bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal‐Free Catalyst for the Chemoselective Methylation of Amines Using Carbon Dioxide as a Carbon Source
Authors: Das Shoubhik , Bobbink Felix D. , Laurenczy Gabor , Dyson Paul J. 
Published: September 2014

AbstractN‐methylation of amines is an important step in the synthesis of many pharmaceuticals and has been widely applied in the preparation of other key intermediates and chemicals. Therefore, the development of efficient methylation methods has attracted considerable attention. In this respect, carbon dioxide is an attractive C1 building block because it is an abundant, renewable, and nontoxic carbon source. Consequently, we developed a highly chemoselective, metal‐free catalytic system that operates under ambient conditions for the N‐methylation of amines.
Synthesis of Chlorosilicates
Authors: Steinhauer Simon , Böttcher Tobias , Schwarze Nico , Neumann Beate , Stammler Hans‐Georg , Hoge Berthold 
Published: September 2014

AbstractChlorosilicates represent important intermediates in SN2 reactions of chlorosilanes. They can be stabilized by the introduction of electron‐withdrawing substituents. Salts of various (pentafluoroethyl)chlorosilicates have been isolated and structurally characterized.
Conjugated Donor‐Acceptor‐Acceptor (D‐A‐A) Molecule for Organic Nonvolatile Resistor Memory
Authors: Dong Lei , Li Guangwu , Yu An‐Dih , Bo Zhishan , Liu Cheng‐Liang , Chen Wen‐Chang 
Published: September 2014

AbstractA new donor‐acceptor‐acceptor (D‐A‐A) type of conjugated molecule, N‐(4‐(N′,N′‐diphenyl)phenylamine)‐4‐(4′‐(2,2‐dicyanovinyl)phenyl) naphthalene‐1,8‐dicarboxylic monoimide (TPA‐NI‐DCN), consisting of triphenylamine (TPA) donors and naphthalimide (NI)/dicyanovinylene (DCN) acceptors was synthesized and characterized. In conjunction with previously reported D‐A based materials, the additional DCN moiety attached as end group in the D‐A‐A configuration can result in a stable charge transfer (CT) and charge‐separated state to maintain the ON state current. The vacuum‐deposited TPA‐NI‐DCN device fabricated as an active memory layer was demonstrated to exhibit write‐once‐read‐many (WORM) switching characteristics of organic nonvolatile memory due to the strong polarity of the TPA‐NI‐DCN moiety.
Molecular basis of the recognition of arachidonic acid by cytochrome P450 2E1 along major access tunnel
Authors: Cui Ying‐Lu , Zheng Qing‐Chuan , Zhang Ji‐Long , Zhang Hong‐Xing 
Published: September 2014

ABSTRACTCytochrome P450 2E1 is widely known for its ability to oxidize both low molecular weight xenobiotics and endogenous fatty acids (e.g., arachidonic acid (AA)). In this study, we investigated the structural features of the AA‐bound CYP2E1 complex utilizing molecular dynamics (MD) and found that the distinct binding modes for both AA and fatty acid analog are conserved. Moreover, multiple random acceleration MD simulations and steered MD simulations uncovered the most possible tunnel for fatty acids. The main attractions are derived from three key residues, His107, Ala108, and His109, whose side chains reorient to keep ligands bound via hydrogen bonds during the initial unbinding process. More importantly, based on the calculated binding free energy results, we hypothesize that the hydrogen bonds between the receptor and the ligand are the most important contributors involved in the binding affinity. Thus, it is inferred that the hydrogen bonds between these three residues and the ligand may help offer insights into the structural basis of the different ligand egress mechanisms for fatty acids and small weight compounds. Our investigation provides detailed atomistic insights into the structural features of human CYP2E1–fatty acid complex structures. Furthermore, the ligand‐binding characteristics obtained in the present study are helpful for both experimental and computational studies of CYPs and may allow future researchers to achieve desirable changes in enzymatic activities. © 2014 Wiley Periodicals, Inc. Biopolymers 103: 53–66, 2015.
Supramolecular Stabilization of Metastable Tautomers in Solution and the Solid State
Authors: Juribašić Marina , Bregović Nikola , Stilinović Vladimir , Tomišić Vladislav , Cindrić Marina , Šket Primož , Plavec Janez , Rubčić Mirta , Užarević Krunoslav 
Published: September 2014

AbstractThis work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non‐heterocyclic, tautomeric solids. Quantum‐chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3‐methoxysalicylaldehyde and 2‐amino‐3‐hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen‐bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid‐state and solvent‐mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions.
Catalytic Asymmetric Construction of 3,3′‐Spirooxindoles Fused with Seven‐Membered Rings by Enantioselective Tandem Reactions
Authors: Wang Yang , Shi Feng , Yao Xi‐Xi , Sun Meng , Dong Liang , Tu Shu‐Jiang 
Published: September 2014

AbstractThe first catalytic asymmetric construction of a spirooxindole scaffold incorporated with a seven‐membered benzodiazepine moiety has been established by a three‐component (isatin, 1,2‐phenylenediamine, cyclohexane‐1,3‐dione) tandem reaction catalyzed by a chiral phosphoric acid. Structurally complex spirobenzodiazepine oxindoles with one quaternary stereogenic center are obtained in high yield with excellent enantioselectivity (up to 99 % yield, enantiomeric ratio>99.5:0.5). This approach takes advantage of organocatalytic asymmetric tandem reactions to efficiently construct the structurally rigid spirobenzodiazepine oxindole architecture with high enantiopurity in a single transformation, which involves a cascade enamine–imine formation/intramolecular Mannich reaction sequence.
Palladium–N‐Heterocyclic Carbene (NHC)‐Catalyzed Asymmetric Synthesis of Indolines through Regiodivergent C(sp3)H Activation: Scope and DFT Study
Authors: Katayev Dmitry , Larionov Evgeny , Nakanishi Masafumi , Besnard Céline , Kündig E. Peter 
Published: September 2014

AbstractTwo bulky, chiral, monodentate N‐heterocyclic carbene ligands were applied to palladium‐catalyzed asymmetric CH arylation to incorporate C(sp3)H bond activation. Racemic mixtures of the carbamate starting materials underwent regiodivergent reactions to afford different trans‐2,3‐substituted indolines. Although this CArCalkyl coupling requires high temperatures (140–160 °C), chiral induction is high. This regiodivergent reaction, when carried out with enantiopure starting materials, can lead to single structurally different enantiopure products, depending on the catalyst chirality. The CH activation at a tertiary center was realized only in the case of a cyclopropyl group. No CH activation takes place alpha to a tertiary center. A detailed DFT study is included and analyses of methyl versus methylene versus methine CH activation is used to rationalize experimentally observed regio‐ and enantioselectivities.
Long‐Lived Spin States for Low‐Field Hyperpolarized Gas MRI
Authors: Kovtunov Kirill V. , Truong Milton L. , Barskiy Danila A. , Koptyug Igor V. , Coffey Aaron M. , Waddell Kevin W. , Chekmenev Eduard Y. 
Published: September 2014

AbstractParahydrogen induced polarization was employed to prepare a relatively long‐lived correlated nuclear spin state between methylene and methyl protons in propane gas. Conventionally, such states are converted into a strong NMR signal enhancement by transferring the reaction product to a high magnetic field in an adiabatic longitudinal transport after dissociation engenders net alignment (ALTADENA) experiment. However, the relaxation time T1 of ∼0.6 s of the resulting hyperpolarized propane is too short for potential biomedical applications. The presented alternative approach employs low‐field MRI to preserve the initial correlated state with a much longer decay time TLLSS=(4.7±0.5) s. While the direct detection at low‐magnetic fields (e.g. 0.0475 T) is challenging, we demonstrate here that spin‐lock induced crossing (SLIC) at this low magnetic field transforms the long‐lived correlated state into an observable nuclear magnetization suitable for MRI with sub‐millimeter and sub‐second spatial and temporal resolution, respectively. Propane is a non‐toxic gas, and therefore, these results potentially enable low‐cost high‐resolution high‐speed MRI of gases for functional imaging of lungs and other applications.
Design and Synthesis of N‐Acylated Aza‐Goniothalamin Derivatives and Evaluation of Their in vitro and in vivo Antitumor Activity
Authors: Barcelos Rosimeire Coura , Pastre Julio Cezar , Vendramini‐Costa Débora Barbosa , Caixeta Vanessa , Longato Giovanna Barbarini , Monteiro Paula Araújo , de Carvalho João Ernesto , Pilli Ronaldo Aloise 
Published: September 2014

AbstractHerein we describe the synthesis of a focused library of compounds based on the structure of goniothalamin (1) and the evaluation of the potential antitumor activity of the compounds. N‐Acylation of aza‐goniothalamin (2) restored the in vitro antiproliferative activity of this family of compounds. 1‐(E)‐But‐2‐enoyl‐6‐styryl‐5,6‐dihydropyridin‐2(1H)‐one (18) displayed enhanced antiproliferative activity. Both goniothalamin (1) and derivative 18 led to reactive oxygen species generation in PC‐3 cells, which was probably a signal for caspase‐dependent apoptosis. Treatment with derivative 18 promoted Annexin V/7‐aminoactinomycin D double staining, which indicated apoptosis, and also led to G2/M cell‐cycle arrest. In vivo studies in Ehrlich ascitic and solid tumor models confirmed the antitumor activity of goniothalamin (1), without signs of toxicity. However, derivative 18 exhibited an unexpectedly lower in vivo antitumor activity, despite the treatments being administered at the same site of inoculation. Contrary to its in vitro profile, aza‐goniothalamin (2) inhibited Ehrlich tumor growth, both on the ascitic and solid forms. Our findings highlight the importance of in vivo studies in the search for new candidates for cancer treatment.
Strong Asymptotics of the Orthogonal Polynomials with Respect to a Measure Supported on the Plane
Authors: Balogh Ferenc , Bertola Marco , Lee Seung‐Yeop , Mclaughlin Kenneth D. T‐R 
Published: September 2014

We consider the orthogonal polynomials with respect to the measure

urn:x-wiley::media:cpa21541:cpa21541-math-0002

over the whole complex plane. We obtain the strong asymptotic of the orthogonal polynomials in the complex plane and the location of their zeros in a scaling limit where n grows to infinity with N.The asymptotics are described in terms of three (probability) measures associated with the problem. The first measure is the limit of the counting measure of zeros of the polynomials, which is captured by the g‐function much in the spirit of ordinary orthogonal polynomials on the real line. The second measure is the equilibrium measure that minimizes a certain logarithmic potential energy, supported on a region K of the complex plane. The third measure is the harmonic measure of Kc with a pole at ∞. This appears as the limit of the probability measure given (up to the normalization constant) by the squared modulus of the nth orthogonal polynomial times the orthogonality measure, i.e., The compact region K that is the support of the second measure undergoes a topological transition under the variation of the parameter in a double scaling limit near the critical point given by we observe the Hastings‐McLeod solution to Painlevé II in the asymptotics of the orthogonal polynomials. © 2014 Wiley Periodicals, Inc.
Online hot event discovery based on Association Link Network
Authors: Liu Yang , Luo Xiangfeng , Xuan Junyu 
Published: September 2014

SummaryOnline hot event discovery has become a flourishing frontier where online document streams are monitored to discover newly occurring events or assigned to previously detected events. However, hot events have the nature to evolve, and their inherent topically related words are also likely to evolve. It makes event discovery a challenging task for traditional‐mining approaches. Combining word association and semantic community, Association Link Network (ALN) organizes the loosely distributed associated resources. This paper presents an ALN‐based novel online hot event discovery approach. Technically, this approach is enacted around three stages. In the first stage, we extract significant features to represent the content of each document from the online document stream. During the second stage, we classify the online document stream into topically related detected events considering event evolution in the form of ALN. At the third stage, we create an ALN‐based event detection algorithm, which is used to timely discover newly occurring hot events. The online datasets used in our empirical studies are acquired from Baidu News, which spans a range of 1315 hot events and 236,300 documents. Experimental results demonstrate the hot events discovery ability with respect to high accuracy, good scalability, and short runtime. Copyright © 2014 John Wiley & Sons, Ltd.
Concluding the Amyloid Formation Pathway of a Coiled‐Coil‐Based Peptide from the Size of the Critical Nucleus
Authors: Gerling Ulla I. M. , Miettinen Markus S. , Koksch Beate 
Published: September 2014

AbstractThe size of the critical nucleus acting as intermediate in the amyloid formation of a model peptide is calculated. The theoretical approach is based on experimentally determined amyloid formation rates and gives new insights into the amyloid formation pathway.
The Electronic Structures of Small Nin (n=2–4) Clusters and Their Interactions with Ethylene and Triplet Oxygen: A Theoretical Study
Authors: Pakiari Ali H. , Pahlavan Farideh 
Published: September 2014

AbstractDensity functional theory (DFT) calculations of small nickel clusters and their interacting systems are carried out using the BLYP and B97‐2 methods, after DFT calibration. All bare nickel clusters in this study have high multiplicities and are paramagnetic. Our results for the interactions between ethylene and oxygen with Nin (n=2–4) clusters at different adsorption modes show that for ethylene, π‐orientation is preferred, and that oxygen adsorption in a bridge mode is stronger than on‐top coordination. Vibrational frequency analysis reveals that the vibrational modes of ethylene π‐coordinated to nickel clusters converge toward the corresponding value for surface‐bound ethylene, as the cluster size increases from two to four, showing that finite clusters can be used as localized models for ligand adsorption on nickel surfaces. We also calculate DFT global reactivity descriptors, chemical potential and hardness, and use these to predict the relative stability and reactivity of each bare cluster.
Ring Currents in Benzo‐ and Benzocyclobutadieno‐Annelated Biphenylene Derivatives
Authors: Radenković Slavko , Tošović Jelena , Havenith Remco W. A. , Bultinck Patrick 
Published: September 2014

AbstractThe effect of benzo and benzocyclobutadieno annelation on the current density induced in a series of biphenylene derivatives is examined at the B3LYP/cc‐pVDZ level of theory, by using the CTOCD‐DZ method. Angular benzo annelation increases, whereas linear benzo annelation decreases the intensity of paratropic (antiaromatic) current density along the four‐membered ring of biphenylene. The opposite effect is found for benzocyclobutadieno annelation. It is shown that the extent of local aromaticity of the four‐membered ring in biphenylene congeners can vary from highly antiaromatic to nonaromatic, as a result of different modes of annelation.
Use of capillary electrophoresis as a versatile tool to measure interaction constants between a KDR‐binding PEGylated lipopeptide and pegylated phospholipid micelles
Authors: Poitevin Martine , Tranquart François , Cherkaoui Samir 
Published: September 2014

In the frame of our molecular imaging activities, a PEGylated lipopeptide has been developed as a specific ligand for the human vascular endothelial growth factor receptor 2, which is considered as one of the important molecular marker of angiogenesis. In this study, the potential of affinity capillary electrophoresis (ACE) is evaluated to measure the interactions of an active PEGylated lipopeptide, its hydrolysis product and its precursor consisting of a peptide structure with different micelles including Brij‐35, Tween‐20, and pegylated phospholipids. Given the amphiphilic structure of the PEGylated lipopeptide, a MEKC method allowing the simultaneous separation of the compounds of interest was set up, using low percentages of acetonitrile. Analytes were resolved using a BGE consisting of 100 mM borate buffer pH 9.0, 1 mM Brij, and 25% acetonitrile. Optimized conditions were then used to perform ACE experiments. The affinity constants of the analytes with the micelles were calculated on the basis of their mobility decrease when surfactant concentration increased in the electrolyte. The use of different linearization models to estimate affinity constants was discussed and comparison of different surfactants was reported. PEGylated lipopeptide interacted more strongly with pegylated phospholipid micelles than with Brij‐35 or Tween‐20. Moreover, it is likely that the chemical structure of the compounds, and particularly the lipidic part of the molecules, significantly affects the interaction with micelles. In conclusion, the ACE method can be readily applied to investigate interactions of our targeting lipopeptides with various micelles currently used for the preparation of pharmaceutical vehicles.
Show Me Your Friends, and I Shall Show You Who You Are: The Way Attachment and Social Comparisons Influence Body Dissatisfaction
Authors: Lev‐Ari Lilac , Baumgarten‐Katz Inbar , Zohar Ada H. 
Published: September 2014

AbstractWomen with attachment insecurity have greater eating disorder symptoms and poorer prognosis. Socio‐cultural agents, such as peers and family, are predictive of the development of body image dissatisfaction (BID). The present study examines the association of insecure attachment styles and direct and indirect social comparisons of body image to women's BID and drive to thinness. Two hundred and eighty three women aged 18–42 years completed online self‐reports concerning attachment styles, body mass index (BMI), drive for thinness, body image satisfaction, the Figure Rating Scale (FRS), as well as a modified FRS comparing self to mother, to sister closest in age and to best friend. Hierarchical Linear Models reveal that anxious‐ambivalent, but not avoidant attachment style, along with indirect and direct comparisons to best friend and to sister influence drive for thinness and body dissatisfaction, even after controlling for BMI and age. Of all social comparisons, feeling one's best friend is thinner than yourself is the most detrimental to body ideal. Copyright © 2014 John Wiley & Sons, Ltd and Eating Disorders Association.
Temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region, Japan
Authors: Imaizumi Fumitoshi , Sidle Roy C. , Togari‐Ohta Asako , Shimamura Makoto 
Published: September 2014

AbstractThe duration of the soil‐depth recovery needed for reoccurrence of shallow colluvial landslides at a given site in humid regions is much longer than the return period of rainfall needed to generate sufficient pore water pressure to initiate a landslide. Knowledge of the rate of change in soil depth in landslide scars is therefore necessary to evaluate return intervals of landslides. Spatial variation in sediment transport at the Kumanodaira landslide scar in central Japan was investigated by field observations. Spatial distribution of the rate of change in soil depth was estimated using sediment transport data and geographic information system (GIS) analysis. Observations revealed that the timing of sediment transport differed for shallow and deep soil layers. Near‐surface sediment transport (mostly dry ravel and some shallow soil creep at depths ≤0·05 m) measured in sediment traps was active in winter and early spring and was affected by freezing–thawing; soil creep of subsoil (i.e. >0·05 m), monitored by strain probes, was active in summer and autumn when precipitation was abundant. Near‐surface sediment flux was estimated by a power law function of slope gradient. Deeper soil creep was more affected by relative location to the landslide scar, which influences soil depth, than by slope gradient. Our study indicated that the rate of soil‐depth recovery is high just below the head scarp of the landslide. Abrupt changes in the longitudinal slope topography immediately above, within and just below the head scarp became smoother with time due to degradation proximate to the landslide head scarp and flanks, as well as aggradation just below the head scarp. Copyright © 2014 John Wiley & Sons, Ltd.
Interhemispheric somatosensory differences in chronic pain reflect abnormality of the Healthy side
Authors: Di Pietro Flavia , Stanton Tasha R , Moseley G. Lorimer , Lotze Martin , McAuley James H 
Published: September 2014

AbstractIt is widely accepted that complex regional pain syndrome (CRPS) is associated with shrinkage of the primary somatosensory cortex (S1) representation of the affected limb. However, supporting evidence is surprisingly limited and may be compromised by high risk of bias. This study compared the S1 spatial representation of the hand in 17 patients with upper‐limb CRPS to 16 healthy controls, using functional MRI. Innocuous vibration was delivered to digits one (D1) and five (D5) in a block‐design. Resultant activation maxima were located within a bilateral S1 mask, determined a priori. Distance between D1 and D5 activation maxima, calculated for both hands, was used as a measure of S1 representation. Analyses were blinded to group and hand. In patients, S1 representation was smaller for the affected hand than it was for the healthy hand (t(11) = 2.02, P = 0.03), as predicted. However, S1 representation of the affected hand was no different to that of either hand in controls. Critically, S1 representation of the healthy hand of patients was larger than that of controls' hands. CRPS seems to be associated with an enlarged representation of the healthy hand, not a smaller representation of the affected hand. These findings raise important questions about neuroplasticity in CRPS. Hum Brain Mapp 36:508–518, 2015. © 2014 Wiley Periodicals, Inc.