bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative analysis of intracellular sugar phosphates and sugar nucleotides in encapsulated streptococci using HPAEC‐PAD
Authors: Marcellin Esteban , Nielsen Lars K. , Abeydeera Peter , Krömer Jens O.
Published: January 2009

Metabolomics is a powerful tool for the study of biological systems. Besides analytical techniques, cell harvest and extraction are critical steps, especially when studying encapsulated streptococci. We have compared four different harvesting techniques for biomass from liquid culture of the hyaluronic acid (HA)‐producing bacterium Streptococcus zooepidemicus. The best method for cell separation was quick (2 min) centrifugation, which allowed efficient medium removal and enabled quantification of the broadest range of sugar metabolites. Unlike observations for other microbes, changes in metabolite pools due to a delay of extraction by the centrifugation were not observed, so metabolite levels accurately reflected the metabolome at the point of cell harvest. A hypothesis is that the capsule itself isolates the cells from the surroundings and still supports it with nutrients during the harvest. Quantification of sugar phosphates and nucleotide sugars was performed using high‐performance anion exchange chromatography combined with pulsed amperometric detection, achieving limits of quantification of 2.5 pmol for sugar phosphates and 5 pmol on column for nucleotide sugars. Intracellular pool sizes for intermediates of the HA pathway under production conditions ranged from 0.2 to 0.5 μmol/g cell dry weight.
Production of random DNA oligomers for scalable DNA computing
Authors: Wang Sixue S. L. , Johnson John J. X. , Hughes Bradley S. T. , Karabay Dundar A. O. , Bader Karson D. W. , Austin Alan , Habib Aisha , Hatef Husnia , Joshi Megha , Nguyen Lawrence , Mills Allen P.
Published: January 2009

While remarkably complex networks of connected DNA molecules can form from a relatively small number of distinct oligomer strands, a large computational space created by DNA reactions would ultimately require the use of many distinct DNA strands. The automatic synthesis of this many distinct strands is economically prohibitive. We present here a new approach to producing distinct DNA oligomers based on the polymerase chain reaction (PCR) amplification of a few random template sequences. As an example, we designed a DNA template sequence consisting of a 50‐mer random DNA segment flanked by two 20‐mer invariant primer sequences. Amplification of a dilute sample containing about 30 different template molecules allows us to obtain around 1011 copies of these molecules and their complements. We demonstrate the use of these amplicons to implement some of the vector operations that will be required in a DNA implementation of an analog neural network.
Rapid prototyping of scaphoid and lunate bones
Authors: Gittard Shaun D. , Narayan Roger , Lusk Jason , Morel Pierre , Stockmans Filip , Ramsey Michael , Laverde Claire , Phillips Jack , Monteiro‐Riviere Nancy A. , Ovsianikov Aleksandr , Chichkov Boris N.
Published: January 2009

In this study, a novel rapid prototyping technology was used to fabricate scaphoid and lunate bone prostheses, two carpal bones that are prone to avascular necrosis. Carpal prostheses were fabricated with an Envisiontec Perfactory® SXGA stereolithography system using Envisiontec eShell 200 photocurable polymer. Fabrication was guided using 3‐D models, which were generated using Mimics software (Materialise NV, Leuven, Belgium) from patient computer tomography data. The prostheses were fabricated in a layer‐by‐layer manner; ∼ 50‐μm thick layers were observed in the prostheses. Hardness and Young's modulus values of polymerized eShell 200 material were 93.8 ± 7.25 MPa and 3050 ± 90 MPa, respectively. The minimum compressive force required for fracture was 1360 N for the scaphoid prosthesis and 1248 N for the lunate prosthesis. Polymerized Envisiontec eShell material exhibited high human neonatal epidermal keratinocyte cell viability rate in an MTT assay. The results of this study indicate that small bone prostheses fabricated by stereolithography using eShell 200 polymer may have suitable geometry, mechanical properties, and cytocompatibility properties for in vivo use.
Fully in vitro selection of recombinant antibodies
Authors: Moutel Sandrine , Vielemeyer Ole , Jin Hulin , Divoux Séverine , Benaroch Philippe , Perez Franck
Published: January 2009

Antibodies are essential for the identification and characterization of proteins. In the current postgenomic era the need for highly specific antibodies has further increased not only for research applications but also because they represent one of the most promising therapeutic options, especially in the field of cancer treatment. One appealing approach for rapid and inexpensive antibody generation is the use of phage display. This technique allows for a fast and animal‐free selection of highly functional alternatives to classical antibodies. However, one strong limitation of this recombinant approach has been the difficulty in producing and purifying antigens. These steps have to be adjusted for each new target, are time consuming and sometimes present an insurmountable obstacle. Here we report the development of new antibody selection approach where antigens are produced through in vitro translation and are used directly and without the need for purification. With this approach we were able to rapidly select recombinant antibodies directed against GFP and the mammalian protein tsg101, respectively. We believe that our method greatly facilitates antigen preparation and thus may broaden the use of the recombinant approach for antibody generation, especially since the technique could in the future be adapted to a high‐throughput technology, thus further accelerating antibody selection.
Expression system of CotA‐laccase for directed evolution and high‐throughput screenings for the oxidation of high‐redox potential dyes
Authors: Brissos Vânia , Pereira Luciana , Munteanu Florentina‐Daniela , Cavaco‐Paulo Artur , Martins Lígia O.
Published: January 2009

Laccases are useful biocatalysts for many diverse biotechnological applications. In this study we have established efficient and reliable expression systems and high‐throughput screenings for the recombinant CotA‐laccase fromBacillus subtilis. The expression levels ofcotA‐laccasewere compared in five differentEscherichia colihost strains growing in 96‐well microtiter plates under different culture conditions. Lower coefficients of variance (around 15%) were achieved using crude cell lysates of BL21 and KRX host strains growing under microaerobic conditions. Reproducible high‐throughput screenings for the decolorization of high redox potential azo and anthraquinonic dyes were developed and optimized for identification of variants with increased redox potential. The enzymatic assays developed were tested for the screening of one mutant library from CotA‐laccase created by error‐prone PCR.
Transient protein expression in three Pisum sativum (green pea) varieties
Authors: Green Brian J. , Fujiki Masaaki , Mett Valentina , Kaczmarczyk Jon , Shamloul Moneim , Musiychuk Konstantin , Underkoffler Susan , Yusibov Vidadi , Mett Vadim
Published: January 2009

The expression of proteins in plants both transiently and via permanently transformed lines has been demonstrated by a number of groups. Transient plant expression systems, due to high expression levels and speed of production, show greater promise for the manufacturing of biopharmaceuticals when compared to permanent transformants. Expression vectors based on a tobacco mosaic virus (TMV) are the most commonly utilized and the primary plant used, Nicotiana benthamiana, has demonstrated the ability to express a wide range of proteins at levels amenable to purification. N. benthamiana has two limitations for its use; one is its relatively slow growth, and the other is its low biomass. To address these limitations we screened a number of legumes for transient protein expression. Using the alfalfa mosaic virus (AMV) and the cucumber mosaic virus (CMV) vectors, delivered via Agrobacterium, we were able to identify three Pisum sativum varieties that demonstrated protein expression transiently. Expression levels of 420 ( 26.24 mg GFP/kgFW in the green pea variety speckled pea were achieved. We were also able to express three therapeutic proteins indicating promise for this system in the production of biopharmaceuticals.
A strained DNA binding helix is conserved for site recognition, folding nucleation, and conformational modulation
Authors: Wetzler Diana E. , Gallo Mariana , Melis Riccardo , Eliseo Tomasso , Nadra Alejandro D. , Ferreiro Diego U. , Paci Maurizio , Sánchez Ignacio E. , Cicero Daniel O. , de Prat Gay Gonzalo
Published: January 2009

Nucleic acid recognition is often mediated by α‐helices or disordered regions that fold into α‐helix on binding. A peptide bearing the DNA recognition helix of HPV16 E2 displays type II polyproline (PII) structure as judged by pH, temperature, and solvent effects on the CD spectra. NMR experiments indicate that the canonical α‐helix is stabilized at the N‐terminus, while the PII forms at the C‐terminus half of the peptide. Re‐examination of the dihedral angles of the DNA binding helix in the crystal structure and analysis of the NMR chemical shift indexes confirm that the N‐terminus half is a canonical α‐helix, while the C‐terminal half adopts a 310helix structure. These regions precisely match two locally driven folding nucleii, which partake in the native hydrophobic core and modulate a conformational switch in the DNA binding helix. The peptide shows only weak and unspecific residual DNA binding, 104‐fold lower affinity, and 500‐fold lower discrimination capacity compared with the domain. Thus, the precise side chain conformation required for modulated and tight physiological binding by HPV E2 is largely determined by the noncanonical strained α‐helix conformation, “presented” by this unique architecture. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 432–443, 2009.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Deterring malingered psychopathology: The effect of warning simulating malingerers
Authors: King Joanne , Sullivan Karen A.
Published: January 2009

The utility of a warning to deter malingering on measures of personality and psychopathology was examined. Sixty‐seven first year psychology students were randomly assigned to one of three conditions: unwarned malingerers, warned malingerers, and controls. Participants in the two malingering groups were given a financial incentive to simulate believable psychological impairment. Warned malingerers received an additional warning that the tests could detect malingering and that detection would result in loss of course credit. Controls received standardized test instructions. It was hypothesized that the malingering incentive would be sufficient to induce malingering, but that a deterrence theory warning would have a subsequent deterrent effect. Between‐groups analyses indicated that the warning used in this study significantly altered test performance on the Personality Assessment Inventory (PAI) and revised Symptom Checklist 90 (SCL‐90‐R). Warned malingerers scored significantly lower (faked less) than unwarned malingerers on the majority of the psychopathology scales and frequently approximated control group performances. These results support the effectiveness of a warning to complement existing malingering detection methods. Copyright © 2009 John Wiley & Sons, Ltd.
A latent class factor approach to identifying subtypes of juvenile diversion youths based on psychopathic features
Authors: Wareham Jennifer , Dembo Richard , Poythress Norman G. , Childs Kristina , Schmeidler James
Published: January 2009

Latent class factor analysis allows for the estimation of a dimensional construct such as psychopathy through factor analysis while also examining the heterogeneity of the sample. We report the results of a latent class factor analysis examining the psychometric structure of a widely used measure of psychopathy, as well as internalizing (i.e. anxiety) and externalizing indices, among diversion program youths involved in an intervention study. The results indicated that four subgroups of adolescents existed in the data: one with high psychopathic features and externalizing problems, but low anxiety; one with moderately high affective and behavioral psychopathic features and externalizing problems, but low anxiety; one with moderately high interpersonal and behavioral psychopathic features, externalizing problems, and anxiety; and one with very low psychopathy scores, anxiety, and externalizing problems. The validity of these subgroups was assessed comparing prior family problems, substance use, and offending measures, and one‐year follow‐up measures of recidivism, detention days, substance use, and program completion. This study offers partial support for the existence of psychopathy subgroups and has implications for future studies of psychopathy typologies. In addition, this study employed a methodology for classification that permits consideration of the dimensional nature of a construct, and as such has implications for a variety of research areas. Copyright © 2009 John Wiley & Sons, Ltd.
Heparin Antagonism by Polyvalent Display of Cationic Motifs on Virus‐Like Particles
Authors: Udit Andrew K. , Everett Chris , Gale Andrew J. , Reiber Kyle Jennifer , Ozkan Mihri , Finn M. G.
Published: January 2009

Particles to the rescue! The construction of cationic amino acid motifs on the surface of bacteriophage Qβ by genetic engineering or chemical conjugation gives particles that are potent inhibitors of the anticoagulant action of heparin, which is a common anticlotting agent subject to clinical overdose.

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Polyvalent interactions allow biological structures to exploit low‐affinity ligand–receptor binding events to affect physiological responses. We describe here the use of bacteriophage Qβ as a multivalent platform for the display of polycationic motifs that act as heparin antagonists. Point mutations to the coat protein allowed us to generate capsids bearing the K16M, T18R, N10R, or D14R mutations; because 180 coat proteins form the capsid, the mutants provide a spectrum of particles differing in surface charge by as much as +540 units (K16M vs. D14R). Whereas larger poly‐Arg insertions (for example, C‐terminal Arg8) did not yield intact virions, it was possible to append chemically synthesized oligo‐Arg peptides to stable wild‐type (WT) and K16M platforms. Heparin antagonism by the particles was evaluated by using the activated partial thrombin time (aPTT) clotting assay; this revealed that T18R, D14R, and WT‐(R8G2)95 were the most effective at disrupting heparin‐mediated anticoagulation (>95 % inhibition). This activity agreed with measurements of ζ potential (ZP) and retention time on cation exchange chromatography for the genetic constructs, which distribute their added positive charge over the capsid surface (+180 and +360 for T18R and D14R relative to WT). The potent activity of WT‐(R8G2)95, despite its relatively diminished overall surface charge is likely a consequence of the particle's presentation of locally concentrated regions with high positive charge density that interact with heparin's extensively sulfated domains. The engineered cationic capsids retained their ability to inhibit heparin at high concentrations and showed no anticlotting activity of the kind that limits the utility of antiheparin polycationic agents that are currently in clinical use.
Synthesis of Sulfated Glucosaminides for Profiling Substrate Specificities of Sulfatases and Fungal β‐N‐Acetylhexosaminidases
Authors: Loft Karen J. , Bojarová Pavla , Slámová Kristýna , Křen Vladimír , Williams Spencer J.
Published: January 2009

Systematic sulfation: Sulfated glycoconjugates are degraded either by desulfation followed by glycoside cleavage, or by glycoside cleavage followed by desulfation. To study these processes, here we report the synthesis of four regioisomerically sulfated p‐nitrophenyl glucosaminides from the common precursor p‐nitrophenyl N‐acetyl‐β‐D‐glucosaminide. These substrates allowed the rapid analysis of the substrate preferences of a set of four sulfatases and 24 hexosaminidases.

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Sulfated carbohydrates are components of many glycoconjugates, and are degraded by two major processes: cleavage of the sulfate ester by a sulfatase, or en bloc removal of a sulfated monosaccharide by a glycoside hydrolase. However, these processes have proved difficult to study owing to a lack of homogeneous, defined substrates. We describe here the synthesis of a series of p‐nitrophenyl β‐D‐glucosaminides bearing sulfate esters at the 2‐, 3‐, 4‐ or 6‐positions, by divergent routes starting with p‐nitrophenyl 2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside. The sulfated p‐nitrophenyl β‐D‐glucosaminides were used to study the substrate specificity of four sulfatases (from Helix pomatia, Patella vulgata, abalone, and Pseudomonas aeruginosa), and revealed significant differences in the preference of each of these enzymes for desulfation at different positions around the sugar ring. The 3‐, 4‐ and 6‐sulfated p‐nitrophenyl 2‐acetamido‐2‐deoxy‐β‐D‐glucosaminides were screened against a panel of 24 fungal β‐N‐acetylhexosaminidases to assess their substrate specificity. While the 4‐ and 6‐sulfates were substrates for many of the fungal enzymes investigated, only a single β‐N‐acetylhexosaminidase, that from Penicillium chrysogenum, could hydrolyze the 3‐sulfated p‐nitrophenyl glycoside. Together these results demonstrate the utility of sulfated p‐nitrophenyl β‐D‐glucosaminides for the study of both sulfatases and glycoside hydrolases.
Understanding the Plasticity of the α/β Hydrolase Fold: Lid Swapping on the Candida antarctica Lipase B Results in Chimeras with Interesting Biocatalytic Properties
Authors: Skjøt Michael , De Maria Leonardo , Chatterjee Robin , Svendsen Allan , Patkar Shamkant A. , Østergaard Peter R. , Brask Jesper
Published: January 2009

The best of both worlds. Long molecular dynamics (MD) simulations of Candida antarctica lipase B (CALB) confirmed the function of helix α5 as a lid structure. Replacement of the helix with corresponding lid regions from CALB homologues from Neurospora crassa and Gibberella zeae resulted in new CALB chimeras with novel biocatalytic properties. The figure shows a snapshot from the MD simulation.

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The Candida antarctica lipase B (CALB) has found very extensive use in biocatalysis reactions. Long molecular dynamics simulations of CALB in explicit aqueous solvent confirmed the high mobility of the regions lining the channel that leads into the active site, in particular, of helices α5 and α10. The simulation also confirmed the function of helix α5 as a lid of the lipase. Replacing it with corresponding lid regions from the CALB homologues from Neurospora crassa and Gibberella zeae resulted in two new CALB mutants. Characterization of these revealed several interesting properties, including increased hydrolytic activity on simple esters, specifically substrates with Cα branching on the carboxylic side, and much increased enantioselectivity in hydrolysis of racemic ethyl 2‐phenylpropanoate (E>50), which is a common structure of the profen drug family.
Synthesis, Characterization, Cytotoxicity, and Hydrolytic Behavior of C2‐ and C1‐Symmetrical TiIV Complexes of Tetradentate Diamine Bis(Phenolato) Ligands: A New Class of Antitumor Agents
Authors: Peri Dani , Meker Sigalit , Shavit Michal , Tshuva Edit Y.
Published: January 2009

Carefully design your ligand! A new family of highly cytotoxic TiIV complexes demonstrates strong dependence of activity on the particular ligand employed, in which small structural modifications dramatically affect both hydrolytic behavior and biological activity (see picture). Different structure‐dependence patterns are observed for hydrolysis and cytotoxicity, which are, nonetheless, strongly related.

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We recently introduced a new class of bis(isopropoxo)–TiIV complexes with diamine bis(phenolato) ligands that possess antitumor activity against colon HT‐29 and ovarian OVCAR‐1 cells that is higher than that of the known TiIV compounds titanocene dichloride and budotitane as well as that of cisplatin. Herein, we elaborate on this family of compounds; we discuss the effect of structural parameters on the cytotoxic activity and hydrolytic behavior of these complexes, seeking a relationship between the two. Whereas complexes with small steric groups around the metal center possess high activity and lead mostly to formation of O‐bridged polynuclear complexes with bound bis(phenolato) ligand upon water addition, bulky complexes hydrolyze to release all free ligands and are inactive. Slightly increasing the size of the N‐donor substituents probably weakens the ligand binding in solution, and, thus, rapid hydrolysis is observed, leading to a lack of cytotoxicity, supporting the requirement for ligand inertness. Replacing the two isopropoxo ligands with a single catecholato unit gives a complex with a different geometry that exhibits slower hydrolysis and reduced cytotoxicity, suggesting some participation of labile ligand hydrolysis in the cytotoxicity mechanism. A crystallographically characterized O‐bridged polynuclear species obtained from a biologically active bis(isopropoxo) complex upon water addition is inactive, which rules out its participation as the active species, yet suggests some role of the particular steric and electronic requirements allowing its formation in the activity mechanism. Additional measurements support rapid formation of the active species in the presence of cells prior to O‐bridged TiIV cluster formation.
Enzymatic Esterification in Aqueous Miniemulsions
Authors: Aschenbrenner Eugen M. , Weiss Clemens K. , Landfester Katharina
Published: January 2009

Just a drop of water: Esterification in water is possible by confining the reactants in small miniemulsion droplets protected by nonionic surfactants. A lipase located at the interface between the droplet and aqueous surroundings catalyzes the esterification and expels generated water from the reaction site (see picture). High yields of the ester can be obtained after short reaction times under ambient conditions.

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Monoesters of various linear carboxylic acids (C7–C12) with ω‐phenyl‐labeled primary alcohols (C1–C5) were synthesized in aqueous miniemulsions with various lipases as biocatalysts. The reactants were dispersed in an aqueous solution of a nonionic surfactant to form long‐term stable miniemulsions. The esterification of all of the systems could be catalyzed by the applied enzyme and yielded significant conversions of about 90 %. The hydrophilicity of the reactants and the specificity of the enzyme toward the substrates determine the reaction velocity and the final conversion. As a model system the reaction of nonanoic acid and 3‐phenylpropanol was extensively studied. Among various lipases, Lipase PS was determined to be the most effective, and for this reaction the parameters were optimized. A maximum conversion of 80 % could be obtained in less than one hour of reaction time. In comparison with an acid‐catalyzed esterification performed in miniemulsion with the same reaction parameters, the enzyme‐catalyzed reaction showed a significantly faster conversion. The reactions proved that the application of the miniemulsion technique enables efficient direct enzyme‐catalyzed esterification reactions from carboxylic acids and alcohols in the presence of large amounts of water.
Single‐Crystalline Molybdenum Trioxide Nanoribbons: Photocatalytic, Photoconductive, and Electrochemical Properties
Authors: Cheng Liang , Shao Mingwang , Wang Xiuhua , Hu Haibo
Published: January 2009

Molecular highways: A facile one‐step, surfactant‐free route was applied to produce high‐purity and uniform α‐MoO3 nanoribbons (see figure), and their photocatalytic, photoconductive, and electrochemical properties were investigated. The results showed that the as‐prepared products had superior photo and electro properties.

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Large‐scale, high‐purity and uniform α‐MoO3 nanoribbons have been synthesized by a facile hydrothermal route without employing surfactants or templates. The as‐prepared α‐MoO3 nanoribbons were up to several micrometers in length, 100 nm in width, 15–20 nm in thickness, and grew along the [001] direction. The obtained nanoribbons exhibited a quantum size effect in optical properties, showing a blue shift of the band gap and direct transitions compared with the values of bulk MoO3. The nanoribbons also showed superior photocatalytic ability in the photodegradation reaction of an aqueous solution of Rhodamine B under visible light. Furthermore, the as‐prepared α‐MoO3 materials exhibited linear current–voltage (I–V) characteristics and excellent photoresponse. As the light source was switched on and off, the currents could be reversibly switched between high and low value at the voltage of 0.1 V. Electrochemical measurements predicted that the α‐MoO3/carbon fiber modified microelectrode would display excellent electrochemical characters and high sensitivity toward neurotransmitter dopamine. The modified electrode was also quite stable and had good reproducibility, which might have application in the electrochemical analysis.
Nucleation and Growth of CeF3 and NaCeF4 Nanocrystals
Authors: Li Shuai , Xie Ting , Peng Qing , Li Yadong
Published: January 2009

Studying growth: The diffusion‐controlled kinetic (DCK) model and the surface chemical thermodynamics (SCT) model have been successfully applied to interpret the nucleation and growth mechanism of CeF3 (see TEM images) and NaCeF4 nanocrystals, and may generally give light to the size‐control and morphology prediction of rare‐earth fluorides at the nanoscale level.

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Monodisperse CeF3 and NaCeF4 nanocrystals have been synthesized by using the liquid–solid–solution (LSS) approach. The nucleation and growth of nanocrystalline CeF3 and NaCeF4 were controlled by both kinetics and thermodynamics, which can be investigated by the diffusion‐controlled kinetic (DCK) model and surface chemical thermodynamics (SCT) theory. The DCK and SCT models were introduced to explain how the ripening time, reaction temperature, and initial concentrations affected the size transition of CeF3 and NaCeF4 nanocrystals in detail. Also, these models are believed to be universal and can be applied to explore the morphology evolution of almost all rare‐earth fluoride nanocrystals.
Chiral Poly(4‐ethynylbenzoyl‐L‐valine)‐Induced Helical Self‐Assembly of Alkynylplatinum(II) Terpyridyl Complexes with Tunable Electronic Absorption, Emission, and Circular Dichroism Changes
Authors: Chan Kenneth Hoi‐Yiu , Lam Jacky Wing‐Yip , Wong Keith Man‐Chung , Tang Ben‐Zhong , Yam Vivian Wing‐Wah
Published: January 2009

The aggregation and self‐assembly of square‐planar alkynylplatinum(II) complexes is induced by the use of a chiral polyacetylene with a helical conformation (see scheme). The chain helicity of the chiral polyacetylene under basic conditions has also been demonstrated to be enhanced by the presence of the positively charged platinum(II) complexes.

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A chiral amino acid‐containing polyacetylene, poly(4‐ethynylbenzoyl‐L‐valine), was found to induce the aggregation and self‐assembly of square‐planar alkynylplatinum(II) terpyridyl complexes by electrostatic binding of the positively charged metal complexes to the anionic sites of the polyacetylene, as revealed by the appearance of new UV/Vis absorption and emission bands upon mixing under basic conditions. The induced complex self‐assembly was found to be influenced by the polyacetylene and/or base concentration, and the effect of pH on the reversibility of the aggregate/monomer interconversion was also studied. The conformational changes of the polyacetylene were probed by circular dichroism (CD) spectroscopy, in which the chirality signal of the corresponding chain helicity in the presence of the base was enhanced and stabilized upon addition of the platinum(II) complexes. The induced complex aggregation was dependent on the structural properties of the polyacetylene, while the chirality of the polyacetylene was strongly influenced by the introduction of the complex.
Supramolecular Templates for Nanoflake–Metal Surfaces
Authors: Shen Yanfei , Wang Jiaobing , Kuhlmann Uwe , Hildebrandt Peter , Ariga Katsuhiko , Möhwald Helmuth , Kurth Dirk G. , Nakanishi Takashi
Published: January 2009

A sustainable method for the fabrication of metallic surfaces with flower‐like fractal morphology was developed by using a three‐dimensional supramolecular assembly as a template. Modifying Au nanoflakes with self‐assembled monolayers or polymers allows the surface wettability to be adjusted from superhydrophobic to superhydrophilic (see figure). Furthermore, Au nanoflakes present excellent substrates for surface‐enhanced Raman spectroscopy (SERS).

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ESI‐FTICRMS Characterization of the Intermediates in Cycloisomerization of Trifluoromethyl‐substituted Enynols through Changing the Protecting Group of Substrate
Authors: QIAN Rong , GUO Yinlong , LÜ Long
Published: January 2009

A chemical method of changing the protecting group was coupled to MS, deuterium‐labeled and NMR methods to characterize the intermediates in the palladium(II)‐catalyzed cycloisomerization of trifluoromethyl‐substituted enynols. It was demonstrated that the method of changing the protecting group of substrates not only caused a decrease in reaction speed, but also provided long‐lived reaction intermediates detectable by conventional spectroscopic techniques. In this sense, two assumed reaction intermediates were intercepted and detected by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FTICRMS). For further characterization of these intermediates, the gas‐phase behavior of these intermediates was studied by sustained off‐resonance irradiation collision‐activated dissociation (SORI‐CAD) experiments. On the basis of the detailed, spectral interpretation of the palladium‐containing species, the fragmentation pathways of the intermediates have been proposed. The deuterium‐labeled experiment helped confirm the nature of the intermediates.
Synthesis and Complexation Studies of Calix[4]crown Telomers Intermolecularly Bridged with Calixarene Segments
Authors: LI Haibing , TIAN Demei , CHEN Yuanyin , GAO Zhinong
Published: January 2009

Three derivatived calix[4]crowns were condensed with calixarene segments: 2,6‐bis(bromomethyl)‐4‐methyl‐anisole (BBA) to afford their telomers TCA[4] in rational yields. The binding sites may complex metal ions or amino acids selectively. The telomers shows different metal ions selectivity in comparison with their monomers, which suggests that calixarene segment bridges play an important role in ion‐binding. The liquid‐liquid extraction experiment showed that telomer TCA[4]‐III was excellent receptor for zwitterionic α‐amino acids and soft cations Ag+ and Pb2+. The extraction percentage of tryptophan and histidine was as high as 87.9% and 91.5%, respectively.
Reaction of Perfluoroalkanesulfinyl Chlorides with Enamines: A Facile Synthesis of α‐Perfluoroalkanesulfinyl Ketones and Aldehydes
Authors: LI Xiaobo , CHEN Lingjun , WANG Xiaojin , LIU Jintao
Published: January 2009

The reaction of perfluoroalkanesulfinyl chlorides with enamines was achieved in the presence of triethylamine, and α‐perfluoroalkanesulfinyl carbonyl compounds were obtained in moderate to good yields after hydrolysis of the reaction intermediates with dilute hydrochloric acid.
Facile Synthesis of Monofluoro γ ‐Lactones and Pyrrolidine Derivatives via Electrophilic Fluorination of Allenoic Acids and Amides
Authors: CUI Haifeng , CHAI Zhuo , ZHAO Gang , ZHU Shizheng
Published: January 2009

A convenient method to synthesize a series of monofluoro γ‐lactones and pyrrolidine derivatives in moderate to good yields via the electrophilic fluorination of γ‐allenoic acids and tosylamides using Selectfluor was developed.
An Efficient Method for the Preparation of Pentafluoroiodoethane from Chloropentafluoroethane
Authors: ZHANG Chengpan , LIN Jinhong , QIANG Zhenwei , XIAO Jichang
Published: January 2009

An efficient method was developed for the synthesis of pentafluoroiodoethane from chloropentafluoroethane. Sulfinatodechlorination of CF3CF2Cl was carefully investigated. Subsequent iodination can be conducted in one pot without further purification, giving the corresponding CF3CF2I in practically acceptable yield.
Versatile Chiral Building Blocks from D‐Xylose
Authors: ZHEN Zhibin , GAO Jian , WU Yikang
Published: January 2009

Several new chiral building blocks containing a hidden 1,3‐syn diol motif were developed from inexpensive and readily available D‐xylose through an efficient route without involving any expensive/highly toxic reagents or tedious operations.
Chiral Separation of Calcium (−)‐2(S)‐2‐Benzyl‐4‐oxo‐4‐(cis‐hexahydro‐2‐isoindolinyl)butyrate Enantiomers by High‐performance Liquid Chromatography
Authors: ZHANG Zhefeng , YANG Gengliang , GAO Wenhui , CHEN Yi
Published: January 2009

A chiral high‐performance liquid chromatographic method was developed for the enantioseparation of a new insulinotropic drug of the glinide class with rapid onset. The chiral separation was performed on a Sumichiral OA‐3300 column (250 mm×4.6 mm, 5 µm) with methanol containing 0.05 mol/L ammonium acetate as the optimized mobile phase at detection wavelengh 210 nm. Baseline separation of the two enantiomers was obtained in 22 min with a resolution of 3.01. Calibration graphs were constructed in a range of 0.028–5.6 µg·mL−1forS‐ and 0.03–6.0 µg·mL−1forR‐(−)‐enantiomer, respectively. The linear correlation equations are:y=1.32×103x−2.54 (r=0.9997) forS‐enantiomer andy=1.15×103x−1.78 (r=0.9998) forR‐enantiomer, respectively. The limits of detection obtained byS/N=3 were 0.15 ng forS‐ and 0.10 ng forR‐enantiomer, respectively. RSD of the method was below 1.0% (n=5).
Theoretical Studies on the Reaction Mechanisms of C3H2 (cyclopropenylidene) and O(3P) Radicals
Authors: XIE Xiaohua , SHEN Wei , HE Rongxing , ZHANG Jinsheng , LI Ming
Published: January 2009

The complex potential energy surface for the reaction of C3H2 (cyclopropenylidene) with O(3P) was explored computationally using a density functional and ab initio QCISD(T) methods. The geometries of all the stationary points (transition states, intermediates and products) were fully optimized at the B3LYP/6‐311++G∗︁∗︁ computational level, and the single point calculation including full population analysis was performed by employing QCISD(T). Our results show that the product P1 (C2H+HCO) is the major product, while the products P2 (C2H2+CO) and P3 (HC3O+H) are minor products, as confirmed by experiment. Product P1 could be gained through the path: R→IM1→IM2→P1, and the C3H2+O(3P) reaction was expected to be rapid. So, the C3H2+O(3P) reaction may be an efficient strategy for producing C2H using cyclopropenylidene in atmosphere. The present results can lead us to understand deeply the mechanism of the title reaction.
Pt and Pt‐Ru Nanoparticles Dispersed on Ethylenediamine Grafted Carbon Nanotubes as New Electrocatalysts: Preparation and Electrocatalytic Properties for Ethanol Electrooxidation
Authors: ZHONG Xinxian , ZHANG Xiaohua , SUN Xinping , LIU Bo , KUANG Yafei , CHEN Jinhua
Published: January 2009

As the support of Pt and Pt‐Ru catalysts for ethanol electrooxidation, the ethylenediamine (ED)‐grafted multiwalled carbon nanotubes (MWNT) were prepared by a chemical synthesis method and characterized by Fourier transform infrared spectroscopy. The morphology and elemental composition of the Pt‐Ru/ED/MWNT and Pt/ED/MWNT catalysts were characterized by transmission electron microscopy (TEM) and energy dispersive X‐ray spectroscopy. TEM results demonstrate that the ED‐grafted MWNT is beneficial to loading Pt‐Ru and Pt electrocatalysts with well dispersion and small particle sizes. On the other hand, the electrocatalytic properties of the Pt‐Ru/ED/MWNT and Pt/ED/MWNT catalysts were characterized by cyclic voltammetry and chronoamperometry. Under the same loading mass of catalyst, the electrocatalytic activities of both Pt‐Ru/MWNT/graphite and Pt/MWNT/graphite electrodes are enhanced obviously by the introduction of ED. The electrocatalytic activity of the Pt/ED/MWNT/graphite electrode is even higher than that of the Pt‐Ru/MWNT/graphite electrode. These results indicate that the ED/MWNT is a promising catalyst support for ethanol electrooxidation.
DNA Probe and Cleavage Studies Based on the Interaction between DNA and Yb, Er Complexes of 2‐[(Trifluoroaceto)aceto]thinophene‐piperidine Ligands
Authors: YIN Caixia , HUO Fangjun , WU Yanbo , LIU Yanlin , YANG Pin
Published: January 2009

Two kinds of Ln complexes of [Ln(TTA)4]·HP (Ln=Yb or Er, TTA=2‐[(Trifluoroaceto)aceto]thinophene, HP=piperidine) have been synthesized and characterized, and their DNA‐binding properties investigated using UV spectra, fluorescent spectra, viscometry and molecular modeling. The results show that they can intercalate into the double helices of DNA. More important thing is that their fluorescence intensity can be enhanced by DNA, thererfore, a sensitive fluorescence method for the determination of DNA may be developed. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. Interestingly, the complexes can cleave circular plasmid pBR322 DNA at pH=7.2 and 37 °C. In addition, BDNPP [bis(2,4‐dinitrophenyl)‐phosphate] was chosen as a model compound to further study their cleavage mechanism of pBR322 DNA. From the first‐order kinetics equation, it was proved indirectly that the mechanism may be a hydrolytic cleavage.
Synthesis, Crystal Structure and Photoluminescent Properties of Two Novel Two‐dimensional Coordination Networks Assembled by Lanthanide Salts and Carboxylate Ligand
Authors: LI Yajuan , SONG Huihua , LIANG Qing , HE Rong , WEI Zhen
Published: January 2009

Two novel two‐dimensional (2D) lanthanide(III) coordination polymers [Ln(PDC)(OH)(H2O)2]n (Ln=Eu (1) and Tb (2), H2PDC=pyridine‐3,4‐dicarboxylic acid) have been synthesized under hydrothermal conditions, and characterized by elemental analysis, IR, TGA and single‐crystal X‐ray diffraction. Both compounds show the same 2D layer containing 1D Ln–O–Ln chains, and the layers are further connected through hydrogen‐bonding as well as π‐π stacking interactions into a three‐dimensional supramolecular network. Furthermore, both compounds exhibit intense fluorescent emission bands in the solid state at room temperature.
Brønsted Acid Mediated (sp3)Carbon‐Fluorine Bond Activation: Inter‐ and Intramolecular Arylation of Trifluoromethylated Arenes
Authors: WANG Fei , HU Jinbo
Published: January 2009

Trifluoromethanesulfonic acid (triflic acid) was found to be able to efficiently activate the benzylic sp3 C–F bond. Thus, under the catalysis of triflic acid at room temperature, trifluoromethylated arenes readily reacted with benzene to give benzophenones in moderate to good yields. Under similar B?nsted acid catalysis, intramolecular arylation also happened in the cases of some CF3‐arene substrates bearing an additional nucleophilic aryl group. Strong CF···H+ interaction or hydrogen bonding, is believed to play an important role in the current Br?nsted acid‐mediated C–F bond activation chemistry.
Increased ovarian cancer risk associated with menopausal estrogen therapy is reduced by adding a progestin
Authors: Pearce Celeste Leigh , Chung Karine , Pike Malcolm C. , Wu Anna H.
Published: January 2009

BACKGROUND.

It has become increasingly clear that use of menopausal hormone therapy (HT) is associated with an increased risk of ovarian cancer; however, the effects by type of formulation and duration of use are less clear. A systematic review of the HT and ovarian cancer literature was conducted to identify population‐based case‐control studies, cohort studies, and randomized trials that examined effects by formulation of HT (estrogen‐alone [ET] and estrogen plus progestin [EPT]) and duration of use.

METHODS.

Pub‐Med (www.pubmed.gov) was used to identify relevant publications through December 2007; 14 studies were identified. The authors abstracted relative risks (RRs) and 95% confidence intervals (CIs) in relation to duration of HT use (ET and EPT separately). The authors used the risk estimates per year of HT use if these were provided; otherwise, they calculated a duration‐response for a log‐linear model of the duration of HT use against risk.

RESULTS.

Ovarian cancer risk was increased among ET users (RR per 5 years of use, RR5 = 1.22; 95% CI, 1.18‐1.27; P < .0001), and a lower but still statistically significant increased risk was seen with EPT use (RR5 = 1.10; 95% CI, 1.04‐1.16; P = .001). The increased risk in ET users was statistically significantly higher than the increased risk in EPT users (P = .004).

CONCLUSIONS.

ET use increases risk of ovarian cancer in a duration‐dependent manner, and it appears that the addition of progestins blocks this effect, at least to some extent. Whether the effect of estrogens would be completely blocked if progestins were given every day is unclear. Cancer 2009. © 2009 American Cancer Society.
Long‐term incidence of cervical cancer in women with human immunodeficiency virus
Authors: Massad L. Stewart , Seaberg Eric C. , Watts D. Heather , Minkoff Howard , Levine Alexandra M. , Henry Donna , Colie Christine , Darragh Teresa M. , Hessol Nancy A.
Published: January 2009

BACKGROUND:

The objective of this study was to estimate the incidence of invasive cervical cancer (ICC) in women with human immunodeficiency virus (HIV) and compare it with the incidence in HIV‐uninfected women.

METHODS:

In a cohort study of HIV‐infected and uninfected women who had Papanicolaou tests obtained every 6 months, pathology reports were retrieved for women who had biopsy results or a self‐report of ICC. Histology was reviewed when reports confirmed ICC. Incidence rates were calculated and compared with those in HIV‐negative women.

RESULTS:

After a median follow‐up of 10.3 years, 3 ICCs were confirmed in HIV‐seropositive women, and none were confirmed in HIV‐seronegative women. The ICC incidence rate was not found to be associated significantly with HIV status (HIV‐negative women [0 of 100,000 person‐years] vs HIV‐positive women [21.4 of 100,000 person‐years]; P = .59). A calculated incidence rate ratio standardized to expected results from the Surveillance Epidemiology and End Results database that was restricted to HIV‐infected Women's Interagency HIV Study participants was 1.32 (95% confidence interval, 0.27‐3.85; P = 0.80).

CONCLUSIONS:

Among women with HIV in a prospective study that incorporated cervical cancer prevention measures, the incidence of ICC was not significantly higher than that in a comparison group of HIV‐negative women. Cancer 2009. Published 2009 by the American Cancer Society.
Postmenopausal hormone use and breast cancer associations differ by hormone regimen and histologic subtype
Authors: Calle Eugenia E. , Feigelson Heather Spencer , Hildebrand Janet S. , Teras Lauren R. , Thun Michael J. , Rodriguez Carmen
Published: January 2009

BACKGROUND:

Data from large prospective studies are needed to fully characterize the impact of exogenous hormones on breast cancer incidence by type of hormone preparation and histology of the cancer.

METHODS:

In a prospective cohort of 67,754 postmenopausal women in the US, 1821 cases of invasive ductal cancer and 471 cases of invasive lobular or mixed lobular cancer occurred during 13 years of follow‐up. The authors computed age‐adjusted rates, as well as age‐adjusted and multivariate‐adjusted rate ratios (RR) for ductal and lobular breast cancer and for the use of estrogen only (E‐only) and estrogen and progesterone (E + P) for current and former hormone users by duration of use and years since last use.

RESULTS:

Current use of E + P was associated with an increased risk of both ductal (RR of 1.75; 95% confidence interval [95% CI], 1.53‐2.01) and lobular (RR of 2.12; 95% CI, 1.62‐2.77) breast cancer. Risk increased within the first 2 to 3 years of use and attenuated 2 years after cessation. In contrast, current use of E‐only was not associated with an overall increased risk of invasive ductal cancer. The only exceptions to this finding were in lean (body mass index <25) women and for ductal cancers diagnosed at the regional/distant stage, where in both cases the use of E‐only was associated with an increased risk. E‐only use was associated with a 50% increased risk of invasive lobular cancer after ≥10 years of use.

CONCLUSIONS:

Use of E + P is more detrimental to the breast than E‐only use, in terms of both ductal and lobular cancer. The findings from the current study suggest a window of 2 to 3 years for the risks of E + P both to become apparent after initial use and to attenuate after cessation. Cancer 2009. © 2009 American Cancer Society.
Infections and association with different intensity of chemotherapy in children with acute myeloid leukemia
Authors: Sung Lillian , Gamis Alan , Alonzo Todd A. , Buxton Allen , Britton Kristen , DeSwarte‐Wallace Joetta , Woods William G.
Published: January 2009

BACKGROUND:

The objectives were to compare infections during different intensities of therapy in children with acute myeloid leukemia (AML).

METHODS:

Subjects were children enrolled in Children's Cancer Group 2891 with AML. In phase 1 (induction), patients were randomized to intensive or standard timing. In phase 2 (consolidation), those with a family donor were allocated allogeneic stem cell transplantation (SCT); the remainder were randomized to autologous SCT or chemotherapy. This report compares infections between different treatments on an intent‐to‐treat basis.

RESULTS:

During phase 1, intensive timing was associated with more bacterial (57.7% vs 39.4%; P < .001), fungal (27.4% vs 9.9%; P < .001), and viral (14.0% vs 3.9%; P < .001) infections compared with standard timing. During phase 2, chemotherapy was associated with more bacterial (56.5% vs 40.1%; P = .005), but similar fungal (9.5% vs 6.1%; P = 1.000) and viral (4.2% vs 12.9%; P = .728) infections compared with allogeneic SCT. No differences between chemotherapy and autologous SCT infections were seen. Fatal infections were more common during intensive compared with standard timing induction (5.5% vs 0.9%; P = .004). Infectious deaths were similar between chemotherapy, autologous SCT, and allogeneic SCT.

CONCLUSIONS:

Prevalence of infection varies depending on the intensity and type of treatment. This information sheds insight into the mechanisms behind susceptibility and outcome of infections in pediatric AML. Cancer 2009. © 2009 American Cancer Society.