bluuebunny/crossref_metadata_2025 huggingface dataset:
Overproduction of Threonine Aldolase Circumvents the Biosynthetic Role of Pyruvate Decarboxylase in Glucose-Limited Chemostat Cultures ofSaccharomyces cerevisiae
Authors: van Maris Antonius J. A. , Luttik Marijke A. H. , Winkler Aaron A. , van Dijken Johannes P. , Pronk Jack T.
Published: April 2003

Pyruvate decarboxylase-negative (Pdc−) mutants ofSaccharomyces cerevisiaerequire small amounts of ethanol or acetate to sustain aerobic, glucose-limited growth. This nutritional requirement has been proposed to originate from (i) a need for cytosolic acetyl coenzyme A (acetyl-CoA) for lipid and lysine biosynthesis and (ii) an inability to export mitochondrial acetyl-CoA to the cytosol. To test this hypothesis and to eliminate the C2requirement of Pdc−S. cerevisiae, we attempted to introduce an alternative pathway for the synthesis of cytosolic acetyl-CoA. The addition ofl-carnitine to growth media did not restore growth of a Pdc−strain on glucose, indicating that the C2requirement was not solely due to the inability ofS. cerevisiaeto synthesize this compound. TheS. cerevisiae GLY1gene encodes threonine aldolase (EC 4.1.2.5), which catalyzes the cleavage of threonine to glycine and acetaldehyde. Overexpression ofGLY1enabled a Pdc−strain to grow under conditions of carbon limitation in chemostat cultures on glucose as the sole carbon source, indicating that acetaldehyde formed by threonine aldolase served as a precursor for the synthesis of cytosolic acetyl-CoA. Fractionation studies revealed a cytosolic localization of threonine aldolase. The absence of glycine in these cultures indicates that all glycine produced by threonine aldolase was either dissimilated or assimilated. These results confirm the involvement of pyruvate decarboxylase in cytosolic acetyl-CoA synthesis. The Pdc−GLY1overexpressing strain was still glucose sensitive with respect to growth in batch cultivations. Like any other Pdc−strain, it failed to grow on excess glucose in batch cultures and excreted pyruvate when transferred from glucose limitation to glucose excess.
Gene Encoding the Hydrolase for the Product of the
meta
-Cleavage Reaction in Testosterone Degradation by
Comamonas testosteroni
Authors: Horinouchi Masae , Hayashi Toshiaki , Koshino Hiroyuki , Yamamoto Takako , Kudo Toshiaki
Published: April 2003

In a previous study we isolated the
meta-
cleavage enzyme gene,
tesB
, that encodes an enzyme that carries out a
meta
-cleavage reaction in the breakdown of testosterone by
Comamonas testeroni
TA441 (M. Horinouchi et al., Microbiology 147:3367-3375, 2001). Here we report the isolation of a gene,
tesD
, that encodes a hydrolase which acts on the product of the
meta
-cleavage reaction. We isolated
tesD
by using a Tn
5
mutant of TA441 that showed limited growth on testosterone. TesD exhibited ca. 40% identity in amino acid sequence with BphDs, known hydrolases of biphenyl degradation in
Pseudomonas
spp. The TesD-disrupted mutant showed limited growth on testosterone, and the culture shows an intense yellow color. High-pressure liquid chromatography analysis of the culture of TesD-disrupted mutant incubated with testosterone detected five major intermediate compounds, one of which, showing yellow color under neutral conditions, was considered to be the product of the
meta
-cleavage reaction. The methylation product was analyzed and identified as methyl-4,5-9,10-diseco-3-methoxy-5,9,17-trioxoandrosta-1(10),2-dien-4-oate, indicating that the substrate of TesD in testosterone degradation is 4,5-9,10-diseco-3-hydroxy-5,9,17-trioxoandrosta-1(10),2-dien-4-oic acid. 4,5-9,10-Diseco-3-hydroxy-5,9,17-trioxoandrosta-1(10),2-dien-4-oic acid was transformed by
Escherichia coli-
expressed TesD. Downstream of
tesD
, we identified
tesE
,
F
, and
G
, which encode for enzymes that degrade one of the products of 4,5-9,10-diseco-3-hydroxy-5,9,17-trioxoandrosta-1(10),2-dien-4-oic acid converted by TesD.
Phylogenetic Analysis of Anaerobic Psychrophilic Enrichment Cultures Obtained from a Greenland Glacier Ice Core
Authors: Sheridan Peter P. , Miteva Vanya I. , Brenchley Jean E.
Published: April 2003

The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at −9°C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 × 10
7
cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at −2°C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma
Proteobacteria
as well as relatives of the
Thermus
,
Bacteroides
,
Eubacterium
, and
Clostridium
groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.
PCR Detection of a Newly Emerged Pandemic
Vibrio parahaemolyticus
O3:K6 Pathogen in Pure Cultures and Seeded Waters from the Gulf of Mexico
Authors: Myers Michael L. , Panicker Gitika , Bej Asim K.
Published: April 2003

This study describes the optimization of PCR parameters and testing of a wide number of microbial species to establish a highly specific and sensitive PCR-based method of detection of a newly emerged pandemic
Vibrio parahaemolyticus
O3:K6 strain in pure cultures and seeded waters from the Gulf of Mexico (gulf water). The selected open reading frame 8 (ORF8) DNA-specific oligonucleotide primers tested were found to specifically amplify all 35 pathogenic
V. parahaemolyticus
O3:K6 pandemic isolates, whereas these primers were not found to detectably amplify two strains of
V. parahaemolyticus
O3:K6 that were isolated prior to the 1996 outbreaks, 122 non-O3:K6 strains of
V. parahaemolyticus
, 198 non-
V.
parahaemolyticus
spp., or 16 non-
Vibrio
bacterial spp. The minimum level of detection by the PCR method was 1 pg of purified genomic DNA or 10
2
ORF8-positive
V. parahaemolyticus
O3:K6 cells in 100 ml of water. The effectiveness of this method for the detection of ORF8-positive isolates in environmental samples was tested in gulf water seeded with 10-fold serial dilutions of this pathogen. A detection level of 10
3
cells per 100 ml of gulf water was achieved. Also, the applicability of this methodology was tested by the detection of this pathogen in gulf water incubated at various temperatures for 28 days. This PCR approach can potentially be used to monitor with high specificity and well within the required range of sensitivity the occurrence and distribution of this newly emerged pathogenic
V. parahaemolyticus
O3:K6 strain in coastal, marine, and ship ballast waters. Early detection of
V. parahaemolyticus
O3:K6 will help increase seafood safety and decrease the risk of infectious outbreaks caused by this pathogen.
Bacterioplankton Community Shifts in an Arctic Lake Correlate with Seasonal Changes in Organic Matter Source
Authors: Crump Byron C. , Kling George W. , Bahr Michele , Hobbie John E.
Published: April 2003

Seasonal shifts in bacterioplankton community composition in Toolik Lake, a tundra lake on the North Slope of Alaska, were related to shifts in the source (terrestrial versus phytoplankton) and lability of dissolved organic matter (DOM). A shift in community composition, measured by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes, occurred at 4°C in near-surface waters beneath seasonal ice and snow cover in spring. This shift was associated with an annual peak in bacterial productivity ([
14
C]leucine incorporation) driven by the large influx of labile terrestrial DOM associated with snow meltwater. A second shift occurred after the flux of terrestrial DOM had ended in early summer as ice left the lake and as the phytoplankton community developed. Bacterioplankton communities were composed of persistent populations present throughout the year and transient populations that appeared and disappeared. Most of the transient populations could be divided into those that were advected into the lake with terrestrial DOM in spring and those that grew up from low concentrations during the development of the phytoplankton community in early summer. Sequencing of DNA in DGGE bands demonstrated that most bands represented single ribotypes and that matching bands from different samples represented identical ribotypes. Bacteria were identified as members of globally distributed freshwater phylogenetic clusters within the α- and β-
Proteobacteria
, the
Cytophaga-Flavobacteria-Bacteroides
group, and the
Actinobacteria
.
Virus-Contaminated Oysters: a Three-Month Monitoring of Oysters Imported to Switzerland
Authors: Beuret Christian , Baumgartner Andreas , Schluep Jakob
Published: April 2003

Molluscan shellfish are known to be carriers of viral and bacterial pathogens. The consumption of raw oysters has been repeatedly linked to outbreaks of viral gastroenteritis and hepatitis A. Switzerland imports over 300 tons of oysters per year, 95% of which originate in France. To assess the level of viral contamination, a 3-month monitoring study was conducted. Therefore, the sensitivities of several previously described methods for virus concentration were compared, and one protocol was finally chosen by using dissected digestive tissues. Eighty-seven samples consisting of five oysters each were analyzed for Norwalk-like viruses (NLVs), enteroviruses, and hepatitis A viruses from November 2001 to February 2002. The oysters were exported by 31 French, three Dutch, and two Irish suppliers. Eight oyster samples from six French suppliers were positive for NLVs, and four samples from four French suppliers were positive for enteroviruses; two of the latter samples were positive for both viral agents. No hepatitis A viruses were detected. The sequences of NLV and enterovirus amplicons showed a great variety of strains, especially for the NLVs (strains similar to Bristol, Hawaii, Mexico, and Melksham agent). The data obtained indicated that imported oysters might be a source of NLV infection in Switzerland. However, further studies are needed to determine the quantitative significance of the risk factor within the overall epidemiology of NLVs.
Characterization of TsaR, an Oxygen-Sensitive LysR-Type Regulator for the Degradation ofp-Toluenesulfonate inComamonas testosteroniT-2
Authors: Tralau Tewes , Mampel Jörg , Cook Alasdair M. , Ruff Jürgen
Published: April 2003

TsaR is the putative LysR-type regulator of thetsaoperon (tsaMBCD) which encodes the first steps in the degradation ofp-toluenesulfonate (TSA) inComamonas testosteroniT-2. Transposon mutagenesis was used to knock outtsaR. The resulting mutant lacked the ability to grow with TSA andp-toluenecarboxylate (TCA). Reintroduction oftsaRintranson an expression vector reconstituted growth with TSA and TCA. ThetsaRgene was cloned intoEscherichia coliwith a C-terminal His tag and overexpressed as TsaRHis. TsaRHiswas subject to reversible inactivation by oxygen, which markedly influenced the experimental approaches used. Gel filtration showed TsaRHisto be a monomer in solution. Overexpressed TsaRHisbound specifically to three regions within the promoter between the divergently transcribedtsaRandtsaMBCD. The dissociation constant (KD) for the whole promoter region was about 0.9 μM, and the interaction was a function of the concentration of the ligand TSA. A regulatory model for this LysR-type regulator is proposed on the basis of these data.
Heat Shock Response by the Hyperthermophilic Archaeon
Pyrococcus furiosus
Authors: Shockley Keith R. , Ward Donald E. , Chhabra Swapnil R. , Conners Shannon B. , Montero Clemente I. , Kelly Robert M.
Published: April 2003

Collective transcriptional analysis of heat shock response in the hyperthermophilic archaeon
Pyrococcus furiosus
was examined by using a targeted cDNA microarray in conjunction with Northern analyses. Differential gene expression suggests that
P
.
furiosus
relies on a cooperative strategy of rescue (thermosome [Hsp60], small heat shock protein [Hsp20], and two VAT-related chaperones), proteolysis (proteasome), and stabilization (compatible solute formation) to cope with polypeptide processing during thermal stress.
Lack of effects of hydrocortisone pretreatment on zinc-induced changes in protein assemble
Authors: Walther U I , Miickter H , Fichtl B , Forth W
Published: April 2003

Inhalational zinc intoxication may lead to the develoment of acute respiratory distress syndrome (ARDS). Pharmacological treatment of ARDS is based on gluccorticoids, while the efficiency of glucocorticoid treatment is discussed controversially. Glucocorticoid pretreatment of lung cell lines is known to cause disparate effects with regard to zinc susceptibility. Both substances are known to each interact with protein metabolism. In the present study, zinc effects were examined on hydrocortisone (HC)-pretreated lung cell lines by detection of content and synthesis of different proteins after two-dimensional (2D) gel electrophoresis. (1) In HC-pretreated fibroblaslike ll Lu and alveolar epithelial L2 cells, no zinmediated changes after silver staining of 2D gels were seen. Few differences occurred in HC-pretreated alveolar epithelial A549 cells that might be explained by the appearance of heat shock proteins (hsp) after zinc exposure. (2) In autoradiographs after 35S et icorporation only in 1l Lu cells, small differences occurred after HC treatment as compared to controls without HC. (3) All cell lines tested demonstrated the same zinmediated changes in autoradiographs with a nearly complete loss of synthesized proteins and an appearance of a few new spots. These changes were reversible in all cell lines after washing out of external zinc. The new spots were transiently expressed for a few hours after zinc exposure. (4) The overall effect of HC pretreatment was rather unimpressive. The virtual lack of major effects does not support the hypothesis that a gross interaction between glucocorticoids and zinc at the cellular protein synthesis level would be an important mechanism of influence in zinc-induced lung injury.
Alcohol and aldehyde dehydrogenase activity in the stomach and small intestine of rats poisoned with methanol
Authors: Chrostek L , Szczepura D , Szmitkowski M , Jelski W , Wierzchowski J
Published: April 2003

The activities of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) were measured with fluorogenic naphthaldehydes in the stomach and small intestine homogenates of rats dosed with 6 g methanol/kg bw after 6, 12, 24 h and 2, 5, 7 days. After intoxication with a sublethal dose, the ADH activity measured with these naphthaldehydes andALDH activities in the stomach and small intestine were significantly decreased. This inhibition is stronger in the stomach and probably depends on cell damage and protein denaturation. We conclude that the activity measured with 6-methoxy-2-naphthaldehyde (MONAL-62) may be due to the activity of rat ADH-1 isoenzyme, and the activity detected with 4-methoxy-1-naphthaldehyde (MONAL-41) to the activity of rat ADH-2 isoenzyme.
In vitro cytotoxicity evaluation of plastic biomedical devices
Authors: Pant A B , Agarwal A K , Sharma V P , Seth P K
Published: April 2003

Cytotoxic potential of four plastic biomedical devices (intravenous transfusion sets, IV sets; dextrose normal saline bottles, DNS bottles; Ringer lactate bottles, RL bottles; and Ryle's tubes) including 17different brands was evaluated by investigating growth inhibition, percent survival, mitotic index and colony-forming ability (cfa) in L929, an adherent type mouse fibroblast cell line. Experimental sets were exposed with leachates of biomedical products in serumfree minimum essential medium (MEM) for 1 h at 378Cina CO2 incubator. After 1 h, medium was replaced with serumrich MEM containing essential amino acids and reincubated up to 96 h. Cells in serum-free MEM only were processed under identical conditions and served as the control. The leachates from all types of biomedical devices evaluated exhibitedreductioninthegrowthandsurvivalofthecellline in the first 12 h postexposure followed by their gradual recoveryupto96h.Asignificantreductionincellgrowthwas apparent in the six brands of IV sets from 24 h onwards up to 36 h (59% growth inhibition). Though the cfa was also reduced in all the brands tested, the magnitude of reduction was less compared to growth inhibition. The results indicate that leachates of IV sets were more toxic compared to other biomedical devices screened, and growth inhibition assay was found to be more sensitive and suitable for cytotoxicity evaluation of biomedical devices.
Preclinical evaluation of the cardiotoxicity of PK2: A novel HPMA copolymer–doxorubicin–galactosamine conjugate antitumour agent
Authors: Hopewell J W , Duncan R , Wilding D , Chakrabarti K
Published: April 2003

PK2 is a polymeric anticancer conjugate composed of an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer backbone and pendant doxorubicin (DOX) linked via a Gly-Phe-Leu-Gly peptide spacer. Additionally galactose residues are present to facilitate liver targeting. To justify clinical evaluation of PK2 it was necessary to determine its late cardiotoxicity compared to that of free DOX. A well standardised Sprague–Dawley rat model was used with either intravenous (IV) administration (4, 8 and 12 mg/kg DOX equivalent) or intraperitoneal (IP) administration (12, 18, 24 and 36 mg/kg DOX equivalent) of PK2. This variation in the route was due to the limited solubility of PK2 at higher doses. PK2 showed two to three times less acute toxicity (assessed by the maximum reduction in body weight in the first 2 weeks) than free DOX, and both compounds were less toxic when given IP. No animals given PK2 IV showed clinical signs of cardiotoxicity, the only toxicity seen was abnormal tooth growth (50% of the animals receiving 12 mg/kg, DOX equivalent). In contrast, several animals receiving free DOX (1–4 mg/kg) IV died due to cardiotoxicity in an approximately dose-related manner. All animals receiving free DOX (4 mg/kg) died by 12 weeks. Following IPadministration of PK2 there were only two late deaths related to cardiotoxicity and these were in the 24 mg/kg DOX equivalent group. All animals receiving PK2 at the highest dose (36 mg/kg DOX equivalent) died within 4 weeks, cardiotoxicity was not the main contributing factor. In this study, PK2 displayed a ∼5-fold reduction in cardiotoxicity relative to free DOX and this supported the progression of PK2 into early clinical investigation.
A Novel T608R Missense Mutation in Insulin Receptor Substrate-1 Identified in a Subject with Type 2 Diabetes Impairs Metabolic Insulin Signaling
Authors: Esposito Diana L. , Li Yunhua , Vanni Cinzia , Mammarella Sandra , Veschi Serena , Della Loggia Fulvio , Mariani-Costantini Renato , Battista Pasquale , Quon Michael J. , Cama Alessandro
Published: April 2003

Naturally occurring mutations in insulin receptor substrate-1 (IRS-1) have previously been implicated in impaired insulin action. We now report a novel mutation in IRS-1 with substitution of Arg for Thr608 that was identified in a patient with type 2 diabetes mellitus. We detected the T608R mutation in 1 of 136 chromosomes from diabetic patients and in 0 of 120 chromosomes from nondiabetic controls, suggesting that this is a rare IRS-1 variant. Conservation of Thr608 in human, monkey, rat, mouse, and chicken IRS-1 sequences is consistent with a crucial function for this residue. Moreover, Thr608 is located near the YMXM motif containing Tyr612 that is important for binding and activation of phosphoinositol 3-kinase (PI 3-kinase). To investigate whether the T608R mutation impairs insulin signaling, we transiently transfected NIH-3T3IR cells with hemagglutinin-tagged wild-type or T608R mutant IRS-1 constructs. Recombinant IRS-1 immunoprecipitated from transfected cells treated with or without insulin was subjected to immunoblotting for the p85 regulatory subunit of PI 3-kinase as well as a PI 3-kinase assay. As expected, in control cells transfected with wild-type IRS-1, insulin stimulation caused an increase in p85 coimmunoprecipitated with IRS-1 as well as a 10-fold increase in IRS-1-associated PI 3-kinase activity. Interestingly, when cells transfected with IRS1-T608R were stimulated with insulin, both the amount of p85 coimmunoprecipitated with IRS1-T608R as well as the associated PI 3-kinase activity were approximately 50% less than those observed with wild-type IRS-1. Moreover, in rat adipose cells, overexpression of IRS1-T608R resulted in significantly less translocation of GLUT4 to the cell surface than comparable overexpression of wild-type IRS-1. We conclude that a naturally occurring substitution of Arg for Thr608 in IRS-1 is a rare human mutation that may contribute to insulin resistance by impairing metabolic signaling through PI 3-kinase-dependent pathways.
Defective Activation of Skeletal Muscle and Adipose Tissue Lipolysis in Type 1 Diabetes Mellitus during Hypoglycemia
Authors: Enoksson Staffan , Caprio Sonia K. , Rife Frances , Shulman Gerald I. , Tamborlane William V. , Sherwin Robert S.
Published: April 2003

The increased risk of hypoglycemia during intensified treatment of type 1 diabetes mellitus (T1DM) patients, who have a deficient glucagon secretory response, is largely attributed to the development of suppressed adrenomedullary responses. A consequence of this impairment of catecholamine secretion might be reduced lipolysis in major target tissues (muscle and adipose) and, in turn, increased glucose metabolism. To test this hypothesis, we used microdialysis to monitor glycerol (index of lipolysis) in the extracellular fluid of skeletal muscle and adipose tissue and assessed whole-body glucose use by measuring [6,6-2H2]glucose enrichment in plasma in seven intensively treated T1DM patients and eight nondiabetic subjects who received a 3-h insulin infusion (0.8 mU/kg·min) on two occasions: during mild-moderate hypoglycemia or euglycemia. In the hypoglycemic study, the rise in plasma epinephrine was approximately 50% less in the T1DM patients despite a greater fall in plasma glucose (to 3.0 vs. 3.5 mm in controls; P < 0.05). Moreover, the rate of glucose flux and the plasma-extracellular fluid glucose gradient in muscle was increased during hypoglycemia in T1DM subjects compared with controls. Glycerol levels in muscle, adipose, and plasma fell similarly in both groups in the first hour. Thereafter, tissue glycerol remained suppressed in the T1DM patients but rebounded significantly (P < 0.01) in the control subjects. The glycerol response in muscle and adipose tissue was significantly correlated with plasma epinephrine concentration (r = 0.73, P = 0.002; and r = 0.52, P = 0.04, respectively), and inversely correlated with whole-body glucose disposal (r = −0.51, P = 0.05; and r = −0.50, P = 0.05). To determine whether the absence of the lipolytic response is limited to deficient catecholamine release, we perfused muscle and adipose tissue in situ with the selective β2-agonist terbutaline during hyperinsulinemic euglycemia. Local addition of agonist increased glycerol and blood flow in both muscle and adipose (P < 0.01 and P < 0.05, respectively) similarly in T1DM and control subjects. We conclude that deficient release of (rather than impaired responsiveness to) catecholamines in T1DM prevents the local fat breakdown within muscle and adipose tissue that normally occurs during mild-moderate hypoglycemia. This defect within peripheral tissues may lead to a delayed increase in glucose disposal that could contribute to the severity of hypoglycemia when it is prolonged.
The Association between Bone Mineral Density, Metacarpal Morphometry, and Upper Limb Fractures in Children: A Population-Based Case-Control Study
Authors: Ma Deqiong , Jones Graeme
Published: April 2003

The aim of this population-based case-control study was to examine the association between bone mass and upper limb fractures in children aged 9–16 yr. Areal bone mineral density and bone mineral apparent density (BMAD) were measured by both dual energy absorptiometry (DXA) and metacarpal index (MI) by hand radiograph. A total of 321 fracture cases and 321 randomly selected individually matched controls were studied. For all fractures, cases had lower DXA measures at all sites (1.1–3.3%; all P < 0.05). A larger reduction was observed for those with wrist and forearm fractures (1.2–4.5%; all P < 0.05, except total body BMAD) but not other upper limb fractures (hand, −1.6 to +1.2%; upper arm: 0.9–4.8%; all P > 0.05). For metacarpal measures, cases had a thinner cortical width and lower MI for wrist and forearm fractures only. In multivariate modeling, both spine BMAD (odds ratio, 1.4/sd reduction) and MI (odds ratio, 1.5/sd reduction) remained statistically significant predictors of wrist and forearm fractures. In conclusion, both DXA measures and MI are independently associated with wrist and forearm but not other upper limb fractures. The magnitude of this association is somewhat weaker than in adults but suggests that optimizing age-appropriate bone mass will lessen the risk of fracture in children.
First-Principles Energy Band Calculation for ZnSb2O6 with Trirutile-Type Structure
Authors: Matsushima Shigenori , Tanizaki Takumi , Nakamura Hiroyuki , Nonaka Moriyasu , Arai Masao
Published: April 2003

The electronic structure of ZnSb2O6 is calculated by using the FLAPW method and the DV-Xα method. The valence band with the width of ca. 10.5 eV is roughly classified into the two bands, where O 2p orbitals are dominant and hybridize with Zn 3d and Sb 5s orbitals. On the other hand, the lower conduction band is mainly constructed from Sb 5s orbitals which have large spatial extent. Therefore, ZnSb2O6 crystal is expected to have large electron mobility with doping carriers.
Improvement of the Catalytic Performance of Pd/WO3/ZrO2 in the Selective NO–CH4–O2 Reaction by the Addition of Water Vapor
Authors: Okumura Kazu , Kusakabe Tetsuji , Yasunobu Naoko , Niwa Miki
Published: April 2003

The Pd/WO3/ZrO2 catalyst exhibited activity for the NO–CH4–O2 reaction in the presence of water vapor when WO3 monolayer covered the ZrO2 surface. The selectivity of methane consumption for NO reduction was considerably improved by the addition of 10% of water vapor.
Sonochemical Coreduction Route to Single-Crystalline InSb Dendrites
Authors: Xiong Yujie , Xie Yi , Du Guoan , Liu Xianming , Tian Xiaobo
Published: April 2003

Single-crystalline InSb dendrites were prepared by a sonochemical coreduction route. The result of supplementary experiments shows the experiment was carried out along the coreduction mechanism. It is found that the ultrasonic power, reaction temperature and solvent played crucial roles in the crystallinity and yield of products.
Hydration of Ca A-Type Zeolite and Ca(OH)2
Authors: Uehara Motoki , Sasaki Takahiko
Published: April 2003

The hydration reaction of Ca A-type zeolite and calcium hydroxide was studied. The results revealed that an isostructural material of hydrocalumite (C-A-H) is generated at the early stage of hydration, and following that of strätlingite–vertumnite is generated. Only 0.77 nm of the C-A-H phase was observed at a humidity below 40% while part of the 0.77 nm phase swelled to 0.82 nm at a humidity of 40% or above.
Manufacturing of Activated Carbon Using Furfural Residue as Raw Material
Authors: Wang Yanhua , Noda Kiyoshi , Kagawa Shoji
Published: April 2003

In a series of study, furfural residue that is a kind of waste byproduct was first utilized for manufacturing activated carbon, by self-activation. Pore characteristics and specific surface area of the resulting activated carbon was examined. It is noted that the self-activation with water content contributed mainly to the development of macropore volumes. This shows good trend for adsorption of sulfur dioxide in exhaust gas and other flue gas.
Generation and Behavior of Naphthoyloxyl Radicals in Photocleavage of 1-(Naphthoyloxy)-2-pyridones
Authors: Najiwara Toshihiro , Segawa Katsunori , Sakuragi Hirochika
Published: April 2003

A series of 1- and 2-naphthoyloxyl radicals are generated from photocleavage of 1-(naphthoyloxy)-2-pyridones in acetonitrile. Introduction of a methoxy group in the naphthalene ring stabilized the naphthoyloxyl radicals to prevent decarboxylation completely and reduced remarkably their reactivities of addition to olefins and hydrogen-atom abstraction.
Gas-Phase Bismuth Sulfide Clusters Produced by Gas-Aggregation Source
Authors: Yamada Yasuhiro
Published: April 2003

Bismuth sulfide clusters BixSy were produced using a gas-aggregation source and investigated by time-of-flight mass spectrometry following ionization with a 266-nm YAG laser. Stable bismuth sulfide cluster ions Bi4S10+ and Bi6S11+, as well as Bi2S2+, Bi3S2+, Bi2S6+, Bi3S9+, Bi4S7+, and Bi6S4+, were observed, indicative of the production of stable neutral bismuth sulfide clusters in the gas phase. The cluster structure was predicted by density-functional calculations.
Evidence for the HCl+(A) Formation in the Reaction of Ne(3P) with the Size-Selected HCl Dimer Using an Electrostatic Hexapole Field
Authors: Imura Kohei , Ohoyama Hiroshi , Kasai Toshio
Published: April 2003

Penning ionization of Ne(3P) metastable atom with size-selected HCl dimer was studied by using an electrostatic hexapole field and chemiluminescence detection. We found that the HCl dimer can also produce HCl+(A) ions in the reaction with Ne(3P) just like its corresponding monomer reaction. The internal energy distribution of HCl+(A) in the dimer reaction is cooler than that in the monomer reaction, reflecting the third-body effect due to the other HCl in the dimer.
Photo-Controllable and Fixative Optical Properties of Non-polymeric Liquid Crystals with Azobenzene Chromophore
Authors: Moriyama Masaya , Tamaoki Nobuyuki
Published: April 2003

A new series of non-polymer photochromic liquid crystalline compounds which form glassy solids maintaining the liquid crystalline molecular alignment has been synthesized; their optical properties such as cholesteric reflections, controlled by the intramolecular photoreaction and temperature, can be utilized for the construction of information-storing materials.
Crystal Structure Consisting Both of Segregated and Mixed Donor–Acceptor Columns
Authors: Otsuki Joe , Matsui Hiroyuki , Imamura Koichiro , Yoshikawa Isao , Araki Koji , Seno Manabu
Published: April 2003

A host molecule in which two acridine arms are held by an anthraquinone spacer cocrystallizes with TCNQ into a new type of organic donor–acceptor structure consisting both of segregated acceptor (anthraquinone) columns and mixed donor–acceptor columns (acridine–TCNQ) extending in different directions.
Supramolecular Liquid Crystals with Hydrogen-Bonding Self-Assembled T-Shaped Mesogens
Authors: Chen Dongzhong , Wan Lei , Fang Jianglin , Yu Xuehai
Published: April 2003

A new class of supramolecular liquid crystals with T-shaped mesogens are obtained by doubly hydrogen-bonded self-assembly of 2,6-bis(4-hexyloxybenzoylamino)pyridine and benzoic acid derivatives.
1H NMR Study of Hydroxy Groups in Mesoporous Molecular Sieve SBA-15
Authors: Shi Lei , Zou Yan , He Heyong
Published: April 2003

Three types of hydroxy groups, which are attributed to single, hydrogen-bonded and geminal SiOHs in mesoporous molecular sieve SBA-15 are directly and quantitatively observed by 1H ultrafast MAS NMR spectroscopy.
Probing the Nature of Cholera Toxin B Oligomer by the Atomic Force Microscopy
Authors: Wang Rong , Vengasandra Srikanth , Yan Funing
Published: April 2003

The nature of cholera toxin B oligomer was examined via the atomic force microscopy on the nanometer scale at the fluid tapping mode. The specific binding force between the B oligomer and the ganglioside GM1 receptor was quantified.
Novel Photocycloaddition of Aromatic Ketones to Cyclic Oligosilanes
Authors: Kako Masahiro , Gu Mei , Takenaka Yohei , Takagi Kentaro , Kondo Kazuhiro , Nakadaira Yasuhiro , Wakasa Masanobu , Hayashi Hisaharu
Published: April 2003

Photolysis of aromatic ketones (2,2,2-trifluoroacetophenone, acetophenone, and benzophenone) in the presence of cyclic oligosilanes afforded two types of cycloadducts depending on the nature of the ketone employed. The quenching of the excited triplet state of benzophenone by oligosilanes was investigated by laser flash photolysis.
Preparation of Organoytterbium Reagent from Ytterbium Trichloride and Organomagnesium
Authors: Matsubara Seijiro , Ikeda Takanori , Oshima Koichiro , Utimoto Kiitiro
Published: April 2003

The preparation of organolanthanoid species from diorganomagnesium and lanthanoid salt is discussed. Treatment of cerium trichloride or ytterbium trichloride with diorganomagnesium gave the corresponding organolanthanoid species much more efficiently than treatment of the salt with organomagnesium halide.
Orientation of Rotational Isomers of 1,2-Bis(2-anthryl)ethene in Liquid Crystals
Authors: Karatsu Takashi , Tanaka Yuuki , Imakawa Masanori , Fukui Keijiro , Kitamura Akihide
Published: April 2003

The fluorescence spectra of three rotational isomers of E-1,2-bis(2-anthryl)ethene (1) were obtained by the principal component analysis-self modeling (PCA-SM) method in solution. Based on the resolved spectra, the orientation of the rotational isomers in nematic and cholesteric liquid crystals (LC) were investigated. 1 mainly exists as the (s-trans, s-trans) conformer in these LC phases.
Formation Mechanism of Peroxides in Reactions of Cyclic Olefins with Ozone in Air
Authors: Hatakeyama Shiro , Sivanesan Subramanian , Urabe Taichiro
Published: April 2003

We carried out reactions of methyl-substituted cyclohexenes and α-pinene with ozone in air and elucidated the mechanisms of formation of the minor products (peroxides and formic acid). Peroxyacetic acid was formed only from the cyclohexenes with a methyl group on the double bond, whereas formic acid was produced in higher yields from the cyclohexenes without a methyl group on the double bond. These differences in product yields allowed us to elucidate the mechanism of formation of the products.
Enhanced Molecular-Shape Selectivity for Polyaromatic Hydrocarbons through Isotropic-to-Crystalline Phase Transition of Poly(octadecyl acrylate)
Authors: Ihara Hirotaka , Goto Yoshihiro , Sakurai Toshihiko , Takafuji Makoto , Sagawa Takashi , Nagaoka Shoji
Published: April 2003

We report temperature-triggered enhancement of molecular-shape selectivity by poly(octadecyl acrylate) which undergoes isotropic-to-crystalline phase transition. In this communication, it is also proposed that π–π interaction is included in this selective interaction and is enhanced through orientation of the carbonyl groups which are in a crystalline state.
Alignment Behavior of Discotic Nematic and Rectangular Columnar Phases on Self-Assembled Monolayers of Alkanethiol and Asymmetrical Disulfide
Authors: Monobe Hirosato , Azehara Hiroaki , Shimizu Yo , Fujihira Masamichi
Published: April 2003

Alignment behavior of a discotic liquid crystalline triphenylene (C8OBT) on substrates coated with self-assembled monolayers (SAMs) of alkanethiol and asymmetrical disulfide was investigated by polarized microscopy. Discotic nematic (ND) and rectangular columnar (Colr) phases of C8OBT shows a different alignment behavior depending on the element of SAMs. C8OBT exhibits a fan-shaped texture on an alkanethiol SAM in Colr phase, while it shows a planar alignment on a SAM of asymmetrical disulfide.
Thermal Stability of Alumina Modified Silica Fiber
Authors: Hasegawa Akira
Published: April 2003

Alumina modified silica fibers were prepared by covering with alumina fibrils. The modification induced the thermal stability under a stream of water at 1273 K without α-alumina formation. The morphology of alumina fibrils anchored on silica surface play an important role for the thermal stability in the presence of steam.
Electrochemical Behavior of Graphite–Lithium Intercalation Electrode in AlCl3–EMIC–LiCl–SOCl2 Room-Temperature Molten Salt
Authors: Koura Nobuyuki , Etoh Keiko , Idemoto Yasushi , Matsumoto Futoshi
Published: April 2003

The electrochemical behavior of a graphite (comprising only artificial graphite particles) electrode for intercalation and deintercalation of Li+, in AlCl3–1-ethyl-3-methylimidazolium chloride (EMIC)–LiCl–thionyl chloride (SOCl2) melt was studied.
Chiral Recognition by Multicenter Single Proton Hydrogen Bonding of Trifluorolactates
Authors: Katagiri Toshimasa , Uneyama Kenji
Published: April 2003

An X-ray crystallographic analysis of optically pure isopropyl trifluorolactate suggested possible seven centered hydrogen bondings with chirality. The hydroxy group was surrounded by three intra- and three intermolecular proton acceptors within reasonable hydrogen bonding distances.
A Facile Synthesis of 1,1-Disilylethenes via Me3MgLi-Induced Monomethylation of Dibromodisilylmethanes
Authors: Inoue Atsushi , Kondo Junichi , Shinokubo Hiroshi , Oshima Koichiro
Published: April 2003

Lithium trimethylmagnesate (Me3MgLi) induces monomethylation of dibromodisilylmethanes in excellent yields. Subsequent dehydrobromination of the resulting 1-bromo-1,1-disilylethanes with DBU affords 1,1-disilylethenes in good yields.
Sterically Protected Dipotassium Germanedithiolate
Authors: Matsumoto Tsuyoshi , Tatsumi Kazuyuki
Published: April 2003

The germanedithiols Dmp(Ar)Ge(SH)2 [Dmp=2,6-dimesitylphenyl; Ar = Dep (2,6-diethylphenyl) 1a, Tip (2,4,6-triisopropylphenyl) 1b] were synthesized by the reduction of hexathiagermepanes Dmp(Ar)GeS6 and tetrathiagermolanes Dmp(Ar)GeS4 with NaBH4. The treatment of 1awith 2 equiv of potassium hydride afforded the dipotassium germanedithiolate 2.
A Silicon–Silicon Triple Bond Surrounded by Bulky Terphenyl Groups
Authors: Takagi Nozomi , Nagase Shigeru
Published: April 2003

In search of a stable disilyne, effects of bulky 2,6-bis(2,4,6-triisopropylphenyl)phenyl (Ar*) groups on silicon–silicon triple bonding are investigated using density functional theory. It is predicted that Ar*Si≡SiAr* is very stable to isomerization and dimerization.
Highly Diastereoselective Aziridination of α,β-Unsaturated Amides Using Diaziridine
Authors: Ishihara Hiroyuki , Ito Yoshio N , Katsuki Tsutomu
Published: April 2003

Racemic 3-cyclohexyl-1-methyldiaziridine was found to react with α,β-unsaturated amides in basic conditions, giving N-unprotected trans-aziridines, while 3,3-pentamethylenediaziridine had been reported to afford cis-aziridines in high diastereoselectivity. The trans-selectivity was partially dependent on the stereochemistry of the substrate. The stereochemistries of these reactions were reasonably explained by the conformational analysis of the intermediary enolates.
Influence of Ti‐Based Fillers on the Thermal Decomposition and Phase Development of Polysiloxane Derived Materials
Authors: Hönack F. , Riedel R.
Published: March 2003

The addition of carbide‐forming filler particles like titanium or TiH2 is a suitable way to adjust the thermal decomposition behavior and the phase development of polysiloxane precursors. Besides TiC as the main crystalline phase formed at 1100°C, titanium silicides are found, but no oxygen‐containing crystalline phases. Thermal simultaneous analysis shows that the reaction of filler particles and matrix starts approximately at 300°C.
Predicting the Mircostructure in Semi‐Crystalline Thermoplastics using Software for the Simulation of Recrystallization in Metals
Authors: Michaeli W. , Hoffmann S. , Cramer A. , Dilthey U. , Brandenburg A. , Kretschmer M.
Published: March 2003

A software for the simulation of spherulite growth during the cooling of a quiescent melt has been developed and tested vs. experimental data by the authors. The tests have verified good qualitative results: the calculated crystal microstructure and distribution (see Figure for a simulated pattern close to the mold surface) correspond well with the real morphology.
Fabrication of Micromolds for Gearwheels by Micro Powder Injection Molding
Authors: Gietzelt T. , Piotter V. , Jacobi O. , Ruprecht R. , Hausselt J.
Published: March 2003

Isolated ceramic microstructures, e.g., micromolds for gearwheels (see Figure) were produced by micro powder injection molding at very tight tolerances. Concomitantly, methods were developed and demonstrated for the isolation of metallic or ceramic micro parts, and for one‐step exact fixation of microparts onto a substrate with excellent control over thickness and surface quality.
Evaluation and Modeling of Chemical Segregation Effects for Thixoforming Processing
Authors: Noll T. , Friedrich B. , Hufschmidt M. , Modigell M. , Nohn B. , Hartmann D.
Published: March 2003

Why and how does chemical segregation happen during thixoforming of complex‐shaped parts? The authors identified critical parameters and developed a computer software which simulates the forming process and detects separation phenomena. The Figure shows a simulated step shot process; light and dark areas represent different compositions of the alloy.
In‐Situ Processing of Al Alloy Composites
Authors: Zheng Q. , Wu B. , Reddy R.G.
Published: March 2003

In‐situ processing of discontinuously reinforced Al alloy composites (DRACs) by gas‐bubbling method was investigated in this paper. Fine SiC and AlN particles were synthesized by bubbling C‐bearing and N‐bearing gases respectively. These results show that processing of DRACs through in‐situ gas‐bubbling route is technically feasible. Compared with conventional processing techniques, this method has the potential to produce DRACs with better microstructure and properties while with lower cost.
Preparation and Organization of Nanoscale Polyelectrolyte‐Coated Gold Nanoparticles
Authors: Mayya K.S. , Schoeler B. , Caruso F.
Published: March 2003

The layer‐by‐layer (LbL) desposition of oppositely charged polyelectrolytes from adsorption solutions of different ionic strength onto ∼7 nm diameter carboxylic acid‐derivatized gold nanoparticles has been studied. The polyelectrolyte‐modified nanoparticles were characterized by UV‐vis spectrophotometry, microelectrophoresis, analytical ultracentrifugation, and transmission electron microscopy. UV‐vis data showed that the peak plasmon absorption wavelength of the gold nanoparticles red‐shifted after each adsorption step, and microelectrophoresis experiments revealed a reversal in the surface charge of the nanoparticles following deposition of each layer. These data are consistent with the formation of polyelectrolyte layers on the nanoparticles. Analytical ultracentrifugation showed an increase in mean nanoparticle diameter on adsorption of the polyelectrolytes, confirming the formation of gold‐core/polyelectrolyte‐shell nanoparticles. Transmission electron microscopy studies showed no signs of aggregation of the polyelectrolyte‐coated nanoparticles. The adsorption of the polyelectrolyte‐coated gold nanoparticles onto oppositely charged planar supports has also been examined. UV‐vis spectrophotometry and atomic force microscopy showed increased amounts of nanoparticles were adsorbed with increasing ionic strength of the nanoparticle dispersions. This allows control of the nanoparticle surface loading by varying the salt content in the nanoparticle dispersions used for adsorption. The LbL strategy used in this work is expected to be applicable to other nanoparticles (e.g., semiconductors, phosphors), thus providing a facile means for their controlled surface modification through polyelectrolyte nanolayering. Such nanoparticles are envisaged to have applications in the biomedical and bioanalytical fields, and to be useful building blocks for the creation of advanced nanoparticle‐based films.
Chemical and Structural Investigations of Biomimetically Grown Fluorapatite–Gelatin Composite Aggregates
Authors: Busch S. , Schwarz U. , Kniep R.
Published: March 2003

Deeper understanding of the basic principles of biomineralization is a major challenge for present and future research. The high complexity of in‐vivo conditions calls for simplified model systems that still involve dynamic processes like reorganization, formation, self‐organization, and development of patterns, respectively. The present contribution deals with hierarchically ordered spherical aggregates of fluorapatite–gelatin composites with fractal architecture that are grown in gelatin matrices. The model system was chosen to mimic formation conditions on a lower level of complexity compared with the natural formation of calcified tissue (bone, teeth). In order to gain insight into structure formation and the motif for this special kind of morphogenesis we investigated the interaction of the organic and inorganic components of aggregates in different growth stages by detailed chemical analyses, thermoanalytical measurements, X‐ray diffraction on solitary particles, and scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) investigations. The close relation of the results and observations to calcified tissue may stimulate advanced interests in the fields of medical and materials development.
Low‐k Insulators as the Choice of Dielectrics in Organic Field‐Effect Transistors
Authors: Veres J. , Ogier S.D. , Leeming S.W. , Cupertino D.C. , Mohialdin Khaffaf S.
Published: March 2003

In this paper, we present a new effect influencing the operation of organic field‐effect transistors resulting from the choice of gate insulator material. In a series of studies it was found that the interaction between the insulator and the semiconductor materials plays an important role in carrier transport. The insulator is not only capable of affecting the morphology of the semiconductor layer, but can also change the density of states by local polarization effects. Carrier localization is enhanced by insulators with large permittivities, due to the random dipole field present at the interface. We have investigated this effect on a number of disordered organic semiconductor materials, and show here that significant benefits are achievable by the use of low‐k dielectrics as opposed to the existing trend of increasing the permittivity for low operational voltage. We also discuss fundamental differences in the case of field‐effect transistors with band‐like semiconductors.
Near‐Infrared Light‐Emitting Diodes (LEDs) Based on Poly(phenylene)/Yb‐tris(β‐Diketonate) Complexes
Authors: Kang T.‐S. , Harrison B.S. , Bouguettaya M. , Foley T.J. , Boncella J.M. , Schanze K.S. , Reynolds J.R.
Published: March 2003

Near‐infrared‐emitting electroluminescent (EL) devices using blue‐light‐emitting polymers blended with the Yb complexes Yb(DBM)3phen (DBM = dibenzoylmethane), Yb(DNM)3phen (DNM = dinaphthoylmethane), and Yb(TPP)L(OEt) (L(OEt) = [(C5H5)Co{P(O)Et2}3]–) have been studied. EL devices composed of Yb(DNM)3phen blended with PPP‐OR11 showed enhanced near‐IR output at 977 nm when compared to those fabricated with Yb(DBM)3phen/PPP‐OR11 blends. The maximum near‐IR external efficiencies of the devices with Yb(DBM)3phen and Yb(DNM)3phen are, respectively, 7 × 10–5 (at 6 V and at 0.81 mA mm–2) and 4 × 10–4 (at 7 V, and 0.74 mA mm–2). The optimal blend composition for EL device performance consisted of PPP‐OR11 blended with 10–20 mol‐% Yb(DNM)3phen. A device fabricated using Yb‐(TPP)L(OEt)/PPP‐OR11 showed significantly enhanced near‐IR output efficiency, and future efforts will focus on devices fabricated using porphyrin‐based materials.