bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Near‐Infrared‐Emissive Alkynyl‐Protected Au24 Nanocluster
Authors: Wan Xian‐Kai , Xu Wen Wu , Yuan Shang‐Fu , Gao Yi , Zeng Xiao‐Cheng , Wang Quan‐Ming 
Published: June 2015

AbstractAn alkynyl‐protected gold nanocluster [Au24(CCPh)14(PPh3)4](SbF6)2 has been prepared by a direct reduction method. Single‐crystal X‐ray diffraction reveals that the molecular structure contains a Au22 core that is made of two Au13‐centered cuboctahedra that share a square face. Two staple‐like PhCCAuCCPh motifs are located around the center of the rod‐like Au22 core. This Au24 nanocluster is highly emissive in the near‐infrared region with λmax=925 nm and the nature of the HOMO–LUMO transition is investigated by time‐dependent DFT calculations.
Protonation‐Dependent Base Flipping at Neutral pH in the Catalytic Triad of a Self‐Splicing Bacterial Group II Intron
Authors: Pechlaner Maria , Donghi Daniela , Zelenay Veronika , Sigel Roland K. O. 
Published: June 2015

AbstractNMR spectroscopy has revealed pH‐dependent structural changes in the highly conserved catalytic domain 5 of a bacterial group II intron. Two adenines with pKa values close to neutral pH were identified in the catalytic triad and the bulge. Protonation of the adenine opposite to the catalytic triad is stabilized within a G(syn)–AH+(anti) base pair. The pH‐dependent anti‐to‐syn flipping of this G in the catalytic triad modulates the known interaction with the linker region between domains 2 and 3 (J23) and simultaneously the binding of the catalytic Mg2+ ion to its backbone. Hence, this here identified shifted pKa value controls the conformational change between the two steps of splicing.
Intracellular Self‐Assembly of Taxol Nanoparticles for Overcoming Multidrug Resistance
Authors: Yuan Yue , Wang Lin , Du Wei , Ding Zhanling , Zhang Jia , Han Tao , An Linna , Zhang Huafeng , Liang Gaolin 
Published: June 2015

AbstractMultidrug resistance (MDR) remains the biggest challenge in treating cancers. Herein we propose the intracellular self‐assembly of nanodrugs as a new strategy for overcoming MDR. By employing a biocompatible condensation reaction, we rationally designed a taxol derivative Ac‐Arg‐Val‐Arg‐Arg‐Cys(StBu)‐Lys(taxol)‐2‐cyanobenzothiazole (CBT‐Taxol) which could be subjected to furin‐controlled condensation and self‐assembly of taxol nanoparticles (Taxol‐NPs). In vitro and in vivo studies indicated that, compared with taxol, CBT‐Taxol showed a 4.5‐fold or 1.5‐fold increase in anti‐MDR effects, respectively, on taxol‐resistant HCT 116 cancer cells or tumors without being toxic to the cells or the mice. Our results demonstrate that structuring protease‐susceptible agents and assembling them intracellularly into nanodrugs could be a new optimal strategy for overcoming MDR.
A Phosphine‐Coordinated Boron‐Centered Gomberg‐Type Radical
Authors: Rosenthal Amos J. , Devillard Marc , Miqueu Karinne , Bouhadir Ghenwa , Bourissou Didier 
Published: June 2015

AbstractThe P‐coordinated boryl radical [Ph2P(naphthyl)BMes]. (Mes=mesityl) was prepared by (electro)chemical reduction of the corresponding borenium salt or bromoborane. Electron paramagnetic resonance (EPR) analysis in solution and DFT calculations indicate large spin density on boron (60–70 %) and strong P–B interactions (P→B σ donation and B→P negative hyperconjugation). The radical is persistent in solution and participates in a Gomberg‐type dimerization process. The associated quinoid‐type dimer has been characterized by single‐crystal X‐ray diffraction.
Metal‐Free Radical [2+2+1] Carbocyclization of Benzene‐Linked 1,n‐Enynes: Dual C(sp3)H Functionalization Adjacent to a Heteroatom
Authors: Hu Ming , Fan Jian‐Hong , Liu Yu , Ouyang Xuan‐Hui , Song Ren‐Jie , Li Jin‐Heng 
Published: June 2015

AbstractA new metal‐free oxidative radical [2+2+1] carbocyclization of benzene‐linked 1,n‐enynes with two C(sp3)H bonds adjacent to the same heteroatom is described. This method achieves two C(sp3)H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five‐membered carbocyclic hydrocarbons.
Cobalt Boryl Complexes: Enabling and Exploiting Migratory Insertion in Base‐Metal‐Mediated Borylation
Authors: Frank René , Howell James , Campos Jésus , Tirfoin Rémi , Phillips Nicholas , Zahn Stefan , Mingos D. Michael P. , Aldridge Simon 
Published: June 2015

AbstractCobalt boryl complexes, which have only been sporadically reported, can be accessed systematically with remarkable (but controllable) variation in the nature of the MB bond. Complexes incorporating a very strong trans σ‐donor display unparalleled inertness, reflected in retention of the MB bond even in the presence of extremely strong acid. By contrast, the use of the strong π‐acceptor CO in the trans position, results in significant CoB elongation and to labilization of the boryl ligand via unprecedented CO migratory insertion. Such chemistry provides a pathway for the generation of coordinative unsaturation, thereby enabling ligand substitution and/or substrate assimilation. Alkene functionalization by boryl transfer, a well‐known reaction for noble metals such as Rh or Pt, can thus be effected by an 18‐electron base‐metal complex.
Four Decades of the Chemistry of Planar Hypercoordinate Compounds
Authors: Yang Li‐Ming , Ganz Eric , Chen Zhongfang , Wang Zhi‐Xiang , Schleyer Paul von Ragué 
Published: June 2015

AbstractThe idea of planar tetracoordinate carbon (ptC) was considered implausible for a hundred years after 1874. Examples of ptC were then predicted computationally and realized experimentally. Both electronic and mechanical (e.g., small rings and cages) effects stabilize these unusual bonding arrangements. Concepts based on the bonding motifs of planar methane and the planar methane dication can be extended to give planar hypercoordinate structures of other chemical elements. Numerous planar configurations of various central atoms (main‐group and transition‐metal elements) with coordination numbers up to ten are discussed herein. The evolution of such planar configurations from small molecules to clusters, to nanospecies and to bulk solids is delineated. Some experimentally fabricated planar materials have been shown to possess unusual electrical and magnetic properties. A fundamental understanding of planar hypercoordinate chemistry and its potential will help guide its future development.
Two‐Dimensional Layered Heterostructures Synthesized from Core–Shell Nanowires
Authors: Zhang Qi , Xiao Xu , Zhao Ruiqi , Lv Danhui , Xu Guanchen , Lu Zhixing , Sun Lifei , Lin Shizhe , Gao Xiang , Zhou Jun , Jin Chuanhong , Ding Feng , Jiao Liying 
Published: June 2015

AbstractControlled stacking of different two‐dimensional (2D) atomic layers will greatly expand the family of 2D materials and broaden their applications. A novel approach for synthesizing MoS2/WS2 heterostructures by chemical vapor deposition has been developed. The successful synthesis of pristine MoS2/WS2 heterostructures is attributed to using core–shell WO3−x/MoO3−x nanowires as a precursor, which naturally ensures the sequential growth of MoS2 and WS2. The obtained heterostructures exhibited high crystallinity, strong interlayer interaction, and high mobility, suggesting their promising applications in nanoelectronics. The stacking orientations of the two layers were also explored from both experimental and theoretical aspects. It is elucidated that the rational design of precursors can accurately control the growth of high‐quality 2D heterostructures. Moreover, this simple approach opens up a new way for creating various novel 2D heterostructures by using a large variety of heteronanomaterials as precursors.
Deciphering the Non‐Equivalence of Serine and Threonine O‐Glycosylation Points: Implications for Molecular Recognition of the Tn Antigen by an anti‐MUC1 Antibody
Authors: Martínez‐Sáez Nuria , Castro‐López Jorge , Valero‐González Jessika , Madariaga David , Compañón Ismael , Somovilla Víctor J. , Salvadó Míriam , Asensio Juan L. , Jiménez‐Barbero Jesús , Avenoza Alberto , Busto Jesús H. , Bernardes Gonçalo J. L. , Peregrina Jesús M. , Hurtado‐Guerrero Ramón , Corzana Francisco 
Published: June 2015

AbstractThe structural features of MUC1‐like glycopeptides bearing the Tn antigen (α‐O‐GalNAc‐Ser/Thr) in complex with an anti MUC‐1 antibody are reported at atomic resolution. For the α‐O‐GalNAc‐Ser derivative, the glycosidic linkage adopts a high‐energy conformation, barely populated in the free state. This unusual structure (also observed in an α‐S‐GalNAc‐Cys mimic) is stabilized by hydrogen bonds between the peptidic fragment and the sugar. The selection of a particular peptide structure by the antibody is thus propagated to the carbohydrate through carbohydrate/peptide contacts, which force a change in the orientation of the sugar moiety. This seems to be unfeasible in the α‐O‐GalNAc‐Thr glycopeptide owing to the more limited flexibility of the side chain imposed by the methyl group. Our data demonstrate the non‐equivalence of Ser and Thr O‐glycosylation points in molecular recognition processes. These features provide insight into the occurrence in nature of the APDTRP epitope for anti‐MUC1 antibodies.
Structure Elucidation and Activity of Kolossin A, the D‐/L‐Pentadecapeptide Product of a Giant Nonribosomal Peptide Synthetase
Authors: Bode Helge B. , Brachmann Alexander O. , Jadhav Kirtikumar B. , Seyfarth Lydia , Dauth Christina , Fuchs Sebastian W. , Kaiser Marcel , Waterfield Nick R. , Sack Holger , Heinemann Stefan H. , Arndt Hans‐Dieter 
Published: June 2015

AbstractThe largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D‐/ L‐peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness.
Three‐Component Azidation of Styrene‐Type Double Bonds: Light‐Switchable Behavior of a Copper Photoredox Catalyst
Authors: Fumagalli Gabriele , Rabet Pauline T. G. , Boyd Scott , Greaney Michael F. 
Published: June 2015

Abstract[Cu(dap)2]Cl effectively catalyzes azide addition from the Zhdankin reagent to styrene‐type double bonds, and subsequent addition of a third component to the benzylic position. In the presence of light, a photoredox cycle is implicated with polar components such as methanol or bromide adding to a benzylic cation. In the absence of light, by contrast, double azidation takes place to give diazides. Therefore, regioselective double functionalization can be achieved in good to excellent yields, with a switch between light and dark controlling the degree of azidation.
Asymmetric Synthesis of Axially Chiral Isoquinolones: Nickel‐Catalyzed Denitrogenative Transannulation
Authors: Fang Zhi‐Jia , Zheng Sheng‐Cai , Guo Zhen , Guo Jing‐Yao , Tan Bin , Liu Xin‐Yuan 
Published: June 2015

AbstractThe first Ni0/bis(oxazoline)‐catalyzed asymmetric denitrogenative transannulation of 1,2,3‐benzotriazin‐4(3H)‐ones with bulky internal alkynes to form novel axially chiral isoquinolones in an atroposelective manner has been developed. This method provides direct asymmetric access to axially chiral isoquinolones with excellent functional‐group tolerance in excellent yields and stereoselectivities from readily available starting materials under mild reaction conditions. These axially chiral isoquinolones exhibit high cytotoxicity against a number of human cancer cell lines. DFT calculations reveal the nature of the transition state in the key annulation step.
Highly Efficient CSeCF3 Coupling of Aryl Iodides Enabled by an Air‐Stable Dinuclear PdI Catalyst
Authors: Aufiero Marialuisa , Sperger Theresa , Tsang Althea S.‐K. , Schoenebeck Franziska 
Published: June 2015

AbstractBuilding on our recent disclosure of catalysis at dinuclear PdI sites, we herein report the application of this concept to the realization of the first catalytic method to convert aryl iodides into the corresponding ArSeCF3 compounds. Highly efficient CSeCF3 coupling of a range of aryl iodides was achieved, enabled by an air‐, moisture‐, and thermally stable dinuclear PdI catalyst. The novel SeCF3‐bridged dinuclear PdI complex 3 was isolated, studied for its catalytic competence and shown to be recoverable. Experimental and computational data are presented in support of dinuclear PdI catalysis.
Reductive Insertion of Elemental Chalcogens into Boron–Boron Multiple Bonds
Authors: Braunschweig Holger , Dellermann Theresa , Ewing William C. , Kramer Thomas , Schneider Christoph , Ullrich Stefan 
Published: June 2015

AbstractThe syntheses of sulfur‐ and selenium‐bridged cyclic compounds containing boron stabilized by N‐heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron–boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six‐electron reduction reactions, resulting in the formation of [2.2.1]‐bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron–boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC‐stabilized trisulfidodiborolane. The demonstration of these six‐ and four‐electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.
Toward Naphthocyclinones: Doubly Connected Octaketide Dimers with a Bicyclo[3.2.1]octadienone Core by Thiolate‐Mediated Cyclization
Authors: Ando Yoshio , Hori Subaru , Fukazawa Takumi , Ohmori Ken , Suzuki Keisuke 
Published: June 2015

AbstractA viable method is reported for the synthesis of the bicyclo[3.2.1]octadienone scaffold in naturally occurring octaketide dimers. The procedure employs a reductive cyclization reaction mediated by an unusual ethanedithiol monosodium salt.
Reversible α‐Hydrogen and α‐Alkyl Elimination in PC(sp3)P Pincer Complexes of Iridium
Authors: Jonasson Klara J. , Polukeev Alexey V. , Marcos Rocío , Ahlquist Mårten S. G. , Wendt Ola F. 
Published: June 2015

AbstractDespite significant progress in recent years, the cleavage of unstrained C(sp3)C(sp3) bonds remains challenging. A CC coupling and cleavage reaction in a PC(sp3)P iridium pincer complex is mechanistically studied; the reaction proceeds via the formation of a carbene intermediate and can be described as a competition between α‐hydrogen and α‐alkyl elimination; the latter process was observed experimentally and is an unusual way of C(sp3)C(sp3) bond scission, which has previously not been studied in detail. Mechanistic details that are based upon kinetic studies, activation parameters, and DFT calculations are also discussed. A full characterization of a CC agostic intermediate is presented.
Multidimensional Design of Anticancer Peptides
Authors: Lin Yen‐Chu , Lim Yi Fan , Russo Erica , Schneider Petra , Bolliger Lea , Edenharter Adriana , Altmann Karl‐Heinz , Halin Cornelia , Hiss Jan A. , Schneider Gisbert 
Published: June 2015

AbstractThe computer‐assisted design and optimization of peptides with selective cancer cell killing activity was achieved through merging the features of anticancer peptides, cell‐penetrating peptides, and tumor‐homing peptides. Machine‐learning classifiers identified candidate peptides that possess the predicted properties. Starting from a template amino acid sequence, peptide cytotoxicity against a range of cancer cell lines was systematically optimized while minimizing the effects on primary human endothelial cells. The computer‐generated sequences featured improved cancer‐cell penetration, induced cancer‐cell apoptosis, and were enabled a decrease in the cytotoxic concentration of co‐administered chemotherapeutic agents in vitro. This study demonstrates the potential of multidimensional machine‐learning methods for rapidly obtaining peptides with the desired cellular activities.
Ring Expansion to 1‐Bromo‐1‐alumacyclonona‐2,4,6,8‐tetraene by Insertion of Two Alkyne Molecules into the AlC Bonds
Authors: Agou Tomohiro , Wasano Tatsuya , Sasamori Takahiro , Guo Jing‐Dong , Nagase Shigeru , Tokitoh Norihiro 
Published: June 2015

AbstractTreatment of 1‐bromo‐2,3,4,5‐tetraethylalumole (1) with 3‐hexyne afforded the corresponding product 1‐bromo‐1‐alumacyclonona‐2,4,6,8‐tetraene (2), accompanied by the formation of hexaethylbenzene. In the crystalline state, 2 forms a Br‐bridged dimer with a pseudo C2‐symmetric and twisted AlC8 nine‐membered ring. Deuterium‐labeling experiments and DFT calculations on the reaction of 1 with 3‐hexyne suggested that 1‐bromo‐1‐alumacyclohepta‐2,4,6‐triene, which is formed by the insertion of one molecule of 1‐hexyne into the AlC bond of alumole 1, is the key intermediate for the generation of 2 as well as hexaethylbenzene.
A Multidimensional Research Strategy for the Evaluation of Settlement Pits: 3D Electrical Resistivity Tomography, Magnetic Prospection and Soil Chemistry
Authors: Nowaczinski Erich , Schukraft Gerd , Rassmann Knut , Reiter Samantha , Müller‐Scheeßel Nils , Hecht Stefan , Eitel Bernhard , Bubenzer Olaf , Bátora Jozef 
Published: June 2015

AbstractIrrespective of the region and time period, settlement pits are common features at archaeological sites. Variations in shape, size and fill reflect great diversity in terms of primary and secondary functions. Careful analysis of these aspects and a pit's refilling history yield key information for the reconstruction of economic, social and chronological aspects of settlement history. At present, it is unusual for a settlement site to undergo complete excavation; in most cases, only small areas within a larger settlement are opened to archaeological inquiry and, accordingly, only a scarce few pits can be excavated. Therefore, the application of a combination of new prospection methods can help to classify and preselect representative pits for subsequent excavation in order to guarantee the highest information output. The interdisciplinary investigations at the Early Bronze Age of Fidvár in Slovakia enabled the development of just such a multidimensional research strategy for the evaluation of settlement pits. Used in concert, magnetic survey and electromagnetic prospection delivered 2D data which revealed the locations of pits at the site. This was the basis for the 3D electrical resistivity tomography measurements which followed, enabling the three‐dimensional reconstruction of prehistoric pits' geometries. Supplementary sedimentological and geochemical investigations of the pits' contents revealed important information about the pits' former functions as well as the mechanisms of the processes through which they were filled in. Thus, the integrated approach provides us with a new means of obtaining an overview of pit assemblages at archaeological sites in general and demonstrates its potential for the acquisition of valuable information about the food acquisition and storage processes at Fidvár in specific. Copyright © 2015 John Wiley & Sons, Ltd.
Tea consumption is not associated with reduced plasma folate concentration among chinese pregnant women
Authors: Liu Jufen , Jin Lei , Zhang Yali , Zhang Le , Li Zhiwen , Wang Linlin , Ye Rongwei , Ren Aiguo 
Published: June 2015

BackgroundThe aim of this study was to evaluate the relationship between tea consumption and plasma folate concentration in populations with high and low prevalence of neural tube defects (NTDs) in China.MethodsCross‐sectional survey was conducted in three cities/counties in China, in which 1724 pregnant women during early second trimester were recruited and interviewed about tea consumption and folic acid use in 2011 to 2012. A total of 5‐ml nonfasting blood sample was collected and plasma folate concentration was determined by microbiological assay.ResultsApproximately 16.2% of the women reported that they had ever drank tea during and before the current pregnancy, women with higher educational level, and those who resided in urban were more likely to drink tea. Most of them prefer green tea (55.2%); 13.6% of women drank tea “>6 times/week,” and 29.0% of them drank “less than once a week.” The median of plasma folate concentration was 48.7 nmol/L in women who drank tea while it is 45.2 nmol/L in women who did not drink tea, with no statistical difference. The results showed there was no association between tea drinking and plasma folate concentration in Chinese pregnant women stratified by folic acid supplementation and other selected characteristics.ConclusionLow level of tea drinking is not associated with decreased plasma folate concentration in the Chinese populations with high and low prevalence of NTDs. Birth Defects Research (Part A) 103:747–753, 2015. © 2015 Wiley Periodicals, Inc.
Peptide Fragments of Odin‐Sam1: Conformational Analysis and Interaction Studies with EphA2‐Sam
Authors: Mercurio Flavia A. , Di Natale Concetta , Pirone Luciano , Scognamiglio Pasqualina L. , Marasco Daniela , Pedone Emilia M. , Saviano Michele , Leone Marilisa 
Published: June 2015

AbstractOdin is a protein belonging to the ANKS family, and has two tandem Sam domains. The first, Odin‐Sam1, binds to the Sam domain of the EphA2 receptor (EphA2‐Sam); this interaction could be crucial for the regulation of receptor endocytosis and might have an impact on cancer. Odin‐Sam1 associates with EphA2‐Sam by adopting a “mid‐loop/end‐helix” model. In this study three peptide sequences, encompassing the mid‐loop interacting portion of Odin‐Sam1 and its C‐terminal α5 helix, were designed. Their conformational properties were analyzed by CD and NMR. In addition, their abilities to interact with EphA2‐Sam were investigated by SPR studies. The peptides adopt a predominantly disordered state in aqueous buffer, but a higher helical content is evident in the presence of the cosolvent trifluoroethanol. Dissociation constants towards EphA2‐Sam were in the high micromolar range. The structural findings suggest further routes for the design of potential anti‐cancer therapeutics as inhibitors of EphA2‐Sam heterotypic interactions.
Hydrothermal Preparation of a Robust Boehmite‐Supported N,N‐Dimethyldodecylamine N‐Oxide‐Capped Cobalt and Palladium Catalyst for the Facile Utilization of Formic Acid as a Hydrogen Source
Authors: Choudhary Hemant , Nishimura Shun , Ebitani Kohki 
Published: June 2015

AbstractBimetallic CoPd nanoparticles (NPs) on boehmite (AlOOH) were synthesized under hydrothermal conditions using three different capping agents for the facile utilization of formic acid (FA) as a hydrogen source. The CoPd NPs capped with N,N‐dimethyldodecylamine N‐oxide (DDAO) supported on AlOOH (CoPd‐DDAO/AlOOH) exhibited superior catalysis and recyclability in the hydrogenation of maleic anhydride (MAn) in water without metal leaching. The formation of monodispersed CoPd‐DDAO NPs on AlOOH that contained both cobalt oxides and CoPd alloy in each NP was indicated by TEM with energy‐dispersive spectroscopy, XRD, and X‐ray absorption spectroscopy (XAS) studies. X‐ray photoelectron spectroscopy and XAS supported the partial electron transfer phenomenon in CoPd‐DDAO NPs. The as‐prepared CoPd‐DDAO/AlOOH catalyst showed activity for the utilization of FA formed in situ from biomass for the hydrogenation of MAn. It suggested that the DDAO capping agent contributed strongly to the favorable electronic/geometric changes in CoPd alloy for the facile utilization of FA.