bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification, Quantification, and Determination of the Absolute Configuration of the Bacterial Quorum‐Sensing Signal Autoinducer‐2 by Gas Chromatography–Mass Spectrometry
Authors: Thiel Verena , Vilchez Ramiro , Sztajer Helena , Wagner‐Döbler Irene , Schulz Stefan 
Published: December 2008

AbstractSensing the signal: A gas chromatography–mass spectrometry (GC–MS) method for the analysis of the quorum‐sensing autoinducer‐2 is described. It allows, for the first time, the direct analysis and accurate determination of this highly water soluble signaling compound, which exists in complex equilibria. The application on the caries‐causing bacterium Streptococcus mutans is described.magnified imageAutoinducer‐2 (AI‐2) is an important, small extracellular signaling molecule that is used by many bacteria. It is part of the AI‐2 pool, a group of equilibrium‐connected compounds derived from (S)‐4,5‐dihydroxy‐2,3‐pentanedione [(S)‐DPD, 1]. Currently, these compounds are analyzed by indirect methods relying on the luminescence of sensor strains, the fluorescence of receptor proteins modified with fluorophores, or by isolation procedures not practical for quantitative analysis. Herein, we report a direct analytical procedure that allows for the unambiguous identification and quantification of molecular species by mass spectrometry. Phenylenediamine reacts readily and quantitatively with 1 to form the quinoxalinediol 12 under aqueous conditions. The extraction and silylation of this compound results in the formation of a silyl ether (13), which is amenable for analysis by gas chromatography–mass spectrometry. The use of an isotopically labeled variant (16) of 12 as an internal standard opens the possibility for the accurate quantification of samples containing AI‐2 or its equilibrium products. The analysis of cell‐free culture supernatants of Vibrio harveyi and Streptococcus mutans allowed for the accurate quantification of the AI‐2 concentration above the limit of detection (0.7 ng mL−1). No compounds were detected in mutants lacking the capability to produce AI‐2. In addition, the absolute configuration of 1 can be analyzed using the derivative 13 by chiral gas chromatography.
Magnetic Interactions and Magnetic Anisotropy in Exchange Coupled 4f–3d Systems: A Case Study of a Heterodinuclear Ce3+–Fe3+ Cyanide‐Bridged Complex
Authors: Sorace Lorenzo , Sangregorio Claudio , Figuerola Albert , Benelli Cristiano , Gatteschi Dante 
Published: December 2008

AbstractWe report here a detailed single‐crystal EPR and magnetic study of a homologous series of complexes of the type Ln–M (Ln=LaIII, CeIII; M=FeIII, CoIII). We were able to obtain a detailed picture of the low‐lying levels of CeIII and FeIII centres through the combined use of single‐crystal EPR and magnetic susceptibility data. We show that classical ligand field theory can be of great help in rationalising the energies of the low‐lying levels of both the transition‐metal and rare‐earth ions. The combined analysis of single‐crystal EPR and magnetic data of the coupled system Ce–Fe confirmed the great complexity of the interactions involving rare‐earth elements. With little uncertainty, it turned out clearly that the description of the interaction involving the lowest lying spin levels requires the introduction of the isotropic, anisotropic and antisymmetric terms.
MALDI‐TOF Mass‐Spectrometry‐Based Versatile Method for the Characterization of Protein Kinases
Authors: Kondo Noriyasu , Nishimura Shin‐Ichiro 
Published: December 2008

AbstractWe describe a MALDI‐TOF mass‐spectrometry‐based method that is rapid and versatile for the characterization of protein kinases and their inhibitors. We have designed new kinase substrates by the modification of common synthetic peptides, such as kemptide (LRRALSG), CaMKII substrate (KRQQSFDLF), erktide (ATGPLSPGPFGRR), abltide (EAIYAAPFAKKK), srctide (AEEEIYGEFEAKKKK), neurogranin (AAAKIQASFRGHMARKK), and casein kinase I (CKI) substrate (RRKDLHDDEEDEAMSITA). There are two fundamental points on which the proposed method is based to improve the mass‐spectrometric response: 1) mass tag technology by N‐derivatization through stable isotope labeling and 2) C‐terminal conjugation with tryptophanylarginine (WR). It was suggested that C‐terminal conjugation with the WR moiety enhances the ionization potency of these new substrates 1.5–13.7 times as much as those of the original peptides. We demonstrated, by using modified abltide (Ac‐EAIYAAPFAKKKWR‐NH2), that WR conjugation at the C‐terminus in combination with stable‐isotope labeling at the N‐terminus allowed the quantitative assay of recombinant c‐Abl kinase in the presence of adenosine 5′‐triphosphate (ATP; KM,ATP=18.6 μM and Vmax=642 pmol min−1 μg−1). The present protocol made a simple and reliable inhibition assay of recombinant c‐Abl kinase by imatinib possible (IC50(recombinant)=291 nM; STI571, Gleevec; Novartis Pharma). Moreover, it was also demonstrated that this ATP noncompetitive inhibitor differentiates between two conformers of c‐Abl kinases: the phosphorylated active and dephosphorylated inactive forms (IC50(active form)=1049 nM and IC50(inactive form)=54 nM). The merit of this approach is evident because the present protocol can be applied to the direct monitoring of the activities of living cell kinases by using cancer‐cell lines, such as mouse B16 melanoma cells and human lung cancer K562 cells. A multiple‐kinase assay that uses K562 cell lysate in the presence of seven new synthetic substrates made high‐throughput inhibitor profiling possible. It should be emphasized that this radioactive isotope‐free quantitative kinase assay will greatly accelerate the discovery of a new generation of potential kinase inhibitors that exhibit highly selective or unique inhibitory profiles.
Osmotically Shrunken LIPOCEST Agents: An Innovative Class of Magnetic Resonance Imaging Contrast Media Based on Chemical Exchange Saturation Transfer
Authors: Terreno Enzo , Delli Castelli Daniela , Violante Elisabetta , Sanders Honorius M. H. F. , Sommerdijk Nico A. J. M. , Aime Silvio 
Published: December 2008

AbstractThe peculiar properties of osmotically shrunken liposomes acting as magnetic resonance imaging–chemical exchange saturation transfer (MRI–CEST) contrast agents have been investigated. Attention has been primarily devoted to assessing the contribution arising from encapsulated and incorporated paramagnetic lanthanide(III)‐based shift reagents in determining the chemical shift of the intraliposomal water protons, which is a relevant factor for generating the CEST contrast. It is demonstrated that a highly shifted resonance for the encapsulated water can be attained by increasing the percentage of the amphiphilic shift reagent incorporated in the liposome bilayer. It is also demonstrated that the shift contribution arising from the bulk magnetic susceptibility can be optimized through the modulation of the osmotic shrinkage. In terms of sensitivity, it is shown that the saturation transfer efficiency can be significantly improved by increasing the size of the vesicle, thus allowing a high number of exchangeable protons to be saturated. In addition, the role played by the intensity of the saturating radiofrequency field has also been highlighted.
Regio‐ and Chemoselective Metalation of Chloropyrimidine Derivatives with TMPMgCl⋅LiCl and TMP2Zn⋅2 MgCl2⋅2 LiCl
Authors: Mosrin Marc , Knochel Paul 
Published: December 2008

AbstractEfficient zincation and magnesiation of chlorinated pyrimidines can be performed at convenient temperatures (e.g., 25 and 55 °C) by using TMPMgCl⋅LiCl and TMP2Zn⋅2 MgCl2⋅2 LiCl (TMP=2,2,6,6‐tetramethylpiperidyl) as effective bases. Quenching of the resulting zincated or magnesiated pyrimidines with various electrophiles furnishes highly functionalized pyrimidines in 51–93 % yield. Oxidative aminations were carried out, thus leading to aminated pyrimidines. By using this methodology, we have also prepared pharmaceutically relevant pyrazolopyrimidines and the fungicide Mepanipyrim.
Solid‐State Gas Sensors Developed from Functional Difluoroboradiazaindacene Dyes
Authors: Ziessel Raymond , Ulrich Gilles , Harriman Anthony , Alamiry Mohammed A. H. , Stewart Beverly , Retailleau Pascal 
Published: December 2008

AbstractThis article describes the synthesis and characterization of several new difluoroboradiazaindacene (BODIPY™) dyes functionalized at the central 8‐position by a phenyliodo, phenylheptynoate or phenylheptynoic fragment and at the 3‐ or 3/5‐position(s) by 4‐dimethylaminophenylstyryl residue(s). Single‐crystal structural determinations confirm the planarity of the dyes, while the absorption and fluorescence spectroscopic properties are highly sensitive to the state of protonation (or alkylation) of the terminal anilino donor group(s). Reversible color tuning from green to blue for absorption and from colorless (i.e., near‐IR region) to red for fluorescence is obtained on successive addition of acid and base. The difunctionalized derivative is especially interesting in this respect and shows two well‐resolved pKa values of 5.10 and 3.04 in acetonitrile. Addition of the first proton causes only small spectral changes and deactivates the molecule towards addition of the second proton. It is this latter step that accommodates the large change in absorption and emission properties, due to the reversible extinction of the intramolecular charge‐transfer character inherent to this type of dye. The main focus of the work is the covalent anchoring of the dyes to inert, porous polyacrylate beads so as to form a solid‐state sensor suitable for analysis of gases or flowing liquids. The final material is highly stable—its performance is undiminished after more than one year—and fully reversible over many cycles. The sensitivity is such that reactions can be followed by the naked eye and the detection limit is about 600 ppb for HCl and about 80 ppb for ammonia. Trace amounts of diphosgene can be detected, as can alkylating agents. The sensing action is indiscriminate and also operates when the beads are dispersed in aqueous media.
FeNCN and Fe(NCNH)2: Synthesis, Structure, and Magnetic Properties of a Nitrogen‐Based Pseudo‐oxide and ‐hydroxide of Divalent Iron
Authors: Liu Xiaohui , Stork Ludwig , Speldrich Manfred , Lueken Heiko , Dronskowski Richard 
Published: December 2008

AbstractIron man challenge: Iron carbodiimide, FeNCN, and its precursor iron (bis)monohydrocyanamide, Fe(NCNH)2, have been synthesized and physically characterized. Both FeNCN and Fe(NCNH)2 exhibit nitrogen‐mediated antiferromagnetic superexchange interactions with reduced magnetic moments very similar, but not identical, to the correlated 3d oxides.magnified imageNo Abstract
Morphology and deactivation behaviour of Co–Ru/γ‐Al2O3 Fischer–Tropsch synthesis catalyst
Authors: Tavasoli Ahmad , Irani Mohammad , Abbaslou Reza M. Malek , Trépanier Mariane , Dalai Ajay K. 
Published: December 2008

AbstractDeactivation of Co–Ru/γ‐Al2O3 Fischer–Tropsch (FT) synthesis catalyst along the catalytic bed over 850 h of time‐on‐stream (TOS) was investigated. Catalytic bed was divided into four parts and structural changes of the spent catalysts collected from each catalytic bed after FT synthesis were studied using BET, ICP, XRD, TPR, carbon determination, H2 chemisorption and oxygen titration techniques. Rapid deactivation was observed during first 200 h of FT synthesis. In this case, the deactivation rate was not dependent on the number of the catalyst active sites. It was zero order to CO conversion and independent of the size of active sites. Beyond the TOS of 200 h, the deactivation could be simulated with a power law expression: $- {\rm d}X_{{\rm CO}} /{\rm d}t = kX_{{\rm CO}}^{28.5}$. The physical properties of the catalyst charged in 1st half of the reactor did not change significantly. Interaction of cobalt with alumina and formation of mixed oxides of the form xCoO·yAl2O3 and CoAl2O4 was increased along the catalytic bed. Percentage reducibility and dispersion decreased by 2.4–25.5% and 0.5–8.8% for the catalyst in the beds 1 and 4, respectively. Particle diameter increased by 0.8–6.1% for the catalyst in the beds 1 and 4 respectively suggesting higher rate of sintering at last catalytic bed. The amount of coke formation in the 4th catalytic bed was 6 times more than that of in bed 1.
Properties of uniaxially stretched polypropylene films
Authors: Sadeghi Farhad , Carreau Pierre J. 
Published: December 2008

AbstractPolypropylene (PP) films have been prepared through two different cast extrusion processes: one using a machine direction orientation (MDO) unit and the other stretching the films at the die under high cooling conditions (lab unit). Films for two PP resins different in molecular structure have been prepared using both processing techniques. The effect of the resin structure and the processing conditions on the film properties has been examined. It was found that the MDO unit generated a highly oriented fibrillar crystalline structure with a distribution of elongated thick fibrils while extrusion under high cooling conditions generated an oriented row nucleated lamellar structure. The films showed distinctive tensile responses in stretching, with a strong solid‐elastic response for the oriented MDO films and a steady strain hardening after yielding for the sample obtained from lab unit cast extrusion. It was found that the strength in the transverse direction (TD) was particularly very low for the oriented MDO films made of the bimodal PP. The oxygen permeability was reduced with increasing draw ratio (DR) for the MDO films. The haze property for the MDO samples reduced to a plateau for DR up to 5 while clarity improved continuously with DR.
The influence of distributor structure on the solids distribution and flow development in circulating fluidized beds
Authors: Yan Aijie , Huang Weixing , Zhu Jesse (Jingxu) 
Published: December 2008

AbstractThe influence of distributor structure on solids distribution is studied in two riser circulating fluidized bed reactors with different distributor structures but similar diameters. Optic fibre probes were used for the measurement of local solids distribution. The axial and radial distribution of solids holdup in the riser with a multi‐tube distributor is more uniform than that with a multi‐orifice distributor. The radial profiles of particle velocity in the riser with the multi‐tube distributor are also more uniform than that with the multi‐orifice distributor. In the riser with the multi‐tube distributor, both gas and particles are distributed more uniformly across the section, so that the flow acceleration is much more uniform and faster. The flow development is much faster and the fully developed region is reached early for the riser with the multi‐tube distributor. The distributor design is an important factor for the design of circulating fluidized bed reactor.
Assembly properties of the Bacillus subtilis actin, MreB
Authors: Mayer Joshua A. , Amann Kurt J. 
Published: December 2008

AbstractThe bacterial actin MreB has been implicated in a variety of cellular roles including cell shape determination, cell wall synthesis, chromosome condensation and segregation, and the establishment and maintenance of cell polarity. Toward elucidating a clearer understanding of how MreB functions inside the bacterial cell, we investigated biochemically the polymerization of MreB from Bacillus subtilis. Light scattering and sedimentation assays revealed pH‐, ionic‐, cationic‐, and temperature‐dependent behavior. B. subtilis MreB polymerizes in the presence of millimolar divalent cations in a protein concentration‐dependent manner. Polymerization is favored by decreasing pH and inhibited by monovalent salts and low temperatures. Although B. subtilis MreB binds and hydrolyzes both ATP and GTP, it does not require a bound nucleotide for assembly and polymerizes indistinguishably regardless of the nucleotide species bound, with a critical concentration of ∼900 nM. A number of the presently reported properties of B. subtilis MreB differ significantly from those of T. maritima MreB1 (Bean and Amann [2008]: Biochemistry 47: 826–835), including the nucleotide requirements and temperature and ionic effects on polymerization state. These observations collectively suggest that additional factors interact with MreB to account for its complex dynamic behavior in cells. Cell Motil. Cytoskeleton 2009. © 2008 Wiley‐Liss, Inc.
A selective cyclooxygenase‐2 inhibitor prevents inflammation‐related squamous cell carcinogenesis of the forestomach via duodenogastric reflux in rats
Authors: Oba Masaru , Miwa Koichi , Fujimura Takashi , Harada Shinichi , Sasaki Shozo , Oyama Katsunobu , Ohta Tetsuo , Hattori Takanori 
Published: December 2008

AbstractBACKGROUND:Duodenal reflux causes inflammation‐related squamous cell carcinogenesis in the forestomach of rats without any carcinogens. The aim of this study was to investigate the efficacy of a selective cyclooxygenase (COX)‐2 inhibitor, meloxicam, in preventing this carcinogenesis.METHODS:A series of 188 rats underwent a surgical duodenogastric reflux procedure and were divided into 2 groups. One group was given commercial chow (control group), and the other was given experimental chow containing meloxicam (0.3 mg/kg body weight/day) (meloxicam group). The animals were sequentially sacrificed at Weeks 20, 30, 40, 50, and 60 after surgery. The forestomach was examined for the presence of carcinoma, the incidence of reflux‐related morphological changes, COX‐2 expression, and its activity.RESULTS:At Week 60, squamous cell carcinoma developed in 8 of 21 animals (38%) in the control group, but none of 20 (0%) in the meloxicam group (P < .05). In addition, basal cell dysplasia developed in 19 of 21 (90%) animals in the control group, but only 4 of 20 (20%) in the meloxicam group (P < .01). COX‐2 immunoreactivity was predominantly detected in macrophages in the epithelial stroma. Compared with nonsurgical rats, RNA expression of COX‐2 in the epithelium was up‐regulated, reaching peak at an early stage of Week 20 in both groups (P < .005). The expression of microsomal prostaglandin E synthase‐1 was lower in the meloxicam group than in the control group. PGE2 production was significantly suppressed throughout the experiment in the meloxicam group compared with the control group (P < .005).CONCLUSIONS:Meloxicam was effective in preventing reflux‐induced squamous cell carcinogenesis via an inflamed squamous epithelium. Cancer 2009. © 2009 American Cancer Society.
Mental health, treatment preferences, advance care planning, location, and quality of death in advanced cancer patients with dependent children
Authors: Nilsson Matthew E. , Maciejewski Paul K. , Zhang Baohui , Wright Alexi A. , Trice Elizabeth D. , Muriel Anna C. , Friedlander Robert J. , Fasciano Karen M. , Block Susan D. , Prigerson Holly G. 
Published: December 2008

AbstractBACKGROUND:Clinicians observe that advanced cancer patients with dependent children agonize over the impact their death will have on their children. The objective of this study was to determine empirically whether advanced cancer patients with and without dependent children differ in treatment preferences, mental health, and end‐of‐life (EOL) outcomes.METHODS:Coping with Cancer is a National Cancer Institute/National Institute of Mental Health‐funded, multi‐institutional, prospective cohort study of 668 patients with advanced cancer. Patients with and without dependent children were compared on rates of psychiatric disorders, advance care planning (ACP), EOL care, quality of their last week of life, and location of death.RESULTS:In adjusted analyses, patients with advanced cancer who had dependent children were more likely to meet panic disorder criteria (adjusted odds ratio [AOR], 5.41; 95% confidence interval [95% CI], 2.13–13.69), more likely to be worried (mean difference in standard deviations [δ], 0.09; P = .006), and more likely to prefer aggressive treatment over palliative care (AOR, 1.77; 95% CI, 1.07–2.93). Patients with dependent children were less likely to engage in ACP (eg, do not resuscitate orders: AOR, 0.44; 95% CI, 0.26–0.75) and had a worse quality of life in the last week of life (δ, 0.15; P = .007). Among spousal caregivers, those with dependent children were more likely to meet criteria for major depressive disorder (AOR, 4.53; 95% CI, 1.47–14) and generalized anxiety disorder (AOR, 3.95; 95% CI, 1.29–12.16).CONCLUSIONS:Patients with dependent children were more anxious, were less likely to engage in ACP, and were more likely to have a worse quality of life in their last week of life. Advanced cancer patients and spousal caregivers with dependent children represent a particularly distressed group that warrants further clinical attention, research, and support. Cancer 2009. © 2009 American Cancer Society.
Consideration of hereditary nonpolyposis colorectal cancer in BRCA mutation‐negative familial ovarian cancers
Authors: South Stacey A. , Vance Heidi , Farrell Carolyn , DiCioccio Richard A. , Fahey Cathy , Piver M. Steven , Rodabaugh Kerry J. 
Published: December 2008

AbstractBACKGROUND:Inherited mutations account for approximately 10% of all epithelial ovarian cancers. Breast cancer (BRCA1 and BRACA2) gene mutations are responsible for up to 85% of inherited breast and/or ovarian cancer. Another condition that has been associated with ovarian cancer is hereditary nonpolyposis colorectal cancer syndrome (HNPCC), which carries a lifetime risk of up to 13% for ovarian cancer. The objective of this study was to determine the incidence of HNPCC‐related gene mutations in patients with familial ovarian cancer who previously tested negative for BRCA1 and BRCA2 gene mutations.METHODS:Seventy‐seven probands were identified who had familial ovarian cancer and negative BRCA gene mutation testing. Their pedigrees were analyzed for HNPCC syndrome. DNA samples underwent gene sequencing and Southern blot analysis for mutations in the 3 most common HNPCC‐associated genes: mutL homolog 1 (MLH1) and mutS homolog 2 (MSH2) with reflex testing for MSH6 if tests for the first 2 genes were negative.RESULTS:None of the probands met Amsterdam criteria for the clinical diagnosis of HNPCC. DNA testing revealed 2 patients (2.6%) with deleterious mutations in the MSH2 gene. An additional 8 patients (10.4%) had substitutions in either the MLH1 gene or the MSH2 gene that were classified as variants of uncertain significance. If Amsterdam criteria were expanded to include ovarian cancer, then 15 of 77 patients (19.5%) would have met these expanded criteria. One deleterious mutation was noted in this group, yielding a mutation incidence of 6.7%. This percentage may be even higher if any of the identified variants of uncertain significance are confirmed to be deleterious.CONCLUSIONS:HNPCC should be considered when evaluating patients with suspected hereditary ovarian cancer who have had negative BRCA mutation testing. Cancer 2009. © 2009 American Cancer Society.