bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multianalyte Electrochemical Biosensor Based on Aptamer‐ and Nanoparticle‐Integrated Bio‐Barcode Amplification
Authors: Li Xuemei , Xia Jianping , Li Wei , Zhang Shusheng 
Published: January 2010

AbstractIn the present work, a signal‐on electrochemical sensing strategy for the simultaneous detection of adenosine and thrombin is developed based on switching structures of aptamers. An Au electrode as the sensing surface is modified with two kinds of thiolated capture probes complementary to the linker DNA that contains either an adenosine aptamer or thrombin aptamer. The capture probes hybridize with their corresponding linker DNA, which has prehybridized with the reporter DNA loaded onto the gold nanoparticles (AuNPs). The AuNP contained two kinds of bio‐barcode DNA: one is complementary to the linker DNA (reporter), whereas the other is not (signal) and is tagged with different metal sulfide nanoparticles. Thus a “sandwich‐type” sensing interface is fabricated for adenosine and thrombin. With the introduction of adenosine and thrombin, the aptamer parts bind with their targets and fold to form the complex structures. As a result, the bio‐barcoded AuNPs are released into solution. The metal sulfide nanoparticles are measured by anodic stripping voltammetry (ASV), and the concentrations of adenosine and thrombin are proportional to the signal of either metal ion. With the dual amplification of the bio‐barcoded AuNP and the preconcentration of metal ions through ASV technology, detection limits as low as 6.6×10−12 M for adenosine and 1.0×10−12 M for thrombin are achieved. The sensor exhibits excellent selectivity and detectability in biological samples.
Pyridyl‐Substituted Corrole Isomers: Synthesis and their Regulation to G‐quadruplex Structures
Authors: Ma Heng , Zhang Ming , Zhang Dan , Huang Rong , Zhao Yang , Yang Hao , Liu Yijing , Weng Xiaocheng , Zhou Yangyang , Deng Minggang , Xu Liang , Zhou Xiang 
Published: January 2010

AbstractG‐quadruplex DNA plays an important role in the potential therapeutic target for the design and development of anticancer drugs. As various G‐quadruplex sequences in the promoter regions or telomeres can form different secondary structural modes and display a diversity of biology functions, variant G‐quadruplex interactive agents may be necessary to cure different disease by differentiating variant types of G‐quadruplexes. We synthesize five cationic methylpyridylium corroles and compare the interactions of corroles with different types of G‐quadruplexes such as cmyc, htelo, and bcl2 by using surface plasmon resonance. Because of the importance of human telomere G‐quadruplex DNA, we focus on the biological properties of the interactions between human telomere G‐quadruplex DNA and corrole isomers using CD, Tm, PCR‐stop (PCR= polymerase chain reaction), and polymerase‐stop assay, which demonstrate the excellent ability of the corrole to induce and stabilize the G‐quadruplex. This study provides the first experimental insight into how selectivity might be achieved for different G‐quadruplexes by a single group of methylpyridylium corrole isomers that may be optimized for potential selective cancer therapy.
Concentration Dependent Transformation of Oligopeptide based Nanovesicles to Nanotubes and an Application of Nanovesicles
Authors: Naskar Jishu , Banerjee Arindam 
Published: January 2010

AbstractThe concentration dependent transformation of an oligopeptide nanostructure from nanovesicles to nanotubes at neutral pH is presented. The oligopeptide Acp‐Tyr‐Glu (Acp: 6‐aminohexanoic acid) forms nanovesicles at a concentration of 6.9 mg mL−1. At a concentration of 2.3 mg mL−1 these vesicular structures completely disappear and nanotubular structures are observed. We have also successfully optimized an intermediate concentration (3.4 mg mL−1) where an ordered array of fused vesicular structures are formed, which actually leads to the transition from nanovesicles to nanotubes. These vesicular structures are very much sensitive toward metal ions and pH. Biocompatible calcium ions and high pH (10.7) can trigger the rupturing of these nanovesicles. One important property of these nanovesicular structures is the encapsulation of a potent anticancer drug doxorubicin, which can also be released in the presence of calcium ions promising a future use of these nanovesicles as vehicles for carrying biologically important molecules.
Functionalized Carbon Nanomaterials Derived from Carbohydrates
Authors: Jagadeesan Dinesh , Eswaramoorthy Muthusamy 
Published: January 2010

AbstractA tremendous growth in the field of carbon nanomaterials has led to the emergence of carbon nanotubes, fullerenes, mesoporous carbon and more recently graphene. Some of these materials have found applications in electronics, sensors, catalysis, drug delivery, composites, and so forth. The high temperatures and hydrocarbon precursors involved in their synthesis usually yield highly inert graphitic surfaces. As some of the applications require functionalization of their inert graphitic surface with groups like COOH, OH, and NH2, treatment of these materials in oxidizing agents and concentrated acids become inevitable. More recent works have involved using precursors like carbohydrates to produce carbon nanostructures rich in functional groups in a single‐step under hydrothermal conditions. These carbon nanostructures have already found many applications in composites, drug delivery, materials synthesis, and Li ion batteries. The review aims to highlight some of the recent developments in the application of carbohydrate derived carbon nanostructures and also provide an outlook of their future prospects.
A Sub‐50‐nm Monosized Superparamagnetic Fe3O4@SiO2T2‐Weighted MRI Contrast Agent: Highly Reproducible Synthesis of Uniform Single‐Loaded Core–Shell Nanostructures
Authors: Chen Feng , Bu Wenbo , Chen Yu , Fan Yuchi , He Qianjun , Zhu Min , Liu Xiaohang , Zhou Liangping , Zhang Shengjian , Peng Weijun , Shi Jianlin 
Published: January 2010

AbstractOleic acid stabilized superparamagnetic iron oxide nanoparticles (SPION) were selected as the cores for fabrication of sub‐50‐nm monodisperse single‐loaded SPION@SiO2 core–shell nanostructures. Parameters that influence the formation of SPION@SiO2 in the water‐in‐oil reverse microemulsion system have been systematically investigated. The sufficiently high concentration of well‐dispersed SPION, together with an appropriately low injection rate of tetraethoxysilane, were found to be the keys to efficiently prevent the homogeneous nucleation of silica and obtain a high‐quality single‐loaded core–shell nanocomposite. A more detailed mechanism for incorporating oleic acid capped inorganic functional nanoparticles into silica is proposed on the basis of previous reports and our new experimental results. Finally, the as‐synthesized SPION@SiO2 nanospheres are exploited as an MRI‐enhanced contrast agent, and their contrast effect in solution is tested by using a clinical MRI instrument.
Formation of α‐Lithio Siloles from Silylated 1,4‐Dilithio‐1,3‐Butadienes: Mechanism and Applications
Authors: Luo Qian , Wang Chao , Gu Li , Zhang Wen‐Xiong , Xi Zhenfeng 
Published: January 2010

AbstractA full account of a useful transformation from silylated 1,4‐dilithio‐1,3‐butadienes to α‐lithio siloles is described. These lithio siloles formed by this procedure are general, in terms of substitution patterns and synthetic methods, affording diversified silole derivatives. Notably, some structurally complex molecules, such as bridged bis‐silole compounds, have been synthesized easily and successfully by applying our protocol. The structure of the α‐lithio silole, which adopts a dimeric fashion through two lithium bridges, was confirmed by X‐ray analysis. Furthermore, a possible mechanism of the skeleton rearrangements via E/Z isomerization of 1‐silyl‐1‐lithio alkene and nucleophilic attack on silicon is proposed, and is also proved by experimental investigations.
Stereospecific Construction of Chiral Tertiary and Quaternary Carbon by Nucleophilic Cyclopropanation with Bis(iodozincio)methane
Authors: Nomura Kenichi , Matsubara Seijiro 
Published: January 2010

AbstractThe reaction of a ketone having a leaving group at the α‐position, such as α,β‐epoxy ketone or α‐sulfonyloxy ketone, with bis(iodozincio)methane affords a zinc alkoxide of cyclopropanol. The reaction proceeds by nucleophilic addition of the dizinc to the carbonyl group and a sequential intramolecular nucleophilic substitution of the introduced iodozinciomethyl group to the adjacent electrophilic carbon that has a leaving group. When an optically active α,β‐epoxy ketone or α‐sulfonyloxy ketone is treated with the dizinc, a zinc alkoxide of cyclopropanol having a chiral tertiary or quaternary carbon in the cyclopropane ring is obtained, and the obtained zinc alkoxide of cyclopropanol acts as a chiral homoenolate. When it is treated with an electrophile in the presence of copper cyanide, it gives an optically active α‐tertiary or ‐quaternary ketone that retains high optical purity.
Synthesis and Characterization of Water‐Soluble Conjugated Glycopolymer for Fluorescent Sensing of Concanavalin A
Authors: Shi Jianbing , Cai Liping , Pu Kan‐Yi , Liu Bin 
Published: January 2010

AbstractA neutral polyfluorene derivative that contains 20 mol % 2,1,3‐benzothiadiazole (BT) is synthesized by Suzuki cross‐coupling polymerization. A cationic conjugated polymer A and an α‐mannose‐bearing polymer B are subsequently obtained through different post‐polymerization methods. As a result of the charged pendant groups or sugar‐bearing groups attached to the polymer side chains, both A and B show good water‐solubility. The titration of Concanavalin A (Con A) into polymer aqueous solution leads to different fluorescent responses for polymers A and B. Polymer A does not show any obvious fluorescence change upon interaction with Con A, whereas polymer B shows fluorescence increase in BT emission intensity when Con A is added. This is because of the specific interaction between α‐mannose and Con A, which induces polymer aggregation, and then facilitates energy transfer from the phenylene–fluorene segments to the BT units. A practical calibration curve ranging from 1 nM to 250 nM is obtained by correlating the changes in BT emission intensity with Con A concentration. The advantage of polymer B‐based Con A macromolecular probe is that it shows signal increase upon Con A recognition, which is significantly different from other conjugated polymer‐based fluorescence quenching assays.
Redox Multifunctionality in a Series of PtII Dithiolene Complexes of a Tetrathiafulvalene‐Based Diphosphine Ligand
Authors: Lee Su‐Kyung , Shin Kyong‐Soon , Noh Dong‐Youn , Jeannin Olivier , Barrière Frédéric , Bergamini Jean‐François , Fourmigué Marc 
Published: January 2010

AbstractThe redox‐active and chelating diphosphine, 3,4‐dimethyl‐3′,4′‐bis(diphenylphosphino)‐tetrathiafulvalene, denoted as P2, is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2‐benzenedithiolate (bdt), 1,3‐dithiole‐2‐thione‐4,5‐dithiolate (dmit), and 5,6‐dihydro‐1,4‐dithiin‐2,3‐dithiolate (dddt). The complexes are structurally characterized by X‐ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)]. Four successive reversible electron‐transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron‐rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands.
Platinum‐Catalyzed Multi‐Step Reaction of Propargyl Alcohols with N‐Heteroaromatics
Authors: Bhuvaneswari Sivakolundu , Jeganmohan Masilamani , Cheng Chien‐Hong 
Published: January 2010

AbstractN‐Methyl indole reacts with but‐2‐yn‐1‐ol in the presence of PtCl2 in MeOH giving indole derivatives having a substituted 3‐oxobutyl group at the 3‐position in good yield. Under the reaction conditions, various substituted indoles and substituted propargyl alcohols are successfully involved in the reaction giving the corresponding addition products in good to moderate yields. The catalytic reaction can be further extended to N‐phenyl pyrrole. In the present multi‐step reaction, PtCl2 likely plays dual roles: as the catalyst for the rearrangement of propargyl alcohols to the corresponding alkenyl ketones and as the catalyst for the addition of indoles to the alkenyl ketones. Experimental evidence is provided to support the proposed mechanism.
An Efficient and Convenient Synthesis of Ethyl 1‐(4‐Methoxyphenyl)‐5‐phenyl‐1H‐1,2,3‐triazole‐4‐carboxylate
Authors: Chen Jung‐Hsuan , Liu Shuan‐Ru , Chen Kwunmin 
Published: January 2010

AbstractThe “click chemistry” of using organic azides and terminal alkynes is arguably the most efficient and straightforward route to the synthesis of 1,2,3‐triazoles. In this paper, an alternative and direct access to ethyl 1‐(4‐methoxyphenyl)‐5‐phenyl‐1H‐1,2,3‐triazole‐4‐carboxylate is described. Treatment of ethyl diazoacetate with 4‐methoxyaniline derived aryl imines in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene provided fully substituted 1,2,3‐triazoles in good to high chemical yields. The base‐mediated reaction tolerates various substituted phenyl imines as well as ethyl diazoacetate or the more bulky diazoacetamide. A reasonable mechanism is proposed that involves the addition of an imine nitrogen atom to the terminal nitrogen atom of the diazo compound, followed by aromatization to give the 1,2,3‐triazole. The presence of the 4‐carboxy group is advantageous as it can be easily transformed into other functional groups.
Synthesis of N‐Arylated 1,2‐Dihydroheteroaromatics Through the Three‐Component Reaction of Arynes with N‐Heteroaromatics and Terminal Alkynes or Ketones
Authors: Jeganmohan Masilamani , Bhuvaneswari Sivakolundu , Cheng Chien‐Hong 
Published: January 2010

AbstractThe reaction of benzynes with N‐heteroaromatics including quinolines, isoquinolines, and pyridines and various terminal alkynes or ketones with an α‐hydrogen in the presence of KF and 18‐crown‐6 in THF at room temperature for 8 h gave various N‐arylated 1,2‐dihydroheteroaromatics in good to moderate yields. Some of these product structures are found in various naturally occurring and biologically active heterocyclic compounds. The reaction involves an unusual multiple construction of new CC, CN, and CH bonds and the cleavage of a CH bond in one pot. It is likely that the three‐component coupling proceeds through the nucleophilic addition of quinoline to benzyne, which generates a zwitterionic species. The latter then attracts a proton from terminal alkyne (or ketone) to generate an N‐arylated quinolinium cation and an acetylide anion. Further reaction of these two ions provides the final substituted 1,2‐dihydroquinolines. In the reaction, the terminal alkyne acts first as a proton donor and then as a nucleophile. The application of a three‐component coupling reaction product, 1,2‐dihydro‐2‐pyridinyl alkyne in a stereospecific [4+2] Diels–Alder cycloaddition reaction with N‐phenyl maleimide to give an isoquinuclidine derivative, an important core present in various natural products, is demonstrated.
Vesicle Formation from an Amphiphilic Porphyrin Derivative at the Air–Water Interface
Authors: Ghosh Amrita , Choudhury Sipra , Das Amitava 
Published: January 2010

AbstractA tetraphenyl porphyrin derivative with two C16 alkyl chains covalently bound to each of the four peripheral phenyl rings through ether linkages formed multilayer clusters or vesicles at the air–water surface. More interestingly, spherical vesicles were also formed when deposited on appropriate solid surfaces, and these vesicles were stable even in dry conditions. Various microscopic images of the cast film deposited on a mica surface confirmed closed‐ended nanotube/nanorod‐type formation with necking and bulging. These narrow tubes are proposed to be intermediates for the formation of vesicles by fission at either side of the bulge. Such vesicular formation is not common when either cast or Langmuir–Blodgett films were deposited on a solid surface.
Phase‐Transfer‐Catalyzed Asymmetric Alkylation of α‐Benzoyloxy‐β‐keto Esters: Stereoselective Construction of Congested 2,3‐Dihydroxycarboxylic Acid Esters
Authors: Hashimoto Takuya , Sasaki Keigo , Fukumoto Kazuhiro , Murase Yuichi , Abe Naoyuki , Ooi Takashi , Maruoka Keiji 
Published: January 2010

AbstractHighly enantioselective phase‐transfer‐catalyzed alkylation of tert‐butyl 2‐benzoyloxy‐3‐oxobutanoate was realized by the use of an N‐spiro chiral quaternary ammonium salt, as a complementary approach to the asymmetric hydroxylation of α‐alkyl‐β‐keto esters. The synthetic utility of the alkylated compounds is highlighted by the diastereoselective reduction and alkylation of the remaining ketone moiety to give various enantiomerically enriched congested 2,3‐dihydroxycarboxylic acid esters.
RhII‐Catalyzed Reaction of α‐Diazocarbonyl Compounds Bearing β‐Trichloroacetylamino Substituent: CH Insertion versus 1,2‐H Shift
Authors: Zhang Zhenhua , Shi Weifeng , Zhang Jian , Zhang Bo , Liu Bingge , Liu Yiyang , Fan Bo , Xiao Fengping , Xu Feng , Wang Jianbo 
Published: January 2010

AbstractThe RhII‐carbene reaction is dramatically affected by the neighboring substituents. If the neighboring substituent is an OH group, a1,2‐H shift is the exclusive pathway. If it is an OAc group, a 1,2‐acetoxy migration is observed. If it is p‐toluenesulfonyl group, 1,3 and 1,5‐CH insertion are the major pathways, and the 1,2‐H shift is completely suppressed. If the adjacent substituent is a trichloroacetyl amino group, 1,5‐CH insertion competes with the 1,2‐hydride shift, and no 1,3‐CH insertion can be observed. Both electronic and steric factors are responsible for the switching of the RhII‐carbene reaction pathway. The highly stereoselective 1,5‐CH insertions in RhII‐catalyzed reaction of α‐diazocarbonyl compounds, bearing β‐trichloroacetylamino substituent, can be utilized as a novel way to synthesize five‐membered cyclic β‐amino acid derivatives.
Controllable Synthesis and Optical Properties of Connected Zinc Oxide Nanoparticles
Authors: Wu Wei , Xiao Xiangheng , Peng Tangchao , Jiang Changzhong 
Published: January 2010

AbstractConnected zinc oxide (ZnO) nanoparticles are successfully synthesized by a simple solution‐based chemical route that uses evaporation and concentration technology. The influences of processing parameters, especially the evaporation and concentration time on the size and morphology of the nanoparticles, have been investigated by transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM). The structure and optical properties are systematically characterized by X‐ray diffraction (XRD), UV/Vis spectrophotometery, and fluorescence spectroscopy (FL). It is found that the average diameter and morphology are strongly affected by the evaporation and concentration time. Additionally, the formation mechanism of the nanoparticles is also discussed. The studies revealed that the evaporation and concentration are important aggregation or nucleation processes for ZnO growth, which leads to the macro‐differences in morphology. These results provide some insight into the growth mechanism of ZnO nanostructures. The synthetic strategy developed in this study may also be extended to the preparation of other nanomaterials and promising applications in various fields of nanotechnology.
Oxidative Dissolution of Silver Nanoparticles by Biologically Relevant Oxidants: A Kinetic and Mechanistic Study
Authors: Ho Chi‐Ming , Yau Sammi King‐Woon , Lok Chun‐Nam , So Man‐Ho , Che Chi‐Ming 
Published: January 2010

AbstractThe oxidative dissolution of silver nanoparticles (AgNPs) plays an important role in the synthesis of well‐defined nanostructured materials, and may be responsible for their activities in biological systems. In this study, we use stopped‐flow spectrophotometry to investigate the kinetics and mechanism of the oxidative dissolution of AgNPs by H2O2 in quasi‐physiological conditions. Our results show that the reaction is first order with respect to both [Ag0] and [H2O2], and parallel pathways that involve the oxidation of H2O2 and HO2− are proposed. The order of the reaction is independent of the size of the AgNPs (≈5–20 nm). The rate of dissolution increases with increasing pH from 6.0 to 8.5. At 298 K and I=0.1 M, the value of kb is five orders of magnitude higher than that of ka (where ka and kb are the rate constants for the oxidative dissolution of AgNPs by H2O2 and HO2−, respectively). In addition, the effects of surface coating and the presence of halide ions on the dissolution rates are investigated. A possible mechanism for the oxidative dissolution of AgNPs by H2O2 is proposed. We further demonstrate that the toxicities of AgNPs in both bacteria and mammalian cells are enhanced in the presence of H2O2, thereby highlighting the biological relevance of investigating the oxidative dissolution of AgNPs.
Mechanistic Insights into Selectivity Control for Heterogeneous Olefin Oxidation: Styrene Oxidation on Au(111)
Authors: Quiller Ryan G. , Liu Xiaoying , Friend Cynthia M. 
Published: January 2010

AbstractWe demonstrate that intermolecular interactions, controlled by both oxygen and styrene coverage, alter reaction selectivity for styrene oxidation on oxygen‐covered Au(111). Several partial oxidation products are formed—styrene oxide, acetophenone, benzoic acid, benzeneacetic acid, and phenylketene—in competition with combustion. The maximum ratio of the yields of styrene oxide to the total CO2 produced is obtained for the maximum styrene coverage for the first two layers (0.28 ML) adsorbed on Au(111) precovered with 0.2 ML of O. Furthermore, our reactivity and infrared studies support a mechanism whereby styrene oxidation proceeds via two oxametallacycle intermediates which, under oxygen‐lean conditions, lead to the formation of styrene oxide, acetophenone, and phenylketene. Benzoate, identified on the basis of infrared reflection absorption spectroscopy, is converted into benzoic acid during temperature‐programmed reaction. These results demonstrate the ability to tune the epoxidation selectivity using reactant coverages and provide important mechanistic insight into styrene oxidation reactions.
Synthesis and Rearrangement of Stable NHC→Silylene Adducts and Their Unique Reactivity towards Cyclohexylisocyanide
Authors: Xiong Yun , Yao Shenglai , Driess Matthias 
Published: January 2010

AbstractThe syntheses and reactivity of the two N‐heterocyclic carbene (NHC)→ silylene complexes 2 and 4 have been investigated. The latter are easily accessible by reaction of the zwitterionic, N‐heterocyclic silylene LSi: 1 [L=Ar‐N‐C(=CH2)CHC(Me)‐N‐Ar, Ar=2,6‐iPr2C6H3] with 1,3,4,5‐tetramethylimidazol‐2‐ylidene and 1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene, respectively. While compound 2 undergoes facile rearrangement above −20 °C to give the unsymmetrical N‐heterocyclic silylcarbene 3, the derivative 4 remains unchanged even after boiling in benzene. The remarkable reactivity of 3 and 4 towards cyclohexylisocyanide has been examined which leads in a unique series of CH, SiH, and CN bond activations to the new triaminosilanes 5 and 6, respectively. The novel compounds 3, 4, 5, and 6 were fully characterized by 1H, 13C, and 29Si NMR spectroscopy, EI‐MS, elemental analysis, and single‐crystal X‐ray diffraction.