bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Single-Walled Carbon Nanotubes Using a Chemical Bond Element Model
Authors: Lu Ji-nan , Chen Hai-bo
Published: December 2008

A three dimensional nano-scale finite element model (FEM), called the chemical bond element model, is proposed for the simulation of mechanical properties of single-walled carbon nanotubes (SWCNTs) based upon molecular mechanics method. Chemical bonds between carbon atoms are modeled by chemical bond elements. The constants of a sub-stiffness matrix are determined by using a linkage between molecular mechanics and continuum mechanics. In order to evaluate the correctness and performance of the proposed model, simulation was done to determine the influence of nanotube wall thickness, radius and length on the elastic modulus (Young's modulus and shear modulus) of SWCNTs. The simulation results show that the choice of wall thickness significantly affects the Young's modulus and shear modulus. The force field constants is also very important, because the elastic modulus is sensitive to force field constants and the elastic properties of SWCNT are related to the radii of the tubes. The contribution of length to elastic modulus is insignificant and can be ignored. In comparison with the Young's modulus and shear modulus reported in the literature, the presented results agree very well with the corresponding theoretical results and many experimental measurements. Furthermore, if the force constants are properly chosen, the present method could be conveniently used to predict the mechanical behavior of other single-walled nanotubes such as boron nitride nanotubes. The results demonstrate the value of the proposed model as a valuable tool in the study of mechanical behaviors of carbon nanotubes and in the analysis of nanotube-based equipments.
DFT Study on the Structure and Racemization Mechanism of 1,1-Binaphthalene-8,8-diol
Authors: Da Liang-guo , Lu Tong-tong , Xiang Mei , He Tian-jing , Chen Dong-ming
Published: December 2008

Density functional theory (DFT) was applied to study the ground state geometries and isomerization processes of 1,1-binaphthalene-8,8-diol. Three isomers, denoted as ISO1, ISO2, and ISO3, were found, distinguished by different orientations of the OH groups, and each OH-orientational isomer has R- and S-enantiomer. The conformational stabilities of these isomers were investigated by tracking the energy change with respect to the ring-to-ring torsion. The inter-conversions between the three OH-orientational S-isomers were found to have quite low barriers owing to the nearly free rotation of OH groups around the O-C single bonds. The S-R enantiomerization of ISO1 and ISO2 can take place through the ring-ring torsion around the C1C1 single bond, either in the anti-rotation manner or in the syn-rotation manner. The barriers of the anti routes are lower than those of the corresponding syn routes by 87.95 and 75.04 kJ/mol. For the S-R enantiomerization of ISO3, only the anti route was found. The barriers for the anti route enantiomerizations of ISO1, ISO2, and ISO3 are 119.61, 120.43, and 121.59 kJ/mol, respectively. A parallel reaction mechanism via three anti enantiomerization routes was proposed for the racemization of 1,1-binaphthalene-8,8-diol.
Formation of [3]Pseudorotaxanes from -cyclodextrin and a Series of Dicarboxylic Acids with Their Corresponding , -alkanedicarboxylate Anions
Authors: Gao Jian-gang , Ding Yu-jie , Chen Hong-wei , Song Qing-ping , Zhang Qi-jin
Published: December 2008

Inclusion complexes between -cyclodextrin (-CD) and a series of dicarboxylic acids (DAn, n = 1115) were prepared by co-grinding and co-precipitation methods and the [3]pseudorotaxane structure of them was elucidated by FTIR, DTA and XRD characterizations. Inclusion complexes of -CD and , -alkanedicarboxylate anions (DAn2) were acquired by neutralizing -CD/DAn different inclusion complexes with sodium hydroxide and the structure was also proved to be a pseudorotaxane structure by 1H-NMR spectra and NOESY spectrum. Both the inclusion complexes of -CD/DAn and -CD/DAn2 adopt the [3]pseudorotaxane structure with -CD arranged in dimers threaded onto one aliphatic chain and the binding mode of 1:1 inclusion complex was excluded based on the consideration of chain conformations.
Low-temperature Catalytic Reduction of Nitrogen Monoxide with Carbon Monoxide on Copper Iron and Copper Cobalt Composite Oxides
Authors: Shu Jun-sheng , Xia Wen-shui , Zhang You-jin , Cheng Tao , Gao Min-rui
Published: December 2008

Copper iron composite oxides (CuO/Fe2O3) and copper cobalt composite oxides (CuO/Co3O4) for the catalytic reduction of NO with CO at low temperature were prepared by co-precipitation. The catalytic activity and thermal stability of the catalysts were evaluated by a microreactor-GC system. The 100% conversion temperatures of NO are 80C for CuO/Fe2O3 and 90C for CuO/Co3O4. The catalysts possess high catalytic activity and favorable thermal stability for NO reduction with CO in a wide temperature range and long time range. A systematic study of the molar ratios of the reactants, the volume of NaOH, aging time, and calcination temperature/time was carried out to investigate the influence preparation conditions on the catalytic activity of the catalysts.
Rate Constants for Reaction Between Hydroxyl Radical and Dimethyl Sulfide Under Real Atmospheric Condition
Authors: Wang Hai-tao , Hu Chang-jiang , Mu Yu-jing , Zhang Yu-jie
Published: December 2008

The rate constants of the reaction between hydroxyl radical (OH) and dimethyl sulfide (DMS) were investigated by using the relative methods in air, N2, and O2. Strong influences of ground state oxygen O(3P) on DMS consumption were found by the photolysis of HONO and CH3ONO as OH sources, and the rate constants obtained in these systems varied significantly. The rate constants of the reaction between DMS and OH (generated by photolysis of H2O2) at room temperature were 8.56 1012, 11.31 1012, and 4.50 1012 cm3/(molecule-s), in air, O2, and N2, respectively. The temperature dependence of the rate constants for OH with DMS over the temperature range of 287338 K was also investigated in nitrogen and air, and the Arrhenius expression was obtained as follows: kair = (7.240.28) 1013exp[(770.797.2)/T], kN2 = (3.400.15) 1011exp[(590.3165.9)/T].
High-resolution Absorption Spectra of Acetylene in 142.8152.3 nm
Authors: Hu Ya-hua , Zhen Chen , Dai Jing-hua , Zhou Xiao-guo , Liu Shi-lin
Published: December 2008

The absorption spectra of acetylene molecules was measured under jet-cooled conditions in the wavelength range of 142.8152.3 nm, with a tunable and highly resolved vacuum ultraviolet (VUV) laser generated by two-photon resonant four wave difference frequency mixing processes. Due to the sufficient vibrational and rotational cooling effect of the molecular beam and the higher resolution VUV laser, the observed absorption spectra exhibit more distinct spectral features than the previous works measured at room temperature. The major three vibrational bands are assigned as a C-C symmetry stretching vibrational progress (u2 = 02) of the C1 IIu state of acetylene. The observed shoulder peak at 148.2 nm is assigned to the first overtone band of the trans-bending mode u4 of the C1 IIustate of acetylene. Additionally, the two components, 4o2(1IIu) and 4o2(1 IIuare suggested to exhibit in the present absorption spectra, due to their RennerTeller effect and transition selection rule. All band origins and bandwidths are obtained subsequently, and it is found that bandwidths are broadened and lifetimes decrease gradually with the excitation of vibration.
Dynamic Alignment of D2 Enhanced by Two Few-cycle Pulses
Authors: Yang Zeng-qiang , Guo Zhi-rong , Yin Bao-xiang , Sun Mao-zhu
Published: December 2008

Dynamic alignment of D2 induced by two few-cycle pulses was investigated by solving the time-dependent Schrodinger equation numerically based on a rigid rotor model. The results show that alignment of D2 can be enhanced by two few-cycle pulses compared with the level achievable by a single few-cycle pulse as long as the time delay between two pulses is chosen properly, and the pulse duration of two lasers plays an important role in the aligning process of D2 molecules.
Study on Atomic Fluorescence Spectrometry Excited by Synchrotron Radiation
Authors: Guo Jia-jia , Gan Wu-er , Zhang Guo-bin , Su Qing-de
Published: December 2008

A novel analysis approach using atomic fluorescence excited by synchrotron radiation is presented. A system for synchrotron radiation-atomic fluorescence spectrometry is developed, and experimental conditions such as flow rate, analyte acidity, concentration of pre-reducing and hydrogenation system are optimized. The proposed method is successfully applied to get an excitation spectrum of arsenic. Seven of ten primary spectral lines, four of which have never been reported by means of atomic fluorescence spectrometry, agree well with the existing reports. The other three are proposed for the first time. Excitation potentials and possible transitions are investigated. Especially for the prominent line at 234.99 nm, the mechanism of generation is discussed and a model of energy transition processes is proposed.
Theoretical Studies on the FeM Interactions and 31P NMR in Fe(CO)3(EtPhPpy)2MX2 (X = NCS, SCN, Cl; M = Zn, Cd, Hg)
Authors: Huang Xiao-xuan , Xu Xuan , Xie Mei-xiang
Published: December 2008

To study the Fe-M interactions and their effects on 31P NMR, the structures of Fe(CO)3(EtPhPpy)2 1, Fe(CO)3(EtPhPpy)2M(NCS)2 (2: M = Zn, 3: M = Cd, 4: M = Hg) and Fe(CO)3(EtPhPpy)2CdX2 (5: X = C1, 6: X = SCN) were investigated by density functional theory (DFT) PBE0 method. The stabilities S of complexes follow S(2)>S(3)>S(4) and S(3)S(6)>S(5), indicating that 6 is stable and may be synthesized. The complexes with thiocyanate are more stable than that with chloride in Fe(CO)3(EtPhPpy)2CdX2. The strength / of FeM interactions follows I(2)I(3)I(4). The Fe-Cd interactions of 3 and 6, which contain thiocyanate, are stronger than that of 5 with chloride. The charge-transfer, which enhances with the increasing of FeM interaction strength, comes from Et, Ph, py, CO groups towards P, Fe, and M atoms. Because the delocalization of thiocyanate disperses the charge of M2+, the charge-transfer of the complexes with thiocyanate is stronger than that with chloride. There is a -bond between Fe and Hg atoms in 4. However, in binuclear complexes except 4, the FeM interactions act as nFenm, -FenM and cFenM delocalization, and the NM interactions mainly act as nNnm delocalization. In binuclear complexes, due to the FeM interactions, the strong Fe-c*FeP or Fe_Hg*Fep delocalization and the charge-transfer, the electron density on P nucleus is increased, and thus upfield 31P chemical shifts are caused (compared with mononuclear complex 1).
Adsorption Behavior of CH2 and CH3 on Metal Clusters Cun (n= 16)
Authors: Cheng Xi-hui , Jin Ming-xing , Hu Zhan , Hu Fei-fei , Ding Da-jun
Published: December 2008

Using density functional theory with generalized gradient approximation and hybrid functional, we studied the properties of energy, charge population, and vibration of CH2 and CH3 adsorbed on Cun (n = 16) clusters. The results show that the DFT calculation with the hybrid functional matches the experimental results better in both cases. The calculation results indicate that the adsorption of CH2 is stronger than that of CH3. During adsorption, the charges transfer from Cu to CH2 or CH3. The obtained vibrational frequencies for different modes of CH2 and CH3 adsorbed on Cun agree well with the experimental results for the adsorption on Cu(lll) surface.
Collision-induced Rotational Energy Transfer in an Atom-Diatom System
Authors: Ni Yan-qing , Li Jian , Ma Feng-cai
Published: December 2008

As a further theoretical study of the collision-induced quantum interference on rotational energy transfer in an atom-diatom system, based on the first-Born approximation of time-dependent perturbation theory, taking into account the anisotropic LennardJones interaction potential and the long-range interaction potential, the differential interference angles in singlet-triplet mixed states of CO A1 (v = 0)-e3 (v = l) system in collision with He, Ne, Ar, and other partners were calculated theoretically. The relationships of differential interference angle versus impact parameters, including collision parameter b and velocity, are obtained.
Elastic Behavior of Polymer Chains
Authors: Lu Teng , Chen Tao , Liang Hao-jun
Published: December 2008

The elastic behavior of the polymer chain was investigated in a three-dimensional off-lattice model. We sample more than 109 conformations of each kind of polymer chain by using a Monte Carlo algorithm, then analyze them with the non-Gaussian theory of rubberlike elasticity, and end with a statistical study. Through observing the effect of the chain flexibility and the stretching ratio on the mean-square end-to-end distance, the average energy, the average Helmholtz free energy, the elastic force, the contribution of energy to the elastic force, and the entropy contribution to elastic force of the polymer chain, we find that a rigid polymer chain is much easier to stretch than a flexible polymer chain. Also, a rigid polymer chain will become difficult to stretch only at a quite high stretching ratio because of the effect of the entropy contribution. These results of our simulation calculation may explain some of the macroscopic phenomena of polymer and biomacromolecular elasticity.
High Temperature Seedless Synthesis of Au NRs Using BDAC/CTAB Co-surfactant
Authors: Li Min , Wei Lai , Zhang Xian , Yu Xue-feng
Published: December 2008

Au nanorods have been successfully synthesized at 90C by using hexadecyltrimethylammonium bromide (CTAB) and benzyldimethylammoniumchloride hydrate (BDAC) co-surfactant. At 90C, the reaction time was less than 10 s, and the longitudinal surface plasmon absorption band could vary between 680 and 770 nm by adjusting the molar ratio of BDAC to CTAB from 2 to 0.5. At 90C, nanorods with a longitudinal surface plasmon absorption peak of 770 nm can be obtained when the molar ratio of BDAC to CTAB was 3:2.
Glow Discharge Plasma-Assisted Preparation of Nickel-Based Catalyst for Carbon Dioxide Reforming of Methane
Authors: Guo Fang , Chu Wei , Xu Jun-qiang , Zhong Lin
Published: December 2008

A plasma-assisted method was employed to prepare Ni/-Al2O3 catalyst for carbon dioxide reforming of methane reaction. The novel catalyst possessed higher activity and better coke-suppression performance than those of the conventional calcination catalyst. To achieve the same CH4 conversion, the conventional catalyst needed higher reaction temperature, about 50C higher than that of the N2 plasma-treated catalyst. After the evaluation test, the deactivation rate of the novel catalyst was 1.7%, compared with 15.2% for the conventional catalyst. Different from the characterization results of the calcined catalyst, a smaller average pore diameter and a higher specific surface area were obtained for the plasma-treated catalyst. The variations of the reduction peak temperatures and areas indicated that the catalyst reducibility was promoted by plasma assistance. The dispersion of nickel was also remarkably improved, which was helpful for controlling the ensemble size of metal atoms on the catalyst surface. The modification effect of plasma-assisted preparation on the surface property of alumina supported catalyst was speculated to account for the concentration increase of absorbed CO2. An enhancement of CO2 adsorption was propitious to the inhibition of carbon formation. The coke amount deposited on plasma treated catalyst was much smaller than that on the conventional catalyst.
Nondoped-type White Organic Light-Emitting Diode Using Star-Shaped Hexafluorenylbenzene as an Energy Transfer Layer
Authors: Yu Jun-sheng , Ma Tao , Lou Shuang-ling , Jiang Ya-dong , Zhang Qing
Published: December 2008

White organic light-emitting diodes (WOLEDs) with a structure of indium-tin-oxide (ITO)/N,N-bis-(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine (NPB)/1,2,3,4,5,6-hexakis(9,9-diethyl-9H-fluoren-2-yl)benzene (HKEthFLYPh)/5,6,11,12 -tetraphenylnaphtacene (rubrene)/tris(8-hydroxyquinoline) aluminum (Alq3)/Mg:Ag were fabricated by vacuum deposition method, in which a novel star-shaped hexafluorenylbenzene HKEthFLYPh was used as an energy transfer layer, and an ultrathin layer of rubrene was inserted between HKEthFLYPh and Alq3 layers as a yellow light-emitting layer instead of using a time-consuming doping process. A fairly pure WOLED with Commissions Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.33) was obtained when the thickness of rubrene was 0.3 nm, and the spectrum was insensitive to the applied voltage. The device yielded a maximum luminance of 4816 cd/m2 at 18 V.
Cohesin Associates with Spindle Poles in a Mitosis-specific Manner and Functions in Spindle Assembly in Vertebrate Cells
Authors: Kong Xiangduo , Ball Alexander R. , Sonoda Eiichiro , Feng Jie , Takeda Shunichi , Fukagawa Tatsuo , Yen Tim J. , Yokomori Kyoko
Published: December 2008

Cohesin is an essential protein complex required for sister chromatid cohesion. Cohesin associates with chromosomes and establishes sister chromatid cohesion during interphase. During metaphase, a small amount of cohesin remains at the chromosome-pairing domain, mainly at the centromeres, whereas the majority of cohesin resides in the cytoplasm, where its functions remain unclear. We describe the mitosis-specific recruitment of cohesin to the spindle poles through its association with centrosomes and interaction with nuclear mitotic apparatus protein (NuMA). Overexpression of NuMA enhances cohesin accumulation at spindle poles. Although transient cohesin depletion does not lead to visible impairment of normal spindle formation, recovery from nocodazole-induced spindle disruption was significantly impaired. Importantly, selective blocking of cohesin localization to centromeres, which disrupts centromeric sister chromatid cohesion, had no effect on this spindle reassembly process, clearly separating the roles of cohesin at kinetochores and spindle poles. In vitro, chromosome-independent spindle assembly using mitotic extracts was compromised by cohesin depletion, and it was rescued by addition of cohesin that was isolated from mitotic, but not S phase, cells. The combined results identify a novel spindle-associated role for human cohesin during mitosis, in addition to its function at the centromere/kinetochore regions.
Localization to Mature Melanosomes by Virtue of Cytoplasmic Dileucine Motifs Is Required for Human OCA2 Function
Authors: Sitaram Anand , Piccirillo Rosanna , Palmisano Ilaria , Harper Dawn C. , Dell'Angelica Esteban C. , Schiaffino M. Vittoria , Marks Michael S.
Published: December 2008

Oculocutaneous albinism type 2 is caused by defects in the gene OCA2, encoding a pigment cell-specific, 12-transmembrane domain protein with homology to ion permeases. The function of the OCA2 protein remains unknown, and its subcellular localization is under debate. Here, we show that endogenous OCA2 in melanocytic cells rapidly exits the endoplasmic reticulum (ER) and thus does not behave as a resident ER protein. Consistently, exogenously expressed OCA2 localizes within melanocytes to melanosomes, and, like other melanosomal proteins, localizes to lysosomes when expressed in nonpigment cells. Mutagenized OCA2 transgenes stimulate melanin synthesis in OCA2-deficient cells when localized to melanosomes but not when specifically retained in the ER, contradicting a proposed primary function for OCA2 in the ER. Steady-state melanosomal localization requires a conserved consensus acidic dileucine-based sorting motif within the cytoplasmic N-terminal region of OCA2. A second dileucine signal within this region confers steady-state lysosomal localization in melanocytes, suggesting that OCA2 might traverse multiple sequential or parallel trafficking routes. The two dileucine signals physically interact in a differential manner with cytoplasmic adaptors known to function in trafficking other proteins to melanosomes. We conclude that OCA2 is targeted to and functions within melanosomes but that residence within melanosomes may be regulated by secondary or alternative targeting to lysosomes.
Galectin-1 Induces Reversible Phosphatidylserine Exposure at the Plasma Membrane
Authors: Stowell Sean R. , Karmakar Sougata , Arthur Connie M. , Ju Tongzhong , Rodrigues Lilian C. , Riul Thalita B. , Dias-Baruffi Marcelo , Miner Jonathan , McEver Rodger P. , Cummings Richard D.
Published: December 2008

Cells normally undergo physiological turnover through the induction of apoptosis and phagocytic removal, partly through exposure of cell surface phosphatidylserine (PS). In contrast, neutrophils appear to possess apoptosis-independent mechanisms of removal. Here we show that Galectin-1 (Gal-1) induces PS exposure independent of alterations in mitochondrial potential, caspase activation, or cell death. Furthermore, Gal-1–induced PS exposure reverts after Gal-1 removal without altering cell viability. Gal-1–induced PS exposure is uniquely microdomain restricted, yet cells exposing PS do not display evident alterations in membrane morphology nor do they exhibit bleb formation, typically seen in apoptotic cells. Long-term exposure to Gal-1 prolongs PS exposure with no alteration in cell cycle progression or cell growth. These results demonstrate that Gal-1–induced PS exposure and subsequent phagocytic removal of living cells represents a new paradigm in cellular turnover.
Genome-wide Analysis of AP-3–dependent Protein Transport in Yeast
Authors: Anand Vikram C. , Daboussi Lydia , Lorenz Todd C. , Payne Gregory S.
Published: December 2008

The evolutionarily conserved adaptor protein-3 (AP-3) complex mediates cargo-selective transport to lysosomes and lysosome-related organelles. To identify proteins that function in AP-3–mediated transport, we performed a genome-wide screen in Saccharomyces cerevisiae for defects in the vacuolar maturation of alkaline phosphatase (ALP), a cargo of the AP-3 pathway. Forty-nine gene deletion strains were identified that accumulated precursor ALP, many with established defects in vacuolar protein transport. Maturation of a vacuolar membrane protein delivered via a separate, clathrin-dependent pathway, was affected in all strains except those with deletions of YCK3, encoding a vacuolar type I casein kinase; SVP26, encoding an endoplasmic reticulum (ER) export receptor for ALP; and AP-3 subunit genes. Subcellular fractionation and fluorescence microscopy revealed ALP transport defects in yck3Δ cells. Characterization of svp26Δ cells revealed a role for Svp26p in ER export of only a subset of type II membrane proteins. Finally, ALP maturation kinetics in vac8Δ and vac17Δ cells suggests that vacuole inheritance is important for rapid generation of proteolytically active vacuolar compartments in daughter cells. We propose that the cargo-selective nature of the AP-3 pathway in yeast is achieved by AP-3 and Yck3p functioning in concert with machinery shared by other vacuolar transport pathways.
The Conserved RIC-3 Coiled-Coil Domain Mediates Receptor-specific Interactions with Nicotinic Acetylcholine Receptors
Authors: Biala Yoav , Liewald Jana F. , Ben-Ami Hagit Cohen , Gottschalk Alexander , Treinin Millet
Published: December 2008

RIC-3 belongs to a conserved family of proteins influencing nicotinic acetylcholine receptor (nAChR) maturation. RIC-3 proteins are integral membrane proteins residing in the endoplasmic reticulum (ER), and containing a C-terminal coiled-coil domain (CC-I). Conservation of CC-I in all RIC-3 family members indicates its importance; however, previous studies could not show its function. To examine the role of CC-I, we studied effects of its deletion on Caenorhabditis elegans nAChRs in vivo. Presence of CC-I promoted maturation of particular nAChRs expressed in body-wall muscle, whereas it was not required for other nAChR subtypes expressed in neurons or pharyngeal muscles. This effect is receptor-specific, because it could be reproduced after heterologous expression. Consistently, coimmunoprecipitation analysis showed that CC-I enhances the interaction of RIC-3 with a nAChR that requires CC-I in vivo; thus CC-I appears to enhance affinity of RIC-3 to specific nAChRs. However, we found that this function of CC-I is redundant with functions of sequences downstream to CC-I, potentially a second coiled-coil. Alternative splicing in both vertebrates and invertebrates generates RIC-3 transcripts that lack the entire C-terminus, or only CC-I. Thus, our results suggest that RIC-3 alternative splicing enables subtype specific regulation of nAChR maturation.
Characterization of the LacI-type transcriptional repressor RbsR controlling ribose transport in Corynebacterium glutamicum ATCC 13032
Authors: Nentwich Svenja S. , Brinkrolf Karina , Gaigalat Lars , Hüser Andrea T. , Rey Daniel A. , Mohrbach Tobias , Marin Kay , Pühler Alfred , Tauch Andreas , Kalinowski Jörn
Published: December 2008

The gene products of therbsRACBD(rbs) operon ofC. glutamicum(cg1410–cg1414) encode a ribose-specific ATP-binding cassette (ABC) transport system and its corresponding regulatory protein (RbsR). Deletion of the structural genesrbsACBDprohibited ribose uptake. Deletion of the regulatory generbsRresulted in an increased mRNA level of the whole operon. Analysis of the promoter region of therbsoperon by electrophoretic mobility shift assays identified a catabolite-responsive element (cre)-like sequence as the RbsR-binding site. Additional RbsR-binding sites were identified in front of the recently characterizeduriRoperon (uriR-rbsK1-uriT-uriH) and the ribokinase generbsK2.In vitro, the repressor RbsR bound to its targets in the absence of an effector. A probable negative effector of RbsRin vivois ribose 5-phosphate or a derivative thereof, since in a ribokinase (rbsK1rbsK2) double mutant, no derepression of therbsoperon in the presence of ribose was observed. Analysis of the ribose stimulon in theC. glutamicumwild-type revealed transcriptional induction of theuriRandrbsoperons as well as of therbsK2gene. The inconsistency between the existence of functional RbsR-binding sites upstream of the ribokinase genes, their transcriptional induction during growth on ribose, and the missing induction in therbsRmutant suggested the involvement of a second transcriptional regulator. Simultaneous deletion of the regulatory genesrbsRanduriRfinally demonstrated a transcriptional co-control of therbsanduriRoperons and therbsK2gene by both regulators, RbsR and UriR, which were furthermore shown to recognize the same cognate DNA sequences in the operators of their target genes.
Regulation of the PcoI/PcoR quorum-sensing system in Pseudomonas fluorescens 2P24 by the PhoP/PhoQ two-component system
Authors: Yan Qing , Gao Wei , Wu Xiao-Gang , Zhang Li-Qun
Published: December 2008

A quorum-sensing locus, pcoI/pcoR, which is involved in the regulation of root colonization and plant disease-suppressive ability, was previously identified in Pseudomonas fluorescens 2P24. In this study, we performed random mutagenesis using mini-Tn5 in order to screen the upstream transcriptional regulators of pcoI, a biosynthase gene responsible for the synthesis of N-acylhomoserine lactone signal molecules. Two mutants, PM400 and PM410, with elevated pcoI gene promoter activity, were identified from ∼10 000 insertion clones. The amino acid sequences of the interrupted genes in these two mutants were highly similar to PhoQ, a sensor protein of the two-component regulatory system PhoP/PhoQ, which responds to environmental Mg2+ starvation and regulates virulence in Salmonella typhimurium and antimicrobial peptide resistance in Pseudomonas aeruginosa. The promoter activity of pcoI was also induced under low-Mg2+ conditions in the 2P24 strain of P. fluorescens. Deletion mutagenesis and complementation experiments demonstrated that the transcription of pcoI was negatively regulated by the sensor PhoQ but positively regulated by the response regulator PhoP. Genetic evidence also indicated that transcription of the outer-membrane protein gene oprH was induced by Mg2+ starvation through regulation of the wild-type PhoP/PhoQ system. Additionally, PhoQ was involved in biofilm formation by 2P24 under low-Mg2+ conditions through a PhoP-independent pathway.
Attenuated enzootic (pestoides) isolates of Yersinia pestis express active aspartase
Authors: Bearden Scott W. , Sexton Christopher , Pare Joshua , Fowler Janet M. , Arvidson Cindy G. , Yerman Lyudmyla , Viola Ronald E. , Brubaker Robert R.
Published: December 2008

It is established thatYersinia pestis, the causative agent of bubonic plague, recently evolved from enteropathogenicYersinia pseudotuberculosisby undergoing chromosomal degeneration while acquiring two unique plasmids that facilitate tissue invasion (pPCP) and dissemination by fleabite (pMT). Thereafter, plague bacilli spread from central Asia to sylvatic foci throughout the world. These epidemic isolates exhibit a broad host range including man as opposed to enzootic (pestoides) variants that remain in ancient reservoirs where infection is limited to muroid rodents. Cells ofY. pseudotuberculosisare known to express glucose-6-phosphate dehydrogenase (Zwf) and aspartase (AspA); these activities are not detectable in epidemicY. pestisdue to missense mutations (substitution of proline for serine at amino position 155 of Zwf and leucine for valine at position 363 of AspA). In this study, functional Zwf was found in pestoides strains E, F and G but not seven other enzootic isolates; enzymic activity was associated with retention of serine at amino acid position 155. Essentially, full AspA activity occurred in pestoides isolates where valine (pestoides A, B, C and D) or serine (pestoides E, F, G and I) occupied position 363. Reduced activity occurred in strains Angola and A16, which contained phenylalanine at this position. Thekcatbut notKmof purified AspA from strain Angola was significantly reduced. In this context,aspAof the recently described attenuated enzootic microtus biovar encodes active valine at position 363, further indicating that functional AspA is a biomarker for avirulence ofY. pestisin man.
Disruption of the epithelial barrier by botulinum haemagglutinin (HA) proteins – differences in cell tropism and the mechanism of action between HA proteins of types A or B, and HA proteins of type C
Authors: Jin Yingji , Takegahara Yuki , Sugawara Yo , Matsumura Takuhiro , Fujinaga Yukako
Published: December 2008

Orally ingested botulinum neurotoxin (BoNT) causes food-borne botulism, but BoNT must pass through the gut lining and enter the bloodstream. We have previously found that type B haemagglutinin (HA) proteins in the toxin complex play an important role in the intestinal absorption of BoNT by disrupting the paracellular barrier of the intestinal epithelium, and therefore facilitating the transepithelial delivery of BoNT. Here, we show that type A HA proteins in the toxin complex have a similar disruptive activity and a greater potency than type B HA proteins in the human intestinal epithelial cell lines Caco-2 and T84 and in the canine kidney epithelial cell line MDCK I. In contrast, type C HA proteins in the toxin complex (up to 300 nM) have no detectable effect on the paracellular barrier in these human cell lines, but do show a barrier-disrupting activity and potent cytotoxicity in MDCK I. These findings may indicate that type A and B HA proteins contribute to the development of food-borne botulism, at least in humans, by facilitating the intestinal transepithelial delivery of BoNTs, and that the relative inability of type C HA proteins to disrupt the paracellular barrier of the human intestinal epithelium is one of the reasons for the relative absence of food-borne human botulism caused by type C BoNT.
Metabolite and transcriptome analysis of Campylobacter jejuni in vitro growth reveals a stationary-phase physiological switch
Authors: Wright John A. , Grant Andrew J. , Hurd Douglas , Harrison Marcus , Guccione Edward J. , Kelly David J. , Maskell Duncan J.
Published: December 2008

Campylobacter jejuniis a prevalent cause of food-borne diarrhoeal illness in humans. Understanding of the physiological and metabolic capabilities of the organism is limited. We report a detailed analysis of theC. jejunigrowth cycle in batch culture. Combined transcriptomic, phenotypic and metabolic analysis demonstrates a highly dynamic ‘stationary phase’, characterized by a peak in motility, numerous gene expression changes and substrate switching, despite transcript changes that indicate a metabolic downshift upon the onset of stationary phase. Video tracking of bacterial motility identifies peak activity during stationary phase. Amino acid analysis of culture supernatants shows a preferential order of amino acid utilization. Proton NMR (1H-NMR) highlights an acetate switch mechanism whereby bacteria change from acetate excretion to acetate uptake, most probably in response to depletion of other substrates. Acetate production requirespta(Cj0688) andackA(Cj0689), although theacshomologue (Cj1537c) is not required. Insertion mutants inCj0688andCj0689maintain viability less well during the stationary and decline phases of the growth cycle than wild-typeC. jejuni, suggesting that these genes, and the acetate pathway, are important for survival.
SMb20651 is another acyl carrier protein from Sinorhizobium meliloti
Authors: Ramos-Vega Ana Laura , Dávila-Martínez Yadira , Sohlenkamp Christian , Contreras-Martínez Sandra , Encarnación Sergio , Geiger Otto , López-Lara Isabel M.
Published: December 2008

Acyl carrier proteins (ACPs) are small acidic proteins that carry growing acyl chains during fatty acid or polyketide synthesis. In rhizobia, there are four different and well-characterized ACPs: AcpP, NodF, AcpXL and RkpF. The genome sequence ofSinorhizobium meliloti1021 reveals two additional ORFs that possibly encode additional ACPs. One of these,smb20651, is located on the plasmid pSymB as part of an operon. The genes of the operon encode a putative asparagine synthetase (AsnB), the predicted ACP (SMb20651), a putative long-chain fatty acyl-CoA ligase (SMb20650) and a putative ammonium-dependent NAD+synthetase (NadE1). When SMb20651 was overexpressed inEscherichia coli,[3H]β-alanine, a biosynthetic building block of 4′-phosphopantetheine, was incorporated into the proteinin vivo. The purified SMb20651 was modified with 4′-phosphopantetheine in the presence ofS. melilotiholo-ACP synthase (AcpS). Also, holo-SMb20651 was modifiedin vitrowith a malonyl group by malonyl CoA-ACP transacylase. InE. coli, coexpression of SMb20651 together with other proteins such as AcpS and SMb20650 led to the formation of additional forms of SMb20651. In this bacterium, acylation of SMb20651 with C12 : 0 or C18 : 0 fatty acids was detected, demonstrating that this protein is involved in fatty acid biosynthesis or transfer. Expression of SMb20651 was detected inS. melilotias holo-SMb20651 and acyl-SMb20651.
Mechanism of conjugated linoleic acid and vaccenic acid formation in human faecal suspensions and pure cultures of intestinal bacteria
Authors: McIntosh Freda M. , Shingfield Kevin J. , Devillard Estelle , Russell Wendy R. , Wallace R. John
Published: December 2008

Faecal bacteria from four human donors and six species of human intestinal bacteria known to metabolize linoleic acid (LA) were incubated with LA in deuterium oxide-enriched medium to investigate the mechanisms of conjugated linoleic acid (CLA) and vaccenic acid (VA) formation. The main CLA products in faecal suspensions, rumenic acid (cis-9,trans-11-CLA; RA) andtrans-9,trans-11-CLA, were labelled at C-13, as were other 9,11 geometric isomers. Traces oftrans-10,cis-12-CLA formed were labelled to a much lower extent. In pure culture,Bifidobacterium breveNCFB 2258 formed labelled RA andtrans-9,trans-11-CLA, whileButyrivibrio fibrisolvens16.4,Roseburia hominisA2-183T,Roseburia inulinivoransA2-192TandRuminococcus obeum-like strain A2-162 converted LA to VA, labelled in a manner indicating that VA was formed via C-13-labelled RA.Propionibacterium freudenreichiisubsp.shermaniiDSM 4902T, a possible probiotic, formed mainly RA with smaller amounts oftrans-10,cis-12-CLA andtrans-9,trans-11-CLA, labelled the same as in the mixed microbiota. Ricinoleic acid (12-OH-cis-9-18 : 1) did not form CLA in the mixed microbiota, in contrast to CLA formation described forLactobacillus plantarum. These results were similar to those reported for the mixed microbiota of the rumen. Thus, although the bacterial genera and species responsible for biohydrogenation in the rumen and the human intestine differ, and a second route of RA formation via a 10-OH-18 : 1 is present in the intestine, the overall labelling patterns of different CLA isomers formation are common to both gut ecosystems. A hydrogen-abstraction enzymic mechanism is proposed that may explain the role of a 10-OH-18 : 1 intermediate in 9,11-CLA formation in pure and mixed cultures.
The two-component system BfrAB regulates expression of ABC transporters in Streptococcus gordonii and Streptococcus sanguinis
Authors: Zhang Yongshu , Whiteley Marvin , Kreth Jens , Lei Yu , Khammanivong Ali , Evavold Jamie N. , Fan Jingyuan , Herzberg Mark C.
Published: December 2008

The putative two-component system BfrAB is involved inStreptococcus gordoniibiofilm development. Here, we provide evidence that BfrAB regulates the expression ofbfrCDandbfrEFG, which encode two ATP-binding cassette (ABC) transporters, andbfrH, which encodes a CAAX amino-terminal protease family protein. BfrC and BfrE are ATP-binding proteins, and BfrD, BfrF and BfrG are homologous membrane-spanning polypeptides. Similarly, BfrABss, the BfrAB homologous system inStreptococcus sanguinis, controls the expression of twobfrCD-homologous operons (bfrCDssandbfrXYss), abfrH-homologous gene (bfrH1ss) and another CAAX amino-terminal protease family protein gene (bfrH2ss). Furthermore, we demonstrate that the purified BfrA DNA-binding domain fromS. gordoniibinds to the promoter regions ofbfrCD,bfrEFG,bfrH,bfrCDss,bfrXYssandbfrH1ssin vitro. Finally, we show that the BfrA DNA-binding domain recognizes a conserved DNA motif with a consensus sequence of TTTCTTTAGAAATATTTTAGAATT. These data suggest, therefore, thatS. gordoniiBfrAB controls biofilm formation by regulating multiple ABC-transporter systems.
Early molecular-recognition events in the synthesis and export of group 2 capsular polysaccharides
Authors: Vimr Eric R. , Steenbergen Susan M.
Published: December 2008

The outer membrane (OM) of almost all Gram-negative bacteria is composed of phospholipids, lipopolysaccharide, proteins and capsular or loosely adherent polysaccharides that together mediate cellular interactions with diverse environments. Most OM components are synthesized intracellularly or at the inner membrane (IM) and thus require an export mechanism. This mini-review focuses on recent progress in understanding how synthesis of one kind of capsular polysaccharide (group 2) is coupled to the export apparatus located in the IM and spanning the periplasmic space, thus providing a transport channel to the cell surface. Although the model system for these investigations is the medically important extraintestinal pathogenEscherichia coliK1 and its polysialic acid capsule, the conclusions are general for other group 2 and group 2-like polysaccharides synthesized by many different bacterial species.
Role of the sRNA GcvB in regulation of cycA in Escherichia coli
Authors: Pulvermacher Sarah C. , Stauffer Lorraine T. , Stauffer George V.
Published: December 2008

InEscherichia coli, thegcvBgene encodes a small non-translated RNA that regulates several genes involved in transport of amino acids and peptides (includingsstT,oppAanddppA). Microarray analysis identifiedcycAas an additional regulatory target of GcvB. ThecycAgene encodes a permease for the transport of glycine,d-alanine,d-serine andd-cycloserine. RT-PCR confirmed that GcvB and the Hfq protein negatively regulatecycAmRNA in cells grown in Luria–Bertani broth. In addition, deletion of thegcvBgene resulted in increased sensitivity tod-cycloserine, consistent with increased expression ofcycA. AcycA : : lacZtranslational fusion confirmed that GcvB negatively regulatescycAexpression in Luria–Bertani broth and that Hfq is required for the GcvB effect. GcvB had no effect oncycA : : lacZexpression in glucose minimal medium supplemented with glycine. However, Hfq still negatively regulated the fusion in the absence of GcvB. A set of transcriptional fusions ofcycAtolacZidentified a sequence incycAnecessary for regulation by GcvB. Analysis of GcvB identified a region complementary to this region ofcycAmRNA. However, mutations predicted to disrupt base-pairing betweencycAmRNA and GcvB did not alter expression ofcycA : : lacZ. A model for GcvB function in cell physiology is discussed.
A pivotal role for the response regulator DegU in controlling multicellular behaviour
Authors: Murray Ewan J. , Kiley Taryn B. , Stanley-Wall Nicola R.
Published: December 2008

Bacteria control multicellular behavioural responses, including biofilm formation and swarming motility, by integrating environmental cues through a complex regulatory network. Heterogeneous gene expression within an otherwise isogenic cell population that allows for differentiation of cell fate is an intriguing phenomenon that adds to the complexity of multicellular behaviour. This review focuses on recent data about how DegU, a pleiotropic response regulator, co-ordinates multicellular behaviour inBacillus subtilis. We review studies that challenge the conventional understanding of the molecular mechanisms underpinning the DegU regulatory system and others that describe novel targets of DegU during activation of biofilm formation byB. subtilis. We also discuss a novel role for DegU in regulating multicellular processes in the food-borne pathogenListeria monocytogenes.
Adenosine increases anagen hair growth and thick hairs in Japanese women with female pattern hair loss: A pilot, double‐blind, randomized, placebo‐controlled trial
Authors: OURA Hajimu , IINO Masato , NAKAZAWA Yosuke , TAJIMA Masahiro , IDETA Ritsuro , Nakaya Yutaka , ARASE Seiji , KISHIMOTO Jiro
Published: December 2008

Adenosine upregulates the expression of vascular endothelial growth factor and fibroblast growth factor‐7 in cultured dermal papilla cells. It has been shown that, in Japanese men, adenosine improves androgenetic alopecia due to the thickening of thin hair due to hair follicle miniaturization. To investigate the efficacy and safety of adenosine treatment to improve hair loss in women, 30 Japanese women with female pattern hair loss were recruited for this double‐blind, randomized, placebo‐controlled study. Volunteers used either 0.75% adenosine lotion or a placebo lotion topically twice daily for 12 months. Efficacy was evaluated by dermatologists and by investigators and in phototrichograms. As a result, adenosine was significantly superior to the placebo according to assessments by dermatologists and investigators and by self‐assessments. Adenosine significantly increased the anagen hair growth rate and the thick hair rate. No side‐effects were encountered during the trial. Adenosine improved hair loss in Japanese women by stimulating hair growth and by thickening hair shafts. Adenosine is useful for treating female pattern hair loss in women as well as androgenetic alopecia in men.
Effect of rosmarinic acid on atopic dermatitis
Authors: LEE Jongsung , JUNG Eunsun , KOH Jassook , KIM Yeong Shik , PARK Deokhoon
Published: December 2008

Rosmarinic acid is known to have anti‐inflammatory and immunomodulatory activities. This study was performed to evaluate the effect of rosmarinic acid on atopic dermatitis (AD), one of the inflammatory disorders of the skin. Twenty‐one subjects (14 women and seven men, 5–28 years of age) with mild AD participated in this study. Rosmarinic acid (0.3%) emulsion was topically applied to the elbow flexures of AD patients twice a day (once in the morning and once in the evening). All subjects were evaluated for skin conditions before treatment at the first visit, and then at 4 and 8 weeks after treatment. According to local Severity Scoring of Atopic Dermatitis index results, erythema on antecubital fossa was significantly reduced at 4 and 8 weeks (P < 0.05). Transepidermal water loss of the antecubital fossa was significantly reduced at 8 weeks compared to before treatment (P < 0.05). The results from self‐questionnaires on the efficacy of rosmarinic acid indicated that dryness, pruritus and general AD symptoms improved. Our investigation into the AD‐mitigating effect of rosmarinic acid through in vivo experiments demonstrated the possible clinical use of rosmarinic acid as a therapeutic agent for AD.
Systemic lupus erythematosus‐associated cutaneous cryptococcosis treated successfully with an intermittent 3‐day on/off cycle of itraconazole
Authors: UENO Takashi , KUME Hikaru , MITSUISHI Tsuyoshi , MORIMOTO Kensuke , KIKUCHI Izumi , KAWANA Seiji
Published: December 2008

We describe a case of systemic lupus erythematosus (SLE)‐associated cutaneous cryptococcosis. A 32‐year‐old woman with SLE and lupus nephritis presented with the erythematous maculae on the chest and the extremities, in which encapsulated yeasts were revealed, and was diagnosed with secondary cutaneous cryptococcosis. We administered fluconazole (FLCZ) and then itraconazole (ITCZ) instead of amphotericin B (AMPH‐B) to avoid the risk of renal toxicity of AMPH‐B in the patient. While treatment with FLCZ was not particularly effective, repeated intermittent administration of ITCZ on a “3‐day on/off cycle” (i.e. medication on 3 consecutive days and suspension for the next 3 days in turn) achieved complete remission of the cryptococcosis.
Post‐steroid panniculitis in an adult
Authors: KIM Sang Tae , KIM Tae Kwon , LEE Jin Woo , ROH Hyo Jin , CHOI Soo Young , JEON Young Seung , SUH Kee Suck
Published: December 2008

Post‐steroid panniculitis is known to be very rare and most of the reported cases have been in children after corticosteroid therapy. We present a case of post‐steroid panniculitis occurring in a 60‐year‐old man after massive, long‐term administration of corticosteroids for acute exacerbation of chronic obstructive pulmonary disease (COPD). Histopathological examination of a nodule revealed a patchy area of fat necrosis, several multinucleated giant cells containing needle‐shaped clefts. The lesions subsided completely in approximately 12 weeks without any treatment. We suggest that post‐steroid panniculitis is not confined to childhood but also occurs in adulthood.
Association of single nucleotide polymorphisms in the endothelial differentiation sphingolipid G‐protein‐coupled receptor 1 gene with marbling in Japanese Black beef cattle
Authors: Yamada T. , Itoh M. , Nishimura S. , Taniguchi Y. , Miyake T. , Sasaki S. , Yoshioka S. , Fujita T. , Shiga K. , Morita M. , Sasaki Y.
Published: December 2008

Marbling defined by the amount and distribution of intramuscular fat, so‐called Shimofuri, is an economically important trait of beef cattle in Japan. The endothelial differentiation sphingolipid G‐protein‐coupled receptor 1 (EDG1) gene, involved in blood vessel formation, has been previously shown to be expressed at different levels in musculus longissimus muscle between low‐marbled and high‐marbled steer groups. It is located within the genomic region of a quantitative trait locus for marbling, and thus was considered as a positionally functional candidate for the gene responsible for marbling. In this study, two single nucleotide polymorphisms (SNPs) in the 5′ untranslated region (UTR) and the 3′ UTR of EDG1, referred to as c.‐312A>G and c.*446G>A, respectively, were detected between the two steer groups. The two SNPs were associated with the predicted breeding value for beef marbling standard number by analyses using a population of Japanese Black beef cattle. The effect of genotypes at each of the SNPs on the predicted breeding value for subcutaneous fat thickness was not statistically significant (P > 0.05). Reporter gene assays revealed no significant differences in gene expression between alleles at each of the SNPs. These findings suggest that EDG1 SNPs, although they may not be regarded as a causal mutation, may be useful for effective marker‐assisted selection to increase the levels of marbling in Japanese Black beef cattle.