bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochromic Metal–Organic Frameworks: Reversible Control of Singlet Oxygen Generation
Authors: Park Jihye , Feng Dawei , Yuan Shuai , Zhou Hong‐Cai 
Published: December 2014

AbstractThe controlled generation of singlet oxygen is of great interest owing to its potential applications including industrial wastewater treatment, photochemistry, and photodynamic therapy. Two photochromic metal–organic frameworks, PC‐PCN and SO‐PCN, have been developed. A photochromic reaction has been successfully realized in PC‐PCN while maintaining its single crystallinity. In particular, as a solid‐state material which inherently integrates the photochromic switch and photosensitizer, SO‐PCN has demonstrated reversible control of 1O2 generation. Additionally, SO‐PCN shows catalytic activity towards photooxidation of 1,5‐dihydroxynaphthalene.
Unified Total Syntheses of (−)‐Medicarpin, (−)‐Sophoracarpan A, and (±)‐Kushecarpin A with Some Structural Revisions
Authors: Feng Zhen‐Gao , Bai Wen‐Ju , Pettus Thomas R. R. 
Published: December 2014

AbstractThe total syntheses of medicarpin, sophoracarpan A, and kushecarpin A from a common intermediate are achieved by using ortho‐ and para‐quinone methide chemistry. Additionally, the relative stereochemistry of sophoracarpan A and B have been reassigned.
Long‐Lived Engineering of Glycans to Direct Stem Cell Fate
Authors: Pulsipher Abigail , Griffin Matthew E. , Stone Shannon E. , Hsieh‐Wilson Linda C. 
Published: December 2014

AbstractGlycans mediate many critical, long‐term biological processes, such as stem cell differentiation. However, few methods are available for the sustained remodeling of cells with specific glycan structures. A new strategy that enables the long‐lived presentation of defined glycosaminoglycans on cell surfaces using HaloTag proteins (HTPs) as anchors is reported. By controlling the sulfation patterns of heparan sulfate (HS) on pluripotent embryonic stem cell (ESC) membranes, it is demonstrated that specific glycans cause ESCs to undergo accelerated exit from self‐renewal and differentiation into neuronal cell types. Thus, the stable display of glycans on HTP scaffolds provides a powerful, versatile means to direct key signaling events and biological outcomes such as stem cell fate.
A Heterobimetallic Superoxide Complex formed through O2 Activation between Chromium(II) and a Lithium Cation
Authors: Schax Fabian , Suhr Simon , Bill Eckhard , Braun Beatrice , Herwig Christian , Limberg Christian 
Published: December 2014

AbstractThe reaction of 1,1,3,3‐tetraphenyl‐1,3‐disiloxandiol (LH2) with n‐butyllithium and CrCl2 results in a mononuclear chromium(II) complex (1) that further reacts with O2 at low temperatures to yield a mononuclear chromium(III) superoxide complex [L2CrO2(THF)][Li2(THF)3] (2). The crystal structure revealed that the chromium superoxido entity is stabilized by the coordination to an adjacent lithium cation. Complex 2 thus contains an unprecedented heterobimetallic [CrIII(μ‐O2)Li+] core; beyond this it is the first chromium superoxide for which a temperature‐dependent magnetic characterization could be achieved, and the first structurally characterized representative with chromium in an exclusive O‐donor environment.
Spontaneous CO Release from RuII(CO)2–Protein Complexes in Aqueous Solution, Cells, and Mice
Authors: Chaves‐Ferreira Miguel , Albuquerque Inês S. , Matak‐Vinkovic Dijana , Coelho Ana C. , Carvalho Sandra M. , Saraiva Lígia M. , Romão Carlos C. , Bernardes Gonçalo J. L. 
Published: December 2014

AbstractWe demonstrate that RuII(CO)2–protein complexes, formed by the reaction of the hydrolytic decomposition products of [fac‐RuCl(κ2‐H2NCH2CO2)(CO)3] (CORM‐3) with histidine residues exposed on the surface of proteins, spontaneously release CO in aqueous solution, cells, and mice. CO release was detected by mass spectrometry (MS) and confocal microscopy using a CO‐responsive turn‐on fluorescent probe. These findings support our hypothesis that plasma proteins act as CO carriers after in vivo administration of CORM‐3. CO released from a synthetic bovine serum albumin (BSA)–RuII(CO)2 complex leads to downregulation of the cytokines interleukin (IL)‐6, IL‐10, and tumor necrosis factor (TNF)‐α in cancer cells. Finally, administration of BSA–RuII(CO)2 in mice bearing a colon carcinoma tumor results in enhanced CO accumulation at the tumor. Our data suggest the use of RuII(CO)2–protein complexes as viable alternatives for the safe and spatially controlled delivery of therapeutic CO in vivo.
Assessing the Viability of Extended Nonmetal Atom Chains in MnF4n+2 (M=S and Se)
Authors: Popov Ivan A. , Averkiev Boris B. , Starikova Alyona A. , Boldyrev Alexander I. , Minyaev Ruslan M. , Minkin Vladimir I. 
Published: December 2014

AbstractTheoretical investigations to evaluate the viability of extended nonmetal atom chains on the basis of molecular models with the general formula MnF4n+2 (M=S and Se) and corresponding solid‐state systems exhibiting direct SS or SeSe bonding were performed. The proposed high‐symmetry molecules were found to be minima on the potential energy surface for all SnF4n+2 systems studied (n=2–9) and for selenium analogues up to n=6. Phonon calculations of periodic structures confirmed the dynamic stability of the ‐(SF4–SF4)∞‐ chain, whereas the analogous ‐(SeF4–SeF4)∞‐ chain was found to have a number of imaginary phonon frequencies. Chemical bonding analysis of the dynamically stable ‐(SF4–SF4)∞‐ structure revealed a multicenter character of the SS and SF bonds. A novel definition and abbreviation (ENAC) are proposed by analogy with extended metal atom chain (EMAC) complexes.
A Neutral Tetraphosphacyclobutadiene Ligand in Cobalt(I) Complexes
Authors: Yao Shenglai , Lindenmaier Nils , Xiong Yun , Inoue Shigeyoshi , Szilvási Tibor , Adelhardt Mario , Sutter Jörg , Meyer Karsten , Driess Matthias 
Published: December 2014

AbstractThe unusual reactivity of the newly synthesized β‐diketiminato cobalt(I) complexes, [(LDepCo)2] (2 a, LDep=CH[C(Me)N(2,6‐Et2C6H3)]2) and [LDippCo⋅toluene] (2 b, LDipp=CH[CHN(2,6‐iPr2C6H3)]2), toward white phosphorus was investigated, affording the first cobalt(I) complexes [(LDepCo)2(μ2:η4,η4‐P4)] (3 a) and [(LDippCo)2(μ2:η4,η4‐P4)] (3 b) bearing the neutral cyclo‐P4 ligand with a rectangular‐planar structure. The redox chemistry of 3 a and 3 b was studied by cyclic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [(LDepCo)2(μ2:η4,η4‐P4)][K(dme)4] (4 a) and [(LDippCo)2(μ2:η4,η4‐P4)][K(dme)4] (4 b). Unexpectedly, the monoanionic Co2P4 core in 4 a and 4 b, respectively, contains the two‐electron‐reduced cyclo‐P42− ligand with a square‐planar structure and mixed‐valent cobalt(I,II) sites. The electronic structures of 3 a, 3 b, 4 a, and 4 b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken‐symmetry DFT calculations.
Chemical Reactivity on Gas‐Phase Metal Clusters Driven by Blackbody Infrared Radiation
Authors: Parry Imogen S. , Kartouzian Aras , Hamilton Suzanne M. , Balaj O. Petru , Beyer Martin K. , Mackenzie Stuart R. 
Published: December 2014

AbstractWe report the observation of chemical reactions in gas‐phase Rhn(N2O)m+ complexes driven by absorption of blackbody radiation. The experiments are performed under collision‐free conditions in a Fourier transform ion cyclotron resonance mass spectrometer. Mid‐infrared absorption by the molecularly adsorbed N2O moieties promotes a small fraction of the cluster distribution sufficiently to drive the N2O decomposition reaction, leading to the production of cluster oxides and the release of molecular nitrogen. N2O decomposition competes with molecular desorption and the branching ratios for the two processes show marked size effects, reflecting variations in the relative barriers. The rate of decay is shown to scale approximately linearly with the number of infrared chromophores. The experimental findings are interpreted in terms of calculated infrared absorption rates assuming a sudden‐death limit.
X‐Ray Characterization of an Electron Donor–Acceptor Complex that Drives the Photochemical Alkylation of Indoles
Authors: Kandukuri Sandeep R. , Bahamonde Ana , Chatterjee Indranil , Jurberg Igor D. , Escudero‐Adán Eduardo C. , Melchiorre Paolo 
Published: December 2014

AbstractA metal‐free, photochemical strategy for the direct alkylation of indoles was developed. The reaction, which occurs at ambient temperature, is driven by the photochemical activity of electron donor–acceptor (EDA) complexes, generated upon association of substituted 1H‐indoles with electron‐accepting benzyl and phenacyl bromides. Significant mechanistic insights are provided by the X‐ray single‐crystal analysis of an EDA complex relevant to the photoalkylation and the determination of the quantum yield (Φ) of the process.
The Reactivities of Iminoboranes with Carbenes: BN Isosteres of Carbene–Alkyne Adducts
Authors: Braunschweig Holger , Ewing William C. , Geetharani K. , Schäfer Marius 
Published: December 2014

AbstractThe first examples of adducts of cyclic alkyl(amino) carbenes (CAAC) and N‐heterocyclic carbenes (NHCs) with iminoboranes have been synthesized and isolated at low temperature (−45 °C). The adducts show short BN bonds and planarity at boron, mimicking the structures of the isoelectronic imine functionality. When di‐tert‐butyliminoborane was reacted with 1,3‐bis(isopropyl)imidazol‐2‐ylidene (IPr), the initially formed Lewis acid–base adduct quickly rearranged to form a new carbene substituted with an aminoborane at the 4‐position. Warming the iminoborane–CAAC adduct to room temperature resulted in an intramolecular cyclization to give a bicyclic 1,2‐azaborilidine compound.
SN2P2: A Neutral Five‐Membered Sulfur–Pnictogen(III) Ring
Authors: Zeng Xiaoqing , Li Hongmin , Sun Hailong , Beckers Helmut , Willner Helge , Schaefer Henry F. 
Published: December 2014

AbstractThe novel aromatic ring compound 2,4‐diphospha‐3,5‐diaza‐thiole (cyclo‐SNPNP) was synthesized via flash pyrolysis of SP(N3)3 and characterized by IR spectroscopy and 15N isotope labeling. Quantum chemical computations indicate its formation by head‐to‐tail dimerization of SNP and subsequent elimination of a sulfur atom from the highly unstable boatlike six‐membered‐ring compound cyclo‐SNPSNP.
Enantioselective Synthesis of α‐Aminosilanes by Copper‐Catalyzed Hydroamination of Vinylsilanes
Authors: Niljianskul Nootaree , Zhu Shaolin , Buchwald Stephen L. 
Published: December 2014

AbstractThe synthesis of α‐aminosilanes by a highly enantio‐ and regioselective copper‐catalyzed hydroamination of vinylsilanes is reported. The system employs Cu‐DTBM‐SEGPHOS as the catalyst, diethoxymethylsilane as the stoichiometric reductant, and O‐benzoylhydroxylamines as the electrophilic nitrogen source. This hydroamination reaction is compatible with differentially substituted vinylsilanes, thus providing access to amino acid mimics and other valuable chiral organosilicon compounds.
Total Synthesis of (±)‐Hippolachnin A
Authors: Ruider Stefan A. , Sandmeier Tobias , Carreira Erick M. 
Published: December 2014

AbstractThe first total synthesis of the marine polyketide (±)‐hippolachnin A has been achieved in nine linear steps and an overall yield of 9 %. Rapid access to the oxacyclobutapentalene core structure was secured by strategic application of an ene cyclization.
Palladium‐Catalyzed Intramolecular CH Difluoroalkylation: Synthesis of Substituted 3,3‐Difluoro‐2‐oxindoles
Authors: Shi Shi‐Liang , Buchwald Stephen L. 
Published: December 2014

AbstractThe synthesis of 3,3‐difluoro‐2‐oxindoles through a robust and efficient palladium‐catalyzed CH difluoroalkylation is described. This process generates a broad range of difluorooxindoles from readily prepared starting materials. The use of BrettPhos as the ligand was crucial for high efficiency. Preliminary mechanistic studies suggest that oxidative addition is the rate‐determining step for this process.
Towards Maintenance‐Free Biosensors for Hundreds of Bind/Release Cycles
Authors: Potyrailo Radislav A. , Murray Anthony J. , Nagraj Nandini , Pris Andrew D. , Ashe Jeffrey M. , Todorovic Milos 
Published: December 2014

AbstractA single aptamer bioreceptor layer was formed using a common streptavidin–biotin immobilization strategy and employed for 100–365 bind/release cycles. Chemically induced aptamer unfolding and release of its bound target was accomplished using alkaline solutions with high salt concentrations or deionized (DI) water. The use of DI water scavenged from the ambient atmosphere represents a first step towards maintenance‐free biosensors that do not require the storage of liquid reagents. The aptamer binding affinity was determined by surface plasmon resonance and found to be almost constant over 100–365 bind/release cycles with a variation of less than 5 % relative standard deviation. This reversible operation of biosensors based on immobilized aptamers without storage of liquid reagents introduces a conceptually new perspective in biosensing. Such new biosensing capability will be important for distributed sensor networks, sensors in resource‐limited settings, and wearable sensor applications.
Close Link between Protoporphyrin IX Accumulation and Developmental Toxicity Induced by N‐Phenylimide Herbicides in Rats
Authors: Kawamura Satoshi , Kato Terushige , Fantel Alan G. 
Published: December 2014

BACKGROUNDS‐53482, 7‐fluoro‐6‐[(3,4,5,6‐tetrahydro)phthalimido]‐4‐(2‐propynyl)‐1,4‐benzoxazin‐3(2H)‐one (flumioxazin), is an N‐phenylimide herbicide and developmentally toxic to rats, but not to rabbits. The day of greatest sensitivity to S‐53482 is gestational day (GD) 12 in rats. There is a compound‐specific difference in developmental toxicity among structurally similar compounds including S‐23121 (N‐[4‐chloro‐2‐fluoro‐5‐[(1‐methyl‐2‐propynyl)oxy]phenyl]‐3,4,5,6‐tetrahydrophthalimide; teratogenic) and S‐23031 (pentyl 2‐chloro‐4‐fluoro‐5‐(3,4,5,6‐tetrahydrophthalimido)phenoxyacetate (flumiclorac pentyl); nonteratogenic). The herbicidal action is due to photodynamic action of accumulating protoporphyrin IX (PPIX), resulting from the inhibition of protoporphyrinogen oxidase (PPO), an enzyme in porphyrin biosynthesis. Species difference in PPIX accumulation in embryos corresponded to those of the developmental toxicity. Our objective in this study was to further investigate a link between PPIX accumulation resulting from PPO inhibition and developmental toxicity. This article is part of a series of studies to be published serially.METHODSTo investigate compound‐specific differences, each compound was orally administered to rats on GD 12. To define peak period of PPIX accumulation, single oral treatments of S‐53482 were given to rats or rabbits at 19:30 on GD 10 through GD 15. PPIX was extracted from embryos 14 hr after treatment.RESULTSRemarkable PPIX accumulation was observed when treated with S‐53482 or S‐23121, but not with S‐23031. The greatest accumulation of PPIX was observed when treated with S‐53482 at 19:30 on GD 11 or GD 12. No PPIX accumulation was found on any GDs in rabbits.CONCLUSIONSThe developmentally toxic compounds caused PPIX accumulation in embryos. The peak period of PPIX accumulation corresponded to that of developmental effects. This correlation suggests a close link between PPO inhibition and developmental abnormality
Human Serum Transferrin Fibrils: Nanomineralisation in Bacteria and Destruction of Red Blood Cells
Authors: Mukherjee Arindam , Barnett Mark A. , Venkatesh V. , Verma Sandeep , Sadler Peter J. 
Published: December 2014

AbstractFibrils formed by human serum transferrin [(1–3 μM) apo‐Tf, partially iron‐saturated (Fe0.6‐Tf) and holo‐Tf (Fe2‐Tf) forms], from dilute bicarbonate solutions, were deposited on formvar surfaces and studied by electron microscopy. We observed that possible bacterial contamination appears to give rise to long, pea‐pod‐like (PPL) structures for Fe2‐Tf, attributable to the formation of polyhydroxybutyrate (PHB) storage granules, under the nutrient‐limiting conditions used. These PPL structures contained periodic nanomineralisation sites susceptible to uranyl stain. Extended incubation of transferrin solutions (about four days) gave rise to extensive transferrin fibril structures. Optical microscopy and AFM studies showed that red blood cells (RBCs) readily adhere to these fibrils. Moreover, the fibrils appear to penetrate RBC membranes and to induce rapid cell destruction (within about 5 h). It is speculated that in situations in vivo where transferrin fibrils can form, such interactions might have adverse physiological consequences, and further studies could aid the understanding of related pathological events.
Elucidating the Catalytic Subunit Composition of Distinct Proteasome Subtypes: A Crosslinking Approach Employing Bifunctional Activity‐Based Probes
Authors: Cornish Carmony Kimberly , Sharma Lalit Kumar , Lee Do‐Min , Park Ji Eun , Lee Wooin , Kim Kyung‐Bo 
Published: December 2014

AbstractIn addition to two well‐recognized proteasome subtypes—constitutive proteasomes and immunoproteasomes—mounting evidence also suggests the existence of intermediate proteasome subtypes containing unconventional mixtures of catalytic subunits. Although they appear to play unique biological roles, the lack of practical methods for detecting distinct proteasome subtypes has limited functional investigations. Here, we report the development of activity‐based probes that crosslink two catalytic subunits within intact proteasome complexes. Identification of the crosslinked subunit pairs provides direct evidence of the catalytic subunit composition of proteasomes. Using these probes, we found that U266 multiple myeloma cells contain intermediate proteasomes comprising both β1i and β2, but not β1 and β2i, consistent with previous findings with other cell types. Our bifunctional probes can be utilized in functional investigations of distinct proteasome subtypes in various biological settings.
GLUE That Sticks to HIV: A Helix‐Grafted GLUE Protein That Selectively Binds the HIV gp41 N‐Terminal Helical Region
Authors: Walker Susanne N. , Tennyson Rachel L. , Chapman Alex M. , Kennan Alan J. , McNaughton Brian R. 
Published: December 2014

AbstractMethods for the stabilization of well‐defined helical peptide drugs and basic research tools have received considerable attention in the last decade. Here, we report the stable and functional display of an HIV gp41 C‐peptide helix mimic on a GRAM‐Like Ubiquitin‐binding in EAP45 (GLUE) protein. C‐peptide helix‐grafted GLUE selectively binds a mimic of the N‐terminal helical region of gp41, a well‐established HIV drug target, in a complex cellular environment. Additionally, the helix‐grafted GLUE is folded in solution, stable in human serum, and soluble in aqueous solutions, and thus overcomes challenges faced by a multitude of peptide drugs, including those derived from HIV gp41 C‐peptide.
Hydrogen‐Bonding‐Driven Enantioselective Resolution against the Kazlauskas Rule To Afford γ‐Amino Alcohols by Candida rugosa Lipase
Authors: Min Bora , Park Jeemin , Sim Yong‐Kyun , Jung Suhyun , Kim Seong‐Ho , Song Jae Kwang , Kim Bum Tae , Park Sang Youn , Yun Jaesook , Park Seongsoon , Lee Hyuk 
Published: December 2014

AbstractMost lipases resolve secondary alcohols in accordance with the “Kazlauskas rule” to give the R enantiomers. In a similar manner to other lipases, Candida rugosa lipase (CRL) exhibits R enantioselectivity towards heptan‐2‐ol, although the enantiomeric ratio (E) is low (E=1.6). However, unexpected enantioselectivity (i.e., S enantioselectivity, E=58) of CRL towards 4‐(tert‐butoxycarbonylamino)butan‐2‐ol, which has a similar chain length to heptan‐2‐ol, has been observed. To develop a deeper understanding of the molecular basis for this unusual enantioselectivity, we have conducted a series of molecular modeling and substrate engineering experiments. The results of these computational and experimental analyses indicated that a hydrogen bond between the Ser450 residue and the nitrogen atom of the carbamate group is critical to stabilize the transition state of the S enantiomer.
One‐pot Conversion of Cycloalkanes to Lactones
Authors: Pennec Alizé , Hollmann Frank , Smit Martha S. , Opperman Diederik J. 
Published: December 2014

AbstractThe one‐pot conversion of cycloalkanes to their corresponding lactones was achieved through the use of a synthetic pathway consisting of a cytochrome P450 monooxygenase (CYP450) for initial oxyfunctionalization of the cycloalkane, an alcohol dehydrogenase for ketone production and a Baeyer–Villiger monooxygenase for lactone formation. Through variation of the cofactor dependence of the biocatalysts and the cofactor regeneration system, final product concentrations of nearly 3 g L−1 enantholactone (2‐oxocanone) from cycloheptane was reached within 12 h with a total turnover number (TTN) of 4185 with respect to the CYP450.
Synthesis of Palladium Colloidal Nanocrystal Clusters and Their Enhanced Electrocatalytic Properties
Authors: Ding Ruixue , Wu Xinyan , Han Guangting , Wang Qinchao , Lu Hailong , Li Hongliang , Fu Aiping , Guo Peizhi 
Published: December 2014

AbstractColloidal nanocrystal clusters (CNCs) and nanoparticles of palladium (Pd) were synthesized controllably by using an amino‐acid‐assisted hydrothermal method in the presence of polyvinylpyrrolidone. Experimental results showed that crystalline Pd nanoparticles were synthesized by adding alanine into the synthetic solutions, whereas sub‐micrometer Pd CNCs composed of small nanocrystals were obtained from phenylalanine systems. Electrochemical measurements showed that Pd CNCs displayed a much better electrocatalytic performance than nanoparticles, because CNCs were formed by the in situ self‐assembly of primary nanocrystals. The structure of Pd CNCs can also be maintained after electrocatalytic cycle testing. Both Pd‐based electrocatalysts showed the highest electrocatalytic activity towards the electrooxidation of ethanol among the used alcohols. The formation mechanisms and electrocatalytic properties of the Pd nanoparticles and CNCs are discussed and analyzed based on the experimental data.
Redox‐ and Protonation‐Induced Fluorescence Switch in a New Triphenylamine with Six Stable Active or Non‐Active Forms
Authors: Quinton Cassandre , Alain‐Rizzo Valérie , Dumas‐Verdes Cécile , Miomandre Fabien , Clavier Gilles , Audebert Pierre 
Published: December 2014

AbstractThe synthesis, photophysical and electrochemical properties as well as theoretical calculation studies of a newly designed triphenylamine derivative are described. This original compound displays one neutral form, three oxidized forms, and two protonated forms with distinct photophysical characteristics. The interplay of the emission with the protonation or the redox state (electrofluorochromism) has been explored and an on–off–on–off fluorescence switching was observed in the case of oxidation and an on–on–off fluorescence switching in the case of protonation.
Phosphinoyl and Thiophosphinoylcarbodithioates: Synthesis, Molecular Structure, and Application as New Efficient Mediators for RAFT Polymerization
Authors: Mazières Stéphane , Kulai Ihor , Geagea Roland , Ladeira Sonia , Destarac Mathias 
Published: December 2014

AbstractNew phosphinoyl and thiophosphinoylcarbodithioates were synthesized in a one‐pot reaction from the corresponding phosphinochalcogenides. Compounds of this new generation of thiocarbonylthio derivatives have been fully characterized by IR as well as 1H, 31P, and 13C NMR spectroscopy and by mass spectrometry. Their solid‐state structures reveal that they are isostructural but crystallize in different space groups. These new compounds are highly efficient reversible chain‐transfer agents for the reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene (St) and n‐butyl acrylate (nBA), with controlled number‐average molecular weights (Mn) and narrow dispersity values (Ð<1.3). The controlled character of the polymerization was further exemplified by MALDI‐TOF mass spectrometry and the synthesis of PSt‐P(nBA) diblock copolymers.