bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developing Promiscuous Glycosidases for Glycoside Synthesis: Residues W433 and E432 in Sulfolobus solfataricus β‐Glycosidase are Important Glucoside‐ and Galactoside‐Specificity Determinants
Authors: Hancock Susan M. , Corbett Kevin , Fordham‐Skelton Anthony P. , Gatehouse John A. , Davis Benjamin G. 
Published: April 2005

AbstractTwo residues that have been implicated in determining the substrate specificity of the thermophilic β‐glycosidase from the archaeon Sulfolobus solfataricus (SsβG), a member of the glycosyl hydrolase family 1, have been mutated by site‐directed mutagenesis so as to create more versatile catalysts for carbohydrate chemistry. The wild‐type and mutated sequences were expressed in E. coli with a His7‐tag to allow one‐step chromatographic purification. The E432C and W433C mutations removed key interactions with the OH‐4 and OH‐3 of the sugar substrates, thus reducing the discrimination of glucose, galactose and fucose with respect to other glycosides. This resulted in two glycosidases with greatly broadened substrate specificities. Observed changes include a 24‐fold increase in Man:Gal activity and an 18‐fold increase in GalA:Gal activity. This promiscuous substrate tolerance was further illustrated by the parallel synthesis of a β‐glycoside library of glucose, galactose, xylose and mannose in one pot at 50 °C, in organic solvent. The synthetic potential of the catalysts was further evaluated through alkyl glycoside transglycosylation yields, including the first examples of synthesis of β‐mannosides and β‐xylosides with SsβG.
Actin polymerization promotes the reversal of streaming in the apex of pollen tubes
Authors: Cárdenas Luis , Lovy‐Wheeler Alenka , Wilsen Kathleen L. , Hepler Peter K. 
Published: April 2005

AbstractActin polymerization is important in the control of pollen tube growth. Thus, treatment of pollen tubes with low concentrations of latrunculin B (Lat‐B), which inhibits actin polymerization, permits streaming but reversibly blocks oscillatory growth. In the current study, we employ Jasplakinolide (Jas), a sponge cyclodepsipeptide that stabilizes actin microfilaments and promotes polymerization. Uniquely, Jas (2 μM) blocks streaming in the shank of the tube, but induces the formation of a toroidal‐shaped domain in the swollen apex, of which longitudinal optical sections exhibit circles of motion. The polarity of this rotary motion is identical to that of reverse fountain motility in control pollen tubes, with the forward direction occurring at the edge of the cell and the rearward direction in the cell interior. Support for the idea that actin polymerization in the apical domain contributes to the formation of this rotary motility activity derives from the appearance therein of aggregates and flared cables of F‐actin, using immunofluorescence, and by the reduction in G‐actin as indicated with fluorescent DNAse. In addition, Jas reduces the tip‐focused Ca2+ gradient. However, the alkaline band appears in the swollen apex and is spatially localized with the reverse fountain streaming activity. Taken together, our results support the idea that actin polymerization promotes reversal of streaming in the apex of the lily pollen tube. Cell Motil. Cytoskeleton 61:112–127, 2005. © 2005 Wiley‐Liss, Inc.
Ciliary behavior of a negatively phototactic Chlamydomonas reinhardtii
Authors: Josef Keith , Saranak Jureepan , Foster Kenneth W. 
Published: April 2005

AbstractWith an instrument that can record the motion of both cilia of the unicellular alga Chlamydomonas reinhardtii for many hours, the behavioral differences of its two cilia have been studied to determine their specific role in phototaxis. The organism was held on a fixed micropipette with the plane of ciliary beating rotated into the imaging plane of a quadrant photodetector. The responses to square‐wave light patterns of a wide range of temporal frequencies were used to characterize the responses of each cilium. Eighty‐one cells were examined showing an unexpectedly diverse range of responses. Plausible common signals for the linear and nonlinear signals from the cell body are suggested. Three independent ciliary measures—the beat frequency, stroke velocity, and phasing of the two cilia—have been identified. The cell body communicates to the cilia the direction of phototaxis the cell desires to go, the absolute light intensity, and the appropriate graded transient response for tracking the light source. The complexity revealed by each measure of the ciliary response indicates many independent variables are involved in the net phototactic response. In spite of their morphological similarity, the two cilia of Chlamydomonas respond uniquely. Probably the signals from the cell body fan out to independent pathways in the cilia. Each cilium modifies the input in its own way. The change in the pattern of the effective and recovery strokes of each cilium associated with negative phototaxis has been demonstrated and its involvement in phototactic turning is described. Cell Motil. Cytoskeleton 61:97–111, 2005. © 2005 Wiley‐Liss, Inc.
The zero surface tension limit two‐dimensional water waves
Authors: Ambrose D. , Masmoudi N. 
Published: April 2005

AbstractWe consider two‐dimensional water waves of infinite depth, periodic in the horizontal direction. It has been proven by Wu (in the slightly different nonperiodic setting) that solutions to this initial value problem exist in the absence of surface tension. Recently Ambrose has proven that solutions exist when surface tension is taken into account. In this paper, we provide a shorter, more elementary proof of existence of solutions to the water wave initial value problem both with and without surface tension. Our proof requires estimating the growth of geometric quantities using a renormalized arc length parametrization of the free surface and using physical quantities related to the tangential velocity of the free surface. Using this formulation, we find that as surface tension goes to 0, the water wave without surface tension is the limit of the water wave with surface tension. Far from being a simple adaptation of previous works, our method requires a very original choice of variables; these variables turn out to be physical and well adapted to both cases. © 2005 Wiley Periodicals, Inc.
Initial Photoinduced Dynamics of the Photoactive Yellow Protein
Authors: Larsen Delmar S. , van Grondelle Rienk 
Published: April 2005

AbstractThe photoactive yellow protein (PYP) is the photoreceptor protein responsible for initiating the blue‐light repellent response of the Halorhodospira halophila bacterium. Optical excitation of the intrinsic chromophore in PYP, p‐coumaric acid, leads to the initiation of a photocycle that comprises several distinct intermediates. The dynamical processes responsible for the initiation of the PYP photocycle have been explored with several time‐resolved techniques, which include ultrafast electronic and vibrational spectroscopies. Ultrafast electronic spectroscopies, such as pump–visible probe, pump–dump–visible probe, and fluorescence upconversion, are useful in identifying the timescales and connectivity of the transient intermediates, while ultrafast vibrational spectroscopies link these intermediates to dynamic structures. Herein, we present the use of these techniques for exploring the initial dynamics of PYP, and show how these techniques provide the basis for understanding the complex relationship between protein and chromophore, which ultimately results in biological function.
Statistical Evaluation of Single Nano‐Object Fluorescence
Authors: Lippitz Markus , Kulzer Florian , Orrit Michel 
Published: April 2005

AbstractSingle nano‐objects display strong fluctuations of their fluorescence signals. These random and irreproducible variations must be subject to statistical analysis to provide microscopic information. We review the main evaluation methods used so far by experimentalists in the field of single‐molecule spectroscopy: time traces, correlation functions, distributions of “on” and “off” times, higher‐order correlations. We compare their advantages and weaknesses from a theoretical point of view, illustrating our main conclusions with simple numerical simulations. We then review experiments on different types of single nano‐objects, the phenomena which are observed and the statistical analyses applied to them.
Vibronic Transitions in Single Metalloporphyrins
Authors: Lee H. J. , Lee J. H. , Ho W. 
Published: April 2005

AbstractStructural and electronic properties of single zinc etioporphyrin molecules adsorbed on Al2O3/NiAl(110) were probed by a low‐temperature scanning tunneling microscope (STM). Scanning tunneling spectroscopy (STS) revealed progressions of spectral features corresponding to the vibronic states of individual molecules that depend strongly on the molecular conformations. Vibronic features observed by STS were compared with the results from fluorescence induced by tunneling electrons (tunneling‐induced fluorescence, TIF).
The Study of Protein Folding and Dynamics by Determination of Intramolecular Distance Distributions and Their Fluctuations Using Ensemble and Single‐Molecule FRET Measurements
Authors: Haas Elisha 
Published: April 2005

AbstractThe folding and dynamics of globular proteins is a multidimensional problem. The structures of the heterogeneous population of refolding protein molecules are characterized by multiple distances and time constants. Deciphering the mechanism of folding depends on studies of the processes rather than the folded structures alone. Spectroscopy is indispensable for these sorts of studies. Herein, it is shown that the determination of intramolecular distance distributions by ensemble and single‐molecule FRET experiments enable the exploration of partially folded states of refolding protein molecules.
Iridium Anodic Oxidation to Ir(III) and Ir(IV) Hydrous Oxides
Authors: Juodkazytė Jurga , Šebeka Benjaminas , Valsiunas Ignas , Juodkazis Kestutis 
Published: April 2005

AbstractIridium oxide films (IROFs) are known to have an enhanced or the so‐called super‐Nernstian (<59 mV/pH) pH‐sensitivity. The intention in the present study was to find out the reasons of such behavior and also to elucidate the nature of iridium anodic oxidation processes. The methods employed were combined cyclic voltammetry and chronopotentiometry. Iridium layers of 0.1 to 0.2 μm thickness, deposited thermally on titanium or gold‐plated titanium substrates, were used for investigations. IROFs on the surface of working electrodes were formed anodically by applying a constant potential in deaerated and oxygen‐containing solutions of 0.5 M H2SO4, 0.1 M KOH and 0.5 M H3PO4+KOH. Linear pH‐dependences of the stationary open‐circuit potential with the slopes close to 59 mV/pH were found for iridium electrode oxidized at 0.4 V–0.8 V (RHE) in deaerated and at 0.8 V–1.2 V (RHE) in O2‐containing solutions. They were attributed to reversible Ir/Ir(OH)3 and Ir/ IrO2⋅nH2O metal‐oxide electrodes, respectively. It has been suggested that the main current peaks seen in the voltammograms of iridium electrode in acid and alkaline solutions are of different nature. The difference between iridium electrode surface states in acid and alkaline solutions has been presumed to be the main reason of super‐Nernstian pH‐sensitivity of the IROFs. On the basis of the results obtained standard potential of Ir/Ir(OH)3 electrode and the solubility product of Ir(OH)3 have been evaluated: $\rm{E_{\rm Ir/Ir(OH)_3}^{\circ}}$=0.78±0.02 V and Ksp=3.3×10−64.
“Central command” and insular activation during attempted foot lifting in paraplegic humans
Authors: Nowak Markus , Holm Søren , Biering‐Sørensen Fin , Secher Niels H. , Friberg Lars 
Published: April 2005

AbstractThe relationship between cardiovascular regulation and brain activation was investigated during attempted foot lifting in paraplegic subjects and during rhythmic handgrip exercise at one‐third of maximum voluntary contraction force. Brain areas of interest were the primary sensory‐motor area and the insula, a hypothesized center for a central nervous feed‐forward mechanism involved in cardiovascular control (“central command”). This mechanism is complementary to the usual known feedback pathways such as skeletal muscle afferent signals. Regional cerebral blood flow (rCBF) was measured in eight normal and three paraplegic subjects using positron emission tomography (PET) and oxygen‐15‐labeled water. Statistical parametric maps were calculated from the images comparing rest and handgrip. Paraplegics were also scanned during attempted foot lifting, a condition without sensory feedback. During activation tasks, heart rate and mean arterial pressure increased. PET activation responses (P< 0.05, corrected for multiple comparisons) were found in the contralateral primary sensory‐motor area, the supplementary motor area, ipsilateral cerebellum, and bilaterally in the insula. A conjunction analysis showing responses common to handgrip and attempted foot lifting revealed activation in the right central insula (P< 0.05, corrected) in concordance with the concept of a central command feed‐forward hypothesis. Hum Brain Mapp 25:259–265, 2005. © 2005 Wiley‐Liss, Inc.
Towards regional monetary cooperation in East Asia: lessons from other parts of the world
Authors: Kawai Masahiro , Takagi Shinji 
Published: April 2005

AbstractThis paper discusses regional monetary cooperation for East Asia, by drawing lessons from the European Payments Union, the CFA Franc Zone and the Arab Monetary Fund. Along with the well‐known experience of the European Monetary System, these experiences suggest that effective monetary cooperation should include: (1) a surveillance mechanism; (2) a regional financing facility; (3) a common unit of account; and (4) exchange rate coordination. In East Asia, the existing mechanisms of regional surveillance must be strengthened, and the liquidity support mechanism under the Chiang Mai Initiative must evolve into a common pool of foreign exchange reserves. Over the longer term, the region may need to create its own common unit of account and to develop a framework for exchange rate coordination. Copyright © 2005 John Wiley & Sons, Ltd.
Assessment of yeast viability under hyperbaric conditions through a modeling approach
Authors: Coutinho João AP , Belo Isabel , Ferreira Eugénio C , Coelho M Alice Z 
Published: April 2005

AbstractThe effect of pressure (0.1–1.5 MPa) and oxygen concentration on the growth and viability of Saccharomyces cerevisiae was studied. Cell viability was assessed through the Methylene Blue staining method and the percentages of viable and non‐viable cells were estimated using digital image processing. A model taking into account cell viability was developed and used to describe the measured data. The model reveals the opposing effects between oxygen availability and the baric and oxidative stresses present on the system and can successfully describe not only the traditional biomass–product–substrate (X–P–S) evolution but also the ratio of viable cells with time. It is shown that cell viability in general is not constant during the experiments but strongly depends on the environment. Copyright © 2005 Society of Chemical Industry
Intraparticle diffusion of cadmium and zinc ions during adsorption from aqueous solution on activated carbon
Authors: Leyva‐Ramos R , Rangel‐Mendez JR , Bernal‐Jacome LA , Berber Mendoza MS 
Published: April 2005

AbstractThe adsorption isotherms of cadmium(II) and zinc(II) onto activated carbons were obtained in a batch adsorber. The concentration decay data were obtained in a rotating basket adsorber and were interpreted by a mathematical model, which takes into account the adsorption rate, external mass transport and intraparticle diffusion. The results showed that the overall rate of adsorption of Cd(II) and Zn(II) was mainly controlled by the intraparticle diffusion which was solely due to pore volume diffusion. The contribution of the external mass transport resistance was negligible. The effective pore volume diffusivities of Cd(II) and Zn(II) were predicted reasonably well using the ionic diffusivity of the metal and the void fraction and tortuosity of activated carbon. Copyright © 2005 Society of Chemical Industry
Development of a pre‐purification process for homoharringtonine
Authors: Sung Ju‐Li , Kim Byung‐Sik , Kim Jin‐Hyun 
Published: April 2005

AbstractA novel pre‐purification method was developed for producing homoharringtonine from Cephalotaxus koreana, giving high purity and yield. The simple, efficient procedure involved biomass extraction, liquid–liquid extraction, and synthetic adsorbent treatment, followed by low‐pressure chromatography. The use of active clay treatment and silica gel low‐pressure chromatography in the pre‐purification process allowed for the rapid, efficient separation of homoharringtonine from interfering compounds and, compared with alternative processes, increased the yield and purity of crude homoharringtonine for subsequent high‐performance liquid chromatography (HPLC) purification. Homoharringtonine of over 52% purity could be obtained simply with high yield from biomass using this pre‐purification method, while minimizing solvent use and the scale and complexity of HPLC operations for homoharringtonine purification. Copyright © 2005 Society of Chemical Industry
Adsorption of heavy metals from aqueous solutions with by‐products of the steelmaking industry
Authors: Martín M Isabel , López Félix A , Pérez Carlos , López‐Delgado Aurora , Alguacil Francisco J 
Published: April 2005

AbstractThis paper describes the use of two steelmaking industry by‐products (rolling mill scale and blast furnace sludge) as adsorbents for removing heavy metals from aqueous effluent solutions. The adsorption of Pb2+, Zn2+ and Cd2+ on these materials has been studied by the determination of adsorption isotherms from solutions of controlled ionic strength. The effect of time, equilibrium temperature and metal solution concentration on adsorption efficiency was evaluated. The adsorption processes are analysed using the Langmuir theory. Desorption and dumping processes for the metals from loaded steelmaking industry by‐products were also studied under different experimental conditions. The by‐products were shown to be effective adsorbents for the studied cations in aqueous solutions within the range of working concentrations. Copyright © 2005 Society of Chemical Industry
The preparation of 123/125I‐clioquinol for the study of Aβ protein in Alzheimer's disease
Authors: Papazian V. , Jackson T. , Pham T. , Liu X. , Greguric I. , Loc'h C. , Rowe C. , Villemagne V. , Masters C. L. , Katsifis A. 
Published: April 2005

AbstractClioquinol or 5‐chloro‐7‐iodo‐8‐hydroxyquinoline (CQ) is a lipophilic hydroxyquinoline currently under investigation for the treatment of Alzheimer's disease by targeted copper and zinc chelation. CQ was radiolabelled with no‐carrier‐added iodine‐123/125 to give high specific activity analogs for SPECT imaging and biochemical studies. 123I‐clioquinol (123I‐CQ) was prepared by direct iodination of the activated hydroxyquinoline using a variety of oxidants. Highest yields (>85%) and purity were obtained when chloramine‐T or iodogen at pH 4–5 was used. Large‐scale radiolabelled 123I‐CQ was purified by reverse‐phase HPLC using a C‐18 small ‘Rocket®’ column. The radiochemical purity of 123I‐CQ as assessed by analytical HPLC was 99.1±0.6% (n = 9) with specific activity higher than 3 GBq/nmol for 123I‐CQ and 80 MBq/nmol for 125I‐CQ. The total preparation time was 40 min and starting from 3.7 GBq of iodine‐123, more than 2.5 GBq of formulated 123I‐CQ as radiopharmaceutical was available for clinical investigations. Using the same method of preparation, 125I‐CQ was produced in radiochemical and chemical purity higher than 97% with a specific activity of 80 MBq/nmol. Copyright © 2005 John Wiley & Sons, Ltd.
New radiolabelling chemistry: synthesis of phosphorus–[18F]fluorine compounds
Authors: Studenov Andrei R. , Adam Michael J. , Wilson John S. , Ruth Thomas J. 
Published: April 2005

AbstractThe feasibility of synthesizing compounds containing the P–18F bond has been demonstrated by labelling the pesticide, cholinesterase inhibitor Dimefox (N,N,N′N′‐tetramethylphosphorodiamidic fluoride) with F‐18. Radiolabelling was achieved in high radiochemical yield (96%) by nucleophilic substitution of the chloro group attached to phosphorus, in the oxidation state P(V), by 18F− (activated with tetrabutylammonium carbonate in acetonitrile). Given the large number of important biological molecules possessing phosphorus such as oligonucleotides, phospholipids as well as phosphorylated proteins, sugars and steroids, this new labelling chemistry may provide an additional route to radiolabelling these biologically important compounds for use in PET. Copyright © 2005 John Wiley & Sons, Ltd.
Co‐continuous Polyamide 6 (PA6)/Acrylonitrile‐Butadiene‐Styrene (ABS) Nanocomposites
Authors: Li Yongjin , Shimizu Hiroshi 
Published: April 2005

AbstractSummary: Polyamide 6 (PA6)/acrylonitrile‐butadiene‐styrene (ABS) (40/60 w/w) nanocomposites with a novel morphology were prepared by the melt mixing of PA6, ABS and organoclay. The blend nanocomposites had a co‐continuous structure, in which both PA6 and styrene‐acrylonitrile (SAN) were continuous phases. It was found that the toughening rubber particles were only located in the SAN phase and the strengthening clay platelets were selectively dispersed in the PA6 phase. The co‐continuous nanocomposites showed greatly improved mechanical properties over the whole temperature range when compared with the same blend sample without clay.Schematic diagram for the co‐continuous ABS/PA6 blend nanocomposite.imageSchematic diagram for the co‐continuous ABS/PA6 blend nanocomposite.
Preparation and Aggregation of Polypseudorotaxane from Dendronized Poly(methacrylate)‐Poly(ethylene oxide) Diblock Copolymer and α‐Cyclodextrin
Authors: Cheng Caixia , Tang Rupei , Xi Fu 
Published: April 2005

AbstractSummary: Dendronized poly(methacrylate)‐poly(ethylene oxide) (PDMA58‐b‐PEO45) formed as a stoichiometric inclusion complex with α‐cyclodextrin. The incorporation of the rodlike PDMA blocks produced no apparent change in the crystal structure, but its steric hindrance on the PEO chain resulted in lower yield as compared with the pure PEO. Moreover, the architectural transition from rod–coil to rod–rod led to a morphological change from spindly aggregates to rods in a binary solvent mixture of N,N‐dimethylformamide and water.Synthesis and self‐assembly of the α‐cyclodextrin‐[dendronized poly(methacrylate)‐poly(ethylene oxide)] (α‐CD‐PDMA‐PEO) polypseudorotaxane (PR).imageSynthesis and self‐assembly of the α‐cyclodextrin‐[dendronized poly(methacrylate)‐poly(ethylene oxide)] (α‐CD‐PDMA‐PEO) polypseudorotaxane (PR).
Mechanical Properties of a Single Electrospun Fiber and Its Structures
Authors: Gu Shu‐Ying , Wu Qi‐Lin , Ren Jie , Vancso G. Julius 
Published: April 2005

AbstractSummary: A method to measure the Young's modulus of a single electrospun polyacrylonitrile (PAN) fiber is reported. The Young's modulus can be calculated from the force‐displacement curves obtained by the bending of a single fiber attached to an atomic force microscopy (AFM) cantilever. It is suggested that the high modulus of electrospun fibers is caused by the orientation of molecular chains, which is confirmed by wide‐angle X‐ray diffraction (WAXD) measurements. The communication will provide a basic understanding of the relationship between mechanical properties and structures of electrospun fibers.A PAN fiber was attached to a contact mode cantilever to facilitate the measurement of force‐displacement curves and Young's modulus.imageA PAN fiber was attached to a contact mode cantilever to facilitate the measurement of force‐displacement curves and Young's modulus.