kristin , Fröhlich Roland , Würthwein Ernst‐Ulrich 
Published: September 2009

AbstractThe addition of nucleophiles like lithium ester enolates 6 to oxiranecarbaldimines 1 leads to new oxiranyl‐functionalised β‐lactams 7 in excellent enantio‐ and diastereoselectivity. A simple one‐pot procedure affords β‐lactams (azetidin‐2‐ones) with three or four neighbouring stereogenic centres and unlike preference. Products resulting from oxirane ring‐opening reactions were not observed. An enantiomerically enriched example (2S,3S)‐1g gave the corresponding β‐lactam (S,S,R)‐7f in excellent enantiomeric excess. According to quantum chemical calculations the observed diastereoselectivity is the result of a diastereofacial differentiation of the two faces of the iminic double bond in the transition state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
A novel approach to tag and identify geranylgeranylated proteins
Authors: Chan Lai N. , Hart Courtenay , Guo Lea , Nyberg Tamara , Davies Brandon S.J. , Fong Loren G. , Young Stephen G. , Agnew Brian J. , Tamanoi Fuyuhiko 
Published: September 2009

AbstractA recently developed proteomic strategy, the “GG‐azide”‐labeling approach, is described for the detection and proteomic analysis of geranylgeranylated proteins. This approach involves metabolic incorporation of a synthetic azido‐geranylgeranyl analog and chemoselective derivatization of azido‐geranylgeranyl‐modified proteins by the “click” chemistry, using a tetramethylrhodamine‐alkyne. The resulting conjugated proteins can be separated by 1‐D or 2‐D and pH fractionation, and detected by fluorescence imaging. This method is compatible with downstream LC‐MS/MS analysis. Proteomic analysis of conjugated proteins by this approach identified several known geranylgeranylated proteins as well as Rap2c, a novel member of the Ras family. Furthermore, prenylation of progerin in mouse embryonic fibroblast cells was examined using this approach, demonstrating that this strategy can be used to study prenylation of specific proteins. The “GG‐azide”‐labeling approach provides a new tool for the detection and proteomic analysis of geranylgeranylated proteins, and it can readily be extended to other post‐translational modifications.
Formation of CaSO4(aq) and CaSeO4(aq) studied as a function of ionic strength and temperature by CE
Authors: Philippini Violaine , Aupiais Jean , Vercouter Thomas , Moulin Christophe 
Published: September 2009

AbstractCa2+ complexation by both sulfate and selenate ligands was studied by CE. The species were observed to give a unique retention peak as a result of a fast equilibrium between the free ions and the complexes. The change in the corresponding retention time was interpreted with respect to the equilibrium constant of the complexation reaction. The results confirmed the formation of CaSO4(aq) and CaSeO4(aq) under our experimental conditions. The formation data were derived from the series of measurements carried out at about 15, 25, 35, 45 and 55°C in 0.1 mol/L NaNO3 ionic strength solutions, and in 0.5 and 1.0 mol/L NaNO3 ionic strength solutions at 25°C. Using a constant enthalpy of reaction enabled to fit all the experimental data in a 0.1 mol/L medium, leading to the thermodynamic parameters: ΔrG0.1M(25°C)=−(7.59±0.23) kJ/mol, ΔrH0.1 M=5.57±0.80 kJ/mol, and ΔrS0.1 M(25°C)=44.0±3.0 J mol−1 K−1 for CaSO4(aq) and ΔrG0.1 M(25°C)=−(6.66±0.23) kJ/mol, ΔrH0.1 M=6.45±0.73 kJ/mol, and ΔrS0.1 M(25°C)=44.0±3.0 J mol−1 K−1 for CaSeO4(aq). Both formation reactions were found to be endothermic and entropy driven. CaSO4(aq) appears to be more stable than CaSeO4(aq) by 0.93 kJ/mol under these experimental conditions, which correlates with the difference of acidity of the anions as expected for interactions between hard acids and hard bases according to the hard and soft acids and bases theory. The effect of the ionic medium on the formation constants was successfully treated using the Specific ion Interaction Theory, leading to significantly different binary coefficients ${\rm {\varepsilon}}_{{{{\rm Na}^+}, {{\rm SO}_{4}^{2-}}}}= -{(0.15 \pm 0.06)}\,$mol/kg−1 and ${\rm {\varepsilon}}_{{{{\rm Na}^+}, {{\rm SO}_{4}^{2-}}}}= -{(0.26 \pm 0.10)}\,$mol/kg−1
Micropump based on electroosmosis of the second kind
Authors: Mishchuk Nataliya A. , Heldal Trond , Volden Tormod , Auerswald Janko , Knapp Helmut 
Published: September 2009

AbstractA microfluidic pump based on electroosmosis of the second kind was designed and fabricated. Experimental results using DC and AC voltages showed a close to second‐order relationship between flow and voltage, in good agreement with theory. The experimental flow rates were considerably lower than the predicted maximum for the micropumps, which can be attributed to the hydrodynamic resistance of the channel network. This also indicates that higher flow velocities are obtainable for modified pump designs.
Theoretical performance evaluation of EDCA in IEEE 802.11e wireless LANs
Authors: Peng Fei 
Published: September 2009

AbstractWhile the original IEEE 802.11 distributed coordinated function (DCF) has been widely analysed by both theoretical and simulation studies, the performance of the new IEEE 802.11e enhanced distributed channel access (EDCA) has not yet been investigated extensively. In this paper, we extend an analytical model to capture the operations of the arbitrary inter‐frame space, contention window differentiation and transmission opportunity in EDCA for the evaluation of throughput performance and collision probability of different service classes. The performance analyses are validated by simulation results. Our analysis provides insightful results for evaluating the impact of different priority parameters on the performance of EDCA service differentiation. Copyright © 2009 John Wiley & Sons, Ltd.
Co‐localization of Nkx6.2 and Nkx2.2 homeodomain proteins in differentiated myelinating oligodendrocytes
Authors: Cai Jun , Zhu Qiang , Zheng Kang , Li Hong , Qi Yingchuan , Cao Qilin , Qiu Mengsheng 
Published: September 2009

AbstractRecent studies have suggested that Nkx6.2/Gtx and Nkx2.2 homeodomain transcription factors are involved in the regulation of oligodendrocyte maturation and/or myelination which occur predominantly in postnatal stages. However, their cellular specificity in postnatal central nervous system has not been characterized and their dynamic expressional relationship during oligodendrocyte lineage progression has not been determined. Here we report that both Nkx2.2 and Nkx6.2 are selectively expressed in Olig2+ cells of oligodendrocyte lineage in postnatal spinal cords. Although Nkx6.2 is specifically expressed in the APC+ mature oligodendrocytes, Nkx2.2 is initially expressed in differentiating oligodendrocyte precursor cells (OPCs) but quickly down‐regulated as OPCs undergo terminal differentiation. Intriguingly, Nkx2.2 expression is up‐regulated in mature myelinating oligodendrocytes at later stages. The co‐expression of Nkx2.2 and Nkx6.2 transcription factors in myelinating oligodendrocytes suggests their functional interactions in the regulation of myelin sheath formation and/or maintenance. © 2009 Wiley‐Liss, Inc.
Collateral neuronal apoptosis in CNS gray matter during an oligodendrocyte‐directed CD8+ T cell attack
Authors: Göbel Kerstin , Melzer Nico , Herrmann Alexander M. , Schuhmann Michael K. , Bittner Stefan , Ip Chi Wang , Hünig Thomas , Meuth Sven G. , Wiendl Heinz 
Published: September 2009

AbstractDemyelination and death of oligodendrocytes accompanied by transection of neurites and neuronal apoptosis are pathological hallmarks of cortical and subcortical gray matter lesions in demyelinating viral and autoimmune inflammatory CNS disorders. In these disorders, leukocortical lesions, containing the perikarya of most efferent neurons, display pronounced infiltration by CD8+ T cells of putative specificity for oligodendrocyte‐ and myelin‐related antigens. Hence, neuronal apoptosis in gray matter lesions may be a collateral effect of an oligodendrocyte‐directed attack by CD8+ T cells. To challenge this hypothesis, we transferred activated antigen‐specific CD8+ T cells (OT‐I T cells) into acute coronal brain slices from mice selectively expressing ovalbumin as a cytosolic neo‐self‐antigen in oligodendrocytes (ODC‐OVA mice). We studied mechanisms and kinetics of oligodendroglial and neuronal apoptosis in the neocortex and hippocampus, using multicolor staining for different cell types and activated caspase‐3. Within the gray matter, a single OT‐I T cell caused simultaneous caspase‐3 activation in about 30 ODCs and 10 neurons within 6 h in a strictly antigen‐dependent manner. Experiments with OT‐I T cells genetically deficient for perforin or the granzyme B‐cluster and with blocking anti‐FasL antibodies as well as proinflammatory cytokines revealed, that collateral apoptosis of neurons was likely due to a spillover of perforin and granzyme(s) from the OT‐I T cell itself or the immunological synapse that it selectively formed with antigen‐presenting oligodendrocytes. Collateral neuronal apoptosis could contribute to substantial neuronal loss in gray matter lesions and cause persistent neurological impairment in both acute and chronic gray matter lesions in various inflammatory CNS disorders. © 2009 Wiley‐Liss, Inc.
The physician workforce in Kuwait to the year 2020
Authors: Al‐Jarallah Khaled , Moussa Mohamed , Al‐Khanfar Khadija Figen 
Published: September 2009

AbstractThe study addresses the supply of and demand for physicians in Kuwait in the light of the emerging variables such as increasing population, economic growth, changes in healthcare strategies, and expansion of healthcare facilities. The objective of the study was to project the future demand for physicians in Kuwait for the years 2007–2020 based on the period 1994–2006. Population projections were derived using the average annual natural increase rate of the 1994–2006 populations. The future demand for physicians was predicted using the average physician to population ratio for the years 1994–2006. The average annual growth rate of indigenous physicians during the period 1994–2006 was 4.08% compared to 2.83% for non‐native expatriot physicians. There is a gap between the numbers of native and foreign physicians. In 2006, native physicians constituted 36.6% of the physician workforce in Kuwait. The disparity between the total number of physicians needed and the number of native physicians is expected to decline from 62.14% in 2007 to 48.1% in 2020. The supply of indigenous physicians should be increased. Without shared culture and language, it will be difficult to provide effective and efficient medical care to the people of Kuwait. This can be achieved through an improvement in recruitment and retention of indigenous physicians and medical students. There is also a need for establishment of a standing advisory committee for continuous monitoring of physician workforce planning and policy strategies in Kuwait. Copyright © 2009 John Wiley & Sons, Ltd.
Autophagosomal glycogen‐degrading activity and its relationship to the general autophagic activity in newborn rat hepatocytes: The effects of parenteral glucose administration
Authors: Kalamidas Stefanos A. , Kondomerkos Dimitrios J. 
Published: September 2009

AbstractThe effects of the administration of parenteral glucose on the postnatal glycogen autophagic activity and its relationship to the general autophagic activity, were studied in newborn rat liver using electron microscopy and biochemical methods. Glucose abolished the normal postnatal hypoglycemia and preserved the hepatocytic hyaloplasmic glycogen to the levels of birth. It also inhibited the normal postnatal increase in the number and volume of autophagic vacuoles. Glucose especially decreased the rate of postnatal development of the glycogen‐containing autophagic vacuoles. This decrease was greater than that of the autophagic vacuoles in general. In the control animals at the age of 6 h, the total volume of the glycogen‐containing autophagic vacuoles accounted for 87% of the autophagic vacuoles in general, whereas in the glucose‐treated animals of the same age, for only 62%. The results of this and previous studies support the view that the general autophagic activity that develops in the immediate postnatal period in rat hepatocytes is mainly expressed as glycogen autophagic activity selectively inhibited by glucose. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.
The anti‐diabetic effect of anthocyanins in streptozotocin‐induced diabetic rats through glucose transporter 4 regulation and prevention of insulin resistance and pancreatic apoptosis
Authors: Nizamutdinova Irina Tsoy , Jin Yong Chun , Chung Jong Il , Shin Sung Chul , Lee Sung Joong , Seo Han Geuk , Lee Jae Heun , Chang Ki Churl , Kim Hye Jung 
Published: September 2009

AbstractHyperglycemia, abnormal lipid and antioxidant profiles are the most usual complications in diabetes mellitus. Thus, in this study, we investigated the anti‐diabetic and anti‐oxidative effects of anthocyanins (ANT) from black soybean seed coats in streptozotocin (STZ)‐induced diabetic rats. The administration of ANT markedly decreased glucose levels and improved heart hemodynamic function (left ventricular end diastolic pressure, ±dp/dt parameters). ANT not only enhanced STZ‐mediated insulin level decreases, but also decreased the triglyceride levels induced by STZ injection in serum. Diabetic rats exhibited a lower expression of glucose transporter 4 proteins in the membrane fractions of heart and skeletal muscle tissues, which was enhanced by ANT. In addition, ANT activated insulin receptor phosphorylation, suggesting an increased utilization of glucose by tissues. Moreover, ANT protected pancreatic tissue from STZ‐induced apoptosis through regulation of caspase‐3, Bax, and Bcl‐2 proteins. Furthermore, ANT significantly suppressed malondialdehyde levels and restored superoxide dismutase and catalase activities in diabetic rats. Interestingly, the observed effects of ANT were superior to those of glibenclamide. Taken together, ANT from black soybean seed coat have anti‐diabetic effects that are due, in part, to the regulation of glucose transporter 4 and prevention of insulin resistance and pancreatic apoptosis, suggesting a possible use as a drug to regulate diabetes.
Experimental and numerical assessment of MRI‐induced temperature change and SAR distributions in phantoms and in vivo
Authors: Oh Sukhoon , Webb Andrew G. , Neuberger Thomas , Park BuSik , Collins Christopher M. 
Published: September 2009

AbstractIt is important to accurately characterize the heating of tissues due to the radiofrequency energy applied during MRI. This has led to an increase in the use of numerical methods to predict specific energy absorption rate distributions for safety assurance in MRI. To ensure these methods are accurate for actual MRI coils, however, it is necessary to compare to experimental results. Here, we report results of some recent efforts to experimentally map temperature change and specific energy absorption rate in a phantom and in vivo where the only source of heat is the radiofrequency fields produced by the imaging coil. Results in a phantom match numerical simulation well, and preliminary results in vivo show measurable temperature increase. With further development, similar methods may be useful for verifying numerical methods for predicting specific energy absorption rate distributions and in some cases for directly measuring temperature changes and specific energy absorption rate induced by the radiofrequency fields in MRI experiments. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.