bluuebunny/crossref_metadata_2025_split huggingface dataset:
Convenient Synthesis of Functionalized Bis‐ureidopyrimidinones Based on Thiol‐yne Reaction
Authors: Peng Hui‐Qing , Sun Cai‐Li , Xu Jiang‐Fei , Niu Li‐Ya , Chen Yu‐Zhe , Wu Li‐Zhu , Tung Chen‐Ho , Yang Qing‐Zheng 
Published: July 2014

AbstractThe preparation of functionalized bis‐ureidopyrimidinones (Bis‐UPy) through the thiol‐yne reaction is described. Various Bis‐UPys with different functional groups were synthesized by using the readily available functionalized alkynes and UPy‐thiol to affirm the simplicity and versatility of the methodology.
New Helical Folds in α‐Peptides with Alternating Chirality
Authors: Sharma Gangavaram V. M. , Venkateshwarlu Gajulapati , Reddy Pothula Purushotham , Kunwar Ajit C. 
Published: July 2014

AbstractIn α‐peptides, the 8/10 helix is theoretically predicted to be energetically unstable and has not been experimentally observed so far. Based on our earlier studies on ‘helical induction’ and ‘hybrid helices’, we have adopted the ‘end‐capping’ strategy to induce the 8/10 helix in α‐peptides by using short α/β‐peptides. Thus, α‐peptides containing a regular string of α‐amino acids with alternating chirality were end capped by α/β‐peptides with 11/9‐helical motifs at the termini. Extensive NMR spectroscopy studies of these peptides revealed the presence of a hitherto unknown 8/10‐helical pattern; the H‐bonds in the shorter pseudorings were rather weak. The approach of using short helical motifs to induce new mixed helices in α‐peptides could provide avenues for more versatile design strategies.
Atomic Mechanism of Predictable Phase Transition in Dual‐Phase H2Ti3O7/TiO2 (B) Nanofiber: An In Situ Heating TEM Investigation
Authors: Lei Yimin , Sun Jie , Liu Hongwei , Cheng Xuan , Chen Fuyi , Liu Zongwen 
Published: July 2014

AbstractThe phase transition from H2Ti3O7 to TiO2 (B) in a 1D single nanocrystal of H2Ti3O7 was observed by in situ heating in a transmission electron microscope experimentally. The results indicate a typical monoclinic‐to‐monoclinic crystallographic orientation relationship between the two phases. Moreover, the fundamental building blocks and invariant deformation element model were both adopted to reveal the atomic mechanism and predict the crystallographic orientation relationship quantitatively for the phase transition. The prediction was precisely consistent with TEM results.
Towards Molecular Construction Platforms: Synthesis of a Metallotricyclic Spirane Based on Bis(2,2′:6′,2“‐Terpyridine)RuII Connectivity
Authors: Xie Ting‐Zheng , Guo Kai , Huang Mingjun , Lu Xiaocun , Liao Sheng‐Yun , Sarkar Rajarshi , Moorefield Charles N. , Cheng Stephen Z. D. , Wesdemiotis Chrys , Newkome George R. 
Published: July 2014

AbstractThe design and construction of the first multicomponent stepwise assembly of a <tpy‐RuII‐tpy>‐based (tpy=terpyridine), three‐dimensional, propeller‐shaped trismacrocycle, 8, are reported. Key steps in the synthesis involve the preparation of a hexaterpyridinyl triptycene and its reaction with dimeric, 60°‐directional, bisterpyridine‐RuII building blocks. Characterization includes ESI‐ and ESI‐TWIM‐MS and TEM, along with 1D and 2D 1H NMR spectroscopy.
Conjugation to Albumin‐Binding Molecule Tags as a Strategy to Improve Both Efficacy and Pharmacokinetic Properties of the Complement Inhibitor Compstatin
Authors: Huang Yijun , Reis Edimara S. , Knerr Patrick J. , van der Donk Wilfred A. , Ricklin Daniel , Lambris John D. 
Published: July 2014

AbstractThe compstatin family of complement inhibitors has shown promise in various immuno‐inflammatory disorders. Although recent analogues show beneficial pharmacokinetics, further extension of the plasma half‐life is expected to benefit systemic application of these peptidic inhibitors. We therefore synthesized conjugates of compstatin analogues and albumin‐binding molecules (ABM) to increase circulatory residence. Equilibrium dialysis in complement‐depleted serum showed a marked increase in plasma protein binding from <8 % to >99 % for a resulting chimera (ABM2‐Cp20). Further analysis confirmed interaction with albumin from different species, primarily via site II. Importantly, ABM2‐Cp20 bound 20‐fold stronger to its target protein C3b (KD=150 pM) than the parent peptide. Kinetic and in silico analysis suggested that ABM2 occupies a secondary site on C3b and improves the dissociation rate via additional contacts. Addition of an ABM modifier thereby not only improved plasma protein binding but also produced the most potent compstatin analogue to date with potential implications for the treatment of systemic complement‐related diseases.
Hydrogen Transport in Non‐Ideal Crystalline Materials
Authors: Auinger Michael 
Published: July 2014

AbstractHydrogen‐transport behaviour under (non‐)isothermal conditions is discussed. An extended modelling approach based on the effective diffusion coefficient is outlined for arbitrary temperature programmes, defect properties and hydrogen‐loading pressures. The influence of mathematical terms, such as the trap equilibrium reaction or microstructural changes, is critically discussed and examples of thermal desorption spectra and isothermal diffusion behaviour are given.
Dynamics of Methanol in Ionic Liquids: Validity of the Stokes–Einstein and Stokes–Einstein–Debye Relations
Authors: Herold Elisabeth , Strauch Matthias , Michalik Dirk , Appelhagen Andreas , Ludwig Ralf 
Published: July 2014

AbstractThe validity of Stokes–Einstein (SE) and Stokes–Einstein–Debye (SED) relations for methanol in the physical environment of the ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide is studied by means of nuclear magnetic resonance (NMR) relaxation time experiments, viscosity measurements and molecular dynamics (MD) simulations. The reorientational correlation times of the hydroxyl groups of pure methanol and of methanol in the IL/methanol mixtures were determined. For that purpose an approach for estimating NMR deuteron quadrupole coupling constants, presented by Wendt and Farrar (Mol. Phys.­ 1998, 95, 1077–1081), was confirmed. The self‐diffusion coefficients of methanol were taken from the MD simulations. The viscosities of all systems were then measured and the SE and SED relations validated. For pure methanol both relations are valid, whereas they become increasingly invalid with increasing IL concentration, as indicated by effective volumes and radii that are too low. The deviation from the SE and SED relations could be related to dynamical heterogeneities described by the non‐Gaussian parameter α(t) obtained from MD simulations. For pure methanol, α(t) is close to zero in accord with the validity of both relations. With increasing IL concentration the dynamical heterogeneities of methanol increase strongly. The times t* at the maximum of α(t) increase linearly with the relative number of methanol monomers in the mixtures. Thus, the dynamical heterogeneities are largest for single methanol molecules fully embedded in the IL environment. In their own environment methanol molecules are highly mobile, whereas in the IL‐rich region the mobility is strongly reduced leading to the non‐validity of SE and SED relations.
Tuning Hydrogen Storage in Lithium‐Functionalized BC2N Sheets by Doping with Boron and Carbon
Authors: Qiu Nian‐xiang , Zhang Cheng‐hua , Xue Ying 
Published: July 2014

AbstractFirst‐principles calculations are used to explore the strong binding of lithium to boron‐ and carbon‐doped BC2N monolayers (BC2NBC and BC2NCN, respectively) without the formation of lithium clusters. In comparison to BC2N and BC2NCB, lithium‐decorated BC2NBC and BC2NCN systems possess stronger s–p and p–p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC2NBC–Li and BC2NCN–Li complexes can serve as high‐capacity hydrogen‐storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively.
Protein Structure Prediction: Assembly of Secondary Structure Elements by Basin‐Hopping
Authors: Hoffmann Falk , Vancea Ioan , Kamat Sanjay G. , Strodel Birgit 
Published: July 2014

AbstractThe prediction of protein tertiary structure from primary structure remains a challenging task. One possible approach to this problem is the application of basin‐hopping global optimization combined with an all‐atom force field. In this work, the efficiency of basin‐hopping is improved by introducing an approach that derives tertiary structures from the secondary structure assignments of individual residues. This approach is termed secondary‐to‐tertiary basin‐hopping and benchmarked for three miniproteins: trpzip, trp‐cage and ER‐10. For each of the three miniproteins, the secondary‐to‐tertiary basin‐hopping approach successfully and reliably predicts their three‐dimensional structure. When it is applied to larger proteins, correctly folded structures are obtained. It can be concluded that the assembly of secondary structure elements using basin‐hopping is a promising tool for de novo protein structure prediction.
Conformational Equilibria and Large‐Amplitude Motions in Dimers of Carboxylic Acids: Rotational Spectrum of Acetic Acid–Difluoroacetic Acid
Authors: Gou Qian , Feng Gang , Evangelisti Luca , Caminati Walther 
Published: July 2014

AbstractWe report the rotational spectra of two conformers of the acetic acid–difluoroacetic acid adduct (CH3COOH–CHF2COOH) and supply information on its internal dynamics. The two conformers differ from each other, depending on the trans or gauche orientation of the terminal CHF2 group. Both conformers display splittings of the rotational transitions, due to the internal rotation of the methyl group of acetic acid. The corresponding barriers are determined to be V3(trans)=99.8(3) and V3(gauche)=90.5(9) cm−1 (where V3 is the methyl rotation barrier height). The gauche form displays a further doubling of the rotational transitions, due to the tunneling motion of the CHF2 group between its two equivalent conformations. The corresponding B2 barrier is estimated to be 108(2) cm−1. The increase in the distance between the two monomers upon OH→OD deuteration (the Ubbelohde effect) is determined.
Organic Superhalogens
Authors: Giri Santanab , Child Brandon Z. , Jena Puru 
Published: July 2014

AbstractUsing first‐principles calculations with predictive capability we show that organic molecules having negative electron affinity can be transformed to superhalogens with electron affinities far exceeding that of chlorine, once its core and ligand atoms are suitably replaced. The discovery of organic superhalogens could have significant impact in chemistry, allowing the synthesis of new materials and compounds.
Synthesis of Bright Alkenyl‐1H‐1,2,4‐triazoles: A Theoretical and Photophysical Study
Authors: Cebrián Cristina , de Mata Muñoz Juan , Strassert Cristian Alejandro , Prieto Pilar , Díaz‐Ortiz Ángel , De Cola Luisa , de la Hoz Antonio 
Published: July 2014

AbstractA sustainable synthesis of alkenyl‐1H‐1,2,4‐triazoles through the Hiyama reaction is reported, which employs water as solvent and sodium hydroxide to activate the silyl group under microwave irradiation, thereby leading to high product yields (51–93 %) in very short reaction times. Two substitution patterns were attained owing to the different reactivity of the third and fifth positions of the 1H‐1,2,4‐triazole unit, as evidenced by calculated condensed Fukui functions. Moreover, all compounds are good blue emitters (ΦF up to 0.69) in THF solution, although they exhibit an optical behavior dependent on the substitution. Excited‐state theoretical investigations by the configuration interaction singles method and time‐dependent density functional theory were performed not only to support and elucidate the studied photophysical properties, but also to create a predictive model to reduce the cost and optimize the search for new blue emitters based on this class of alkenyl‐1H‐1,2,4‐triazoles.
Enhancing Dye‐Sensitized Solar Cell Performances by Molecular Engineering: Highly Efficient π‐Extended Organic Sensitizers
Authors: Grisorio Roberto , De Marco Luisa , Agosta Rita , Iacobellis Rosabianca , Giannuzzi Roberto , Manca Michele , Mastrorilli Piero , Gigli Giuseppe , Suranna Gian Paolo 
Published: July 2014

AbstractThis study deals with the synthesis and characterization of two π‐extended organic sensitizers (G1 and G2) for applications in dye‐sensitized solar cells. The materials are designed with a D–A–π–A structure constituted by i) a triarylamine group as the donor part, ii) a dithienyl‐benzothiadiazole chromophore followed by iii) a further ethynylene‐thiophene (G1) or ethynylene‐benzene (G2) π‐spacer and iv) a cyano‐acrylic moiety as acceptor and anchoring part. An unusual structural extension of the π‐bridge characterizes these structures. The so‐configured sensitizers exhibit a broad absorption profile, the origin of which is supported by density functional theory. The absence of hypsochromic shifts as a consequence of deprotonation as well as notable optical and electrochemical stabilities are also observed. Concerning the performances in devices, electrochemical impedance spectroscopy indicates that the structural modification of the π‐spacer mainly increases the electron lifetime of G2 with respect to G1. In devices, this feature translates into a superior power conversion efficiency of G2, reaching 8.1 %. These results are comparable to those recorded for N719 and are higher with respect to literature congeners, supporting further structural engineering of the π‐bridge extension in the search for better performing π‐extended organic sensitizers.
Compositionally Controlled Self‐Assembly of Hierarchical Pd–Ni Bimetallic Chains
Authors: Jin Peiyu , Liang Xin , He Yeheng , Liu Sijia , Zhu Xiaolin 
Published: July 2014

AbstractMagnetic Pd–Ni bimetals with various compositions were synthesized by a one‐pot reaction, in which chain‐like Pd–Ni bimetals formed through the self‐assembly of Pd–Ni nanoparticles. The self‐assembly behaviour of the Pd–Ni bimetals gradually changes with the changes in composition. The Pd–Ni nanoparticles form simple chains at lower Pd content, while the Pd–Ni bimetals take on a beads‐on‐string structure composed of sphere‐shaped Pd–Ni‐nanoparticle assemblies at higher Pd content. Magnetic hysteresis loops show that Ni‐rich assemblies have a higher saturation magnetization than Pd‐rich assemblies. The formation mechanism for these Pd–Ni assemblies is proposed, in which the self‐assembly behaviours are controlled by the competition of the surfactant interaction and the magnetic dipole interaction. The catalytic activity and selectivity of the hydrogenation of acetophenone over these Pd–Ni bimetals depend on their compositions.
X‐ray Crystallographic Analysis of a Tailor‐Made Bis(phthalocyaninato)‐TbIII Single‐Molecule Magnet as a Fundamental Unit for Supramolecular Spintronic Devices
Authors: Klyatskaya Svetlana , Eichhöfer Andreas , Wernsdorfer Wolfgang 
Published: July 2014

AbstractThe single‐crystal X‐ray diffraction analysis of the title compound, the pyrene‐substituted unsymmetrical bis(phthalocyaninato)terbium(III) Single‐Molecule Magnet (SMM) [Pc–Tb–Pc*]0 (1) (Pc = dianion of phthalocyanine, P* = dianion of phthalocyanine decorated with six flexible hexyl chains and one 4‐pyren‐1yl‐butoxy group), was carried out. Both phthalocyaninato ligands in 1 are distorted from planarity and, therefore, adopt a biconcave shape. Effective π–π interactions between the molecules lead to the formation of head‐to‐tail π dimers. These dimers are stacked in the crystal, forming adjacent, parallel columns, the axes of which are tilted by 30° with respect to the C4 axes of the macrocycles. Herein, we also report the synthesis and characterization of the new isostructural Dy (compound 2) and Ho (compound 3) analogues of 1.
Photoluminescence of Zinc Complexes: Easily Tunable Optical Properties by Variation of the Bridge Between the Imido Groups of Schiff Base Ligands
Authors: Dumur Frédéric , Contal Emmanuel , Wantz Guillaume , Gigmes Didier 
Published: July 2014

AbstractA series of organic–metal chelate complexes of symmetric tetradentate Schiff base ligands derived from salicylaldehyde and 2‐hydroxy‐1‐naphthaldehyde were designed and investigated. The combination of five nonconjugated flexible spacers and five conjugated rigid spacers with four salicylaldehyde derivatives provided a series of forty complexes. The series of blue to red photoluminescent complexes was investigated by UV/Vis absorption and luminescence spectroscopy in solution and in the solid state as well as cyclic voltammetry. The nature of the bridge in the ligand scaffold was determined to be the main parameter that influences the absorption and the emission color of the investigated zinc(II) complexes.
Time course of Algerian Azeradj extra‐virgin olive oil quality during olive ripening
Authors: Bakhouche Abdelhakim , Lozano‐Sánchez Jesús , Bengana Mohamed , Fernández‐Gutiérrez Alberto , Segura‐Carretero Antonio 
Published: July 2014

The aim of this work was the chemical characterization of Algerian Azeradj extra‐virgin olive oil (EVOO) at different harvest dates in terms of oil yield, quality indices, fatty acids, pigments, polyphenols, and oxidative stability, in order to establish the best harvesting period for this variety. For this purpose, Azeradj EVOO samples were taken at three harvest dates corresponding to three ripening stages. Except for K270, the analysis of EVOOs showed a significant increase in the values of all quality parameters as olive ripening progresses (free fatty acids, peroxide index, and K232), while no significant variation was found for oil yield. Moreover, a significant decrease was observed for the monounsaturated fatty acid:polyunsaturated fatty acid (MUFA:PUFA) ratio, chlorophyll, carotenoids, total phenols, and oxidative stability in EVOOs produced at the advanced ripening stage. For better monitoring of the behavior of the phenolic fraction in EVOOs during ripening, for the first time in this work, individual phenolic compounds of Azeradj EVOOs was characterized using HPLC‐ESI‐TOF/MS. A total of 21 phenolic compounds belonging to different families were identified in Azeradj EVOOs. The highest concentrations of secoiridoids and phenolic alcohols were found at the beginning of November (D1); however, lignans and flavones concentrations were higher at the end of November (D2). EVOO obtained at the last harvest date (D3) showed the lowest content on all phenolic families. Finally, according to the results of the analyses performed in this work, early harvesting provides Azeradj EVOO with excellent chemical characteristics.Practical applications: The Algerian olive oil sector is one of the least competitive in the Mediterranean region even if the Algerian olive oil displays some potential assets. Therefore, the chemical characterization of olive oil from one of the main varieties (Azeradj) cultivated in Algeria is of a great importance. The results will be available to all Algerian olive oil producers, and should be helpful in choosing the optimal harvest period to obtain Azeradj EVOO of high chemical quality.Olive ripeness affects the chemical composition of Azeradj extra‐virgin olive oil.
Intravenous lipid microspheres loaded with alkylated norcantharidin derivative norcantharimide: Improved stability and prolonged half‐life
Authors: Pan Zhendong , Niu Yantao , Wang Yueqi , Tang Yilin , Tang Xing , Cai Cuifang 
Published: July 2014

To facilitate the preparation of lipid microspheres, norcantharimide, a C14 alkyl chain derivative of norcantharidin, was synthesized and its physicochemical properties were investigated. The N‐14NCTDA loaded lipid microspheres (N‐14NCTDA LMs) were prepared by a high‐pressure homogenization method and characterized in terms of size, zeta‐potential, encapsulation efficiency and stability. The apparent oil–water partition coefficient of N‐14NCTDA (Log P > 2) was considerably enhanced in comparison to NCTD (Log P (−1.06), pH = 7.4). After optimization of the lipid microsphere formulation, the particle size distribution, zeta‐potential and entrapment efficacy were determined to be 189.2 ± 49.8 nm, −26.78 ± 1.03 mV, and 98.4 ± 0.38%, respectively. High physical and chemical stability was demonstrated in accelerated stability test. A pharmacokinetic study was carried out in rats after intravenous administration of N‐14NCTDA LMs and N‐14NCTDA solution. Their pharmacokinetic profiles were similar with no significant differences in main parameters. Nevertheless, it was noteworthy that a greatly prolonged half‐life and higher Vss was obtained for N‐14NCTDA LMs compared with NCTD loaded lipid microspheres (NCTD LMs). Therefore, the N‐14NCTDA LMs with high encapsulation efficiency and high stability are superior for the treatment of cancer, not only due to reduced venous irritation, but also due to prolonged half‐life.Practical applications: Norcantharidin (NCTD) has been shown to be effective against cancer, especially against primary hepatic carcinoma, but its application is limited by severe renal toxicity and short half‐life. Compared to common injection preparations, lipid microspheres loaded with NCTD lead to greatly reduced venous irritation but problems with low encapsulation efficiency, short half‐life and high kidney toxicity have not been solved. N‐14NCTDA is a new synthetic chemotherapeutic agent, which displayed good broad spectrum cytotoxicity compared with NCTD. In this preformulation study we show that N‐14NCTDA is a promising alternative to NCTD.Significantly enhanced stability and prolonged half‐life were obtained for N‐14NCTDA LMs compared with NCDT LMs.
Ethyl rhamnolipids as a renewable source to produce biopolyurethanes
Authors: Miao Shida , Callow Nicholas V. , Ju Lu‐Kwang 
Published: July 2014

Responding to increasing environmental concerns, lipids are attractive feedstock to produce bio‐based polyurethanes. In this study, ethyl rhamnolipids were used to synthesize polyurethanes by reacting with 1,6‐hexane diisocyanate (HDI). Rhamnolipids were produced by microbial fermentation, providing a novel source for biopolyurethanes. FTIR and gel content analyses confirmed that the hydroxyl groups on rhamnose residues were reacted with isocyanates. DSC analysis revealed an adjustable glass transition temperature (Tg) from 19 to 50°C. Ethyl rhamnolipids are liquid at 50°C, presumably because rhamnose is connected with fatty acid at a mid‐chain position and the unique structure decreases the tendency to crystallize. The liquid polyols were found to have good mixing and reaction properties. The study may inspire future synthesis of novel lipid‐based polyols.Practical applications: Use of vegetable oil‐based polyols for polyurethane production had been extensively investigated. However, synthesis of these polyols mostly involved introduction of petroleum‐based chemicals such as methanol and 1,2‐propanediol. Rhamnolipids are natural glycolipids. Using ethyl rhamnolipids to prepare polyurethanes provides an alternative, more renewable route. In addition, it inspires synthesis of vegetable oil polyols by introducing natural sugars.Bio‐based polyurethanes were prepared from ethyl rhamnolipids, by reaction with 1,6‐hexane diisocyanate (HDI). Rhamnolipids, obtained from fermentation, are an alternative renewable source of reactants for polyurethane production. The unique structure of rhamnolipids may also inspire future synthesis of novel lipid‐based polyols.