bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Second‐Generation Photocage for Zn2+ Inspired by TPEN: Characterization and Insight into the Uncaging Quantum Yields of ZinCleav Chelators
Authors: Bandara H. M. Dhammika , Walsh Timothy P. , Burdette Shawn C. 
Published: March 2011

AbstractPhotocages have been used to elucidate the biological functions of various small molecules and Ca2+; however, there are very few photocages available for other metal ions. ZinCleav‐2 (1‐(4,5‐dimethoxy‐2‐nitrophenyl)‐N,N,N′,N′‐tetrakis‐pyridin‐2‐ylmethyl‐ethane‐1,2‐diamine) is a second‐generation photocage for Zn2+ that releases the metal ion after a light‐induced bifurcation of the chelating ligand. The structure of ZinCleav‐2 was inspired by TPEN (N,N,N′,N′‐tetrakis(2‐pyridylmethyl)ethylenediamine), which is routinely used to sequester metal ions in cells owing to its high binding affinity. Inclusion of a 2‐nitrobenzyl chromophore leads to the formation of two more weakly binding di‐(2‐picolyl)amine (DPA) fragments upon photolysis of the TPEN backbone. The desired ligand was prepared using a modified procedure used to access ZinCleav‐1 (1‐(4,5‐dimethoxy‐2‐nitrophenyl)‐N,N′‐dimethyl‐N,N′‐bis‐pyridin‐2‐ylmethyl‐ethane‐1,2‐diamine). ZinCleav‐2 has a conditional dissociation constant (Kd) of ∼0.9 fM as measured by competitive titration with a quinoline‐based fluorescent sensor for Zn2+. The Kd of the Zn2+ complex of the DPA photoproducts is ∼158 nM; therefore, the ΔKd for ZinCleav‐2 photocage is ∼108. A large ΔKd is required to significantly perturb free metal ion concentrations in biological assays. The quantum yield of photolysis of apo ZinCleav‐2 and the [Zn(ZinCleav‐2)]2+ complex are 4.7 and 2.3 %, respectively, as determined by HPLC analysis. Proof of concept Zn2+ release upon photolysis of [Zn(ZinCleav‐2)]2+ was demonstrated using the fluorescent sensor Zinpyr‐1, and the speciation of Zn2+ complexes was simulated using computational methods. The influence of benzylic substituents on the quantum yield of uncaging is also analyzed with the aim of tuning the photochemical properties caged complexes for in vivo experiments.
Regioselective Double Capping of Cyclodextrin Scaffolds
Authors: Gramage‐Doria Rafael , Rodriguez‐Lucena David , Armspach Dominique , Egloff Coraline , Jouffroy Matthieu , Matt Dominique , Toupet Loïc 
Published: March 2011

AbstractFour different regioselective double capping reactions were applied either to α‐ or β‐cyclodextrin (CD) scaffolds. The first, which relied on the use of a rigid, bulky dialkylating reagent containing two trityl‐like subunits, gave access to an A,B,D,E‐tetrafunctionalised β‐CD regioisomer in large scale reactions. Two further capping reactions, involving the dianions PhP2− and S2−, led to the synthesis of new C1‐symmetrical β‐cyclodextrins in which pairs of neighbouring glucose units are linked by very short spacers. The last double capping reaction described allowed the high‐yield preparation of unprecedented α‐ and β‐cyclodextrins containing two sulfate handles. Proximal capping turned out to be favoured for each of the above difunctional reagents. The structural characterisation of the capped species was achieved by thorough NMR investigations as well as by single‐crystal X‐ray diffraction studies.
Rational Construction of Perylene Bisimide Columnar Superstructures with a Biased Helical Sense
Authors: Seki Tomohiro , Asano Atsushi , Seki Shu , Kikkawa Yoshihiro , Murayama Haruno , Karatsu Takashi , Kitamura Akihide , Yagai Shiki 
Published: March 2011

AbstractDiscotic supramolecular complexes bearing six perylene bisimide (PBI) chromophores were prepared by mixing monotopically triple‐hydrogen‐bonding melamines equipped with two PBI chromophores and two 3,7‐dimethyloctyl chiral handles with tritopically triple‐hydrogen‐bonding cyanuric acid (CA). UV/Vis and fluorescence titration experiments demonstrated that the discotic complexes were formed in methylcyclohexane by the 3:1 complexation between the melamines and CA. TEM and AFM studies revealed that the complexes hierarchically organize into fibrous columnar assemblies, which eventually results in the formation of organogels. Circular dichroism (CD) and flash‐photolysis time resolved microwave conductivity measurements revealed the presence of extended chiral stacks of PBI chromophores within the columns. The anisotropy factors of the columnar assemblies are remarkably high (g=1.5×10−3) when considering the presence of only one 3,7‐dimethyloctyl chiral handle per perylene chromophore, suggesting that the columnar structures have a biased helical sense. The fact that the chiral centers are located inside the discotic complexes rather than at their peripheries might be unique structural property responsible for the rather strong optical activities for the assemblies of this chromophore. The effective transcription of the molecular chirality to the extended columnar assemblies through the formation of unique discotic complexes enables the expression of “majority‐rules” chiral amplification effect, which is unprecedented for the supramolecular assemblies of PBIs.
Extension of a quartic equation of state to pure polar fluids
Authors: Zang Lian‐yun , Zhu Qing‐li , Yun Zhi 
Published: March 2011

AbstractA new approach of calculating the parameters of a quartic equation of state (EOS) (Yun et al., Fluid Phase Equilibria 187‐188, 275‐298 (2001)) was suggested. The parameters of the EOS were correlated to critical constants as well as dipole moment. And the modified quartic EOS was extended to both polar and non‐polar substances without any substance‐dependent empirical constants which are necessary in the original quartic EOS in calculations of polar substances. To validate the new approach, a list of substances, including polar and non‐polar ones, were calculated. The calculated results of both thermodynamic and volumetric properties were obtained with good accuracy.Une nouvelle approche de calcul des paramètres de l'équation quartique d'état (EQE) a été proposée (Z. Yun et coll., «A new quartic equation of state» Fluid Phase Equilibria. 187–188, 275–298 (2001)). Les paramètres de l'équation d'état ont été mis en corrélation avec les constantes critiques et le moment dipolaire. Les EQE modifiées ont été étendues aux substances polaires et non polaires sans les constantes empiriques inhérentes aux substances, qui sont nécessaires dans les EQE originales de calcul des substances polaires. Afin de valider cette nouvelle approche, plusieurs substances polaires et non polaires ont été calculées. Les résultats obtenus pour les propriétés thermodynamiques et volumétriques étaient d'une bonne précision. © 2011 Canadian Society for Chemical Engineering
Turbulent heat and mass transfer from stationary particles
Authors: Pasternak I. S. , Gauvin W. H. 
Published: March 2011

AbstractConvective heat and mass transfer rates for 20 shapes suspended in various orientations in a hot turbulent air stream were correlated by the equation:for turbulent intensities between 9 and 10%, using a new characteristic dimension,L”, in the Reynolds Number. This dimension, defined as the total surface area divided by the maximum perimeter perpendicular to flow, was qualitatively explained from boundary layer considerations and was found to correlate the data for different shapes available in the literature. Qualitative pictures for the relative rates of heat and mass transfer around the various shapes were also obtained.
The effect of temperature on the fluidization of silver powders
Authors: Echigoya E. , Osberg G. L. 
Published: March 2011

AbstractFluidization tests on pure silver and silver catalyst powder show that agglomeration occurs when the bed is heated, which finally results in bed collapse at a comparatively low temperature. If the bed temperature is held constant in the agglomerating temperature range, an induction period is observed before fluidization ceases. A study of the induction period as a function of temperature (10–60°C.) leads to an activation energy of 18 kcal. for the overall agglomeration process for pure silver. Agglomeration is believed to be due to sintering.
A method for the determination of tie‐lines in ternary liquid systems
Authors: Heric E. L. , Rutledge Ronald M. 
Published: March 2011

AbstractA method is described for the determination of tie‐lines in ternary liquid systems which may be used when a satisfactory method of chemical analysis is unavailable. The technique is graphical and is based upon the lever rule principle. The method is illustrated with the system acetic acid‐furfural‐water at 25 ± 0.05°. Results indicate the method is accurate and capable of good precision.
Coprecipitation with Cu(II)‐4‐(2‐Pyridylazo)‐resorcinol for Separation and Preconcentration of Fe(III) and Ni(II) in Water and Food Samples
Authors: Tokalıoğlu Şerife , Daşdelen Osman 
Published: March 2011

AbstractThe coprecipitation method is widely used for the preconcentration of trace metal ions prior to their determination by flame atomic absorption spectrometry (FAAS). A simple and sensitive method based on coprecipitation of Fe(III) and Ni(II) ions with Cu(II)‐4‐(2‐pyridylazo)‐resorcinol was developed. The analytical parameters including pH, amount of copper (II), amount of reagent, sample volume, etc., were examined. It was found that the metal ions studied were quantitatively coprecipitated in the pH range of 5.0–6.5. The detection limits (DL) (n = 10, 3s/b) were found to be 0.68 µg L−1 for Fe(III) and 0.43 µg L−1 for Ni(II) and the relative standard deviations (RSD) were ≤4.0%. The proposed method was validated by the analysis of three certified reference materials (TMDA 54.4 fortified lake water, SRM 1568a rice flour, and GBW07605 tea) and recovery tests. The method was successfully applied to sea water, lake water, and various food samples.
Discovering Small‐Molecule Estrogen Receptor α/Coactivator Binding Inhibitors: High‐Throughput Screening, Ligand Development, and Models for Enhanced Potency
Authors: Sun Aiming , Moore Terry W. , Gunther Jillian R. , Kim Mi‐Sun , Rhoden Eric , Du Yuhong , Fu Haian , Snyder James P. , Katzenellenbogen John A. 
Published: March 2011

AbstractSmall molecules, namely coactivator binding inhibitors (CBIs), that block estrogen signaling by directly inhibiting the interaction of the estrogen receptor (ER) with coactivator proteins act in a fundamentally different way to traditional antagonists, which displace the endogenous ligand estradiol. To complement our prior efforts at CBI discovery by de novo design, we used high‐throughput screening (HTS) to identify CBIs of novel structure and subsequently investigated two HTS hits by analogue synthesis, finding many compounds with low micromolar potencies in cell‐based reporter gene assays. We examined structure–activity trends in both series, using induced‐fit computational docking to propose binding poses for these molecules in the coactivator binding groove. Analysis of the structure of the ER–steroid receptor coactivator (SRC) complex suggests that all four hydrophobic residues within the SRC nuclear receptor box sequence are important binding elements. Thus, insufficient water displacement upon binding of the smaller CBIs in the expansive complexation site may be limiting the potency of the compounds in these series, which suggests that higher potency CBIs might be found by screening compound libraries enriched with larger molecules.
Design, Synthesis, and Pharmacological Characterization of Novel Spirocyclic Quinuclidinyl‐Δ2‐Isoxazoline Derivatives as Potent and Selective Agonists of α7 Nicotinic Acetylcholine Receptors
Authors: Dallanoce Clelia , Magrone Pietro , Matera Carlo , Frigerio Fabio , Grazioso Giovanni , De Amici Marco , Fucile Sergio , Piccari Vanessa , Frydenvang Karla , Pucci Luca , Gotti Cecilia , Clementi Francesco , De Micheli Carlo 
Published: March 2011

AbstractA set of racemic spirocyclic quinuclidinyl‐Δ2‐isoxazoline derivatives was synthesized using a 1,3‐dipolar cycloaddition‐based approach. Target compounds were assayed for binding affinity toward rat neuronal homomeric (α7) and heteromeric (α4β2) nicotinic acetylcholine receptors. Δ2‐Isoxazolines 3 a (3‐Br), 6 a (3‐OMe), 5 a (3‐Ph), 8 a (3‐OnPr), and 4 a (3‐Me) were the ligands with the highest affinity for the α7 subtype (Ki values equal to 13.5, 14.2, 25.0, 71.6, and 96.2 nM, respectively), and showed excellent α7 versus α4β2 subtype selectivity. These compounds, tested in electrophysiological experiments against human α7 and α4β2 receptors stably expressed in cell lines, behaved as partial α7 agonists with varying levels of potency. The two enantiomers of (±)‐3‐methoxy‐1‐oxa‐2,7‐diaza‐7,10‐ethanospiro[4.5]dec‐2‐ene sesquifumarate 6 a were prepared using (+)‐dibenzoyl‐L‐ or (−)‐dibenzoyl‐D‐tartaric acid as resolving agents. Enantiomer (R)‐(−)‐6 a was found to be the eutomer, with Ki values of 4.6 and 48.7 nM against rat and human α7 receptors, respectively.
Effectiveness of alternating mammography and magnetic resonance imaging for screening women with deleterious BRCA mutations at high risk of breast cancer
Authors: Le‐Petross Huong T. , Whitman Gary J. , Atchley Deanne P. , Yuan Ying , Gutierrez‐Barrera Angelica , Hortobagyi Gabriel N. , Litton Jennifer K. , Arun Banu K. 
Published: March 2011

AbstractBACKGROUND:Magnetic resonance imaging (MRI) has been used to supplement screening mammography and clinical breast examination (CBE) in women who are at high risk of developing breast cancer. In this study, the authors investigated the efficacy of alternating screening mammography and breast MRI every 6 months in women who had a genetically high risk of developing breast cancer.METHODS:A retrospective chart review was performed on all women who were seen in a high‐risk breast cancer clinic from 1997 to 2009. Patients with breast cancer gene (BRCA) mutations who underwent alternating screening mammography and breast MRI every 6 months were included in the study. Mammography, ultrasonography, MRI, and biopsy results were reviewed.RESULTS:Of 73 patients who met the study criteria, 37 had BRCA1 mutations, and 36 had BRCA2 mutations. Twenty‐one patients (29%) completed 1 cycle of mammography and MRI surveillance, 23 patients (31%) completed 2 cycles, 18 patients (25%) completed 3 cycles, and patients 11 (15%) completed ≥4 cycles. The median follow‐up was 2 years (range, 1‐6 years). Thirteen cancers were detected among 11 women (15%). The mean tumor size was 14 mm (range, 1‐30 mm), and 2 patients had bilateral cancers. Twelve of 13 cancers were detected on an MRI but not on the screening mammography study that was obtained 6 months earlier. One cancer (a 1‐mm focus of ductal carcinoma in situ) was an incidental finding in a prophylactic mastectomy specimen. One patient had ipsilateral axillary lymphadenopathy identified on ultrasonography but had no evidence of lymph node involvement after neoadjuvant chemotherapy and surgery.CONCLUSIONS:In women who were at genetically high risk of developing breast cancer, MRI detected cancers that were not identified on mammography 6 months earlier. Future prospective studies are needed to evaluate the benefits of this screening regimen. Cancer 2011;. © 2011 American Cancer Society.
Enhanced Catalytic Activity of Sub‐nanometer Titania Clusters Confined inside Double‐Wall Carbon Nanotubes
Authors: Zhang Hongbo , Pan Xiulian , Liu Jingyue (Jimmy) , Qian Weizhong , Wei Fei , Huang Yuying , Bao Xinhe 
Published: March 2011

AbstractSub‐nanometer titania clusters have been homogeneously dispersed within double‐wall carbon nantubes (DWNTs) with an inner diameter ranging from 1.0 to 1.5 nm. The confined titania exhibits a much higher activity than the titania particles attached on the outside walls of the DWNTs (the outside titania) in the epoxidation of propylene by H2O2. XPS, XANES and Raman spectroscopy data suggest electron transfer from titanium to the inner surfaces of the DWNTs. In contrast, no electron transfer has been observed for the outside titania. We also found that the extent of this confinement‐induced electron transfer is temperature dependent. The enhanced activity of the confined titania clusters is likely attributed to their small sizes and the interaction with the DWNT surface. The synthesis method that we developed here can be readily applied to incorporation of other metal/metal oxide nanoparticles into carbon nanotubes.
Multistage multiphase switched‐capacitor DC–DC converter with variable‐phase and PWM control
Authors: Chang Yuen‐Haw , Chen Yi‐Ching 
Published: March 2011

SUMMARYA closed‐loop multistage multiphase switched‐capacitor converter (n‐stagep‐phase MPSC) is proposed with a variable‐phase control (VPC) and a pulse‐width‐modulation (PWM) technique for low‐power step‐up conversion and high‐efficiency regulation. In thisn‐stage MPSC,nvoltage doublers are connected in series for boosting the voltage gain up to 2nat most. Here, VPC is suggested to realize a variable multiphase operation by changing the phase numberpand topological path for the more suitable level of voltage gain so as to improve the power efficiency, especially for the lower output voltage Besides, PWM is adopted not only to enhance output regulation for different desired outputs, but also to reinforce output robustness to source/loading variation. Further, some theoretical analyses and designs include:n‐stagep‐phase MPSC model, steady‐state analysis, conversion ratio, power efficiency, output ripple, stability, capacitance selection, and control design. Finally, the closed‐loop MPSC is simulated, and the hardware is implemented and tested. All the results are illustrated to show the efficacy of the proposed scheme. Copyright © 2011 John Wiley & Sons, Ltd.
Regulation of limb bud initiation and limb‐type morphology
Authors: Duboc Veronique , Logan Malcolm P. O. 
Published: March 2011

AbstractWhile the paired forelimb and hindlimb buds of vertebrates are initially morphologically homogeneous, as the limb progenitors differentiate, each individual tissue element attains a characteristic limb‐type morphology that ultimately defines the constitution of the forelimb or hindlimb. This review focuses on contemporary understanding of the regulation of limb bud initiation and formation of limb‐type specific morphologies and how these regulatory mechanisms evolved in vertebrates. We also attempt to clarify the definition of the terms limb‐type identity and limb‐type morphology that have frequently been used interchangeably. Over the last decade, three genes, Tbx4, Tbx5, and Pitx1, have been extensively studied for their roles in limb initiation and determining limb‐type morphologies. The role of Tbx4 and Tbx5 in limb initiation is clearly established. However, their putative role in the generation of limb‐type morphologies remains controversial. In contrast, all evidence supports a function for Pitx1 in determination of hindlimb morphologies. Developmental Dynamics 240:1017–1027, 2011. © 2011 Wiley‐Liss, Inc.
Regulation of leg size and shape: Involvement of the Dachsous‐fat signaling pathway
Authors: Bando Tetsuya , Mito Taro , Nakamura Taro , Ohuchi Hideyo , Noji Sumihare 
Published: March 2011

AbstractHow limb size and shape is regulated is a long‐standing question in developmental and regeneration biology. Recently, the protocadherin Dachsous‐Fat (Ds‐Ft) signaling pathway has been found to be essential for wing development of the fly and leg regeneration of the cricket. The Ds‐Ft signaling pathway is linked to the Warts‐Hippo (Wts‐Hpo) signaling pathway, leading to cell proliferation. Several lines of evidence have suggested that the Wts‐Hpo signaling pathway is involved in the control of organ size, and that this pathway is regulated by Ds‐Ft and Merlin‐Expanded, which are linked to morphogens such as decapentaplegic/bone morphogenic protein, Wingless/Wnt, and epidermal growth factor. Here we review recent progress in elucidating mechanisms controlling leg size and shape in insects and vertebrates, focusing on the Ds‐Ft signaling pathway. We also introduce a working model, Ds‐Ft steepness model, to explain how steepness of the Ds‐Ft gradient controls leg size along the proximodistal axis. Developmental Dynamics 240:1028–1041, 2011. © 2011 Wiley‐Liss, Inc.
Synthesis and Some Chemical Properties of a 1,2λ3σ3‐Thiaphosphirane
Authors: Turcheniuk Kostiantyn V. , Rozhenko Alexander B. , Shevchenko Igor V. 
Published: March 2011

AbstractA rare example of the addition of sulfur to a phosphaalkene double bond leading to 1,2λ3,σ3‐thiaphosphirane 4 is described. The relative accessibility of this compound has allowed the study of some of the chemical properties of the thiaphosphirane ring. The thermodynamic stability of 1,2λ3,σ3‐thiaphosphiranes compared with λ5,σ3‐phosphoranes has been studied by DFT calculations.
Synthesis and Reactivity of New Pyrazolyl‐Functionalized Potassium Silanides
Authors: McNerney Brian , Whittlesey Bruce , Krempner Clemens 
Published: March 2011

AbstractThe pyrazolyl‐functionalized oligosilanes Si(SiMe2PzR)4 (2a R = tBu; 2b R = iPr) were prepared by the reaction of 3‐R‐pyrazole (R = iPr, tBu) with Si(SiMe2Cl)4 in the presence of NEt3. By treatment with tBuOK and 18‐crown‐6 in THF, 2a, b were converted into the new potassium silanides (PzRMe2Si)3SiK(18‐crown‐6) (3a R = tBu; 3b R = iPr), respectively. Upon adding W(CO)6 to THF solutions of 3a, b the tungsten complexes [(PzRMe2Si)3SiW(CO)5]K(18‐crown‐6) (4a R = tBu; 4b R = iPr) were readily formed, whereas upon adding MgBr2 fragmentation occurs leading to the formation of [(PzRMe2Si)2Si‐SiMe2]2 5.
Unusual Expansion of the 1,2,4,5‐Tetrazine Ring in [1,2,4]Triazolo[4,3‐b][1,2,4,5]tetrazines Leading to [1,2,4,6]Tetrazepine Systems
Authors: Ganebnykh Ilya N. , Tolshchina Svetlana G. , Ishmetova Rashida I. , Ignatenko Nina K. , Slepukhin Pavel A. , Rusinov Gennady L. , Charushin Valery N. 
Published: March 2011

AbstractExpansion of the tetrazine ring has first been found to occur when [1,2,4]triazolo[4,3‐b][1,2,4,5]tetrazines were allowed to react with CH‐active compounds in acetonitrile in the presence of triethylamine to give the unexpected series of 8,9‐dihydro‐7H‐[1,2,4]‐triazolo[4,3‐b][1,2,4,6]tetrazepine derivatives.
Orthogonal Synthesis of Fluorinated Acridones and Acridines from Perfluorobenzophenone
Authors: Del Buttero Paola , Gironda Ramona , Moret Massimo , Papagni Antonio , Parravicini Matteo , Rizzato Silvia , Miozzo Luciano 
Published: March 2011

AbstractThe reaction between perfluorobenzophenone and aromatic amines proceeds with the substitution of one or more fluorine atoms. The regiochemistry of this substitution is controlled by solvent polarity, temperature, and nucleophilic character of the amine. o‐Anilinononafluorobenzophenone can be selectively transformed into acridines or acridones by using acid or base catalysis through electrocyclization or aromatic nucleophilic substitution.
A Facile One‐Pot Access to Dibenzo[b,e]oxepines by a Lewis Acid Catalysed Tandem Reaction
Authors: Reddy Chada R. , Ramesh Palacherla , Rao Nagavaram N. , Ali Saiyed A. 
Published: March 2011

AbstractDibenzo[b,e]oxepine derivatives have been constructed efficiently by one‐pot tandem carbon–carbon bond formation reactions. First, 2‐(3,5‐dimethoxybenzyloxy)benzaldehydes were treated with various nucleophiles under I2 catalysis and then 1‐(3,5‐dimethoxybenzyloxy)‐3,5‐dimethoxybenzene was treated with several aromatic as well as heteroaromatic aldehydes under BF3·Et2O catalytic conditions to provide dibenzo[b,e]oxepines in good yields.