bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of mass defect in modern mass spectrometry
Authors: Sleno Lekha
Published: February 2012

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra. Copyright © 2012 John Wiley & Sons, Ltd.
Gas‐phase doubly charged complexes of cyclic peptides with copper in +1, +2 and +3 formal oxidation states: formation, structures and electron capture dissociation
Authors: Afonso Carlos , Tabet Jean‐Claude , Giorgi Gianluca , Tureček František
Published: February 2012

Copper complexes with a cyclic D‐His‐β‐Ala‐L‐His‐L‐Lys and all‐L‐His‐β‐Ala‐His‐Lys peptides were generated by electrospray which were doubly charged ions that had different formal oxidation states of Cu(I), Cu(II) and Cu(III) and different protonation states of the peptide ligands. Electron capture dissociation showed no substantial differences between the D‐His and L‐His complexes. All complexes underwent peptide cross‐ring cleavages upon electron capture. The modes of ring cleavage depended on the formal oxidation state of the Cu ion and peptide protonation. Density functional theory (DFT) calculations, using the B3LYP with an effective core potential at Cu and M06‐2X functionals, identified several precursor ion structures in which the Cu ion was threecoordinated to pentacoordinated by the His and Lys side‐chain groups and the peptide amide or enolimine groups. The electronic structure of the formally Cu(III) complexes pointed to an effective Cu(I) oxidation state with the other charge residing in the peptide ligand. The relative energies of isomeric complexes of the [Cu(c‐HAHK + H)]2+ and [Cu(c‐HAHK − H)]2+ type with closed electronic shells followed similar orders when treated by the B3LYP and M06‐2X functionals. Large differences between relative energies calculated by these methods were obtained for open‐shell complexes of the [Cu(c‐HAHK)]2+ type. Charge reduction resulted in lowering the coordination numbers for some Cu complexes that depended on the singlet or triplet spin state being formed. For [Cu(c‐HAHK − H)]2+ complexes, solution H/D exchange involved only the N–H protons, resulting in the exchange of up to seven protons, as established by ultra‐high mass resolution measurements. Contrasting the experiments, DFT calculations found the lowest energy structures for the gas‐phase ions that were deprotonated at the peptide Cα positions. Copyright © 2012 John Wiley & Sons, Ltd.
Qualitative–(semi)quantitative data acquisition of artemisinin and its metabolites in rat plasma using an LTQ/Orbitrap mass spectrometer
Authors: Du Fuying , Liu Tian , Shen Tao , Zhu Fanping , Xing Jie
Published: February 2012

Artemisinin (QHS) is one of the first‐line antimalarials, and autoinduction of CYP‐mediated metabolism can result in its reduced exposure. To better understand the autoinduction of QHS, we evaluated the pharmacokinetics of QHS and its phase I metabolites in rats using an liquid chromatography‐high resolution mass spectrometry (LC‐HRMS) method. The LC separation was improved, allowing the separation of QHS and its metabolites from their diastereomers, and seven metabolites of QHS with relatively high exposure were identified in rat plasma, including deoxyartemisinin (DQHS), three monoyhydroxylated plus deoxyl metabolites (M1–M3) and three monohydroxylated metabolites (M4–M6). For detection, a high‐resolution LTQ/Orbitrap mass spectrometer with an electrospray ionization (ESI) inlet in the positive ion mode was used. High‐resolution extracted ion chromatograms for each analyte were obtained by processing the full‐scan MS dataset with 10 ppm mass tolerance. The plasma samples were pretreated by protein precipitation with acetonitrile. The standard curve was linear (r2 > 0.99) over the QHS and DQHS concentration range of 5.0–200.0 ng/ml in 50 µl of plasma, which offered sufficient sensitivity and accuracy for the determination of QHS and its metabolites. A 3‐day validation approach was used for absolute quantitation of QHS and DQHS. The other six metabolites of QHS were semiquantified based on the calibration curve of QHS. The present method was applied to the pharmacokinetic study of QHS in rats after a single oral administration. The data shown here also suggest that this type of mass analyzer will be capable of a quantitative–qualitative workflow. Copyright © 2012 John Wiley & Sons, Ltd.
Rapid and simultaneous detection of linear chromosome and large plasmids in Proteobacteria
Authors: Ramírez‐Bahena Martha Helena , Nesme Xavier , Muller Daniel
Published: February 2012

Bacterial genomic architectures are complex and play important roles in genome evolution. While most bacterial lineage genomes contain a single chromosome often accompanied by plasmids, more and more genomes are described as harboring a linear or a second chromosome. Thus, the development of bacterial genomics leads to the study of bacterial genome architectures. In order to avoid laborious techniques combining several methods, we developed an original plug‐free pulsed field gel electrophoresis procedure, that enabled us to co‐characterize reproducibly the presence of linear chromosomes and plasmids ranging between 30 kb and 2000 kb in various proteobacterial lineages. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flagella and bacterial pathogenicity
Authors: Duan Qiangde , Zhou Mingxu , Zhu Liqian , Zhu Guoqiang
Published: February 2012

As locomotive organelles, flagella allow bacteria to move toward favorable environments. A flagellum consists of three parts: the basal structure (rotary motor), the hook (universal joint), and the filament (helical propeller). For ages, flagella have been generally regarded as important virulence factors, mainly because of their motility property. However, flagella are getting recognized to play multiple roles with more functions besides motility and chemotaxis. Recent evidence has pinpointed that the bacterial flagella participate in many additional processes including adhesion, biofilm formation, virulence factor secretion, and modulation of the immune system of eukaryotic cells. This mini‐review summarizes data from recent studies that elucidated how flagella, as a virulence factor, contribute to bacterial pathogenicity.
Characterization of an antifungal compound produced by Bacillus sp. strain A5F that inhibits Sclerotinia sclerotiorum
Authors: Kumar Ankit , Saini Sandeep , Wray Victor , Nimtz Manfred , Prakash Anil , Johri B. N.
Published: February 2012

A potential antagonist, Bacillus sp. strain A5F was isolated from soybean rhizosphere following in vitro dual plate screening. The bacterium displayed strong inhibitory activity in vitro against soybean stem rot pathogen, Sclerotinia sclerotiorum. The culture supernatant of strain A5F completely suppressed the mycelial growth of the pathogen, indicating that suppression was due to the presence of antifungal compounds in the culture filtrate. The culture filtrate also suppressed other phytopathogenic fungi including Fusarium oxysporum and Macrophomina phaseolina, in vitro suggesting a broad spectrum antagonistic activity against fungal pathogens. Chemical extraction followed by chromatographic analysis resulted in two antifungal fractions. The high resolution‐electron spin ionization‐mass spectrometry (HR‐ESI‐MS) and Nuclear Magnetic Resonance (1D and 2D1H) spectra of these antifungal fractions revealed the presence of antifungal compounds, one of which showed similarity to bacillomycin D. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of indigo production by a newly isolated Pseudomonas sp. QM
Authors: Qu Yuanyuan , Ma Qiao , Zhang Xuwang , Zhou Hao , Li Xinliang , Zhou Jiti
Published: February 2012

Optimization of indigo production process from indole using a newly isolated phenol‐degrading bacterial strain was performed by Plackett‐Burman design and response surface methodology. The strain designated as QM was identified as Pseudomonas sp. according to 16S rDNA analysis. Spectrum analysis of indole biotransformation products revealed the presence of indigo and a by‐product indirubin. To improve indigo yield, Plackett‐Burman design was used to select significant factors from 8 viriables. Then response surface methodology based on a 23 central composite design was used to further optimize the transformation process. Under the optimal conditons, strain QM can produce 27.20 mg/l indigo after 24 h cultivation at 30 °C, which was 151.3% higher than that from the initial conversion condition. The results indicated that Pseudomonas sp. QM should be a potential candidate for indigo industial production. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Genetic epidemiology and heritability of AIS: A study of 415 Chinese female patients
Authors: Tang Nelson L.S. , Yeung Hiu‐Yan , Hung Vivian W.Y. , Di Liao Chen , Lam Tsz‐Ping , Yeung Hau‐Man , Lee Kwong‐Man , Ng Bobby Kin‐Wah , Cheng Jack Chun‐Yiu
Published: February 2012

Recent familial segregation studies supported a multifactorial genetic model for the etiology of adolescent idiopathic scoliosis (AIS). However, the extent of quantitative genetic effects, such as heritability, have not been fully evaluated. This genetic epidemiology study examined the sibling recurrent risk and heritability of AIS in first‐degree relatives of 415 Chinese female patients, which is up to now the largest cohort. They were first diagnosed by community screening program and compared to 203 age‐matched normal controls. Out of the total 531 sibs of AIS cases, 94 sibs had scoliosis (sibling recurrence risk = 17.7%). The prevalence of AIS among male and female sibs of an index case were 11.5% (95% CI = 7.5–15.5) and 23.0% (95% CI = 18.1–27.9), respectively. Female sibs of an index case had an increased risk of 8.9‐fold (95% CI = 3.2–34.4) for developing AIS. These recurrent risks were significantly higher than the risk in the control group (p < 0.0001). Overall, heritability was estimated to be 87.5 ± 11.1%. The results confirmed the prevailing impression of strong genetic influence on the risk of AIS. Here we provided a large‐scale study for the genetic aggregation estimates in an Asian population for the first time. The finding also positioned AIS among other common disease or complex traits with a high heritability. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1464–1469, 2012
Obligate crayfish burrow use and core habitat requirements of crawfish frogs
Authors: Heemeyer Jennifer L. , Williams Perry J. , Lannoo Michael J.
Published: February 2012

Crawfish frogs (Lithobates areolatus) have experienced declines across large portions of their former range. These declines are out of proportion to syntopic wetland‐breeding amphibian species, suggesting losses are resulting from unfavorable aspects of non‐breeding upland habitat. Crawfish frogs get their common name from their affinity for crayfish burrows, although the strength of this relationship has never been formally assessed. We used radiotelemetry to address 4 questions related to upland burrow dwelling in crawfish frogs: 1) what burrow types are used and how do they function to affect crawfish frog survivorship; 2) what are the physical characteristics and habitat associations of crawfish frog burrows; 3) what are the home range sizes of crawfish frogs when burrow dwelling; and 4) where are crawfish frog burrows situated with respect to breeding wetlands? We tracked crawfish frogs to 34 burrows, discovered another 7 occupied burrows, and therefore report on 41 burrows. Crawfish frogs exclusively occupied crayfish burrows as primary burrows, which they inhabited for an average of 10.5 months of the year. With one exception, crawfish frogs also used crayfish burrows as secondary burrows—temporary retreats occupied while exhibiting breeding migrations or ranging forays. Burrows were exclusively located in grassland habitats, although crawfish frogs migrated through narrow woodlands and across gravel roads to reach distant grassland primary burrow sites. Home range estimates while inhabiting burrows were 0.05 m2(the area of the burrow entrance plus the associated feeding platform) or 0.01 m3(the estimated volume of their burrow). Crawfish frog burrows were located at distances up to 1,020 m from their breeding wetlands. To protect crawfish frog populations, we recommend a buffer (core habitat plus terrestrial buffer) of at least 1.2 km around each breeding wetland. Within this buffer, at least 3 critical habitat elements must be present: 1) extensive grasslands maintained by prescribed burning and/or logging, 2) an adequate number of upland crayfish burrows, and 3) no soil disturbance of the sort that would destroy crayfish burrow integrity. © 2012 The Wildlife Society.
Music and lexical tone perception in chinese adult cochlear implant users
Authors: Wang Shuo , Liu Bo , Dong Ruijuan , Zhou Yun , Li Jing , Qi Beier , Chen Xueqing , Han Demin , Zhang Luo
Published: February 2012

Objectives/Hypothesis:

The present study's aim was to assess the music perception ability for Chinese adult cochlear implant users and to investigate the correlation between music and Mandarin‐Chinese lexical tone perception.

Study Design:

Case‐control study.

Methods:

Twenty normal‐hearing and 21 adult cochlear implant users participated in the Musical Sounds in Cochlear Implants (MuSIC) perception test, including six objective and two subjective musical subtests. The comparison of music perception performance was made between normal‐hearing and cochlear implant subjects. Sixteen of the 21 cochlear implant users also performed a tone identification test to investigate the correlation between music and tone perception.

Results:

Cochlear implant users performed significantly worse than normal‐hearing subjects on pitch discrimination, instrument identification, and instrument detection tests, whereas close to normal‐hearing subjects on melody discrimination, chords discrimination, rhythm discrimination, and emotion and dissonance rating subtests. Lexical tone perception was significantly correlated with pitch discrimination, melody discrimination, and instrument identification tests. Duration of hearing aid use was found to be correlated with pitch discrimination ability of cochlear implant users.

Conclusions:

Chinese postlingually deafened cochlear implant users performed significantly poorer in pitch discrimination and timbre perception tasks than normal‐hearing listeners. Lexical tone perception was found to be significantly correlated with music pitch perception, supporting the notion that tone and music perception may share a similar pitch perception mechanism.
Competitive Cellular Uptake of Nanoparticles Made From Polystyrene, Poly(methyl methacrylate), and Polylactide
Authors: Höcherl Anita , Dass Martin , Landfester Katharina , Mailänder Volker , Musyanovych Anna
Published: February 2012

The uptake behavior of negatively charged fluorescent nanoparticles made from different polymers (PS, PMMA, and PLLA) is studied on HeLa cells. All particles are obtained by the miniemulsion process using sodium dodecylsulfate as anionic surfactant. The size of the particles is in the range 105–125 nm. Cell uptake is analyzed by flow cytometry and reveals a higher uptake of PLLA particles compared to PMMA and PS particles. In competitive uptake studies two different types of particles are co‐incubated with the HeLa cells; the results indicate a mutual influence of the particles on their uptake behavior. A reduced internalization of PLLA particles in the presence of PS particles is observed, although neither the co‐incubation of PMMA and PLLA nor of PMMA and PS shows similar effect.

magnified image
Preparation of Biodegradable Polylactide Microparticles via a Biocompatible Procedure
Authors: Levato Riccardo , Mateos‐Timoneda Miguel A. , Planell Josep A.
Published: February 2012

PLA MPs are prepared via a novel and toxic‐chemical‐free fabrication route using ethyl lactate, a green solvent and FDA‐approved aroma. MPs are obtained by a solution jet break‐up and solvent displacement method. Adjusting flow parameters allows the tuning of MPs size between 60 and 180 µm, with reduced polydispersity. Morphological analysis shows microporous particles with Janus‐like surface. A fluorophore is successfully loaded into the MPs during their formation step. This versatile green solvent‐based procedure is proven to be suitable for drug encapsulation and delivery applications. The method may be extended to different droplet generation techniques.

magnified image
Influence of SWNTs on the Preferential Alignment of Molecular Moieties in PVA Fibers
Authors: Ford Ericka Nicole Johnson , Minusa Marilyn Lillith , Liu Tao , Choi Ji Il , Jang Seung Soon , Kumar Satish
Published: February 2012

The alignment of electron‐donating moieties in SWNT‐embedded PVA fibers is characterized using infrared dichroism and polarized Raman spectroscopy. The SWNT alignment is found to influence the preferential alignment of PVA functional groups and solvent molecules with respect to the fiber axis. Furthermore, the fraction of oriented functional moieties depends more on the SWNT alignment than on the PVA chain orientation. Charge transfer between functional moieties and SWNTs results in molecular adhesion between the SWNTs and interacting groups, as confirmed by DFT calculations.
Ethylene‐co‐Norbornene Copolymers Grafted Carbon Nanotube Composites by In Situ Polymerization
Authors: Boggioni Laura , Scalcione Giulia , Ravasio Andrea , Bertini Fabio , D'Arrigo Cristina , Tritto Incoronata
Published: February 2012

Vinyl functionalized multiwalled carbon nanotubes (MWCNT‐vinyl) are synthesized and used as monomers to prepare poly(ethylene‐co‐norbornene)‐grafted carbon nanotube composites by in situ polymerization with [Ti(η5‐C5Me5)(NCtBu2)Cl2] activated with methylalumoxane (MAO). The glass transition temperatures (Tg) of grafted MWCNT composites are more than 30 °C higher than those of copolymers. This difference is rationalized by the immobilization of the copolymer chain to the MWCNT surface by a covalent bond. The Young's modulus is shown to increase by more than 200% compared to poly(ethylene‐co‐norbornene) by incorporating 3.4 wt% functionalized MWCNT.
Fast copper catalyzed living radical polymerization of acrylonitrile utilizing a high concentration of radical initiator
Authors: Liu Xiao‐hui , Wang Jin , Yang Jian‐shi , An Shu‐lin , Ren Yuan‐lin , Yu Yun‐hai , Chen Peng
Published: February 2012

This article first reports a fast and controlled living radical polymerization (LRP) of acrylonitrile, evidenced by 81.3% monomer conversion within 40 min and well‐defined the polymers with a narrow polydispersity index (PDI) range of 1.14−1.38. This was achieved by utilizing azobis(isobutyronitrile) as radical initiator with a high concentration up to 190 mM and CuBr2 as catalyst with a very low concentration down to 50 ppm. The polymerization displayed typical LRP characteristics, including pseudo first‐order kinetics of polymerization, the linear increase of number‐average molecular weights (MWs), low PDI values. The influence of various experimental components, radical initiator concentration, catalyst concentration, and reaction temperature, on the polymerization reaction and MW as well as PDI has been investigated in detail. 1H NMR and gel permeation chromatography analyses as well as chain extension reaction confirmed the very high chain‐end functionality of the resultant polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Effect of molar mass and regioregularity on the photovoltaic properties of a reduced bandgap phenyl‐substituted polythiophene
Authors: Ouhib Farid , Dupuis Guillaume , de Bettignies Rémi , Bailly Séverine , Khoukh Abdel , Martinez Hervé , Desbrières Jacques , Hiorns Roger C. , Dagron‐Lartigau Christine
Published: February 2012

Among the numerous reduced bandgap polymers currently being developed, poly[3‐(4‐octylphenyl)thiophene)]s (POPT) may present attractive properties for organic solar cells due to its facile preparation and improved absorption with respect to poly(3‐hexylthiophene). This article appraises methods of preparation, including the use of diphenyl ether as a reaction medium, and discusses the effects of variations in molar masses, from about 3200 to 65,000 g mol−1 and regioregularity on its optoelectronic properties. The photovoltaic properties of POPT with [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) in bulk heterojunction devices are also discussed in the light of morphological variations, as indicated by atomic force microscopy characterizations. With an initial screening of conditions, namely POPT:PCBM ratios and deposition solvent, a power conversion efficiency of 1.58% was obtained using a relatively high molar mass POPT sample. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Systematic study on chemical oxidative and solid‐state polymerization of poly(3,4‐ethylenedithiathiophene)
Authors: Chen Shuai , Lu Baoyang , Duan Xuemin , Xu Jingkun
Published: February 2012

Systematic research on the synthesis, chemical oxidative polymerization of 3,4‐ethylenedithiathiophene (EDTT) in the presence of surfactants or not, and solid‐state polymerization of 2,5‐dibromo‐3,4‐ethylenedithiathiophene (DBEDTT) and 2,5‐diiodo‐3,4‐ethylenedithiathiophene (DIEDTT) under solventless and oxidant‐free conditions has been investigated. Effects of oxidants (Fe3+ salts, persulfate salts, peroxides, and Ce4+ salts), solvents (H2O, CH3CN/H2O, and CH3CN), surfactants, and so forth on polymerization reactions and properties of poly(3,4‐ethylenedithiathiophene) (PEDTT) were discussed. Characterizations indicated that FeCl3 was more suitable oxidant for oxidative polymerization of EDTT, while CH3CN was a better solvent to form PEDTT powders with higher yields and electrical conductivities. Dispersing these powders in aqueous polystyrene sulfonic acid (PSSH) solution showed better stability and film‐forming property than sodium dodecylsulfate and sodium dodecyl benzene sulfonate. Oxidative polymerization of EDTT in aqueous PSSH solutions formed the solution processable PEDTT dispersions with good storing stability and film‐forming performance. Solvent treatment showed indistinctive effect on electrical conductivity of free‐standing PEDTT films. As‐formed PEDTT synthesized from solid‐state polymerization showed similar electrical conductivity, poorer stability, but better thermoelectric property than oxidative polymerization. Contrastingly, PEDTT synthesized from DIEDTT showed higher electrical conductivity (0.18 S cm−1) than DBEDTT which showed better thermoelectric property with higher power factor value (6.7 × 10−9 W m−1 K−2). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Preparation of main‐chain imidazolium‐functionalized amphiphilic block copolymers through combination of condensation polymerization and nitroxide‐mediated free radical polymerization and their micelle study
Authors: Li Xue , Ni Xufeng , Liang Zhenhua , Shen Zhiquan
Published: February 2012

Main‐chain imidazolium‐functionalized amphiphilic block copolymers (PIL‐b‐PS) consisting of polyionic liquid (PIL) and polystyrene (PS) blocks have been first synthesized by condensation polymerization combined with nitroxide‐mediated free radical polymerization (NMP). The di‐functional imidazolium‐based ionic liquid (IL) having both hydroxyl and ester end groups was synthesized through Michael addition between imidazole and methylacrylate (MA) and further quaternization by 2‐chloroethanol. The HTEMPO (4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy) terminated polyionic liquid (HTEMPO‐PIL) as the hydrophilic block was prepared by condensation polymerization of di‐functional imidazolium IL and HTEMPO at a certain ratio. The hydrophobic PS block was synthesized by controlled radical polymerization of styrene using HTEMPO‐PIL through NMP, resulting PIL‐b‐PS block copolymers. The structure of block copolymers obtained has been characterized and verified by FTIR, 1H NMR, and size exclusion chromatography analyses. In addition, the morphology and size of the micelles formed by PIL‐b‐PS block copolymers in water were investigated by transmission electron microscopy and dynamic light scattering. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Fluorene‐ and benzimidazole‐based blue light‐emitting copolymers: Synthesis, photophysical properties, and PLED applications
Authors: Zhu Haifeng , Tong Hui , Gong Yongyang , Shao Shiyang , Deng Chunmei , Yuan Wang Zhang , Zhang Yongming
Published: February 2012

Blue light‐emitting materials are receiving considerable academic and industrial interest due to their potential applications in optoelectronic devices. In this study, blue light‐emitting copolymers based on 9,9′‐dioctylfluorene and 2,2′‐(1,4‐phenylene)‐bis(benzimidazole) moieties were synthesized through palladium‐catalyzed Suzuki coupling reaction. While the copolymer consisting of unsubstituted benzimidazoles (PFBI0) is insoluble in common organic solvents, its counterpart with N‐octyl substituted benzimidazoles (PFBI8) enjoys good solubility in toluene, tetrahydrofuran, dichloromethane (DCM), and chloroform. The PFBI8 copolymer shows good thermal stability, whose glass transition temperature and onset decomposition temperature are 103 and 428 °C, respectively. Its solutions emit blue light efficiently, with the quantum yield up to 99% in chloroform. The electroluminescence (EL) device of PFBI8 with the configuration of indium‐tin oxide/poly(ethylenedioxythiophene):poly(styrene sulfonic acid)/PFBI8/1,3,5‐tris(1‐phenyl‐1H‐benzimidazole‐2‐yl)benzene/LiF/Al emits blue light with the maximum at 448 nm. Such unoptimized polymer light‐emitting diode (PLED) exhibits a maximum luminance of 1534 cd/m2 with the current efficiency and power efficiency of 0.67 cd/A and 0.20 lm/W, respectively. The efficient blue emission and good EL performance make PFBI8 promising for optoelectronic applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
ATRP of styrene catalyzed by elemental Fe(0) and Br2: An easy and economical ATRP process
Authors: Yu Huali , Zhang Zhengbiao , Cheng Zhenping , Zhu Jian , Zhou Nianchen , Zhang Wei , Zhu Xiulin
Published: February 2012

In this work, zero‐valent iron (Fe(0)) (powder or wire) and elemental bromine (Br2) were used as the catalysts for atom transfer radical polymerization (ATRP) of styrene (St) without any additional initiator at 110 °C. The polymerizations happened with controlled evidence at appropriate molar ratio of Fe(0) to Br2: a remarkable increase of molecular weights with St conversions, the narrow molecular weight distributions and living polymer chains end‐capped by Br. More Br2 or less Fe(0) led to a slow polymerization rate but an improved control over molecular weights. After examining the polymer chain ends by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, it was concluded that the polymerization was initiated by thermal self‐initiation, and regulated by the in situ generated FeIIIBr3. The results suggested that the Fe(0)/Br2 catalyzing polymerization was a classical ATRP process with easier operation and more economical components. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Electrical bistability of organic devices with a polymeric thin film for nonvolatile data storage
Authors: Park Jae‐Eun , Eom Jae‐Hoon , Lim Taehoon , Hwang Do‐Hoon , Pyo Seungmoon
Published: February 2012

In this study, organic memory devices with a single active layer between the two external electrodes were fabricated using an electron‐donor type conjugated polymer and an electron‐acceptor type small organic molecule. The active layer of the memory device was prepared by blending polystyrene, poly[10‐(2′‐ethylhexyl)phenothiazine‐3,7‐diyl], and tetracyanoquinodimethane in 1,2‐dichlorobenzene. The device initially showed a low‐conductance state (OFF state) in the low‐voltage range, and an abrupt current increase, corresponding to the transition to a high‐conductance state (ON state), occurred at a certain voltage (Vth). The ON state could be reverted to the OFF state by applying a voltage higher than Vth. The current ratio between the two states was about 103 (up to 105). After this transition, the device remained in the ON state even after the applied voltage was removed, and this indicated the nonvolatile characteristics of the device. There was no sharp current degradation in the OFF or ON states for 4500 s of continuous bias. The device‐to‐device performance fluctuation was measured, and the conduction mechanisms in the ON and OFF states were examined by fitting the data to well‐known theoretical models. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis of amphiphilic tadpole‐shaped copolymers by combination of glaser coupling with living anionic polymerization and ring‐opening polymerization
Authors: Wang Guowei , Hu Bin , Fan Xiaoshan , Zhang Yannan , Huang Junlian
Published: February 2012

The tadpole‐shaped copolymers polystyrene (PS)‐b‐[cyclic poly(ethylene oxide) (PEO)] [PS‐b‐(c‐PEO)] contained linear tail chains of PS and cyclic head chains of PEO were synthesized by combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). First, the functionalized polystyrene‐glycerol (PS‐Gly) with two active hydroxyl groups at ω end was synthesized by LAP of St and the subsequent capping with 1‐ethoxyethyl glycidyl ether and then deprotection of protected hydroxyl group in acid condition. Then, using PS‐Gly as macroinitiator, the ROP of EO was performed using diphenylmethylpotassium as cocatalyst for AB2 star‐shaped copolymers PS‐b‐(PEO‐OH)2, and the alkyne group was introduced onto PEO arm end for PS‐b‐(PEO‐Alkyne)2. Finally, the intramolecular cyclization was performed by Glaser coupling reaction in pyridine/Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine system under room temperature, and tadpole‐shaped PS‐b‐(c‐PEO) was formed. The target copolymers and their intermediates were well characterized by size‐exclusion chromatography, proton nuclear magnetic resonance spectroscopy, and fourier transform infrared spectroscopy in details. The thermal properties was also determined and compared to investigate the influence of architecture on properties. The results showed that tadpole‐shaped copolymers had lower Tm, Tc, and Xc than that of their precursors of AB2 star‐shaped copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Effects of carbon nanotubes on polymer physics
Authors: Grady Brian P.
Published: February 2012

A single carbon nanotube has many similarities with an individual polymer chain including the fact that the end‐to‐end length of both are often about the same and the diameter of the chain is about the same (for single‐walled nanotubes) or only ∼10 to 20 times larger (for multiwalled nanotubes). The combination of the solid surface and the similarity of the two materials means that polymer physics are altered in manners not seen with any other type of commonly used filler. The purpose of this review is to update a chapter that appears in a recent tome by Grady (2011) and describe how polymer physics is altered in composites that contain carbon nanotubes. Subjects that will be discussed include chain configuration, glass transition, polymer diffusion, unit cells and crystalline superstructure (lamellae, spherulites and shish‐kebabs), and crystallization kinetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Organic transistors in the new decade: Toward n‐channel, printed, and stabilized devices
Authors: Kola Srinivas , Sinha Jasmine , Katz Howard E.
Published: February 2012

Significant progress has been made in designing organic semiconducting materials (OSCs) for the past few decades for organic field‐effect transistors (OFETs). Much attention has been paid to the development of p‐channel OSCs, with less but highly significant progress on n‐channel OSCs. In this review, we focus on the advances made with OFETs in the last few years to achieve high performance in n‐channel modes, air stability, and solution processability, leading to printable active electronics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Atmospheric Pressure Plasma Surface Modification of Poly(D,L‐lactic acid) Increases Fibroblast, Osteoblast and Keratinocyte Adhesion and Proliferation
Authors: Renò Filippo , D'Angelo Domenico , Gottardi Gloria , Rizzi Manuela , Aragno Davide , Piacenza Giacomo , Cartasegna Federico , Biasizzo Miriam , Trotta Francesco , Cannas Mario
Published: February 2012

An atmospheric pressure plasma deposition for P(d,L)LA (PLA) film was used to modify polymer surface properties using 1,2‐diaminopropane and acrylic acid as precursors. These two different plasma coatings result in a high density of amino groups (PLA‐NH2) and carboxylic groups (PLA‐COOH) onto PLA surface as demonstrated by Fourier transform infra‐red (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). Plasma coatings modified PLA surface wettability and proteins adsorption from fetal bovine serum (FBS), influencing cell adhesion and proliferation of 3T3 mouse fibroblast, MC‐3T3 E1 mouse pre‐osteoblast, and HaCaT cells (human keratinocytes). In particular both coatings increased pre‐osteoblast and keratinocyte adhesion while no effect was observed on fibroblast. Moreover, cell proliferation assessed after 48 h by Tox‐8 assay was significantly higher for osteoblast cells and keratinocyte seeded onto both PLA‐NH2 and PLA‐COOH compared to cells seeded onto normal PLA. On the basis of the obtained data, the atmospheric pressure plasma deposition described might represent an innovative and useful tool for bone and skin tissue engineering.

magnified image
Long‐chain Alkanes and ent‐Labdane‐type Diterpenes from Gymnosperma glutinosum with Cytotoxic Activity Against the Murine Lymphoma L5178Y‐R
Authors: Gomez‐Flores R. , Quintanilla‐Licea R. , Verde‐Star M. J. , Morado‐Castillo R. , Vázquez‐Díaz D. , Tamez‐Guerra R. , Tamez‐Guerra P. , Rodríguez‐Padilla C.
Published: February 2012

The antitumor potential of Gymnosperma glutinosum was previously reported using the in vitro and in vivo L5178Y‐R lymphoma murine model. The present study was carried out to isolate and identify the cytotoxic compounds present in the Gymnosperma glutinosum leaf hexane extract. Gymnosperma glutinosum was collected in the semi‐arid region of Escobedo, State of Nuevo León, México, but it is commonly found in northeastern Mexico; it is traditionally used as a treatment for diarrhea, ulcers and rheumatism. G. glutinosum leaves were extracted with hexane and further fractioned and subfractioned over silica gel by gradient elution with hexane, chloroform, ethyl acetate and methanol. The cytotoxicity of fractions and subfractions was assessed in vitro against L5178Y‐R lymphoma cells. Structure elucidation of the active compounds was determined by spectroscopic methods. Fractions and subfractions showed significant (p < 0.05) and concentration‐dependent 20% to 56% cytotoxicity against L5178Y‐R cells at concentrations ranging from 7.8 µg/mL to 500 µg/mL. The bioassay‐guided fractionation of the hexane extract resulted in the isolation and identification of the alkane hentriacontane and the diterpene ent‐labd‐7‐en‐13S,14R,15‐triol as the metabolites responsible for the activity. Copyright © 2012 John Wiley & Sons, Ltd.
The conformational preferences of acylphloroglucinols—a promising class of biologically active compounds
Authors: Kabanda Mwadham M. , Mammino Liliana
Published: February 2012

Acylphloroglucinols are a broad class of phloroglucinol derivatives characterized by the presence of a COR group, where R is more often an alkyl chain. They are largely present in natural sources and exhibit a variety of biological activities, including antibacterial, antiviral, antifungal, antitumor, antioxidant, and antimalarial. This work reports the results of a systematic conformational study (in vacuo, chloroform, acetonitrile, and water) of a representative number (118) of actual and model acylphloroglucinol structures, considering the most common R chains and investigating conformational preferences and relative energies as well as the influence of specific structural features characterizing significant subsets of compounds. The study aimed at identifying patterns for conformational preferences and at singling out the conformational aspects more closely related to the individuality of different structures, as these are expected to be more closely linked to the differences in the biological activities of different compounds. The results highlight patterns enabling reliable predictions of the conformational preferences of acylphloroglucinol molecules. © 2012 Wiley Periodicals, Inc.
A natural orbital functional based on an explicit approach of the two‐electron cumulant
Authors: Piris M.
Published: February 2012

The cumulant expansion gives rise to an useful decomposition of the two‐matrix in which the pair correlated matrix (cumulant) is disconnected from the antisymmetric product of the one‐matrices. The cumulant can be approximated in terms of two matrices, Δ and Π, which are explicit functions of the occupation numbers of the natural orbitals. It produces a natural orbital functional (NOF) that reduces to the exact expression for the total energy in two‐electron systems. The N‐representability positivity necessary conditions of the two‐matrix impose several bounds on the matrices Δ and Π. Appropriate forms of these matrices lead to different implementations of the NOF known in the literature as PNOFi (i = 1–5). The basic features of these functionals are reviewed here. The strengths and weaknesses of the different PNOFs are assessed. © 2012 Wiley Periodicals, Inc.
Assessing structural bonding aspects of multiband superconductors through impurity‐induced local lattice distortions: A case study on MgB2
Authors: Pishtshev Aleksandr , Klopov Mihhail
Published: February 2012

To examine how a change in the host cation affects the structural and bonding properties of the local ionic environment, we have performed a series of ab initio simulations of substitutional impurities such as zinc, copper, and zirconium ions incorporated into the magnesium sublattice of MgB2. It was shown that at a low doping level, the induced lattice distortions and additional forces are noticeable small. For the given set of substituents, it was also determined how the impurity ion modifies the initial charge distribution around the host cation position and therefore, affects both the overall picture of the electronic states involved in the chemical bonding and the intrinsic charge‐transfer channels. In the context of the cation properties, by analyzing specific changes in local charge structures caused by the presence of the impurity, the existence of two different trends in the Mg‐site substitution effect was found and discussed. © 2012 Wiley Periodicals, Inc.
Embedding scaling relations in Padé approximants: Detours to tame divergent perturbation series
Authors: Dhatt Sharmistha , Bhattacharyya Kamal
Published: February 2012

A divergent perturbation series is known to yield very unreliable results for observables even at moderate coupling strengths. One of the most popular techniques in handling such series is to express them as rational functions, but it is often faithful only for small coupling. We outline here how one can gain considerable advantages in the large‐coupling regime by properly embedding known asymptotic scaling relations for selected observables during construction of the aforesaid Padé approximants. Three new bypass routes are explored in this context. The first approach involves a weighted geometric mean of two neighboring PA. The second idea is to consider series for specific ratios of observables. The third strategy is to express observables as functionals of the total energy in the form of series expansions. Symanzik's scaling relation, and the virial and Hellmann–Feynman theorems, are used at appropriate places to aid each of the strategies. Pilot calculations on the ground‐state perturbation series of certain observables for the quartic anharmonic oscillator problem reveal readily the benefit and novelty. © 2012 Wiley Periodicals, Inc.
A DFT‐based potential energy surface for the H cluster
Authors: Barragán Patricia , Prosmiti Rita
Published: February 2012

A global potential energy surface (PES) for the H complex is presented based on density functional theory (DFT) calculations. We used the B3(H) hybrid functional, a specifically parameterized B3LYP functional for hydrogen‐only systems, and we first characterize the equilibrium H structure. In turn, by comparing with coupled clusterwith single, double and perturbative triples excitations (CCSD(T)) results, we show that the B3(H) predictions are in overall satisfactory and quantitative good agreement with these higher accurate ab initio data for all aspects of the potential, including the correct estimates asymptotic behavior at long H + H2 distances. Moreover, using the present surface we compute dissociation energies and dissociation enthalpies for the equilibrium H ⇋ H + H2 reaction, and compare them with the data available from experimental measurements. In general, a very good accord is found, with the theoretical values from both DFT/B3(H) and CCSD(T) computations to predict somehow a less bound H cluster than the experimental estimates. Such realistic representations of the potential surfaces of polyatomic systems are of particular interest for studying spectroscopy, collision, and/or fragmentation dynamics, and this is the first attempt for a reasonable description of the H PES suitable for future direct dynamics simulations. © 2012 Wiley Periodicals, Inc.
Excitation energy transfer in GFP‐X‐CFP model peptides (X = amino acids): Direct Versus through‐bridge energy transfers
Authors: Kawatsu Tsutomu , Hasegawa Jun‐ya
Published: February 2012

The excitation energy transfer (EET) between a fluorescent resonance energy transfer (FRET) pair, cyan fluorescent protein chromophore (CFPc)/ green fluorescent protein chromophore (GFPc), is used for measuring molecular proximity in experimental studies. In this article, the role of the bridging protein media has been investigated using the quantum chemical calculations for the EET electronic coupling. We adopted a model peptide connecting GFPc and CFPc, a GFPc‐X‐CFPc model, and examined the X (amino acids) dependence. The major part of the EET coupling element arises from the direct interaction between GFPc and CFPc via the Förster mechanism. The magnitude of the through‐X interactions vary for the type of residues. The contribution of the X was, however, at most 10% of the total value. Together with the contributions from through‐peptide and charge‐transfer types, X gives minor modifications to the total coupling via the super‐exchange mechanism. © 2012 Wiley Periodicals, Inc.
Study on the noncovalent interactions of saikosaponins and cytochrome c by electrospray ionization mass spectrometry
Authors: Liu Yingzhi , Su Bo , Wang Xian
Published: February 2012

RATIONALE

The study of interactions between protein and pharmaceutical molecules including natural extracts has become of increasing interest in biological and biomedical research. An investigation of the interaction between saikosaponins and cytochrome c (Cyt c) by electrospray ionization mass spectrometry (ESI‐MS) is described in this study. Saikosaponins are found in Bupleurum falcatum (a flowering plant), and they are glycosides that consist of saccharides and the sapogenins of triterpenoids.

METHODS

Seven model molecules of saccharides and triterpenes, namely maltose (Mal II), maltotriose (Mal III), raffinose (Raf), and stachyose (Sta), glycyrrhetinic acid (Gly), ursolic acid (Urs) and oleanic acid (Ole), were chosen to perform a series of ESI‐MS control experiments for the exploration of the interaction groups in saikosaponins with Cyt c. The dissociation constants of detected noncovalent complexes were determined by using a direct ESI‐MS assay.

RESULTS

We have observed in the ESI mass spectra the formation of Cyt c complexes with saikosaponins a and c, and these saccharides, with 1:1 and 1:2 stoichiometry. Our results showed that no complex ions of triterpenes and Cyt c were detected in the ESI‐MS and similar Kd values were obtained for the Cyt c complexes of saikosaponins and saccharides. This demonstrates that the glycosyl moiety in the saikosaponins is the effective interaction group with Cyt c. We propose that saikosaponins and saccharides interact with Cyt c by hydrogen bonds. The binding affinity of these six ligands with Cyt c is shown to be in the order Ssa > Ssc > Raf, Mal III > Sta ≥ Mal II.

CONCLUSIONS

The ESI‐MS methodology presented in this study enables us to investigate the interactions of saikosaponins with Cyt c, and allows the direct determination of binding constants. These results could guide further research for providing insights into the structure‐binding relationship of ligands with Cyt c. Copyright © 2012 John Wiley & Sons, Ltd.
Isotopic values of the Amazon headwaters in Peru: comparison of the wet upper Río Madre de Dios watershed with the dry Urubamba‐Apurimac river system
Authors: Lambs L. , Horwath A. , Otto T. , Julien F. , Antoine P.‐O.
Published: February 2012

RATIONALE

The Amazon River is a huge network of long tributaries, and little is known about the headwaters. Here we present a study of one wet tropical Amazon forest side, and one dry and cold Atiplano plateau, originating from the same cordillera. The aim is to see how this difference affects the water characteristics.

METHODS

Different kind of water (spring, lake, river, rainfall) were sampled to determine their stable isotopes ratios (oxygen 18/16 and hydrogen 2/1) by continuous flow isotope ratio mass spectrometry (IRMS). These ratios coupled with chemical analysis enabled us to determine the origin of the water, the evaporation process and the water recycling over the Amazon plain forest and montane cloud forest.

RESULTS

Our study shows that the water flowing in the upper Madre de Dios basin comes mainly from the foothill humid forest, with a characteristic water recycling process signature, and not from higher glacier melt. On the contrary, the water flowing in the Altiplano Rivers is mainly from glacier melts, with a high evaporation process. This snow and glacier are fed mainly by Atlantic moisture which transits over the large Amazon forest.

CONCLUSIONS

The Atlantic moisture and its recycling over this huge tropical forest display a progressive isotopic gradient, as a function of distance from the ocean. At the level of the montane cloud forest and on the altiplano, respectively, additional water recycling and evaporation occur, but they are insignificant in the total water discharge. Copyright © 2012 John Wiley & Sons, Ltd.