bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Model for Barrier Frequencies for Enzymatic Reactions
Authors: Tuñón Iñaki , Hynes James T.
Published: December 2010

We present a simple model to rationalize the effects of environment on the reaction barrier frequencies derived from free energy profiles. These frequencies are relevant in deviations of a rate constant from its transition state theory value and in determining which environmental dynamics participate in the reaction. In particular, this simple model can be used to understand the changes in the reaction barrier frequencies of an enzymatic catalyzed reaction and the corresponding uncatalyzed process in aqueous solution, a change which has implications for dynamical environmental effects on the enzymatic reaction. Two possible cases are analyzed, in which the polarity (charge separation/localization) of the reacting system increases or decreases as the reaction advances. A simple modeling of the environment′s effects allows the explanation of an unusual “inverse” effect on the reaction frequencies, that is, a free energy barrier lowering accompanied by an increase of the reaction frequency, a behavior observed in some enzymes. The model predictions are successfully compared with results from full simulations for four different enzyme reactions.
Neuronal polarization: The cytoskeleton leads the way
Authors: Stiess Michael , Bradke Frank
Published: December 2010

The morphology of cells is key to their function. Neurons extend a long axon and several shorter dendrites to transmit signals in the nervous system. This process of neuronal polarization is driven by the cytoskeleton. The first and decisive event during neuronal polarization is the specification of the axon. Distinct cytoskeletal dynamics and organization of the cytoskeleton determine the future axon while the other neurites become dendrites. Here, we will review how the cytoskeleton and its effectors drive axon specification and neuronal polarization. First, the role of the actin cytoskeleton and microtubules in axon specification will be presented. Then, we will discuss the role of the centrosome in axon determination as well as how microtubules are generated in axons and dendrites. Finally, we will discuss potential mechanisms leading to axon specification, such as positive feedback loops that could be a coordinated interaction between actin and microtubules. Together, this review will present the recent advances on the role of the microtubules and the actin cytoskeleton during neuronal polarization. We will pinpoint the upcoming challenges to gain a better understanding of neuronal polarization on a fundamental intracellular level. Finally, we will outline how reactivation of the intrinsic polarization program may help to induce axon regeneration after CNS injury. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 71: 430–444, 2011
Implication of Wnt signaling in neuronal polarization
Authors: Yang Guo‐Ying , Luo Zhen‐Ge
Published: December 2010

Wnt ligands comprise a large family of secreted glycoproteins that control a variety of developmental processes including cell polarization in diverse organisms. Through various receptors present on receiving cells, Wnts initiate intracellular signaling cascades resulting in changes in gene transcription or cytoskeleton reorganization. Recently, several lines of evidence have suggested the role of Wnt signaling in establishing axon–dendrite polarity in developing neurons. In this review, we summarize the recent results related with the role of Wnt signaling in neuronal polarization. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 71: 495–507, 2011
Voltammetry Coupled with Multiway Chemometrics for Monitoring and Diagnosis of Electrodeposition Process
Authors: Jaworski Aleksander , Wikiel Hanna , Wikiel Kazimierz
Published: December 2010

A system for plating bath process monitoring and diagnosis was developed utilizing a novel approach that combines voltammetric methods with various statistical determinant analysis methods coupled with multiway data decomposition. The voltammetric methods employed were designed to provide a current response predominantly affected by the presence of specific contaminants while being practically insensitive to the varying concentrations of deliberately added bath constituents and other likely bath contaminants. The shape differences between deformed and training set voltammograms were quantified and visualized using two outlier detection chemometric techniques (Mahalanobis Distance (D) and D coupled with Q‐residuals (DQ)) coupled with three‐way decomposition PARAllel FACtor Analysis (PARAFAC) method. The specificity of the response to the presence of a likely contaminant combined with the multi‐parameter quantification of its presence enabled not only early‐fault detection but also its diagnosis, thereby automating the troubleshooting process.
Development of Capillary‐Based SECM Probes for the Characterization of Cell Arrangements for Electrochemically Assisted Injection
Authors: Palatzky Peter , Matysik Frank‐Michael
Published: December 2010

Electrochemically‐assisted injection (EAI) is a new injection concept for capillary electrophoresis (CE). It enables the separation of neutral analyte species by electrochemical ion formation during the injection process. Novel amperometric capillary probes with an integrated microwire electrode have been developed for the characterization of EAI cell arrangements. A scanning electrochemical microscope (SECM) was used for precise positioning of the capillary probes. The capillary‐based SECM probes were characterized regarding their voltammetric behaviour and reproducibility of measurements in the context of EAI injection protocols. These novel SECM probes enabled the study of capillary‐to‐electrode distances and corresponding dependences on the precision of EAI measurements.
The effects of environmental low-dose irradiation on tolerance to chemotherapeutic agents
Authors: Howell Eric K , Gaschak Sergey P , Griffith Kenneth D. W , Rodgers Brenda E
Published: December 2010

The nuclear disaster at Chernobyl, Ukraine, in April of 1986 continues to impact the environment on many different levels. Studies of epidemiological, environmental, and genetic impacts have been prolific since the accident, revealing interesting results concerning the effects of radiation. The long-tailed field mouse, Apodemus flavicollis, was collected from distinct localities near the Chernobyl site and evaluated based on in vivo responses to the current clinically employed chemotherapeutic agents bleomycin (BLM) and vinblastine (VBL), as well as the immune modulator lipopolysaccharide (LPS). Maximum tolerable doses of three different cancer drugs were administered to the rodents from three different lifestyles: native mice living and reproducing in a radioactive environment, native mice living and reproducing in an uncontaminated region, and laboratory-reared mice (Mus musculus BALB/c) with a known sensitivity to the chemical agents tested. The endpoints employed include micronucleus formation, immune cell induction, differential gene expression, and chemotherapeutic side effects such as lethargy and weight loss. In accordance with the well-studied phenomenon termed radio-adaptation, we observed varied tolerance to chemotherapeutic treatment dependent on history of ionizing radiation exposure. The results of the present study demonstrate a differential response to chemotherapeutic treatment with respect to previous levels of radiation exposure, suggesting a potential benefit associated with low-dose radiation exposure. Data reported herein could have a profound impact on the development of novel cancer treatments involving low-dose ionizing radiation. Environ. Toxicol. Chem. 2011; 30:640–649. © 2010 SETAC
Selecting effective divestments in electricity generation markets
Authors: Federico Giulio , López Ángel L.
Published: December 2010

We study the impact of electricity divestments in a stylised model where a dominant producer faces a competitive fringe with the same cost structure and is forced to sell some of its capacity. For a given demand level, the divestment which achieves the greatest reduction in prices can be several times more effective in reducing prices than a divestment of baseload (or low‐cost) plants. We extend this theoretical result to the case with variable electricity demand by considering a numerical example based on data from the Italian market. Copyright © 2010 John Wiley & Sons, Ltd.
Price‐based control of ancillary services for power balancing
Authors: van den Bosch P. P. J. , Jokic A. , Frunt J. , Kling W. L. , Nobel F. , Boonekamp P. , de Boer W. , Hermans R. M. , Virag A.
Published: December 2010

A reliable and an efficient power system is a necessity for any industrialized society. Governments have to enforce regulations to guarantee that such a power system, in spite of many competing stakeholders, participants, companies, and regulating agencies can be operational. This paper analyzes the present arrangements and the future requirements to be posed on incentives and regulation for ancillary services (AS) for power balancing. The paper proposes companies to assess their own needs for AS. A two‐sided market for AS is being described to replace the existing arrangements for secondary control. The proposed solution guarantees a reliable and efficient operation of power systems in a market environment with responsive, reliable, and accountable but also competing prosumers, a large penetration of less‐predictable renewables and continent‐spanning transmission networks. Copyright © 2010 John Wiley & Sons, Ltd.
Instantaneous active and reactive current control technique of shunt active power filter based on the three‐level NPC inverter
Authors: Pouresmaeil Edris , Montesinos‐Miracle Daniel , Gomis‐Bellmunt Oriol , Sudrià‐Andreu Antoni
Published: December 2010

In this paper, the synthesis and performance of a shunt active power filter (SAPF) based on instantaneous active, and reactive current components (id − iq) technique is presented. The proposed active filter acts as a current source, which is connected in parallel with a nonlinear load and controlled to generate the required compensation currents. The proposed control technique for SAPF aims to compensate the harmonic current contents of nonlinear loads by connection of distributed generation (DG) resources based on renewable energy sources to distribution network. This modeling is derived from the 123(abc) to αβ and αβ to dq transformation of the ac system variables. The injected currents by the SAPF to polluted grid are controlled in synchronous orthogonal dq reference frame by using of decoupled current control technique. By use of phase locked loop (PLL) in control circuit of proposed technique, the angle of positive sequence has been detected, in order to synchronize the SAPF injected currents to distribution network. The proposed control strategy has this ability to eliminate wide range of harmonic frequency draws from utility grid, and provide the compensation currents by DG resources. By this control method, replacement of distributed power generation systems as an active power filter can be possible. Three‐phase three‐level neutral‐point‐clamped (NPC) voltage source inverter (VSI) is proposed for the interfacing between renewable energy resources and polluted distribution network. The simulation results demonstrate high performances of proposed SAPF technique. Copyright © 2010 John Wiley & Sons, Ltd.
Protein expression of cancer testis antigens predicts tumor recurrence and treatment response to imatinib in gastrointestinal stromal tumors
Authors: Perez Daniel , Hauswirth Fabian , Jäger Dirk , Metzger Urs , Samartzis Eleftherios Pierre , Went Philip , Jungbluth Achim
Published: December 2010

Cancer testis antigens (CTAs) have been identified in various tumors as immunological tumor targets. In gastrointestinal stromal tumor (GIST), the prediction of malignant potential remains difficult but is crucial in the era of adjuvant imatinib treatment. Here, we analyzed the impact of CTAs on tumor recurrence and its role on the treatment response to imatinib. The expression of the most frequent CTAs MAGE‐A1, MAGE‐A3, MAGE‐A4, MAGE‐C1 and NY‐ESO‐1 was analyzed by immunohistochemistry. The duration between the initial operation and the tumor relapse was defined as recurrence free survival (RFS). All recurrent cases were treated with imatinib. The tumor response to imatinib was graded according to the modified CT response evaluation criteria. Patients with a CTA positive GIST (n = 23, 27%) had a significantly shorter RFS (p = 0.001) compared to negative cases (n = 63, 73%). The median RFS was 25 months in CTA positive patients and was not reached during the study period in CTA negative patients. According to the established staging criteria CTA positive tumors were predominantly high‐risk tumors (p = 0.001). The expression of MAGE‐A3 (p = 0.018) and NY‐ESO‐1 (p = 0.001) were associated with tumor progression under imatinib treatment. A tendency for worse tumor response to imatinib was observed in CTA positive tumors (p = 0.056). Our study confirms the expression of CTAs in GIST and their role as prognostic markers. It also draws attention to the potential impact of CTAs on the tumor response to imatinib.
Effect of irrigation water and processing on the microbial quality of lettuces produced and sold on markets in Dakar (Senegal)
Authors: Ndiaye M.L. , Niang S. , Pfeifer H.‐R. , Peduzzi R. , Tonolla M. , Dieng Y.
Published: December 2010

The aim of this survey is to assess the microbiological impact of irrigation water on lettuces produced on two urban agricultural sites and sold on markets; 6 and 7%, respectively, of lettuces coming from the sites of Pikine and Patte d'Oie were Salmonella spp. positive. Lettuces irrigated with shallow groundwater (“Céanes” water) were more contaminated (8% at both Pikine and Patte d'Oie sites) compared to those irrigated with wastewater (4% at Pikine) or well water (5% at Patte d'Oie). As for the lettuces in marketplaces, their contamination seems to depend on the type of treatment occurring before sale. Lettuces previously washed in the “Céanes” were more contaminated than those rinsed with tap water at the marketplace. Salmonella spp. have been isolated from all marketplaces. However, the rates of contamination in markets surrounding Patte d'Oie are higher (9 and 11% at Grand Yoff and Dalifort) than those surrounding Pikine (4 and 2% at Zinc and Sham) or Rufisque, the control (2%). Our results confirm that the reuse of wastewater in irrigation is an alternative to animal manure. Its risk of microbial contamination can be significantly reduced by washing the vegetables with tap water before they are sold. Copyright © 2010 John Wiley & Sons, Ltd.
Silybin and dehydrosilybin decrease glucose uptake by inhibiting GLUT proteins
Authors: Zhan Tianzuo , Digel Margarete , Küch Eva‐Maria , Stremmel Wolfgang , Füllekrug Joachim
Published: December 2010

Silybin, the major flavonoid of Silybum marianum, is widely used to treat liver diseases such as hepatocellular carcinoma and cirrhosis‐associated insulin resistance. Research so far has focused on its anti‐oxidant properties. Here, we demonstrate that silybin and its derivative dehydrosilybin inhibit glucose uptake in several model systems. Both flavonoids dose‐dependently reduce basal and insulin‐dependent glucose uptake of 3T3‐L1 adipocytes, with dehydrosilybin showing significantly stronger inhibition. However, insulin signaling was not impaired, and immunofluorescence and subcellular fractionation showed that insulin‐induced translocation of GLUT4 to the plasma membrane is also unchanged. Likewise, hexokinase activity was not affected suggesting that silybin and dehydrosilybin interfere directly with glucose transport across the PM. Expression of GLUT4 in CHO cells counteracted the inhibition of glucose uptake by both flavonoids. Moreover, treatment of CHO cells with silybin and dehydrosilybin reduced cell viability which was partially rescued by GLUT4 expression. Kinetic analysis revealed that silybin and dehydrosilybin inhibit GLUT4‐mediated glucose transport in a competitive manner with Ki = 60 and 116 µM, respectively. We conclude that silybin and dehydrosilybin inhibit cellular glucose uptake by directly interacting with GLUT transporters. Glucose starvation offers a novel explanation for the anti‐cancer effects of silybin. J. Cell. Biochem. 112: 849–859, 2011. © 2010 Wiley‐Liss, Inc.
Task‐parallel message passing interface implementation of Autodock4 for docking of very large databases of compounds using high‐performance super‐computers
Authors: Collignon Barbara , Schulz Roland , Smith Jeremy C. , Baudry Jerome
Published: December 2010

A message passing interface (MPI)‐based implementation (Autodock4.lga.MPI) of the grid‐based docking program Autodock4 has been developed to allow simultaneous and independent docking of multiple compounds on up to thousands of central processing units (CPUs) using the Lamarkian genetic algorithm. The MPI version reads a single binary file containing precalculated grids that represent the protein–ligand interactions, i.e., van der Waals, electrostatic, and desolvation potentials, and needs only two input parameter files for the entire docking run. In comparison, the serial version of Autodock4 reads ASCII grid files and requires one parameter file per compound. The modifications performed result in significantly reduced input/output activity compared with the serial version. Autodock4.lga.MPI scales up to 8192 CPUs with a maximal overhead of 16.3%, of which two thirds is due to input/output operations and one third originates from MPI operations. The optimal docking strategy, which minimizes docking CPU time without lowering the quality of the database enrichments, comprises the docking of ligands preordered from the most to the least flexible and the assignment of the number of energy evaluations as a function of the number of rotatable bounds. In 24 h, on 8192 high‐performance computing CPUs, the present MPI version would allow docking to a rigid protein of about 300K small flexible compounds or 11 million rigid compounds. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011
Lipid raft localization of EGFR alters the response of cancer cells to the EGFR tyrosine kinase inhibitor gefitinib
Authors: Irwin Mary E. , Mueller Kelly L. , Bohin Natacha , Ge Yubin , Boerner Julie L.
Published: December 2010

Epidermal growth factor receptor (EGFR) is overexpressed in many cancer types including ∼30% of breast cancers. Several small molecule tyrosine kinase inhibitors (TKIs) targeting EGFR have shown clinical efficacy in lung and colon cancers, but no benefit has been noted in breast cancer. Thirteen EGFR expressing breast cancer cell lines were analyzed for response to EGFR TKIs. Seven were found to be EGFR TKI resistant; while shRNA knockdown of EGFR determined that four of these cell lines retained the requirement of EGFR protein expression for growth. Interestingly, EGFR localized to plasma membrane lipid rafts in all four of these EGFR TKI‐resistant cell lines, as determined by biochemical raft isolation and immunofluorescence. When lipid rafts were depleted of cholesterol using lovastatin, all four cell lines were sensitized to EGFR TKIs. In fact, the effects of the cholesterol biosynthesis inhibitors and gefitinib were synergistic. While gefitinib effectively abrogated phosphorylation of Akt‐ and mitogen‐activated protein kinase in an EGFR TKI‐sensitive cell line, phosphorylation of Akt persisted in two EGFR TKI‐resistant cell lines, however, this phosphorylation was abrogated by lovastatin treatment. Thus, we have shown that lipid raft localization of EGFR correlates with resistance to EGFR TKI‐induced growth inhibition and pharmacological depletion of cholesterol from lipid rafts decreases this resistance in breast cancer cell lines. Furthermore, we have presented evidence to suggest that when EGFR localizes to lipid rafts, these rafts provide a platform to facilitate activation of Akt signaling in the absence of EGFR kinase activity. J. Cell. Physiol. 226: 2316–2328, 2011. © 2010 Wiley‐Liss, Inc.
Delay in treatment of early‐stage hepatocellular carcinoma using radiofrequency ablation may impact survival of cirrhotic patients in a surveillance program
Authors: Chen Wei‐Ting , Fernandes Mark Lee , Lin Chen‐Chun , Lin Shi‐Ming
Published: December 2010

Background

The aim of this study was to evaluate the impact of the interval between diagnosis and treatment using radiofrequency (RF) ablation on the survival of patients with HCC detected through a surveillance program.

Methods

Between January 2004 and July 2007, 121 cirrhotic patients with 157 tumours detected through a surveillance program underwent RF ablation. A delay in treatment was defined as >5 weeks. The mean length of follow‐up was 25 months (range 8–55 months). Cumulative survival of patients was analysed using the Kaplan–Meier method. Cox regression models were used to identify factors associated with patient survival.

Results

The 1‐, 2‐ and 3‐year survival rates were 92.5%, 78.5% and 67.2%. The independent predictors of poorer patient survival were time from diagnosis to treatment >5 weeks (pooled odds ratio [OR], 3.59; 95% confidence interval [CI], 1.58–8.18; P = 0.002), absence of complete ablation after the initial RF session (OR, 2.42; 95% CI 1.07–5.45; P = 0.033) and Child‐Pugh B liver cirrhosis (OR, 2.46; 95% CI 1.06–5.70; P = 0.036).

Conclusions

Delay in the start of effective treatment for HCC using RF ablation may be associated with poorer patient survival. J. Surg. Oncol. 2011; 103:133–139. © 2010 Wiley‐Liss, Inc.
Evaluation of the effects of type II radical hysterectomy in the treatment of 960 patients with stage IB–IIB cervical carcinoma: A retrospective study
Authors: Zheng Min , Huang Long , He Li , Ding Hui , Wang Hui‐Yun , Zheng Li‐Min
Published: December 2010

Background and Objectives

This retrospective study evaluated the feasibility and effectiveness of type II radical hysterectomies alone, or in combination with adjuvant treatment, for the treatment of patients with stage IB–IIB cervical cancer with or without high‐risk factors.

Methods

A total of 960 stage IB–IIB patients who underwent type II radical hysterectomies between 1995 and 2004 were enrolled and retrospectively analyzed.

Results

Uterine corpus invasion, parametrial margin involvement, and pelvic lymph node metastasis were identified as independent prognostic factors for stage IB patients. For stage IIA–IIB patients, histologic type, parametrial margin involvement, and pelvic lymph node metastasis were identified as independent prognostic factors. The 5‐year overall survival (OS) rates for patients with stage IB versus stage IIA–IIB cervical carcinomas were 88.4% and 78.5%, respectively. Moreover, adjuvant radiotherapy and chemotherapy improved the 5‐year OS rates of stage IIA–IIB patients associated with high‐risk factors. The overall recurrence rate for this cohort was 14.4%.

Conclusions

Our findings show that type II radical hysterectomy is a feasible treatment option for stage IB–IIB cervical carcinoma patients. Furthermore, type II radical hysterectomy combined with adjuvant post‐operative therapy improves the OS of women with high‐risk factors for cervical carcinoma. J. Surg. Oncol. 2011; 103:435–441. © 2010 Wiley‐Liss, Inc.
Information seeking behaviors of parents whose children have life‐threatening illnesses
Authors: Knapp Caprice , Madden Vanessa , Marcu Mircea , Wang Hua , Curtis Charlotte , Sloyer Phyllis , Shenkman Elizabeth
Published: December 2010

Objectives

For children with life‐threatening illnesses we sought to (1) understand the associations between parental characteristics and preferred health information sources, and (2) assess the e‐health literacy of Internet‐users.

Study Design

Cross‐sectional, telephone survey of 129 parents whose children are in a pediatric palliative care program in Florida.

Results

Four out of five parents report that they use the Internet, and 64% of Internet‐users use it daily. Parents who never use the Internet, versus parents who do use the Internet, are predominately Hispanic (50%) and have less than a high school education (64%) (P ≤ 0.023). Internet‐users have high levels of e‐health literacy; however, they are not confident or are unsure about the quality of information on the Internet. Not having graduated from high school was associated with a decrease in e‐health literacy and using the Internet as the primary information source (vs. doctor as primary source) was associated with an increase in e‐health literacy.

Conclusion

Parents of children with life‐threatening illnesses have access to and use the Internet as a source of information about their children's health. More information is needed to explore how electronic‐based interventions could be used to impact information seeking of parents whose children are in pediatric palliative care programs. Pediatr Blood Cancer 2011;56:805–811. © 2010 Wiley‐Liss, Inc.
Cancer risk with tumor necrosis factor alpha (TNF) inhibitors: meta‐analysis of randomized controlled trials of adalimumab, etanercept, and infliximab using patient level data
Authors: Askling Johan , Fahrbach Kyle , Nordstrom Beth , Ross Susan , Schmid Christopher H. , Symmons Deborah
Published: December 2010

Purpose

Uncertain short‐ and long‐term cancer risks with anti‐TNF therapies is a concern, and led to a recent black box warning. This meta‐analysis, requested by the European Medicines Agency, aimed at better assessing short‐term risks by using meta‐analytic techniques based on individual patient data from all corporate‐sponsored randomized controlled trials (RCTs) of adalimumab, etanercept, and infliximab.

Methods

All 74 RCTs of TNF inhibitors of at least 4 weeks duration were provided to independent investigators, including case narratives for events occurring between trial start until 30 days after planned end of treatment and indicating a possible cancer. Relative risks were estimated using Bayesian piecewise exponential models.

Results

One hundred thirty (0.84%) of 15 418 individuals randomized to anti‐TNF therapy were diagnosed with cancer, compared to 48 (0.64%) of 7486 individuals randomized to comparators. The relative risks associated with all anti‐TNF were 0.99 (95%CI 0.61–1.68) for cancers excluding non‐melanoma skin cancer (NMSC), and 2.02 (95%CI 1.11–3.95) for NMSC. There were indications of differences in the relative risks for the three anti‐TNF drugs, but also of differences across the cancer rates in the three comparator arms for adalimumab, etanercept, and infliximab.

Conclusions

Despite a reassuring overall short‐term risk, we could neither refute nor verify that individual anti‐TNF therapies affect the short‐term clinical emergence of cancer. Despite representing the best available evidence, statistical precision, and differences in baseline cancer risk and reporting detail between trials of adilumumab, etanercept, and infliximab hampered distinction of drug‐specific from trial effects, illustrating the challenges in safety‐assessments using RCT meta‐analyses. Long‐term risk assessment requires observational studies. Copyright © 2010 John Wiley & Sons, Ltd.
An exploratory analysis of the NEO‐FFI and DSM personality disorders using multivariate canonical correlation
Authors: Aboaja Anne , Duggan Conor , Park Bert
Published: December 2010

It has been argued that some of the difficulties in the Diagnostic and Statistical Manual of Mental Disorders (DSM) personality disorders might be overcome by examining their association with measures of general personality such as the Neuroticism, Extroversion and other Five‐Factor Inventory (NEO‐FFI) model. The study explored associations between the NEO‐FFI and DSM personality disorder in 85 male offenders referred to a personality disorder unit. Although simple correlation showed the expected associations, multivariate canonical correlation revealed more complex and novel associations such as the finding that borderline personality disorder has a more robust conceptual relationship than antisocial personality disorder with the NEO‐FFI. Overall, the NEO‐FFI can be used to conceptualize most DSM personality disorders. Copyright © 2010 John Wiley & Sons, Ltd.
The mechanism of aromatic nucleophilic substitution reaction between ethanolamine and fluoro‐nitrobenzenes: an investigation by kinetic measurements and DFT calculations
Authors: Jose K.B. , Cyriac J. , Moolayil J. T. , Sebastian V.S. , George M.
Published: December 2010

We have studied the kinetics and elucidated the mechanism by DFT calculation of the reaction between ethanolamine (EOA) and 1‐fluoro‐2,4‐dinitrobenzene (DNFB) in acetonitrile and toluene. To determine the contribution of the nitro group, the activation energy of the reaction between ethanolamine and 1‐fluoro‐2‐nitrobenzene (MNFB) vs. DNFB was determined in acetonitrile and calculated by DFT method. Kinetic measurements reveal that the reaction is faster in acetonitrile than in toluene. The reaction follows overall second‐order kinetics: first order with respect to both EOA and DNFB which is similar to the results reported for reaction between other primary amines and 1‐substituted‐2,4‐dinitrobenzenes. The calculations by using DFT methods reveal that the mechanism of the reaction involves the formation and decomposition of a Meisenheimer complex (MC). DFT calculations also reveal that the activation energy of the reaction is highest in vacuum and decreases with increasing polarity of the solvent reaching a minimum in acetonitrile. In addition, activation energies obtained by both DFT calculations and experiments show that the reactivity of MNFB is less than that of DNFB showing the effect of the 4‐nitro group. Copyright © 2010 John Wiley & Sons, Ltd.
Pd(0)‐catalyzed polycondensation of aryl‐substituted propargylic carbonates with bifunctional nucleophiles promoted by aryl group on the acetylenic terminal carbon
Authors: Nishioka Noriyuki , Koizumi Toshio
Published: December 2010

A Pd(0)‐catalyzed polycondensation of bifunctional nucleophiles and propargylic carbonates having an aryl group was investigated. The polycondensation was carried out for tetrahydrofuran at 60 °C for 3 h in the presence of Pd(0) catalyst. The Pd(0)‐catalyzed polycondensation of phenyl‐substituted propargylic carbonates and nucleophiles proceeded efficiently, when bis[(2‐diphenylphosphino)phenyl]ether was used as the ligand. We found that the position of the phenyl group was crucial for the successful polycondensation. The introduction of a phenyl group on the acetylenic terminal carbon remarkably promoted the polycondensation and afforded high molecular weight polymers. On the other hand, a phenyl group at the propargylic position was not effective. Propargylic carbonates having a substituted phenyl group were also examined. Electron‐withdrawing group‐substituted phenyl groups on the acetylenic terminal carbon were found to be more effective for the polycondensation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Optical gain in silicon nanocrystals: Current status and perspectives
Authors: Pelant Ivan
Published: December 2010

The article presents a short overview of the worldwide experimental activity directed towards vindicating the occurrence of positive optical gain in dense assemblies of luminescent silicon nanocrystals. In spite of an intense interest in the field, the achieved results are non‐uniform till now. Hints how to proceed further are given.
Excitons in a cylindrical GaAs Pöschl–Teller quantum dot
Authors: Mora‐Ramos M. E. , Barseghyan M. G. , Duque C. A.
Published: December 2010

The exciton binding energy in a cylindrical quantum dot (QD) with Pöschl–Teller confining potential is studied with the use of the effective mass approximation and a variational calculation procedure. A GaAs prototype structure is particularly considered and both the spatially‐direct (DE) and spatially‐indirect (IE) exciton regimes are taken into account. We show that there is a significant effect of the Pöschl–Teller quantum well (QW) symmetry profile on the exciton properties in both configurations.
Variation of hydrogen adsorption with increasing Li doping on carbon nanotubes
Authors: Rangel E. , Ramirez‐de‐Arellano J. M. , Magana L. F.
Published: December 2010

Density functional theory (DFT) and molecular dynamics (MD) were used to study hydrogen adsorption on the external surface of single‐walled carbon nanotubes decorated with Li. We considered doping ratios of C64Li, C8Li, and C4Li. We found that these systems could store up to 0.77, 3.7, and 7.6 wt.% hydrogen, respectively, at atmospheric pressure and 300 K. The latter case satisfies the requirement for technological applications. However, experimentally, carbon nanotubes are in bundles. Therefore, we studied a bundle of nanotubes each with coverage C4Li, under the same conditions. We found that the hydrogen storage capacity is drastically reduced to 2.7 wt.%. This figure is very similar to experimental results.
Size‐, dimensionality‐, and composition‐dependent Debye temperature of monometallic and bimetallic nanocrystals in the deep nanometer scale
Authors: Yang C. C. , Li S.
Published: December 2010

A nanothermodynamic model was established to describe the Debye temperature of monometallic and bimetallic nanocrystals in the deep nanometer scale with respect to the effects of size, dimensionality, and also composition. The results indicate that the Debye temperature decreases with decreasing crystal size for both monometallic and bimetallic nanocrystals, which is consistent with the experimental data. With considering the physicochemical properties of monometallic and bimetallic nanocrystals in the sub‐5 nm scale, the developed model may provide new insight into the fundamental understanding of their thermal stability for applications in heterogeneous catalysis, sensors as well as microelectronic devices.
Perspective: Björn Roos and direct configuration interaction
Authors: Shavitt Isaiah
Published: December 2010

The introduction, impact, and development of the direct configuration interaction (CI) approach are reviewed. The removal of the limitation on the size of CI calculation by eliminating the need to store the Hamiltonian matrix and the streamlining of the calculation of the eigenvector updates in each iteration are seen to be the key transformative contributions of this approach. The initial introduction, limited to closed‐shell single‐reference CISD (CI with single and double excitations) calculations, underwent successive generalizations, culminating in procedures based on the graphical unitary group approach, allowing applications to multireference CISD calculations for any electronic state. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111:3263–3266, 2010
Unique para‐effect in electron ionization mass spectra of bis(perfluoroacyl) derivatives of bifunctional aminobenzenes
Authors: Tretyakov Kirill V. , Todua Nino G. , Borisov Roman S. , Zaikin Vladimir G. , Stein Stephen E. , Mikaia Anzor I.
Published: December 2010

A new kind of ‘para‐effect’ under electron ionization (EI) conditions has been discovered for a series of bis(perfluoroacyl) derivatives of o‐, m‐ and p‐phenylenediamines, ‐hydroxybenzeneamines and ‐mercaptobenzeneamines of a common structure RCOX–C6H4–NHCOR (X = NH, S, O; R = CF3, C2F5, C3F7). Only the para‐isomers showed successive loss of a radical RCO• and a molecule RCN, leading to very intense peaks in the EI spectra. The composition and the origin of the [M–COR–NCR]+ ions were confirmed by exact mass measurements and linked scan experiments. The proposed mechanism of their formation takes into account likely para‐quinoid structures of the precursor ions. A similar rearrangement has not been observed for para‐isomers in the series of bis(perfluoroacyl) derivatives of benzenediols, mercaptophenols and dimercaptobenzenes. Published in 2010 by John Wiley & Sons, Ltd.
Ultrasound ionization of biomolecules
Authors: Wu Chen‐I , Wang Yi‐Sheng , Chen Nelson G. , Wu Chung‐Yi , Chen Chung‐Hsuan
Published: December 2010

To date, mass spectrometric analysis of biomolecules has been primarily performed with either matrix‐assisted laser desorption/ionization (MALDI) or electrospray ionization (ESI). In this work, ultrasound produced by a simple piezoelectric device is shown as an alternative method for soft ionization of biomolecules. Precursor ions of proteins, saccharides and fatty acids showed little fragmentation. Cavitation is considered as a primary mechanism for the ionization of biomolecules. Copyright © 2010 John Wiley & Sons, Ltd.
Direct analysis of trace level bisphenol A, octylphenols and nonylphenol in bottled water and leached from bottles by ultra‐high‐performance liquid chromatography/tandem mass spectrometry
Authors: Wang Jinyuan , Schnute William C.
Published: December 2010

A high‐throughput method was developed for the direct analysis of trace level bisphenol A (BPA), 4‐n‐octylphenol (4‐n‐OP), 4‐tert‐octylphenol (4‐t‐OP) and 4‐n‐nonylphenol (4‐n‐NP) in water samples by ultra‐high‐performance liquid chromatography/tandem mass spectrometry (uHPLC/MS/MS) using an isotope‐labeled internal standard. Aliquots of water samples were spiked with the internal standard and analyzed without sample cleanup or enrichment. All target analytes were chromatographically separated within 3 min and detected using the highly selective multiple reaction monitoring (MRM) detection mode. The method detection limits were statistically calculated and ranged from 0.040 ppb (BPA) to 0.057 ppb (4‐n‐NP). Excellent correlation of determination was achieved for each analyte with r greater than 0.995. Precision was achieved within 8% relative standard deviation (RSD) for all analytes, and recoveries from spiked samples ranged from 97% to 106.2% except for 4‐n‐OP which may be corrected by using an isotope‐labeled analog as internal standard. This method was used for analyzing eight randomly selected bottled water samples and found no detectable target analytes. This method was also used to analyze target analytes leached from bottles (6 low cost bottles and 6 brand‐name baby‐feeding bottles). Low levels of BPA were found in three bottles after they had been heated in a microwave oven, and a trace amount of 4‐n‐NP was also found in three bottles. 4‐t‐OP, which has not been reported as a leachable chemical, was found in two brand name baby‐feeding bottles from the same manufacturer, and was confirmed with bottles from different batches. Copyright © 2010 John Wiley & Sons, Ltd.
Measurement of the δ34S value in methionine by double spike multi‐collector thermal ionization mass spectrometry using Carius tube digestion
Authors: Mann Jacqueline L. , Kelly W. Robert
Published: December 2010

Methionine is an essential amino acid and is the primary source of sulfur for humans. Using the double spike (33S‐36S) multi‐collector thermal ionization mass spectrometry (MC‐TIMS) technique, three sample bottles of a methionine material obtained from the Institute for Reference Materials and Measurements have been measured for δ34S and sulfur concentration. The mean δ34S value, relative to Vienna Canyon Diablo Troilite (VCDT), determined was 10.34 ± 0.11‰ (n = 9) with the uncertainty reported as expanded uncertainties (U). These δ34S measurements include a correction for blank which has been previously ignored in studies of sulfur isotopic composition. The sulfur concentrations for the three bottles range from 56 to 88 µg/g. The isotope composition and concentration results demonstrate the high accuracy and precision of the DS‐MC‐TIMS technique for measuring sulfur in methionine. Published in 2010 by John Wiley & Sons, Ltd.
Rapid screening and characterization of metabolites from a marine‐derived actinomycete by high‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry
Authors: Liu Cheng‐Wei , Lu Yuan‐Yuan , Yang Zhen‐Zheng , Xing Ying‐Ying , Xi Tao
Published: December 2010

A rapid and reliable method has been optimized and established for the analysis of the metabolites from a marine actinomycete by high‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry (HPLC/QTOF MS/MS). From MS/MS spectra, the product ions of [M + H]+ were recorded to provide abundant structural information of the mother nucleus and peptide moieties. Using the QTOF MS/MS and in‐source collision‐induced dissociation (in‐source CID) techniques, three main metabolites including actinomycin D, actinomycin V and actinomycin I were determined and characterized by elemental compositions of precursor and product ions (<7 ppm). Additionally, this method provided information about the compositions of the peptide residues and the sequences of the amino acid from a series of fragment ions. It proved useful for the identiﬁcation of the metabolites in marine samples which have similar structures especially when there were no reference compounds available. Copyright © 2010 John Wiley & Sons, Ltd.
Rapid characterization of triterpene saponins from Conyza blinii by liquid chromatography coupled with mass spectrometry
Authors: Qiao Xue , Zhang Xing , Ye Min , Su Yan‐fang , Dong Jing , Han Jian , Yin Jun , Guo De‐an
Published: December 2010

Conyza blinii Le'vl is a medicinal herb used for the treatment of inflammation in Chinese folk medicine. Its major bioactive constituents are triterpene saponins, most of which contain 6–8 sugar residues. In this report, electrospray ionization tandem mass spectrometry fragmentation behaviors of bisdesmosidic triterpene saponins (conyzasaponin A, B, and C) were studied in both positive and negative ion modes with an ion‐trap mass spectrometer. In full scan mass spectrometry, these saponins gave predominant [M–H]− and [M+Na]+ ions, which determined the molecular weights. In tandem mass spectrometry (MSn, n = 2–4), the [M–H]− and [M+Na]+ ions yielded fragments [Y0α–H]− and [Bα+Na]+, which were diagnostic for the structures of the triterpene skeleton and sugar chains. The structural elucidation was approved by accurate mass data using IT‐TOF‐MS. An interpretation guideline based on MSn (n = 2–4) diagnostic ions was proposed in order to elucidate the chemical structures of unknown triterpene saponins in C. blinii extract. The saponins in C. blinii were separated by liquid chromatography with a methanol/acetonitrile/water solvent system, and then analyzed by ion‐trap and IT‐TOF mass spectrometers. Based on the interpretation guideline, a total of 35 triterpenoid saponins were tentatively identified. Among them, 15 saponins had been previously reported, and the other 20 saponins were reported from Conyza species for the first time. This study indicates that LC/MS is a powerful technology for the rapid characterization of complicated saponins in herbal extracts. Copyright © 2010 John Wiley & Sons, Ltd.
Characterization of the volatile organic compounds of Italian ‘Fossa’ cheese by solid‐phase microextraction gas chromatography/mass spectrometry
Authors: Gioacchini Anna Maria , De Santi Mauro , Guescini Michele , Brandi Giorgio , Stocchi Vilberto
Published: December 2010

Fossa cheese is an Italian hard cheese, ripened for up to 3 months in underground pits dug into tuffaceous rock. During this period, the cheese develops a unique flavour and intense and somewhat piquant aroma. Solid‐phase microextraction gas chromatography/mass spectrometry (SPME‐GC/MS) was utilized to characterize the volatile organic compounds (VOCs) of Fossa cheese. A total of 75 VOCs were separated and identified; in particular, the major class of compounds found in the cheeses ripened in the pits were the esters of fatty acids. Discriminant analysis of volatile profiles allowed us to distinguish between cheeses in different stages of seasoning (60‐day‐old cheese and cheese ripened an additional 90 days in and out of the pits). Copyright © 2010 John Wiley & Sons, Ltd.
Seabird satellite tracking validates the use of latitudinal isoscapes to depict predators' foraging areas in the Southern Ocean
Authors: Jaeger Audrey , Lecomte Vincent J. , Weimerskirch Henri , Richard Pierre , Cherel Yves
Published: December 2010

Stable isotopes are increasingly being used to trace wildlife movements. A fundamental prerequisite of animal isotopic tracking is a good knowledge of spatial isotopic variations in the environment. Few accessible reference maps of the isotopic landscape (“isoscapes”) are available for marine predators. Here, we validate for the first time an isotopic gradient for higher trophic levels by using a unique combination of a large number of satellite‐tracks and subsequent blood plasma isotopic signatures from a wide‐ranging oceanic predator. The plasma δ13C and δ15N values of wandering albatrosses (n = 45) were highly and positively correlated to the Southern Ocean latitudes at which the satellite‐tracked individuals foraged. The well‐defined latitudinal baseline carbon isoscapes in the Southern Ocean is thus reflected in the tissue of consumers, but with a positive shift due to the cumulative effect of a slight 13C‐enrichment at each trophic level. The data allowed us to estimate the carbon isotopic position of the main oceanic fronts in the area, and thus to delineate robust isoscapes of the main foraging zones for top predators. The plasma δ13C and δ15N values were positively and linearly correlated, thus suggesting that latitudinal isoscapes also occur for δ15N at the base of the food web in oceanic waters of the Southern Ocean. The combination of device deployments with sampling of relevant tissues for isotopic analysis appears to be a powerful tool for investigating consumers' isoscapes at various spatio‐temporal scales. Copyright © 2010 John Wiley & Sons, Ltd.
Multiple‐stage mass spectrometry analysis of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and their derivatives
Authors: Gallart‐Ayala H. , Moyano E. , Galceran M.T.
Published: December 2010

The fragmentation of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives was studied by electrospray ioization tandem mass spectrometry. Multiple‐stage mass spectrometry and accurate mass measurements were combined to establish the fragmentation pathways. BADGEs and BFDGEs tend to form ammonium adducts under electrospray conditions which fragmented easily. The fragmentation of [M+NH4]+ for BADGEs started with the cleavage of the phenyl‐alkyl bond, which was followed by the α‐cleavage of the ether group to generate the characteristic product ions at m/z 135, [C9H11O]+, and m/z 107, [C7H7O]+. The fragmentation of the BFDGE isomer mixtures was studied by on‐line reversed‐phase liquid chromatography coupled to multiple‐stage mass spectrometry (LC/MSn). Information obtained from product ion spectra for each BFDGE isomer and its comparison with the fragmentation pathway of BADGE allowed each isomer and the chromatographic elution order to be identified. Copyright © 2010 John Wiley & Sons, Ltd.