bluuebunny/crossref_metadata_2025 huggingface dataset:
A shifting paradigm: histone deacetylases and transcriptional activation
Authors: Smith Catharine L.
Published: December 2007

Transcriptional repression and silencing have been strongly associated with hypoacetylation of histones. Accordingly, histone deacetylases, which remove acetyl groups from histones, have been shown to participate in mechanisms of transcriptional repression. Therefore, current models of the role of acetylation in transcriptional regulation focus on the acetylation status of histones and designate histone acetyltransferases, which add acetyl groups to histones, as transcriptional coactivators and histone deacetylases as corepressors. In recent years, an accumulation of studies have shown that these enzymes also target non‐histone proteins and that histone deacetylases have clear roles as coactivators at a variety of genes, some of which are key regulators of cell growth and survival. This review summarizes the evidence for histone deacetylases as coactivators and provides models of coactivation mechanisms, some of which integrate roles of acetylated histones and non‐histone proteins in transcription. BioEssays 30:15–24, 2008. © 2007 Wiley Periodicals, Inc.
Drosophila telomeres: an exception providing new insights
Authors: Mason James M. , Frydrychova Radmila Capkova , Biessmann Harald
Published: December 2007

Drosophila telomeres comprise DNA sequences that differ dramatically from those of other eukaryotes. Telomere functions, however, are similar to those found in telomerase‐based telomeres, even though the underlying mechanisms may differ. Drosophila telomeres use arrays of retrotransposons to maintain chromosome length, while nearly all other eukaryotes rely on telomerase‐generated short repeats. Regardless of the DNA sequence, several end‐binding proteins are evolutionarily conserved. Away from the end, the Drosophila telomeric and subtelomeric DNA sequences are complexed with unique combinations of proteins that also modulate chromatin structure elsewhere in the genome. Maintaining and regulating the transcriptional activity of the telomeric retrotransposons in Drosophila requires specific chromatin structures and, while telomeric silencing spreads from the terminal repeats in yeast, the source of telomeric silencing in Drosophila is the subterminal arrays. However, the subterminal arrays in both species may be involved in telomere–telomere associations and/or communication. BioEssays 30:25–37, 2008. © 2007 Wiley Periodicals, Inc.
Conformational flexibility of a model protein upon immobilization on self‐assembled monolayers
Authors: Bigdeli Saharnaz , Talasaz AmirAli H. , Ståhl Patrik , Persson Henrik H.J. , Ronaghi Mostafa , Davis Ronald W. , Nemat‐Gorgani Mohsen
Published: December 2007

The present study reports on the retention of conformational flexibility of a model allosteric protein upon immobilization on self‐assembled monolayers (SAMs) on gold. Organothiolated SAMs of different compositions were utilized for adsorptive and covalent attachment of bovine liver glutamate dehydrogenase (GDH), a well‐characterized allosteric enzyme. Sensitive fluorimetric assays were developed to determine immobilization capacity, specific activity, and allosteric properties of the immobilized preparations as well as the potential for repeated use and continuous catalytic transformations. The allosteric response of the free and immobilized forms towards ADP, L‐leucine and high concentrations of NAD+, some of the well‐known activators for this enzyme, were determined and compared. The enzyme immobilized by adsorption or chemical binding responded similarly to the activators with a greater degree of activation, as compared to the free form. Also loss of activity involving the two immobilization procedures were similar, suggesting that residues essential for catalytic activity or allosteric properties of GDH remained unchanged in the course of chemical modification. A recently established method was used to predict GDH orientation upon immobilization, which was found to explain some of the experimental results presented. The general significance of these observations in connection with retention of native properties of protein structures upon immobilization on SAMs is discussed. Biotechnol. Bioeng. 2008;100: 19–27. © 2007 Wiley Periodicals, Inc.
Effect of solution pH on protein transmission and membrane capacity during virus filtration
Authors: Bakhshayeshi Meisam , Zydney Andrew L.
Published: December 2007

Although virus filtration is now an integral part of the overall viral clearance strategy for the purification of many commercial therapeutic proteins, there is currently little understanding of the factors controlling the performance of the virus filters. The objective of this study was to examine the effects of solution pH on protein transmission and capacity during virus filtration. Data were obtained using bovine serum albumin as a model protein with Viresolve 180 membranes oriented with both the skin‐side up and skin‐side down. Membranes were also characterized using dextran sieving measurements both before and after protein filtration. Membrane capacity and protein yield were minimal at the protein isoelectric point, which was due to the greater degree of concentration polarization associated with the smaller protein diffusion coefficient at this pH. In contrast, the actual protein sieving coefficient was maximum at the protein isoelectric point due to the absence of any strong electrostatic exclusion under these conditions. The yield and capacity were both significantly greater when the membrane was oriented with the skin‐side down. These results provide important insights into the effects of solution conditions on the performance of virus filtration membranes for protein purification. Biotechnol. Bioeng. 2008;100: 108–117. © 2007 Wiley Periodicals, Inc.
Microfluidic delivery of small molecules into mammalian cells based on hydrodynamic focusing
Authors: Wang Fen , Wang Hao , Wang Jun , Wang Hsiang‐Yu , Rummel Peter L. , Garimella Suresh V. , Lu Chang
Published: December 2007

Microfluidics‐based cell assays offer high levels of automation and integration, and allow multiple assays to be run in parallel, based on reduced sample volumes. These characteristics make them attractive for studies associated with drug discovery. Controlled delivery of drug molecules or other exogenous materials into cells is a critical issue that needs to be addressed before microfluidics can serve as a viable platform for drug screening and studies. In this study, we report the application of hydrodynamic focusing for controlled delivery of small molecules into cells immobilized on the substrate of a microfluidic device. We delivered calcein AM which was permeant to the cell membrane into cells, and monitored its enzymatic conversion into fluorescent calcein during and after the delivery. Different ratios of the sample flow to the side flow were tested to determine how the conditions of hydrodynamic focusing affected the delivery. A 3D numerical model was developed to help understand the fluid flow, molecular diffusion due to hydrodynamic focusing in the microfluidic channel. The results from the simulation indicated that the calcein AM concentration on the outer surface of a cell was determined by the conditions of hydrodynamic focusing. By comparing the results from the simulation with those from the experiment, we found that the calcein AM concentration on the cell outer surface correlated very well with the amount of the molecules delivered into the cell. This suggests that hydrodynamic focusing provides an effective way for potentially quantitative delivery of exogenous molecules into cells at the single cell or subcellular level. We expect that our technique will pave the way to high‐throughput drug screening and delivery on a microfluidic platform. Biotechnol. Bioeng. 2008;100: 150–158. © 2007 Wiley Periodicals, Inc.
Thermodynamic and kinetic characterization using process dynamics: Acidophilic ferrous iron oxidation by Leptospirillum ferrooxidans
Authors: Kleerebezem Robbert , van Loosdrecht Mark C.M.
Published: December 2007

Kinetic and stoichiometric properties of acidophilic aerobic ferrous iron oxidation by growing and non‐growing Leptospirillum ferrooxidans cultures were investigated. The use of a continuous stirred tank reactor operated at a variable dilution rate and equipped with on‐line measurement of the electron donor, acceptor and anabolic substrate uptake rate enabled detailed kinetic characterization from a single experiment. It was demonstrated that substrate conversion and microbial growth are tightly coupled processes in L. ferrooxidans, and uncoupling occurs only due to the minor impact of substrate conversion for growth‐independent maintenance purposes. The tight stoichiometric coupling implies bioenergetic uncoupling of the catabolism and anabolism because the Gibbs energy change for ferrous iron oxidation as a function of the actual growth rate of the culture ranges from −45 to −25 kJ mol‐FeII−1. Bioenergetic description of the process could only be achieved by introduction of a growth rate dependent Gibbs energy dissipation term. Removal of carbon dioxide from the influent gas stopped biomass growth, but the biomass specific respiration rate was unaffected or slightly stimulated. The uncoupling of the catabolism and anabolism is suggested to induce instantaneously an energy dissipation pathway. Also dosage of a low concentration propionic acid resulted in complete inhibition of the anabolism. Propionic acid served as an uncoupler of the membrane potential and all catabolic energy is required for the increased maintenance requirements. Recovery of the anabolism after reestablishment of the normal cultivation conditions was obtained only after 1–2 days. The results obtained provide additional constraints on cultivation of L. ferrooxidans for biotechnological application. Biotechnol. Bioeng. 2008;100: 49–60. © 2007 Wiley Periodicals, Inc.
Transcriptional regulation of changes in growth, cell cycle, and gene expression of Saccharomyces cerevisiae due to changes in buoyancy
Authors: Coleman Chasity B. , Allen Patricia L. , Valles James M. , Hammond Timothy G.
Published: December 2007

To understand the cellular effects of magnetic traps requires independent analysis of the effects of magnetic field, gravity, and buoyancy. In the current study, buoyancy is manipulated by addition of Ficoll, a viscous substance that can create gradients of buoyancy without significantly affecting osmolality. Specifically, we investigated whether Ficoll induces concentration dependent changes in cell growth, cell cycle, and gene expression in Saccharomyces cerevisiae, with special attention paid to the neutrally buoyant concentration of 35% Ficoll. Cell growth and cell cycle analysis were examined in three strains: wild‐type (WT) yeast and strains with deletions in transcription factors Msn4 (Msn4Δ) or Sfp1 (Sfp1Δ). Changes in growth were observed in all three strains with WT and Msn4Δ strains showing strong concentration dependence. In addition, these changes in growth were supported by changes in the cell cycle of all three strains. Gene expression changes were observed in seven GFP‐reporter strains including: SSA4, YIL052C, YST2, Msn4ΔSSA4, Sfp1ΔSSA4, Msn4ΔYIL052C, and Sfp1ΔYIL052C. Buoyancy forces had selective concentration dependent effects on gene expression of SSA4 and YIL052C with transcription factor dependence on Msn4. Additionally, SSA4 expression was dependent on Sfp1. YST2 gene expression was not dependent on changes in buoyancy force. This study shows that buoyancy has selective and concentration dependent effects on growth, cell cycle and gene expression, some of which are Msn4 and Sfp1 dependent. For the first time, SSA4 gene expression is shown to be dependent on Sfp1 and YIL052C gene expression is dependent on Msn4. Biotechnol. Bioeng. 2008;100: 334–343. © 2007 Wiley Periodicals, Inc.
Controlling the membrane fluidity of yeasts during coupled thermal and osmotic treatments
Authors: Simonin Hélène , Beney Laurent , Gervais Patrick
Published: December 2007

Yeasts are often exposed to variations in osmotic pressure in their natural environments or in their substrates when used in fermentation industries. Such changes may lead to cell death or activity loss. Previous work by our team has allowed us to relate the mortality of cells exposed to a combination of thermal and osmotic treatments to leakage of cellular components through an unstable membrane when lipid phase transition occurs. In this study, yeast viability was measured after numerous osmotic and thermal treatments. In addition, the fluidity of yeast membranes was assessed according to aw and temperature by means of 1,6‐diphenyl‐1,3,5‐hexatriene (DPH) anisotropy measurement. The results show that there is a negative correlation between the overall fluidity variation undergone by membranes during treatments and yeast survival. Using a diagram of membrane fluidity according to aw and temperature, we defined dehydration and rehydration methods that minimize fluidity fluctuations, permitting significantly increased yeast survival. Thus, such membrane fluidity diagram should be a potential tool for controlling membrane state during dehydration and rehydration and improve yeast survival. Overall fluidity measurements should now be completed by accurate structural analysis of membranes to better understand the plasma membrane changes occurring during dehydration and rehydration. Biotechnol. Bioeng. 2008;100: 325–333. © 2007 Wiley Periodicals, Inc.
An actively mixed mini‐bioreactor for protein production from suspended animal cells
Authors: Diao Jinpian , Young Lincoln , Zhou Peng , Shuler Michael Louis
Published: December 2007

Biopharmaceutical production would benefit from rapid methods to optimize production of therapeutic proteins by screening host cell line/vector combination, culture media, and operational parameters such as timing of induction. Miniaturized bioreactors are an emerging research area aiming at improving the development speed. In this work, a 3 mm thick mini‐bioreactor including two 12 mm wide culture chambers connected by a 5 mm wide channel is described. Active mixing is achieved by pressure shuttling between the two chambers. Gas‐liquid phase exchange for oxygen and carbon dioxide is realized by molecular diffusion through 50 µm thick polymethylpentene membranes. With this unique design, a velocity difference between the middle area and the side areas at the interfaces of the culture chambers and the connecting channel is created, which enhances the mixing efficiency. The observed mixing time is on the order of 100 s. The combination of high permeability toward oxygen of polymethylpentene membranes and fluid movement during active pressure shuttling enables higher volumetric oxygen transfer coefficients, 5.7 ± 0.4–14.8 ± 0.6 h−1, to be obtained in the mini‐bioreactors than the values found in traditional 50 mL spinner flasks, 2.0–2.5 h−1. Meanwhile, the calculated volume averaged shear stress, in the range of 10−2–10−1 N/m2, is within the typical tolerable range of animal cells. To demonstrate the applicability of this mini‐bioreactor to culture suspended animal cells, the insect cell, Spodoptera frugiperda, is cultured in mini‐bioreactors operated under a KLa value of 14.8 ± 0.6 h−1 and compared to the same cells cultured in 50 mL spinner flasks operated under a KLa value of 2.2 h−1. Sf‐21 cells cultured in the mini‐bioreactors present comparable length of lag phases and growth rates to their counterparts cultured in 50 mL spinner flasks, but achieve a higher maximum cell density of 5.3 ± 0.9 × 106 cell/mL than the value of 3.4 ± 0.4 × 106 cell/mL obtained by cells cultured in 50 mL spinner flasks. Sf‐21 cells infected with SEAP‐baculovirus produce a maximum SEAP concentration of 11.3 ± 0.7 U/mL when cultured in the mini‐bioreactor. In contrast, infected Sf‐21 cells cultured in 50 mL spinner flasks produce a maximum SEAP concentration of 7.4 ± 0.9 U/mL and onset of production is delayed from 18 h in minibioreactor to 40 h in spinner flasks. Biotechnol. Bioeng. 2008;100: 72–81. © 2007 Wiley Periodicals, Inc.
Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics
Authors: Kara F. , Gurakan G.C. , Sanin F.D.
Published: December 2007

Multivalent cations have been known to be important components of activated sludge floc structure due to their bridging ability of the negatively charged sites on the biopolymer network. Recently in batch systems it was found that excess concentration of monovalent cations led to the deterioration in settleability, dewaterability of sludges and effluent quality of the system. In this study, effect of influent monovalent cations (potassium and sodium) on activated sludge floc structure was investigated in semi‐continuous reactors. Results revealed that the increase in concentration of both ions correlated to the general increase in total EPS concentration. The zeta potential values were affected by the cation type and dose in such a way that sludge from sodium reactors had always higher zeta potential values (higher negative charge) than the sludges from potassium reactors. Flocs from sodium reactors were more fragile and weak and the capillary suction time values of these sludges were higher compared to those from potassium reactors. The findings of this research conclude that the floc structure is significantly weakened with the increase of monovalent cations. Even though EPS is produced, it is unable to bind the floc components together. With this, the physical properties of sludge deteriorate for both cations. Biotechnol. Bioeng. 2008;100: 231–239. © 2007 Wiley Periodicals, Inc.
Improved production of recombinant human antithrombin III in Chinese hamster ovary cells by ATF4 overexpression
Authors: Ohya Tomoshi , Hayashi Tetsuji , Kiyama Eriko , Nishii Hiroko , Miki Hideo , Kobayashi Kaoru , Honda Kohsuke , Omasa Takeshi , Ohtake Hisao
Published: December 2007

To improve the production of recombinant human antithrombin III (AT‐III) in Chinese hamster ovary (CHO) cells, the genes encoding transcription factors, ATF4 (activating transcription factor 4) and XBP‐1s (the spliced form of X‐box binding protein 1), which were involved in the mammalian unfolded protein response (UPR), were cloned from CHO‐K1 cells. Overexpression of ATF4 significantly enhanced the production of recombinant AT‐III in CHO 13D‐35D cells. The specific rate of AT‐III production in the ATF4‐overexpressed CHO 13D‐35D cells reached approximately 23 pg/cell/day. After 144 h of incubation, the AT‐III concentration in the culture supernatant was twofold greater compared to that observed with parental CHO 13D‐35D cells. In contrast, ectopic expression of XBP‐1s failed to enhance the production of recombinant AT‐III in CHO 13D‐35D cells. RT‐PCR analysis revealed that high levels of XBP‐1s mRNA were present in the CHO cells, regardless of ectopic expression of XBP‐1s. Our results indicate that overexpression of the UPR transcription factor ATF4 is a promising means for improving the production of secreted protein pharmaceuticals in CHO cells. Biotechnol. Bioeng. 2008;100: 317–324. © 2007 Wiley Periodicals, Inc.
Medium factor optimization and fermentation kinetics for phenazine‐1‐carboxylic acid production by Pseudomonas sp. M18G
Authors: He Li , Xu Yu‐Quan , Zhang Xue‐Hong
Published: December 2007

We investigated the production of biofungicide phenazine‐1‐carboxlic (PCA) by Pseudomonas sp. M18G, a gacA‐deficient mutant of M18 for PCA high‐production. Glucose was chosen as the optimal carbon source and soy peptone as the nitrogen source. A Plackett–Burman design revealed that glucose, soy peptone and NaCl were the most significant factors in PCA fermentation. Response surface methodology (RSM) and artificial neural network (ANN) models involving the significant factors were developed using common data. The prediction accuracy of ANN was slightly higher compared to RSM. The genetic algorithm (GA) was used to search the optimal input space of the trained ANN model and find the corresponding PCA yield. The optimum composition was found to be: glucose 34.3 g L−1, soy peptone 43.2 g L−1, NaCl 5.7 g L−1, and the predictive maximum PCA yield reached 980.1 µg mL−1. The optimized medium allowed PCA yield to be increased from 673.3 to 966.7 µg mL−1 after verification experiment tests. Additionally, PCA fermentation kinetics was investigated. Kinetic models based on the modified Logistic and Luedeking–Piret equations were developed, providing a good description of temporal variations of biomass (X), product (P), and substrate (S) in PCA fermentation. Biotechnol. Bioeng. 2008;100: 250–259. © 2007 Wiley Periodicals, Inc.
Microbial Transformation of Spirolaxine, a Bioactive Undecaketide Fungal Metabolite from the Basidiomycete Sporotrichum laxum
Authors: Nasini Gianluca , Bava Adriana , Fronza Giovanni , Giannini Giuseppe
Published: December 2007

Incubation of (+)‐spirolaxine (=(3R)‐5‐hydroxy‐7‐methoxy‐3‐{5‐[(2R,5R,7R)‐2‐methyl‐1,6‐dioxaspiro[4.5]dec‐7‐yl]pentyl}‐2‐benzofuran‐1(3H)‐one; 1a) with Bacillus megaterium afforded two new mono‐ and one new dihydroxylated metabolite(s), all OH groups being introduced on the non‐activated six‐membered ring. In contrast, exposure of 1a to Cunninghamella echinulata gave rise to hydroxylation on the five‐membered ring of the parent structure. The structures and absolute configurations of the new products 1b–e were deduced on the basis of MS and NMR data. The metabolite 1b was investigated, in comparison to 1a, for its cytotoxicity (sulforhodamin‐B test) and for its antiproliferative activity towards bovine microvascular endothelial cells (BMEC).
Transcription‐Inhibition and Antitumor Activities of N‐Alkylated Tetraazacyclododecanes
Authors: Xiong Xiao‐Qin , Liang Feng , Yang Li , Wang Xiao‐Lin , Zhou Xiang , Zheng Cong‐Yi , Cao Xiao‐Ping
Published: December 2007

A series of alkyl‐substituted tetraazacyclododecane congeners were synthesized, and their antitumor activities towards human HeLa cells as well as their effect on the in vitro transcription with T7 RNA polymerase were investigated. A structure–activity‐relationship (SAR) study identified the most‐active congeners as those with medium alkyl‐chain lengths. Three compounds, 5–7, were found to exhibit significant biological activities, with IC50 values towards HeLa cells in the low‐micromolar range.
Synthesis of Oligonucleotides Carrying 5′‐5′ Linkages Using Copper‐Catalyzed Cycloaddition Reactions
Authors: Alvira Margarita , Eritja Ramon
Published: December 2007

There is considerable interest in coupling oligonucleotides to molecules and surfaces. Although amino‐ and thiol‐containing oligonucleotides are being successfully used for this purpose, cycloaddition reactions may offer greater advantages due to their higher chemoselectivity and speed. In this study, copper‐catalyzed 1,3‐dipolar cycloaddition reactions between oligonucleotides carrying azido and alkyne groups are examined. For this purpose, several protocols for the preparation of oligonucleotides carrying these two groups are described. The non‐templated chemical ligation of two oligonucleotides via copper‐catalyzed [3+2] cycloaddition is described. By solid‐phase methodology, oligonucleotides carrying 5′‐5′ linkages can be obtained in good yields.
Arguside A: A New Cytotoxic Triterpene Glycoside from the Sea Cucumber Bohadschia argusJaeger
Authors: Liu Bao‐Shu , Yi Yang‐Hua , Li Ling , Zhang Shi‐Long , Han Hua , Weng Yi‐Yi , Pan Min‐Xiang
Published: December 2007

A new holostane‐based triterpene glycoside, arguside A (1), was isolated from the sea cucumber Bohadschia argus, collected in the South China Sea. The structure of the new compound was elucidated by spectroscopic and mass‐spectrometric analyses, in combination with chemical transformations. Compound 1 exhibited significant cytotoxicity against different human tumor cell lines, being more active towards HCT‐116 cells (IC50=0.14 μM) than 10‐hydroxycamptothecin (HCP) used as positive control.
Glucosides from the Roots of Capparis tenera
Authors: Su Dong‐Min , Wang Ying‐Hong , Yu Shi‐Shan , Yu De‐Quan , Hu You‐Cai , Tang Wen‐Zhao , Liu Geng‐Tao , Wang Wen‐Jie
Published: December 2007

Two new lignan glucosides, compounds 2 and 3, two new 1H‐indole‐alkaloid glucosides, 5 and 6, as well as two new phenolic glucosides, 7 and 10, were isolated from the roots of Capparis tenera, together with five known compounds. Their structures were characterized by chemical and spectroscopic methods. Most of these isolates were obtained for the first time from Capparidaceae. The antioxidant and anti‐inflammatory activities of the new compounds were investigated.
Redox Processes of Sulfur and Manganese in a Constructed Wetland
Authors: Šíma Jan , Diáková Kateřina , Holcová Veronika
Published: December 2007

Constructed wetlands are very popular in terms of wastewater treatment today. Formation of redox potential gradients inside such a system strongly influences the wastewater‐treatment efficiency. Individual oxidation forms of sulfur, and dissolved and precipitated manganese forms were determined in the vegetation bed of the constructed wetland. The aim of the speciation analysis was to contribute to the characterization of its redox properties. Sulfur was mostly oxidized at the inflow. The concentration of sulfates at the inflow varied from 25 to 55 mg/l, while concentration of sulfides was always lower than 6.0 mg/l and mostly even lower than 1.0 mg/l. However, sulfates were reduced during the pretreatment and the wastewater flow through the vegetation bed. The concentration of total manganese varied from 0.2 to 0.8 mg/l. Approximately 60% of Mn was precipitated at the inflow. The content of precipitated Mn forms declined to ca. 40–50% at the inflow zone, this content was almost constant across the vegetation bed to the outflow when water was sampled from 60‐cm depth. However, the content of precipitated Mn forms increased to ca. 74% for samples from 20‐cm depth. With respect to the aeration of the system, manganese can be precipitated as MnO2 in these samples.
Tetralones and Flavonoids from Pyrola calliantha
Authors: Liu Lei , Li An‐Liang , Zhao Ming‐Bo , Tu Peng‐Fei
Published: December 2007

Two new tetralones, pyrolones A (1) and B (2), and a new flavonol glycoside, 2″‐O‐(4‐hydroxybenzoyl)hyperin (3), were isolated from Pyrola calliantha (whole plant), together with six structurally related compounds, including 2″‐O‐galloylhyperin (4), hyperin (5), formononetin (6), quercetin 3‐O‐α‐L‐arabinopyranoside (7), quercetin 3‐O‐α‐L‐arabinofuranoside (8), and kaempferol 3‐O‐β‐D‐galactopyranoside (9). The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic (UV, ORD, CD, NMR) and mass‐spectrometric (HR‐ESI‐MS) analyses.
Decrypting the TEM Images for Deciphering the Microstructural Code of Complex Oxides
Authors: Hervieu Maryvonne , Martin Christine , Pérez Olivier , Retoux Richard , Malo Sylvie
Published: December 2007

The knowledge of the structure of the real solids is required for achieving the desired architectures in the research of new materials and/or optimizing the relationships between structure and properties. Understanding complex oxides needs accurate characterization at different length scales and the combined application of all solid‐state techniques. Deciphering the relationships between all this information provides codes that allow the identification of the different structural levels, their roles and the way they interact. These step‐by‐step routes are illustrated through two basic mechanisms of solid‐state chemistry: to determine the building units of one complex oxide in order to predict the existence of other arrangements on the one hand and to correlate complex ordering phenomena, such as those involving charges, orbitals and spins of manganese atoms in perovskite‐type manganites on the other hand.
Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides
Authors: Zhang Wen‐Xiong , Nishiura Masayoshi , Mashiko Tomohiro , Hou Zhaomin
Published: December 2007

The acid‐base reactions between the rare‐earth metal (Ln) tris(ortho‐N,N‐dimethylaminobenzyl) complexes [Ln(CH2C6H4NMe2‐o)3] with one equivalent of the silylene‐linked cyclopentadiene‐amine ligand (C5Me4H)SiMe2NH(C6H2Me3‐2,4,6) afforded the corresponding half‐sandwich aminobenzyl complexes [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}Ln(CH2C6H4NMe2‐o)(thf)] (2‐Ln) (Ln=Y, La, Pr, Nd, Sm, Gd, Lu) in 60–87 % isolated yields. The one‐pot reaction between ScCl3 and [Me2Si(C5Me4)(NC6H2Me3‐2,4,6)]Li2 followed by reaction with LiCH2C6H4NMe2‐o in THF gave the scandium analogue [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}Sc(CH2C6H4NMe2‐o)] (2‐Sc) in 67 % isolated yield. 2‐Sc could not be prepared by the acid‐base reaction between [Sc(CH2C6H4NMe2‐o)3] and (C5Me4H)SiMe2NH(C6H2Me3‐2,4,6). These half‐sandwich rare‐earth metal aminobenzyl complexes can serve as efficient catalyst precursors for the catalytic addition of various phosphine PH bonds to carbodiimides to form a series of phosphaguanidine derivatives with excellent tolerability to aromatic carbon‐halogen bonds. A significant increase in the catalytic activity was observed, as a result of an increase in the metal size with a general trend of La>Pr, Nd>Sm>Gd>Lu>Sc. The reaction of 2‐La with 1 equiv of Ph2PH yielded the corresponding phosphide complex [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}La(PPh2)(thf)2] (4), which, on recrystallization from benzene, gave the dimeric analogue [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}La(PPh2)]2 (5). Addition of 4 or 5 to iPrNCNiPr in THF yielded the phosphaguanidinate complex [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}La{iPrNC(PPh2)NiPr}(thf)] (6), which, on recrystallization from ether, afforded the ether‐coordinated structurally characterizable analogue [{Me2Si(C5Me4)(NC6H2Me3‐2,4,6)}La{iPrNC(PPh2)NiPr}(OEt2)] (7). The reaction of 6 or 7 with Ph2PH in THF yielded 4 and the phosphaguanidine iPrNC(PPh2)NHiPr (3 a). These results suggest that the catalytic formation of a phosphaguanidine compound proceeds through the nucleophilic addition of a phosphide species, which is formed by the acid‐base reaction between a rare‐earth metal o‐dimethylaminobenzyl bond and a phosphine PH bond, to a carbodiimide, followed by the protonolysis of the resultant phosphaguanidinate species by a phosphine PH bond. Almost all of the rare earth complexes reported this paper were structurally characterized by X‐ray diffraction studies.
Highly Enantio‐ and s‐trans CC Bond Selective Catalytic Hydrogenation of Cyclic Enones: Alternative Synthesis of (−)‐Menthol
Authors: Ohshima Takashi , Tadaoka Hiroshi , Hori Kiyoto , Sayo Noboru , Mashima Kazushi
Published: December 2007

A highly enantioselective catalytic hydrogenation of cyclic enones was achieved by using the combination of a cationic RhI complex, (S)‐5,5′‐bis{di(3,5‐di‐tert‐butyl‐4‐methoxyphenylphosphino)}‐4,4′‐bi‐1,3‐benzodioxole (DTBM‐SEGPHOS), and (CH2CH2PPh3Br)2. The presence of an s‐cis CC bond isopropylidene moiety on the cyclic enone influenced the enantioselectivity of the hydrogenation. Thus, the hydrogenation of 3‐alkyl‐6‐isopropylidene‐2‐cyclohexen‐1‐one, which contains both s‐cis and s‐trans enones, proceeded in excellent enantioselectivity (up to 98 % ee). To obtain high enantio‐ and s‐trans selectivities, the addition of a halogen source to the cationic Rh complex was the essential step. With the key step of the s‐trans selective asymmetric hydrogenation of piperitenone, we demonstrated a new synthetic method for optically pure (−)‐menthol via three atom‐economical hydrogenations. Moreover, we found that the complete s‐trans and s‐cis CC bond selective reactions were also realized by the proper choice of both the chiral ligands and halides.
Conjugate Addition of Indoles to α,β‐Unsaturated Ketones (Chalcones) Catalyzed by KHSO4 under Ultrasonic Conditions
Authors: ZENG Xiao‐Fei , JI Shun‐Jun , SHEN Shu‐Su
Published: December 2007

Conjugate addition of indoles to a variety of α,β‐unsaturated ketones (chalcones) mediated by a catalytic amount of KHSO4 at room temperature under ultrasonic conditions to afford the corresponding Michael adducts in good to excellent yields was reported.
Synthesis of a Novel Carbon Based Acid Catalyst and Its Catalytic Activity for the Acetalization and Ketalization
Authors: LIANG Xue‐Zheng , GAO Shan , CHEN Wen‐Ping , WANG Wen‐Juan , YANG Jian‐Guo
Published: December 2007

A novel carbon based strong solid acid catalyst has been synthesized successfully. The catalytic activity for acetalization and ketalization was investigated. The results showed that the novel catalyst was very efficient with the average yield over 92%. The novel heterogeneous catalyst also has the advantages of high activity, wide applicability even to the preparation of 7 membered ring acetals and ketals, strikingly simple workup procedure, non‐pollution and reusability, which will contribute to the green process greatly.
Fast Determination of Clenbuterol and Salbutamol in Feed and Meat Products Based on Miniaturized Capillary Electrophoresis with Amperometric Detection
Authors: CHU Qing‐Cui , GENG Cheng‐Huai , ZHOU Hui , YE Jian‐Nong
Published: December 2007

The fast separation capability of a novel miniaturized capillary electrophoresis with an amperometric detection (μCE‐AD) system was demonstrated by determining clenbuterol and salbutamol in real samples. The effects of several factors such as the acidity and concentration of the running buffer, the separation voltage, the applied potential and the injection time on CE‐AD were examined and optimized. Under the optimum conditions, the two β‐agonists could be baseline separated within 60 s at a separation voltage of 2 kV in a 90 mmol/L H3BO3‐Na2B4O7 running buffer (pH 7.4), which was not interfered by ascorbic acid and uric acid. Highly linear response was obtained for above compounds over three orders of magnitude with detection limits ranging from 1.20×10−7 to 6.50×10−8 mol/L (S/N=3). This method was successfully used in the analysis of feed and meat products with relatively simple extraction procedures.
Esterification of Carboxylic Acids and Diacids by Trialkyl Borate under Solvent and Catalyst‐Free Conditions
Authors: MANSOORI Yagoub , TATAROGLU SEYIDOV Firdovsi , BOHLOOLI Shahrbanoo , ZAMANLOO Mohammad Reza , IMANZADEH Gholam Hassan
Published: December 2007

Esterification or transesterification reactions are usually carried out in the presence of homogeneous or heterogeneous catalysts. However, recently a new method was reported for the esterification of carboxylic acids by tributyl borate under solvent‐ and catalyst‐free conditions. In order to show the synthetic ability of trialkyl borate esters in the esterification reactions, here, the esterification of other carboxylic acids and diacids by tributyl‐, triisoamyl‐, and tribenzyl borate under the same conditions were reported. Some of the prepared ester and diester products have found wide applications as plasticizers and synthetic ester base lubricants. The esterification reactions have been cleanly carried out in the absence of any solvent under catalyst‐free conditions. The maximum rate belongs to isoamyl trichloroacetate (VIb) which reached about 76% within about 6.5 h. On the basis of obtained findings, it seems that electron withdrawing groups on carboxylic acid facilitate the esterification reaction.
Description of the Structure and Properties of Atactic Polystyrene Melt Using Integral Equation Theory
Authors: ZHAO Lei , LI Yi‐Gui , ZHONG Chong‐Li
Published: December 2007

The polymer reference interaction site model (PRISM) integral equation theory was used to describe the structure and thermodynamic properties of atactic polystyrene (aPS) melt, in which the monomer of aPS is represented with an eight‐site model to characterize its microstructure. The intramolecular structure factors needed in the PRISM calculations were obtained from single chain MD simulations. The calculated results indicate that the results by the integral equation method agrees well with experiments, and can reflect the fine microscopic structure of real aPS melt. This work shows that the PRISM theory is a powerful tool for investigating the structure and properties of complex polymers.
A New matching strategy: Trial of the principal component coordinates
Authors: Agahian Farnaz , Amirshahi Seyed Hossein
Published: December 2007

A new matching strategy based on the equalization of the first three principal component coordinates of sample and target in a 3D eigenvector space is stated. Two series of databases including 1269 specimens of Munsell Color Book and a virtual sample population of textile materials were selected. Their first three basis functions were extracted and considered as axes of eigenvector space. The principal component coordinates of two different collections of textile samples were determined in these spaces and considered as matching criteria. The performance of the proposed algorithm is evaluated by the color difference values under different light sources as well as the root mean square differences of reflectance curves. Results indicate some types of improvements in comparison with previous algorithms in terms of spectral as well as colorimetric accuracy. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 10–18, 2008
Camera color analysis gamut
Authors: Hunt Robert W. G. , Pointer Michael R.
Published: December 2007

Michael Brill has opened a valuable discussion about camera gamuts and Roy Berns has questioned the use of the word “gamut” in that proposal. We would like to stress the importance of associating a gamut with an imaging output device and would thus question the use of the concept proposed for assessing the capabilities of an input device. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 81–82, 2008
Try camera gamut again: Not for size, but for camera and profile evaluation
Authors: Brill Michael H.
Published: December 2007

Hunt and Pointer call into question the utility of the camera color gamut (at least by my definition). Such doubt may be partly due to the connection of gamut with a size metric. Quite apart from gamut size, the sets that define my gamut definition are essential to the evaluation of digital cameras in conjunction with their profiles. The output‐device gamut; emphasized by Hunt and Pointer is also important, but appears at another stage of color management. © 2007 Wiley Periodicals, Inc. Col Res Appl, 33, 82–83, 2008
Particle‐in‐Cell Simulation of Stationary Plasma Thruster
Authors: Taccogna F. , Longo S. , Capitelli M. , Schneider R.
Published: December 2007

A very good example for the application of PIC techniques for detailed studies of low‐temperature plasmas is the Hall thrusters. Here, a variety of models with different complexities are needed to get better insight into the physics of these systems. Particular emphasis has been spent for the geometrical scaling, for the simulation of the plasma‐wall interaction inside the acceleration channel and for ion‐neutral collision into the plume emitted from the thruster. Results show the axial acceleration mechanism, the secondary electron emission instability, the azimuthal fluctuations into the channel and the ion backflow and electron trapping in the plume. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric Microfield Distributions in Dense One‐ and Two‐Component Plasmas
Authors: Sadykova S. , Ebeling W.
Published: December 2007

The electric microfield distributions have been calculated using an integral‐equation method for one‐component plasmas proposed by Iglesias [1] and the coupling‐parameter integration technique for two‐component plasmas proposed by Ortner et al. [2]. Electric microfield distributions are studied in the frame of the Kelbg pseudopotential model, taking into account quantum‐mechanical effects (diffraction, quantum symmetry effects) and screening effects. The screened pseudopotential is represented in a numerically approximated form. The results are compared with simulation results obtained by other authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission Intensity Enhancement of DC Arc Plasma Induced by External Oscillating Magnetic Field
Authors: Stoiljković M. M. , Pavlović M. , Savović J. , Kuzmanović M.
Published: December 2007

Direct current (dc) arc plasma with continuous aerosol supply was coupled with an external oscillatingmagnetic field of a few tens of mT and a frequency of up to 1 kHz. Such configuration was used to alter the plasma‐related radiative properties. The magnetic field was oriented perpendicularly to the electric field in the plasma and forced the arc column to oscillate as a whole with respect to the surrounding atmosphere. The magnitude of the appliedmagnetic.eld controls the amplitude of the oscillatory motion. Several parameters that can contribute to the radiative properties of the plasma were investigated (arc current, composition of aerosol introduced into the plasma, amplitude and frequency of the magnetic field applied). Spectral emission from different zones of the plasma column was measured by optical emission spectroscopy (OES). In comparison to steady‐state plasma, the applied magnetic field induces an intensity enhancement of emission of the most analytes considered. The intensity enhancement is strongly affected by the amplitude and frequency of plasma column oscillations, i.e. by plasma column velocity. Also, intensity enhancement depends on the plasma zone observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of Cathode and Anode Voltage on an Ion Sheath Thickness in a Magnetically Confined Diffusion Plasma
Authors: Mishra M. Kr. , Phukan A.
Published: December 2007

This article reports about the ion sheath thickness variation occurring in front of a negatively biased plate immersed in the target plasma region of a double plasma device. The target plasma is produced due to the local ionization of neutral gas by the high energetic electrons coming from the source region (main discharge region). It is observed that for an increase in cathode voltage (filament bias voltage) in the source region, the ion flux into the plate increases. As a result, the sheath at the plate contracts. Again, for an increase in source anode voltage (magnetic cage bias), the ion flux to the plate decreases. As a result, the sheath expands at the plate. The ion sheath formed at the separation grid of the device is found to expand for an increase in cathode voltage and it contracts for an increase in the anode voltage of the main discharge region. One important observation is that the applied anode bias can control the Bohm speed of the ions towards the separation grid. Furthermore, it is observed that the ion current collected by the separation grid is independent of changes in plasma density in the diffusion region but is highly dependent on the source plasma parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anomalous Diffusion in a Linear Plasma Generator
Authors: Waldmann O. , Meyer H. , Fussmann G.
Published: December 2007

Plasma production and particle transport of the magnetized plasma in the linear device PSI‐2 are investigated by analyzing the radial density and electron temperature pro.les obtained from Langmuir probe measurements. Additional information on the atomic (H) and proton temperatures is obtained from high resolution Doppler spectroscopy. The density profiles are found to be hollow, but do extend radially far beyond the visible rim with an exponential decay length of 3 cm. They can be explained by parallel and perpendicular diffusion in combination with a cylindrical source extending along the magnetic field all over the device. A large perpendicular diffusion coefficient in the range of 5 m2/s is inferred from the experimental results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variations of Plasma Parameters and Sheath Thickness Due to the Extraction of Ion and Electron Flux in a Double Plasma Device
Authors: Mishra M. K. , Phukan A. , Chakraborty M.
Published: December 2007

Influence of charged particle extraction on plasma parameters and on ion sheath has been investigated in a double plasma device. When ions are extracted from the plasma, the plasma density as well as the positive ion flux into the sheath increases. As a result a sheath contraction takes place. Again, in case of electron extraction, it is found that the plasma density as well as the positive ion flux into the sheath decreases. As a result a sheath expansion takes place. Furthermore, it is observed that the floating potential of a plate can be controlled by extracting charged particles from the plasma. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Influence of a Longitudinal Magnetic Fields on a Non‐Uniform Positive Column
Authors: Akbar D. , Bilikmen S.
Published: December 2007

The variations of plasma parameters of a dc discharge in a non‐uniform magnetized plasma were measured using fast floating double Langmuir probes. A solenoid is used to produce a uniform magnetic field parallel to the discharge axis. The axial changes of the plasma parameters are presented in the range of longitudinal magnetic fields 200 to 600 Gauss at the pressure range 0.3 to 2.1 Torr and discharge currents 5 and 15 mA in argon gas. The experimental results indicate that, as a consequence of the axial magnetic.eld and the variations in the discharge tube radii, the plasma parameters at small radius exhibit obvious changes in their distributions along the axis compared to the situation of unmagnetized plasma. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Increased TLR responses in dendritic cells lacking the ITAM‐containing adapters DAP12 and FcRγ
Authors: Chu Ching‐Liang , Yu Yen‐Ling , Shen Kuan‐Yin , Lowell Clifford A. , Lanier Lewis L. , Hamerman Jessica A.
Published: December 2007

The inhibitory effect of DAP12 on macrophages has been revealed by examining myeloid cells from DAP12‐deficient mice. In this report, we demonstrate that both DAP12 and the FcϵRIγ‐chain (FcRγ) are required for negative regulation of TLR responses in bone marrow‐derived dendritic cells (DC). Loss of both DAP12 and FcRγ enhanced the pro‐inflammatory cytokine production and maturation of DC after TLR stimulation, resulting in a greater percentage of DC that produced IL‐12 p40, TNF, and IL‐6, and expressed high levels of MHC class II, CD80, and CD86. Whereas DC lacking only DAP12 showed some increased TLR responses, those lacking only FcRγ had a greater enhancement of maturation and cytokine production, though to a lesser extent than DC lacking both DAP12 and FcRγ. Additionally, antigen‐specific T cell proliferation was enhanced by DAP12–/–FcRγ–/– DC relative to wild‐type DC after maturation. Similar to DAP12–/–FcRγ–/– DC, Syk‐deficient DC also had increased inflammatory cytokine production, maturation, and antigen presentation. These results confirm the inhibitory effect of immunoreceptor tyrosine‐based activation motif (ITAM) signaling in myeloid cells and show that DC and macrophages differ in their dependence on the ITAM‐containing adapters DAP12 and FcRγ for negative regulation of TLR signaling.