bluuebunny/crossref_metadata_2025_split huggingface dataset:
Folding of RNA tertiary structure: Linkages between backbone phosphates, ions, and water
Authors: Draper David E. 
Published: April 2013

ABSTRACTThe functional forms of many RNAs have compact architectures. The placement of phosphates within such structures must be influenced not only by the strong electrostatic repulsion between phosphates, but also by networks of interactions between phosphates, water, and mobile ions. This review first explores what has been learned of the basic thermodynamic constraints on these arrangements from studies of hydration and ions in simple DNA molecules, and then gives an overview of what is known about ion and water interactions with RNA structures. A brief survey of RNA crystal structures identifies several interesting architectures in which closely spaced phosphates share hydration shells or phosphates are buried in environments that provide intramolecular hydrogen bonds or site‐bound cations. Formation of these structures must require strong coupling between the uptake of ions and release of water. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 1105–1113, 2013.
Three Carbons for Complexity! Recent Developments of Palladium‐Catalyzed Reactions of Allenes
Authors: Lechel Tilman , Pfrengle Fabian , Reissig Hans‐Ulrich , Zimmer Reinhold 
Published: April 2013

AbstractThe three carbon atoms of allene moieties allow unique transformations and rapid generation of complexity. Not surprisingly, allenes became extremely versatile building blocks in organic synthesis. Transition‐metal‐catalyzed reactions of these cumulene π‐systems have been particularly successful, and many applications in the synthesis of complex products have been reported. This review summarizes the palladium‐catalyzed transformation of allenes published during the last decade. Many of the examples presented are impressive multicomponent processes or cascade reactions involving two or more steps leading to molecular complexity in simple one‐pot operations. Consequently, several reactions have been developed with the goal of delivering new synthetic routes to natural products.
Formation of Trinuclear Rhodium‐Hydride Complexes [{Rh(PP*)H}3‐ (μ2‐H)3(μ3‐H)][anion]2—During Asymmetric Hydrogenation?
Authors: Kohrt C. , Baumann W. , Spannenberg A. , Drexler H.‐J. , Gridnev I. D. , Heller D. 
Published: April 2013

AbstractRecently described and fully characterized trinuclear rhodium‐hydride complexes [{Rh(PP*)H}3(μ2‐H)3(μ3‐H)][anion]2 have been investigated with respect to their formation and role under the conditions of asymmetric hydrogenation. Catalyst–substrate complexes with mac (methyl (Z)‐ N‐acetylaminocinnamate) ([Rh(tBu‐BisP*)(mac)]BF4, [Rh(Tangphos)(mac)]BF4, [Rh(Me‐BPE)(mac)]BF4, [Rh(DCPE)(mac)]BF4, [Rh(DCPB)(mac)]BF4), as well as rhodium‐hydride species, both mono‐([Rh(Tangphos)‐ H2(MeOH)2]BF4, [Rh(Me‐BPE)H2(MeOH)2]BF4), and dinuclear ([{Rh(DCPE)H}2(μ2‐H)3]BF4, [{Rh(DCPB)H}2(μ2‐H)3]BF4), are described. A plausible reaction sequence for the formation of the trinuclear rhodium‐hydride complexes is discussed. Evidence is provided that the presence of multinuclear rhodium‐hydride complexes should be taken into account when discussing the mechanism of rhodium‐promoted asymmetric hydrogenation.
Screening the Thermodynamics of Trimethylaluminum‐Hydrolysis Products and Their Co‐Catalytic Performance in Olefin‐Polymerization Catalysis
Authors: Linnolahti Mikko , Laine Anniina , Pakkanen Tapani A. 
Published: April 2013

AbstractHerein, we introduce an approach for the computational screening of stoichiometric reactions between trimethylaluminum (TMA) and water. The thermodynamic products of these reactions are methylaluminoxanes (MAOs) with different compositions, which have the general formula (AlOMe)n(AlMe3)m, in which n describes the degree of oligomerization and m is the number of associated TMA molecules. These reaction products were thoroughly explored up to n=4, thus demonstrating the thermodynamically preferable association of up to four AlMe3 molecules, that is, TMA molecules in their monomeric form. The relative Lewis acidities of the Al sites in these MAOs were systematically explored and we found that the associated TMA molecules were a key ingredient for co‐catalytic activity in olefin‐polymerization catalysis. This conclusion was supported by computational studies on catalyst activation, which revealed an exergonic insertion of ethene into the metallocene/MAO complex.
Carbon Dots Prepared by Hydrothermal Treatment of Dopamine as an Effective Fluorescent Sensing Platform for the Label‐Free Detection of Iron(III) Ions and Dopamine
Authors: Qu Konggang , Wang Jiasi , Ren Jinsong , Qu Xiaogang 
Published: April 2013

AbstractA facile, economic and green one‐step hydrothermal synthesis route using dopamine as source towards photoluminescent carbon nanoparticles (CNPs) is proposed. The as‐prepared CNPs have an average size about 3.8 nm. The emission spectra of the CNPs are broad, ranging from approximately 380 (purple) to approximately 525 nm (green), depending on the excitation wavelengths. Due to the favorable optical properties, the CNPs can readily enter into A549 cells and has been used for multicolor biolabeling and bioimaging. Most importantly, the as‐prepared CNPs contain distinctive catechol groups on their surfaces. Due to the special response of catechol groups to Fe3+ ions, we further demonstrate that such wholly new CNPs can serve as a very effective fluorescent sensing platform for label‐free sensitive and selective detection of Fe3+ ions and dopamine with a detection limit as low as 0.32 μM and 68 nM, respectively. The new “mix‐and‐detect” strategy is simple, green, and exhibits high sensitivity and selectivity. The present method was also applied to the determination of Fe3+ ions in real water samples and dopamine in human urine and serum samples successfully.
Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion
Authors: Mochida Tomoyuki , Funasako Yusuke , Inagaki Takashi , Li Meng‐Jiao , Asahara Kotaro , Kuwahara Daisuke 
Published: April 2013

AbstractCrystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (CnF2n+1SO2)2N anions [n=0 (1), 1 (1 a), 2 (1 b), 3 (1 c), and 4 (1 d)] and the 1,1,2,2,3,3‐hexafluoropropane‐1,3‐disulfonylamide anion (2) were investigated. In these solids, the cations are surrounded by four anions around their C5 axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n (1, 1 b, and 1 d), the cation and anion are arranged alternately to form mixed‐stack columns in the crystal. In contrast, in the salts with odd n (1 a and 1 c), the cations and anions independently form segregated‐stack columns. An odd–even effect was also observed in the sum of the phase‐change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest‐temperature phase in 1, 1 a, and 2 are accompanied by order–disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid‐state 13C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher‐temperature phases.
Indirect Transformation of Coordination‐Polymer Particles into Magnetic Carbon‐Coated Mn3O4 (Mn3O4@C) Nanowires for Supercapacitor Electrodes with Good Cycling Performance
Authors: Wang Kuaibing , Ma Xiaoyan , Zhang Zhiyang , Zheng Mingbo , Geng Zhirong , Wang Zhilin 
Published: April 2013

AbstractCarbon‐coated Mn3O4 nanowires (Mn3O4@C NWs) have been synthesized by the reduction of well‐shaped carbon‐coated bixbyite networks and characterized by TEM, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical experiments. To assess the properties of 1D carbon‐coated nanowires for their use in supercapacitors, cyclic voltammetry and galvanostatic charging–discharging measurements were performed. Mn3O4@C NWs could be charged and discharged faster and had higher capacitance than bare Mn3O4 nanostructures and other commercial materials. The capacitance of the Mn3O4@C NWs was 92 % retained after 3000 cycles at a charging rate of 5 A g−1. This improvement can be attributed to the carbon shells, which promote fast Faradaic charging and discharging of the interior Mn3O4 core and also act as barriers to protect the inner core. These Mn3O4@C NWs could be a promising candidate material for high‐capacity, low‐cost, and environmentally friendly electrodes for supercapacitors. In addition, the magnetic properties of the as‐synthesized samples are also reported to investigate the influence of the carbon coating.
Decoration of Gold Nanoparticles by a Double‐Armed Calix[4]pyrrole: A Receptor‐Decorated Nanoensemble for Anion Sensing and Extraction
Authors: Sokkalingam Punidha , Hong Seong‐Jin , Aydogan Abdullah , Sessler Jonathan L. , Lee Chang‐Hee 
Published: April 2013

AbstractGold nanoparticles decorated with a double‐armed, deep‐cavity calix[4]pyrrole were prepared and fully characterized. Transmission electron microscopy imaging revealed that the average diameter of the particles was approximately 4 nm both before and after attachment of the receptor to the surface. The calix[4]pyrrole‐functionalized nanoparticles exhibited highly elevated sensing behavior (approximately 1000 times in dichloromethane) relative to its monomeric congener while maintaining its guest selectivity. The receptor–nanoparticle conjugate (nanoreceptor) showed significant aggregation upon addition of the biphenolate anion, an effect ascribed to anion‐mediated interparticle linking. The receptor–nanoparticle conjugate is also capable of extracting the fluoride anion (as its tetrabutylammonium salt) from an aqueous layer to an organic medium. Control experiments revealed that this extraction is not possible when using the analogous monomeric receptor.
Attosecond Nuclear Dynamics in the Ammonia Cation: Relation between High‐Harmonic and Photoelectron Spectroscopies
Authors: Kraus Peter Michael , Wörner Hans Jakob 
Published: April 2013

AbstractWe report measurements of the umbrella motion in the ammonia cation on the attosecond time scale. The motion is prepared by strong‐field ionization and probed by photorecombination through the process of high‐harmonic generation. Performing such measurements at multiple wavelengths (0.8, 1.44, 1.8 μm) enables us to follow the nuclear dynamics over a broad temporal range (0.8–3.8 fs). The intensity of the driving field is found to have a significant impact on the observed dynamics through the vibrational‐state dependence of the strong‐field ionization rates. We derive a general model that includes these effects and establishes a new link between high‐harmonic spectroscopy and classical photoelectron spectroscopy. Our model reproduces the observed dynamics and their dependence on the intensity of the driving field. Moreover, the model predicts much richer nuclear dynamics on the few‐fs timescale than most previous theories. The newly predicted features are shown to reflect the quantized vibronic level structure of the molecular cation.
Incorporation of Hydrogen‐Bonding Functionalities into the Second Coordination Sphere of Iron‐Based Water‐Oxidation Catalysts
Authors: Hoffert Wesley A. , Mock Michael T. , Appel Aaron M. , Yang Jenny Y. 
Published: April 2013

AbstractEnergy storage and conversion schemes based on environmentally benign chemical fuels will require the discovery of faster, cheaper, and more robust catalysts for the oxygen‐evolution reaction (OER). Although the incorporation of pendant bases into molecular catalysts for hydrogen production and utilization has led to enhanced turnover frequencies, the analogous incorporation of pendant bases into molecular catalysts for water oxidation has received little attention. Herein, the syntheses, structures, and catalytic activities of new iron complexes with pendant bases are reported. Of these new complexes, [Fe(L1)]2+ {L1 = N,N′‐dimethyl‐N,N′‐bis(pyridazin‐3‐ylmethyl)ethane‐1,2‐diamine} is the most active catalyst. Initial turnover frequencies of 141 and 24 h–1 were measured by using ceric ammonium nitrate at pH 0.7 and sodium periodate at pH 4.7, respectively. These results suggest that the incorporation of pendant bases into molecular catalysts for water oxidation might be an effective strategy that can be considered in the development of new catalysts for the OER, but will require the careful balance of many factors.
Growth and Characterization of Centimeter‐Sized Ba2LaFeNb4O15 Crystals from High‐Temperature Solution under a Controlled Atmosphere
Authors: Albino Marjorie , Veber Philippe , Castel Elias , Velázquez Matias , Schenk Kurt , Chapuis Gervais , Lahaye Michel , Pechev Stanislav , Maglione Mario , Josse Michaël 
Published: April 2013

AbstractCentimeter‐sized single crystals of Ba2LaFeNb4O15 were grown from a high‐temperature solution by using LiBO2 flux and a sealed platinum assembly. The obtained single crystals display the same physical properties as their ceramic counterparts. A frequency‐dependent dielectric permittivity maximum was found (Tm = 100 K at 5 kHz), which indicates relaxor behavior. Magnetic susceptibility measurements revealed purely paramagnetic behavior between 10 and 350 K. X‐ray diffraction measurements of Ba2LaFeNb4O15 single crystals revealed an incommensurate structure at room temperature with a bidimensional modulation characterized by vectors q1 = (α, α, 1/2) and q2 = (α, –α, 1/2) with α = 0.295(1). This crystal growth method offers a promising elaboration route to centimeter‐sized crystals of niobate‐based compounds, which may not be grown from the pure liquid phase, especially those with a tetragonal tungsten bronze (TTB) structure.
Synthesis, Molecular Structure, and Electrochemistry of 1‐Ferrocenyl‐1,2‐dicarba‐closo‐dodecaboranes
Authors: Korotvička Aleš , Šnajdr Ivan , Štěpnička Petr , Císařová Ivana , Janoušek Zbyněk , Kotora Martin 
Published: April 2013

AbstractBis(dimethylsulfido)decaborane, 6,9‐(Me2S)2‐arachno‐B10H12, reacts smoothly with ferrocenyl alkynes FcC≡CR [1a–h; Fc = ferrocenyl, R = H (1a), CH3 (1b), Ph (1c), 4‐MeO2CC6H4 (1d), Fc (1e), C≡CFc (1f), C(O)CH3 (1g), and CO2CH2CH3 (1h)] to afford the corresponding 1‐ferrocenyl‐1,2‐dicarba‐closo‐dodecaboranes 2a–h in good yields. Ester 2h was further reduced to the respective hydroxymethyl derivative, 1‐Fc‐2‐CH2OH‐1,2‐closo‐C2B10H10 (3). The reaction of 6,9‐(Me2S)2‐B10H12 with FcC≡CSiMe3 proceeded in a different manner to produce (among other products) an SMe2 adduct of an opened decaborane substituted with a 2‐ferrocenyl‐2‐(trimethylsilyl)ethen‐1‐yl group (4). This compound probably results through hydroboration of the starting alkyne and migration of the SiMe3 group. All prepared compounds were characterized by spectroscopic methods (1H, 13C, and 11B NMR spectroscopy, IR spectroscopy, and mass spectrometry), and their molecular structures were determined by single‐crystal X‐ray diffraction analysis. In addition, the compounds were studied by cyclic and differential pulse voltammetry on a platinum disc electrode to reveal simple ferrocenyl‐centered oxidations for the singly ferrocenylated carboranes and two consecutive oxidation waves for compounds 2e and 2f, which possess two ferrocenyl substituents.
Structural Diversity of Coordination Cores in Homoleptic Tetraaryltin(IV) Dioxolane, Aldehyde and Imines: The First Octacoordinated Double Helicate Tetraorganotin(IV) Compound
Authors: Barbul Ioana , Varga Richard A. , Silvestru Cristian 
Published: April 2013

AbstractReaction of [2‐{(CH2O)2CH}C6H4]Li with SnCl4 in a 4:1 molar ratio afforded [2‐{(CH2O)2CH}C6H4]4Sn (1), which was deprotected to give [2‐(O=CH)C6H4]4Sn (2). Homoleptic [2‐(RN=CH)C6H4]4Sn [R = Me2NCH2CH2 (3), 2,4,6‐Me3C6H2 (4), PhCH2 (5)] were obtained by condensation of 2 with the corresponding amine either in solution or by using a green, solvent‐free procedure for (imino)arylmetal species. All compounds were characterised by multinuclear NMR spectroscopy and mass spectrometry, and their molecular structures were determined by single‐crystal X‐ray diffraction. In all cases, the C4Sn core is distorted tetrahedral as a result of the combined effects of the intramolecular coordination of the heteroatoms from the organic ligands and the steric impediments imposed by the ligands. The overall coordination around tin was found to be different, that is, coordination numbers from six for 1 and 4, to seven for 3 and 5 and eight for 2. Compound 2 is the first example of a mononuclear tetraorganotin(IV) compound that contains an octacoordinated metal centre with a double helicate topology in the solid state. Multinuclear NMR spectroscopy studies in solutions of CDCl3 are consistent with equivalent organic groups attached to a tetracoordinate tin atom.
Iodine/Water‐Mediated Oxidation of o‐Alkynylaroyl Compounds and Application of the Products of Oxidation in the Synthesis of Nitrogen Heterocycles
Authors: Sakthivel Karuppusamy , Srinivasan Kannupal 
Published: April 2013

AbstractA facile iodine/water‐mediated oxidation of the triple bond of o‐alkynylaroyl compounds to furnish tricarbonyl compounds is reported. The reaction proceeds through the formation of isochromenol intermediates by the assistance of the neighbouring aroyl group. The product tricarbonyl compounds are versatile synthetic precursors that, upon treatment with mono‐ and diamines, hydrazines and amino alcohols, afford various heterocyclic scaffolds such as isoindolinones, phthalazines, benzimidazoisoquinolinones, quinoxalines and benzimidazole‐quinoxaline hybrid compounds. Mechanistic aspects of the formation of the above heterocycles are discussed. Finally, a short synthetic route to the isoindolinone natural product, aristolactam BII is reported.
Epicoccolides: Antimicrobial and Antifungal Polyketides from an Endophytic Fungus Epicoccum sp. Associated with Theobroma cacao
Authors: Talontsi Ferdinand Mouafo , Dittrich Birger , Schüffler Anja , Sun Han , Laatsch Hartmut 
Published: April 2013

AbstractIn the search for new compounds to protect plants from fungi, an endophytic fungus, Epicoccum sp. CAFTBO, obtained from Theobroma cacao was found to produce three polyoxygenated polyketides, namely epicolactone (1) and epicoccolides A (2) and B (3), together with seven known metabolites. The structures of these compounds were elucidated by a combination of detailed spectroscopic and spectrometric analyses as well as DFT calculations of the electronic circular dichroism spectra and the single‐crystal X‐ray diffraction analysis of 1. Compounds 1–3 showed potent antimicrobial activities and significant inhibitory effects on the mycelial growth of two peronosporomycete phytopathogens, Pythium ultimum and Aphanomyces cochlioides, and the basidiomycetous fungus Rhizoctonia solani.
Multiple gene polymorphisms can improve prediction of nonvertebral fracture in postmenopausal women
Authors: Lee Seung Hun , Lee Seon Woo , Ahn Seong Hee , Kim Taehyeung , Lim Kyeong-Hye , Kim Beom-Jun , Cho Eun-Hee , Kim Sang-Wook , Kim Tae-Ho , Kim Ghi Su , Kim Shin-Yoon , Koh Jung-Min , Kang Changwon 
Published: April 2013

ABSTRACT

Clinical risk factors (CRFs), with or without bone mineral density (BMD), are used to determine the risk of osteoporotic fracture (OF), which has a heritable component. In this study we investigated whether genetic profiling can additionally improve the ability to predict OF. Using 1229 unrelated Korean postmenopausal women, 39 single-nucleotide polymorphisms (SNPs) in 30 human genomic loci were tested for association with osteoporosis-related traits, such as BMD, osteoporosis, vertebral fracture (VF), nonvertebral fracture (NVF), and any fracture. To estimate the effects of genetic profiling, the genetic risk score (GRS) was calculated using five prediction models: (Model I) GRSs only; (Model II) BMD only; (Model III) CRFs only; (Model IV) CRFs and BMD; and (Model V) CRFs, BMD, and GRS. A total of 21 SNPs within 19 genes associated with one or more osteoporosis-related traits and were included for GRS calculation. GRS associated with BMD before and after adjustment for CRFs (p ranging from &lt;0.001 to 0.018). GRS associated with NVF before and after adjustment for CRFs and BMD (p ranging from 0.017 to 0.045), and with any fracture after adjustment for CRFs and femur neck BMD (p = 0.049). In terms of predicting NVF, the area under the receiver operating characteristic curve (AUC) for Model I was 0.55, which was lower than the AUCs of Models II (0.60), III (0.64), and IV (0.65). Adding GRS to Model IV (in Model V) increased the AUC to 0.67, and improved the accuracy of NVF classification by 11.5% (p = 0.014). In terms of predicting any fracture, the AUC of Model V (0.68) was similar to that of Model IV (0.68), and Model V did not significantly improve the accuracy of any fracture classification (p = 0.39). Thus, genetic profiling may enhance the accuracy of NVF predictions and help to delineate the intervention threshold. © 2013 American Society for Bone and Mineral Research.
Fat – carbohydrate – protein: Storage in plant seeds
Authors: Lüttge Ulrich 
Published: April 2013

AbstractStorage compounds of seeds are carbohydrates, proteins and oils or fats. They are inter‐convertible in metabolism. Most seeds store the whole complement of these compound classes though one or the other may dominate. The storage compounds supply material and energy to young growing seedlings and are of commercial interest of man for food and fuel.
Predicting pKa Values in Aqueous Solution for the Guanidine Functional Group from Gas Phase Ab Initio Bond Lengths
Authors: Griffiths Mark Z. , Alkorta Ibon , Popelier Paul L. A. 
Published: April 2013

AbstractHere we applied a novel method1a to predict pKa values of the guanidine functional group, which is a notoriously difficult. This method, which was developed in our lab, uses only one ab initio bond length obtained at a low level of theory. The method is shown to work for drug molecules, delivers prediction errors of less than 0.5 log units, successfully treats tautomerisation in close relation with experiment, and demonstrates strong correlations with only a few data points. The high structural content of the ab initio bond length makes a given data set essentially divide itself into high correlation subsets. One then observes that molecules within a subset possess a common substructure. Each high correlation subset exists in its own region of chemical space. The high correlation subset method is explored with respect to this position in chemical space, in particular tautomerisation. The proposed method is able to distinguish between different tautomeric forms and the preferred tautomeric form emerges naturally, in agreement with experiment.
Imaging in childhood cancer: A society for pediatric radiology and children's oncology group joint task force report
Authors: Weiser Daniel A. , Kaste Sue C. , Siegel Marilyn J. , Adamson Peter C. 
Published: April 2013

AbstractContemporary medical imaging is a cornerstone of care for children with cancer. As 5‐year survival rates for children with cancer exceed 80%, imaging technologies have evolved in parallel to include a wide array of modalities. Here, we overview the risks and benefits associated with commonly used imaging modalities and survey the current landscape of medical imaging for children with cancer. We find evidence‐based imaging guidelines to assist in protocol development and to guide decision‐making for optimal patient care are often lacking. The substantial variation in protocol‐based recommendations for imaging both during and following therapy may hinder optimal clinical research and clinical care for children with cancer. Pediatr Blood Cancer 2013;601253‐1260. © 2013 Wiley Periodicals, Inc.