bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oligoribonucleotide Analogues Containing a Mixed Backbone of Phosphodiester and Formacetal Internucleoside Linkages, Together with Vicinal 2′‐O‐Methyl Groups
Authors: Rozners Eriks , Katkevica Dace , Strömberg Roger 
Published: February 2007

AbstractOligoribonucleotides containing formacetal internucleoside linkages have been prepared and studied by UV melting experiments. In RNA duplexes, the formacetal substitution is stabilizing (Δtm=0 to +0.9 °C per modification) at physiological salt concentrations (0.1 M) but destabilizing (Δtm=−0.4 to −0.8 °C per modification) at high salt concentrations (1 M); this suggests that reduction of electrostatic repulsion contributes substantially to the stabilization. The presence of 2′‐O‐Me substituents increases the stabilities of the duplexes (Δtm=+0.5 to +1.1 °C per modification). The positive effects of formacetals and 2′‐O‐Me groups were independent and additive. 1H NMR studies on monomeric model compounds containing 3′‐(ethyl phosphate) or 3′‐O‐ethoxymethyl groups showed that the formacetal and 2′‐O‐Me substitutions shift the conformational equilibria of the ribose residues towards the North conformers by 5 to 12 %. Although the preference for the North conformers qualitatively correlates with increased duplex stabilities, changes in thermodynamic parameters (ΔH° and TΔS°) for formation of oligonucleotide duplexes and differences in dependence on concentrations of sodium acetate, sodium chloride and sodium perchlorate suggest that solvation effects are also important for the duplex stabilities. Overall the formacetal linkages fit well in A‐type RNA duplexes, making them potentially interesting modifications for RNA‐based gene‐control strategies (e.g., antisense and RNA interference).
Shaping and Enforcing Coordination Spheres: The Implications of C3 and C1 Chirality in the Coordination Chemistry of 1,1,1‐Tris(oxazolinyl)ethane (“Trisox”)
Authors: Gade Lutz H. , Marconi Guido , Dro Clémence , Ward Benjamin D. , Poyatos Macarena , Bellemin‐Laponnaz Stéphane , Wadepohl Hubert , Sorace Lorenzo , Poneti Giordano 
Published: February 2007

AbstractA key feature of tris(oxazolinyl)ethane (“trisox”) ligands, which have shown broad scope in asymmetric catalysis, is the orientation and steric demand of their oxazoline substituents. This, along with the modularity of their synthesis determines their coordination chemistry. The possibility to combine oxazolines, in which the stereogenic centers adjacent to the N‐donor atoms have different absolute configuration, whilst retaining their ability to coordinate as tripodal ligands, has been demonstrated by the synthesis of the enantiomerically pure C3‐symmetric iPr‐trisox(S,S,S) and C1‐symmetric iPr‐trisox(S,S,R) and their reaction with [Mo(CO)3(NCMe)3] yielding [Mo{iPr‐trisox(S,S,S)}(CO)3] (1 a) and [Mo{iPr‐trisox(S,S,R)}(CO)3] (1 b), respectively. The non‐autocomplementarity of two homochiral trisox ligands at one metal center has been demonstrated by reaction of rac‐C3 iPr‐trisox with one equivalent of [Co(ClO4)2]⋅6 H2O, giving the centrosymmetric heterochiral complex [Co(iPr‐trisox)2](ClO4)2 (3), whereas an analogous reaction with the enantiopure ligand yielded a mixture of CoII complexes, which is characterized by the total absence of a [(trisox)2Co]+/2+ ion. The scope of the trisox ligand in terms of facial coordination to both early and late transition metals was demonstrated by the synthesis and structural characterization of the mononuclear complexes [ScCl3(iPr‐trisox)] (4), [Fe(tBu‐trisox)(NCMe)3](BF4)2 (5), and [Ru(η6‐p‐cymene)(iPr‐trisox)](PF6)2 (6). The facial coordination of their three ligating atoms to a metal center may be impeded if the transition‐metal center stereoelectronically strongly favors a non‐deltahedral coordination sphere, which is generally the case for the heavier d8‐transition‐metal atoms/ions. Reaction of iPr‐trisox with [Rh(cod)2]BF4 led to the formation of the 16‐electron d8‐configured complex [Rh(iPr‐trisox)(cod)](BF4) (7), which is oxidized by CsBr3 to give the RhIII complex [RhBr3(iPr‐trisox)] (8) possessing a C3‐symmetric structure with a κ3‐N‐trisox ligand. The crystalline salts [M2(μ‐Cl3)(iPr‐trisox)2](PF6) (M=FeII: 9, CoII: 10, NiII: 11), were prepared by addition of one molar equivalent of iPr‐trisox and an excess of KPF6 to solutions of the anhydrous (FeCl2) or hydrated metal halides (CoCl2⋅6 H2O, NiCl2⋅6 H2O). All dinuclear complexes display weak magnetic coupling. For the mononuclear species [CuCl2(iPr‐trisox)] (12) the removal of a chloride anion and thus the generation of a dinuclear chloro‐bridged structure failed due to Jahn–Teller destabilization of a potential octahedral coordination sphere.
Allyl ansa‐Lanthanidocenes: Single‐Component, Single‐Site Catalysts for Controlled Syndiospecific Styrene and Styrene–Ethylene (Co)Polymerization
Authors: Rodrigues Anne‐Sophie , Kirillov Evgueni , Lehmann Christian W. , Roisnel Thierry , Vuillemin Bruno , Razavi Abbas , Carpentier Jean‐François 
Published: February 2007

AbstractA series of new neutral allyl Group 3 metal complexes bearing ansa‐bridged fluorenyl/cyclopentadienyl ligands [{Flu‐EMe2‐(3‐R‐Cp)}Ln(η3‐C3H5)(THF)] (E=C, R=H, Ln=Y (2), La (3), Nd (4), Sm (5); R=tBu, Ln=Y (8), Nd (9); E=Si, R=H, Ln=Y (12), Nd (13)) were synthesized in good yields via salt metathesis protocols. The complexes were characterized by elemental analysis, NMR spectroscopy for diamagnetic complexes, and single‐crystal X‐ray diffraction studies for 2, 4, 9 and 12. Some of the allyl ansa‐lanthanidocenes, especially 4, are effective single‐component catalysts for the polymerization of styrene, giving pure syndiotactic polystyrenes (rrrr > 99 %) with low to high molecular weights (Mn=6000–135 000 g mol−1) and narrow polydispersities (Mw/Mn=1.2–2.6). The catalyst systems are remarkably stable, capable of polymerizing styrene up to 120 °C with high activities, while maintaining high syndiotacticity via chain‐end control as established by a Bernoullian analysis. Highly effective copolymerization of styrene with ethylene was achieved using neodymium complex 4 (activity up to 2530 kg PS‐PE mol−1 h−1) to give true copolymers void of homopolymers with Mn=9000–152 000 g mol−1 and narrow polydispersities (Mw/Mn=1.2–2.5). The nature of the resultant P(S‐co‐E) copolymers was ascertained by NMR, size‐exclusion chromatography/refractive index/UV, temperature rising elusion fractionation, and differential scanning calorimetry. It is shown that, regardless the amount of ethylene incorporated (1–50 mol %), P(S‐co‐E) copolymers have a microstructure predominantly made of long highly syndiotactic PS sequences separated by single or few ethylene units. Co‐monomers feed and polymerization temperature can be used straightforwardly to manipulate with the physical and mechanical characteristics of the P(S‐co‐E) copolymers (molecular weights and distributions, co‐monomer content, microstructure, Tm, Tg, Tc).
How important is on‐site adequacy assessment for thyroid FNA? An evaluation of 883 cases
Authors: Zhu Weijian , Michael Claire W. 
Published: February 2007

AbstractImmediate adequacy assessment (IADA) during fine‐needle aspiration (FNA) is not universal and the optimal numberof passes has not been well determined. The aim of this study was to evaluate the nondiagnostic rates (NDR) with and without the IADA forthyroid aspirates. Subsequent cytological and surgical follow‐upwere reviewed for nondiagnostic cases. In addition, we evaluated the numberof passes performed in each FNA to determine the optimal number.Retrospective analysis of NDR was performed on 883 thyroid FNA specimens retrievedthrough a Computer SNOMED Search from our files between January 2001 toDecember 2003. For FNAs with IADA, one Diff‐Quick and one fixedsmear for each pass were prepared, and the needle was rinsed in CytoLytsolution for a ThinPrep and/or a cell‐block. FNAs without IADAwere received in CytoLyt solution, from which a ThinPrep and a cell‐block were prepared for each case.Of the total 883 cases, 443 wereperformed with IADA, of which 417 cases were diagnostic. The remaining440 cases were performed without IADA, of which 300 cases were diagnostic.NDR for IADA was 5.9% (26 cases‐group‐I)compared to 31.8% (140 cases‐group‐II)without IADA. In group‐I, 5 cases were followed‐upby repeat FNA, 10 cases by surgical resection, and 11 cases received notissue follow‐up. In group‐II, 23 cases were followed‐up by repeat FNA, 36 by surgical resection, and 82 cases received notissue follow‐up. Interestingly, follow‐up in group‐Idid not reveal any missed malignancy, while that in group‐II resultedin a malignant diagnosis in 13.8% (8 cases). We alsofound that the optimal number of passes with least NDR was 4–6 passes.NDR was 25% for < 3 passes, 11% for 4 passes, 5.2% for 5 passes, 1.4% for 6 passes, and 2.5% for 7 passesor more. IADA significantly reduces the NDR and increases the sample adequacy for diagnosis. Optimal number of passes is 4–6 passes, and additionalpasses did not improve the diagnostic rate. Our study also emphasizesthe significance of repeat FNA or histological follow‐up for nondiagnostic cases, especially for those without IADA. Diagn. Cytopathol. 2007;35:183–186. © 2007 Wiley‐Liss, Inc.
Primary vascular neoplasms unique to the spleen: Littoral cell angioma and splenic hamartoma diagnosis by fine‐needle aspiration biopsy
Authors: Ramdall Risha B. , Alasio Teresa M. , Cai Guoping , Yang Grace C. H. 
Published: February 2007

AbstractWe report the fine‐needle aspiration (FNA) biopsy diagnosis of two rare cases of primary vascular neoplasms unique to the spleen: a littoral cell angioma from a 31‐yr‐old Caucasian woman and a splenic hamartoma from a 46‐yr‐old black man. The cytologic features of splenic hamartoma and of littoral cell angioma of the spleen were described three times in cytologic literature: two were bench‐top aspirates and one was FNA biopsy thought to be metastatic carcinoma. To the best of our knowledge, the current two cases were the first diagnosed by FNA biopsy. Our approach to the FNA biopsy diagnosis of these rare vascular neoplasms via compact cell block and immunohistochemistry is described. The differential diagnosis with other primary vascular splenic neoplasms is also discussed. Diagn. Cytopathol. 2007;35:137–142. © 2007 Wiley‐Liss, Inc.
Cervical cancer prevention for all the world's women: Genuine promise resides in skilled quality management rather than novel screening approaches
Authors: Suba Eric J. , Donnelly Amber D. , Furia Lisa M. , Huynh My Linh D. , Raab Stephen S. 
Published: February 2007

AbstractThe debate over the best route for cervical cancer prevention in developing countries may be considered part of a larger debate over whether the global health community has become enamored with the promise of new approaches at the expense of delivering available preventives today. Pap screening, which is feasible anywhere cervical screening is appropriate, is the only intervention currently available for the prevention of cervical cancer in developing countries, and the Pap test will be an essential component of future novel preventive approaches. Cervical cancer vaccination, the long‐term effectiveness of which is uncertain, will not eliminate screening requirements and is currently not affordable in developing countries. Root cause analyses, which may appropriately inform the best routes for improving health in developing countries, document that failures of cervical cancer prevention efforts are not attributable to factors specific to the Pap test but to lapses in programmatic quality management to which all screening tests are vulnerable. The genuine promise of cervical cancer prevention for all the world's women therefore resides in skilled quality management rather than novel screening approaches. We propose a global consensus policy by which Pap screening services will be provided in any setting where cervical screening is appropriate but unavailable, with consideration given to novel preventive approaches as they mature. Opportunity costs, borne by the underserved, are associated with prioritizing research on new approaches in any setting where established preventives are feasible but unavailable. Diagn. Cytopathol. 2007;35:187–191. © 2007 Wiley‐Liss, Inc.
Langerhans cell histiocytosis of the skull on cytologic squash preparations
Authors: Kobayashi Tadao K. , Ueda Masami , Nishino Toshihiro , Bamba Masamichi , Echigo Tadashi , Oka Hideki , Hino Akihiko , Fuse Ikuko , Fujimoto Masato , Katsumori Tetsuya , Kaneko Chiyuki 
Published: February 2007

AbstractWe present a case in which a primary cytodiagnosis of Langerhans cell histiocytosis (LCH) of the skull was made using squash preparations. The patient, a 25‐year‐old male, presented with raised intracranial pressure and decreased visual acuity. Magnetic resonance imaging revealed a large skull lesion with osteolytic features in the left frontal bone. The patient underwent surgical resection by the extended basal frontal epidural approach. The squash preparation smears were cellular and demonstrated a mixed population of small, mature lymphocytes, eosinophils, and a high histiocytes content. The histiocytes occurred as isolated or loosely cohesive and clustered. They possessed abundant cytoplasm with rounded cell shape and had characteristic nuclear features, composed of fine chromatin and delicate nuclear membranes. The cytologic features of these histiocytes were consistent with Langerhans cells (LCs). A final impression of LCH of the skull was rendered. Subsequent histopathology confirmed the diagnosis. LCs reacted with both S‐100 protein and CD1a immunohistochemically. The demonstration of Birbeck granules on electron microscopic study was also noted. Whenever squash preparation yields a mixed population of mature lymphocytes, eosinophils, and histiocytes, the cytologists should be aware of and consider LCH as a diagnostic possibility. Diagn. Cytopathol. 2007;35:154–157. © 2007 Wiley‐Liss, Inc.
The serotonergic phenotype is acquired by converging genetic mechanisms within the zebrafish central nervous system
Authors: Lillesaar Christina , Tannhäuser Birgit , Stigloher Christian , Kremmer Elisabeth , Bally‐Cuif Laure 
Published: February 2007

AbstractTo gain knowledge about the developmental origin of serotonergic precursors and the regulatory cascades of serotonergic differentiation in vertebrates, we determined the spatiotemporal expression profile of the Ets‐domain transcription factor‐encoding genepet1in developing and adult zebrafish. We show that it is an early, specific marker of raphe serotonergic neurons, but not of other serotonergic populations. We then usepet1expression together with tracing techniques to demonstrate that serotonergic neurons of rhombomeres (r) 1–2 largely originate from a progenitor pool at the midbrain–hindbrain boundary. Furthermore, by combining expression analyses ofpet1and the raphe tryptophan hydroxylase (Tph2) with rhombomere identity markers, we show that anterior and posterior hindbrain clusters of serotonergic precursors are separated by r3, rather than r4 as in other vertebrates. Our findings establish the origin of r1–2 serotonergic precursors, and strengthen the evidence for molecular, ontogenic and phylogenic heterogeneities among the vertebrate brain serotonergic cell populations. Developmental Dynamics 236:1072–1084, 2007. © 2007 Wiley‐Liss, Inc.
Molecular Recognition Utilizing Complexes with NH,NR‐Stabilized Carbene Ligands
Authors: Meier Nicole , Hahn F. Ekkehardt , Pape Tania , Siering Carsten , Waldvogel Siegfried R. 
Published: February 2007

AbstractTungsten complex [W(NHC)(CO)5] (1) (NHC=NH,N‐ethyl‐substituted benzimidazolin‐2‐ylidene ligand) was prepared by transmetallation of lithiated 1‐ethylbenzimidazole with the pentacarbonyltungsten complex fragment. The hydrogen‐bonding ability of the carbene‐NH group to substrates with carbonyl groups was investigated by NMR titration. Structural analogues to 1 with a catalytically active rhodium center show a distinct substrate‐selective hydrogenation behaviour.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
The Alpher, Bethe and Gamow of IEF, the alpha‐Centaury of electrokinetic methodologies. Part II: Immobilized pH gradients
Authors: Righetti Pier Giorgio 
Published: February 2007

AbstractThe present review (a follow up of Electrophoresis 2006, 27, 923–938 on conventional IEF) highlights the developmental steps of the IPG technology, from a nebulous start limiting the technique to just 1 pH unit intervals up to the description of extended pH gradients, encompassing as much as 8.5 pH units. Although computer algorithms had been developed for optimizing recipes so as to obtain the most precise and most linear pH gradients, it was also realized that nonlinear pH intervals, covering the pH 3–10 range, would be extremely beneficial in 2‐D map analysis, since they would follow the pI distribution of proteins in living systems. The synthesis of a number of Immobiline chemicals (the acrylamido weak acids and bases meant to be incorporated into the nascent polyacrylamide chains) is also reported. The review ends with preparative aspects of IPGs, with the introduction of multicompartment electrolyzers with Immobiline membranes.
Unequal crossover recombination – population screening for PHOX2B gene polyalanine polymorphism using CE
Authors: Hung Chia‐Cheng , Su Yi‐Ning , Tsao Po‐Nien , Chen Pau‐Chung , Lin Shio‐Jean , Lin Cheng‐Hui , Mu Shu‐Chi , Liu Chieh‐An , Chang Ying‐Chao , Lin Win‐Li , Hsieh Wu‐Shiun , Hsu Su‐Ming 
Published: February 2007

AbstractCongenital central hypoventilation syndrome (CCHS) is a rare neurological disorder characterized by abnormal autonomic central nervous system control of breathing during sleep. Mutations in the paired‐like homeobox 2B (PHOX2B) gene, including point mutation, frameshift, and polyalanine expansion, are associated with the pathogenesis of CCHS. In this study, PHOX2B mutations were analyzed in seven CCHS patients, their family members, and 1520 healthy individuals from the general population using CE to provide high sensitivity and resolution screening for the PHOX2B polyalanine polymorphism. Seven mutations in the PHOX2B gene, including two frameshift mutations and five polyalanine expansions in the 20‐residue polyalanine tract, were identified. The various phenotypes observed in CCHS patients with PHOX2B mutations suggest that the size of the expansion allele is associated with the CCHS risk. In addition, significant differences were found in allele and genotype distributions between the healthy individuals. Alleles (GCN)20 and (GCN)15 had the highest population incidence rates of 94.84 and 4.51%, respectively, with the remaining alleles, (GCN)13 and (GCN)7, accounting for 0.59 and 0.06%, respectively. Therefore, it has been demonstrated that CE can be used to improve the detection of polyalanine expansions in the PHOX2B gene. The attractive alternative method is a promising tool for the detection of disorders involving trinucleotide repeat tracts.
CE‐ESI‐MS of biological anions in plastic capillaries at high pH
Authors: Benavente Fernando , Sanz‐Nebot Victoria , Barbosa José , van der Heijden Rob , van der Greef Jan , Hankemeier Thomas 
Published: February 2007

AbstractIn this study, the potential of poly(methylmethacrylate) (PMMA, Plexiglas) and polyether ether ketone (PEEK) tubing for CE‐ESI‐MS separations of anions at high pH values was examined. A set of model compounds of biological interest was used to investigate the main operational parameters for CE‐ESI‐MS, such as the sheath‐flow interface design, the polarity of the ionization voltage, the use of ammonia‐based separation electrolytes, and the sheath liquid composition. Optimum separations and detection sensitivities in negative ESI mode were obtained using a running electrolyte of 75 mM of ammonia at pH 11 and a sheath liquid of 60:40 v/v or 75:25 v/v isopropanol/water with 0.5% v/v of ammonia. At these experimental conditions, PMMA and PEEK capillaries show good hydrolytic stabilities and lower EOF values than fused‐silica columns. Better separation resolutions were obtained with PMMA capillary, but this plastic rapidly swelled and bled because of its limited chemical resistance to the sheath liquid. PMMA columns equipped with a fused‐silica tip were used for a safer exposure to the sheath liquid, but the inner surface of the fused‐silica tips had limited stability at pH 11. On the other hand, good separations and reproducibility on migration times and peak areas were obtained using PEEK capillaries without capillary column deterioration.
Analysis of electrokinetic pumping efficiency in capillary tubes
Authors: Chein Reiyu , Liao Jenchen 
Published: February 2007

AbstractA mathematical model for predicting the maximum pumping efficiency and pressure difference generation by an electrokinetic‐driven fluid pumping system through a capillary tube is presented in this study. Both the maximum pumping efficiency and optimum pressure difference generation are found to depend on a single variable. This single variable is termed as the figure of merit since it determines the performance of electrokinetic pumping. The figure of merit is found to depend on three dimensionless parameters, the normalized Debye length, zeta potential, and Levine number indicating the nominal ratio of convective current to conductive current. All three parameters can be related to the pH value and concentration of aqueous salt solution by the introduction of concentration‐dependent electrical conductivity and pH‐dependent zeta potential. By presenting the maximum pumping efficiency and optimum pressure difference generation as functions of pH value, salt concentration, and capillary tube radius, it is found that both maximum pumping efficiency and optimum pressure difference generation increase with the decrease in capillary radius and salt concentration. The optimum pH values at which the maximum pumping efficiency and optimum pressure difference generation occur are found to be in the range between 6 and 9. For the salt concentration of <$>\displaystyle 10^{ ‐ 6} <$> M, pH 6.9, and a capillary tube radius value of 0.5 μm, the predicted maximum pumping efficiency is 5.4% which is close to the experimental measurement reported in the literature.
Electrokinetic transport and separations in fluidic nanochannels
Authors: Yuan Zhen , Garcia Anthony L. , Lopez Gabriel P. , Petsev Dimiter N. 
Published: February 2007

AbstractThis article presents a summary of theory, experimental studies, and results for the electrokinetic transport in small fluidic nanochannels. The main focus is on the effect of the electric double layer on the EOF, electric current, and electrophoresis of charged analytes. The double layer thickness can be of the same order as the width of the nanochannels, which has an impact on the transport by shaping the fluid velocity profile, local distributions of the electrolytes, and charged analytes. Our theoretical consideration is limited to continuum analysis where the equations of classical hydrodynamics and electrodynamics still apply. We show that small channels may lead to qualitatively new effects like selective ionic transport based on charge number as well as different modes for molecular separation. These new possibilities together with the rapid development of nanofabrication capabilities lead to an extensive experimental effort to utilize nanochannels for a variety of applications, which are also discussed and analyzed in this review.