bluuebunny/crossref_metadata_2025 huggingface dataset:
Miscibility and isomorphic cocrystallization in blends of ferroelectric copolymers of vinylidene fluoride and trifluoroethylene
Authors: Tanaka Hajime , Lovinger Andrew J. , Davis Don D.
Published: April 2003

The miscibility in binary blends of ferroelectric copolymers of vinylidene fluoride (VF2) and trifluoroethylene ( F3E) has been investigated over the full range of blend compositions for three different random copolymers containing 52, 65, or 73 mol % VF2. We found these copolymers miscible in the melt with each other but not with the parent homopolymer, PVF2. In thin solid films we demonstrated, for all blend compositions, the very rare phenomenon of isomorphic cocrystallization in both the ferroelectric and paraelectric phases of the 52 + 65 and the 65 + 73 mol % VF2 copolymers. However, the blend having the largest compositional difference (52 + 73 mol % VF2) was found to consist of two separate ferroelectric and paraelectric phases. These results demonstrate the very close chemical and structural similarities required for coexistence of two different macromolecules within a single crystalline lattice. Moreover, they allow us to probe the compositional limits for such similarity in both the ferroelectric and the paraelectric lattices. Phase diagrams of these blends have been constructed and are discussed. The Curie transition is shown to be an exceptionally sensitive probe of compatibility in the ferroelectric phase.
Phase size/composition dependence in immiscible blends: Experimental and theoretical considerations
Authors: Favis B. D. , Willis J. M.
Published: April 2003

The influence of composition on phase size in immiscible polymer blends is examined both experimentally and theoretically. It was found for eight noncompatibilized blends, of widely varying particle size morphology, that a master curve of phase size versus log‐relative composition could be obtained by shifting the data along the volume fraction axis. The magnitude of the shift factors (aϕ) correlates with the interfacial tension and viscosity ratio of the systems. The theoretical dependence of the master curve is proportional to ϕ + ϕ2 dependence as in Tokita's theory, but estimation of the coefficients to the ϕ and ϕ2 terms indicates that the influence of power and shear stress on breakdown of the dispersed phase is significantly overestimated by the theory. A master curve is also generated for four compatibilized blends and the dispersed phase sizes are significantly less dependent on composition.
Crystallization kinetics and melting of caprolactone random copolymers
Authors: Goulet Louise , Prud'homme Robert E.
Published: April 2003

Spherulitic growth rates and overall rates of crystallization of poly(ε‐caprolactone‐co‐ε‐methyl‐ε‐caprolactone), poly(CL‐co‐MCL), were analyzed over a composition range from pure poly (ε‐caprolactone) (PCL) to a copolymer containing 40% MCL with an equation which contains the classical nucleation and transport terms, but adds an entropic factor to the nucleation term. Using this new equation, linear plots were obtained with slopes corresponding to the value of the nucleation parameter (KG2) The experimental KG2 value, (9.6 ± 0.5) × 104 K2, is independent of the comonomer content; also, the same KG2 value is obtained from measurements of the overall rate of crystallization and from growth rate analysis. The interfacial free energy (σe) is 112 ± 5 erg/cm2. The melting behavior of PCL and poly(CL‐co‐MCL) is also reported. Equilibrium melting temperatures were determined by the Hoffman‐Weeks extrapolation method. It was found, using the melting point depression method, that 71% of the MCL units are incorporated into the PCL crystals at equilibrium. According to the Z criterion proposed by Lauritzen, Regime II applies to the crystallization kinetics of all polymers investigated. Finally, the value of the Avrami parameter n is reported.
Isothermal refolding in crystals of long alkanes in solution. I. Effect of surface ‘self‐poisoning’
Authors: Ungar Goran , Organ Sally J.
Published: April 2003

Lamellar thickening in folded‐chain crystals of the n‐alkane C198H398 in solution has been shown to occur at the crystallization temperature. The transformation is from crystals with their chains folded in half to extended‐chain crystals, with no observable intermediate forms. This conforms with the extensive existing evidence that integer‐folded forms are thermodynamically preferable. Measurements of the kinetics of lamellar thickening have revealed an unexpected maximum in the thickening rate as a function of temperature: above 75°C, thickening slows down with increasing temperature. This unprecedented result is an indirect consequence of another, equally puzzling, anomaly: the rate of extended‐chain nucleation at the side faces of folded‐chain crystals decreases with increasing solution concentration. This unique observation is attributed to “self‐poisoning” of the lateral surface of the growing nucleus by frequent folded‐chain depositions which inhibit the process of molecular extension. The same effect has been invoked previously to explain the anomalous crystallization rate minima in long alkanes and its present manifestation under different circumstances is regarded as an important independent validation of the concept of “self‐poisoning.”
Transfer‐matrix theory of the crystal–columnar transition in polymeric liquid crystals
Authors: Xu Bing‐Chang , Taylor Philip L.
Published: April 2003

The statistical–mechanical problem of the transition between crystalline and columnar phases in a main‐chain liquid–crystalline polymer is treated in a simple model in which only longitudinal motions of the polymer chains are permitted. A mean‐field approximation for the interchain potential is used to obtain a self‐consistent equation for the crystalcolumnar transition temperature. When applied to typical homopolymers this theory correctly predicts transition temperatures above the degradation temperature; when applied to a crude model of a random copolymer a temperature in the observed range is predicted.
Relaxations in thermosets. XVIII. Ultrasonic studies of curing kinetics of ethylene‐diamine‐cured epoxide
Authors: Alig I. , Lellinger D. , Johari G. P.
Published: April 2003

Velocity and attenuation of longitudinal acoustic waves in a frequency range of 5–16 MHz have been measured during the curing of diglycidyl ether of bisphenol‐A with ethylene diamine. The velocity monotonically increases and reaches a limiting value and the attenuation reaches a maximum and thereafter decreases as curing proceeds. Both kinds of data have been transformed into a complex‐longitudinal‐modulus formalism. The complex‐plane plots of the longitudinal modulus show an arc‐skewed shape at the long (curing) time end. It is fitted, for the initial phase of curing, to a stretched exponential decay function with an exponent γ = 0.22 to 0.28. These results then are considered in terms of a process with a negative feedback between molecular diffusion and chemical reactions to obtain the increase in the relaxation time with the curing time. This increase is sigmoidal. Calculations of the complex longitudinal modulus show the consistency of our formalism.
Gel processing of electrically conductive blends of poly(3‐octylthiophene) and ultrahigh molecular weight polyethylene
Authors: Moulton Jeff , Smith Paul
Published: April 2003

The mechanical and electrical properties of solution‐processed [or gel‐spun] blends of poly(3‐octylthiophene) and ultrahigh molecular weight polyethylene are discussed. Tensile drawing at elevated temperatures of the phase‐separated blends resulted in significant improvements of the mechanical properties, in comparison with those of the neat conducting polymer, with values of the Young's modulus reaching > 40 GPa and tensile strengths in excess of 2 GPa. Doping of the undrawn polyblend fibers with iodine vapor or FeCl3 resulted in materials of useful levels of electrical conductivity covering the full range of 10−15 to 10 S/cm. A distinct percolation threshold for electrical conductivity was not observed, even at poly(3‐octylthiophene) concentrations as low as 0.5 w/w %; the electrical conductivity of the latter blend, after doping with iodine vapor, was 8 × 10−8 S/cm.
Influence of uniaxial draw on near‐surface structure in poly(ethyleneterephthalate)
Authors: Walls Dennis J. , Coburn John C.
Published: April 2003

Relative amounts of surface crystallinity and amorphous structure and their respective surface orientations were examined as a function of depth from the surface for a series of uniaxially drawn poly(ethyleneterephthalate) (PET) films using polarized attenuated total‐reflectance infrared spectroscopy (ATR‐IR). Qualitative depth resolution on a scale from ca. 0.5 to 5 μm is obtained. The results indicate a higher degree of extended trans segments and a higher degree of extended trans orientation near the surface in the machine direction, relative to the bulk film. These quantities also increase with increasing uniaxial draw ratio. No evidence for orientation of the gauche conformer at the surface as a function of uniaxial draw ratio is observed. All conclusions are consistent with the presence of increased crystallinity at the surface of the films. Increases in trans structure and orientation measured by ATR‐IR measurements are consistent with bulk crystallinity measurements from density and x‐ray scattering measurements.
The effect of annealing on slow crack growth in an ethylene‐hexene copolymer
Authors: Lu X. , Qian R. , McGhie A. R. , Brown N.
Published: April 2003

A quenched ethylene‐hexene copolymer was annealed in the temperature range of 86 to 127°C. The morphological changes were monitored by differential scanning calorimetry (DSC) and density. The slow crack growth resistance tested at 80°C was a maximum at an annealing temperature of 113°C and a minimum of 123°C. The lifetimes can be varied by more than a factor of 20 depending on the thermal treatment. The increase in slow crack growth resistance between 86 and 113°C is attributed to an increase in the strength of the crystals by becoming more perfect and to the conversion of loose tie molecules into taut tie molecules. The decrease in strength between 113 and 123°C is attributed to the decrease in tie molecules when a large fraction of the as‐quenched crystals begin to melt.
Influence of polymer structure inhomogeneity on oxygen quenching of phenanthrene phosphorescence in poly(methyl methacrylate)
Authors: Bagryansky V. A. , Korolev V. V. , Tolkatchev V. A. , Bazhin N. M.
Published: April 2003

Decay kinetics of phenanthrene phosphorescence in atactic poly(methyl methacrylate) have been studied at 130–170 K in the presence of dissolved oxygen. The kinetics show anomalous behavior and cannot be described in terms of homogeneous diffusion of oxygen. Analysis of the dependence of the kinetics on oxygen concentration shows that such behavior is well accounted for by a polychromatic model assuming a dispersion of diffusion coefficients due to the inhomogeneity of the polymer structure. Possible errors in determining the diffusion coefficient from the phosphorescence quantum yield on the assumption of homogeneous diffusion are discussed. © 1992 John Wiley & Sons, Inc.
Phenomenology and mechanisms of unidimensional stress‐dependent micromolecular transport in a stiff‐chain polymer. I. Unoriented cellulose acetate
Authors: Sanopoulou M. , Petropoulos J. H.
Published: April 2003

The longitudinal penetration of micromolecular liquid solvents (acetone, dioxane) or swelling agents (methylene chloride, methanol) into unoriented (unstretched) cellulose acetate film has been studied in detail by a variety of techniques, including observation of visible penetrant fronts, birefringence profiles, colored tracer microdensitometry, and microinterferometry. The results, in conjunction with those of Part II, provide a fuller picture of the relevant phenomenology than was previously available, leading to further insight into the mechanism of micromolecular transport in stiff‐chain polymers and its dependence on the nature of the penetrant and the structural changes of the swelling polymer. © 1992 John Wiley & Sons, Inc.
Phenomenology and mechanisms of unidimensional stress‐dependent micromolecular transport in a stiff‐chain polymer. II. Uniaxially oriented cellulose acetate
Authors: Sanopoulou M. , Petropoulos J. H.
Published: April 2003

The study of micromolecular transport in cellulose acetate film reported previously is here extended by investigation of the effect of different degrees of semipermanent uniaxial macromolecular orientation, produced by prestretching the film under suitable conditions. The changes noted in penetration rate and kinetics and in birefringence, tracer microdensitometry, and microinterferometry profiles for penetration along and across the axis of preferred orientation, are reported in detail and their implications in terms of the transport mechanism are discussed. © 1992 John Wiley & Sons, Inc.
The in situ reactive compatibilization of nylon‐6/polystyrene blends using anhydride functionalized polystyrenes
Authors: Park Inha , Barlow J. W. , Paul D. R.
Published: April 2003

Nylon‐6/polystyrene (PS) blends were reactively compatibilized by addition of various anhydride functionalized polystyrenes. The morphology of the blends was examined using a scanning electron microscopy (SEM) technique. The particle size of the dispersed styrenic phase was about 3.2 μm for the uncompatibilized 8/2 Nylon‐6/PS blend while those of the compatibilized blends were decreased by as much as two orders of magnitude depending on the amount and type of the functionalized polystyrene (FPS) added. Several low‐molecular weight polystyrenes with terminal anhydride groups, prepared by two different functionalization methods, were examined. The effect of molecular weight on particle size reduction depended on the basis of comparison, mass of additive, or moles of anhydride units. A high‐molecular weight random copolymer of styrene and maleic anhydride was most effective when compared on a mass basis. The increase in adhesion between the Nylon‐6 and the styrenic phases caused by the in situ reaction was evaluated by a lap shear technique. The free polystyrene, Nylon‐6, and Nylon‐FPS copolymer formed were separated by solvent extraction technique using formic acid and toluene. The extent of coupling reaction between the functionalized polystyrenes and Nylon‐6 ranged from 25 to 43%. © 1992 John Wiley & Sons, Inc.
Photoelasticity of textured heterogeneous polymer materials
Authors: Patlazhan S. A.
Published: April 2003

The photoelastic properties of textured polymer composites are considered for the high deformation limit. Photoelasticity equations for incompressible polymers are derived in the correlation function theory approximation. It is shown that the birefringence may be zero for critical stretching across the texture axis. This effect can be used to measure the dispersion of shear moduli of polymer composites. © 1993 John Wiley & Sons, Inc.
Microphase separation of block copolymer solutions in a flow field
Authors: Albalak Ramon J. , Thomas Edwin L.
Published: April 2003

Films of polystyrene–polybutadiene–polystyrene (PS/PB/PS) triblock copolymer and polystyrene‐poly(ethylene/propylene) (PS/PEP) diblock copolymer were cast from toluene solutions subjected to hydrodynamic flow at room temperature using a device based on a novel casting method we term ‘roll‐casting.’ Polymer solutions were rolled between two corotating eccentric cylinders while at the same time the solvent was removed at a controlled rate. As the solvent evaporated, the block copolymers microphase separated into globally oriented structures. A discussion of the flow field that develops during roll‐casting is presented and specific attention is given to the importance of the shear and elongation rates present. For the triblock and diblock, respectively, the processed structures consisted of polystyrene cylinders assembled on a hexagonal lattice in a polybutadiene matrix, and unidirectional lamellae of alternating polystyrene and polyethylene/propylene. Small‐angle x‐ray scattering (SAXS) and transmission electron microscopy (TEM) indicated the near single‐crystal structure both types of films. SAXS also showed the styrene cylinders and the alternating lamellae to be packed closer together in roll‐cast films than in simple quiescently cast films. A molecular orientation mechanism is proposed to describe both these results as well as the changes in packing and in macroscopic sample dimensions measured after complete solvent evaporation and after sample annealing. © 1993 John Wiley & Sons, Inc.
Poly(ethylene oxide) electrolytes containing mixed salts
Authors: Yang H. , Farrington G. C.
Published: April 2003

An unusual conductivity enhancement occurs in PEO‐based ZnBr2/LiBr electrolytes of composition, [xZnBr2 + (1 − x)LiBr](PEO)16 with x = 0.00, 0.05, 0.50, 0.75, 1.00. The conductivity of the mixed‐salt electrolytes is higher than that of either pure salt electrolyte. The highest conductivity, observed for x = 0.5, is two orders of magnitude higher than that of pure LiBr(PEO)16 and one order higher than ZnBr2(PEO)16. In contrast, the conductivity of mixed Mg (CIO4)2/LiCIO4 electrolytes, [xMg(CIO4)2 + (1 − x) LiCIO4](PEO)16 where x = 0.00, 0.20, 0.50, 0.80, 1.00, increases monotonically with the mole fraction of the higher conductivity component, LiCIO4(PEO)16. The conductivity and differential scanning calorimetry (DSC) results suggest that the conductivity enhancement in the ZnBr2/LiBr electrolytes results from a change in charge carrier type and concentration, whereas the conductivity change in the Mg(CIO4)2/LiCIO4 electrolytes arises from a change in the microscopic viscosity of the electrolytes. © 1993 John Wiley & Sons, Inc.
The influence of total number of favourable working conditions and lifestyle on mental health in Japanese workers in a large company
Authors: Suwazono Yasushi , Okubo Yasushi , Kobayashi Etsuko , Kido Teruhiko , Nogawa Koji
Published: April 2003

Healthy Work and Lifestyle Scores were totalled, and their influence on the prevalence of mental symptoms was investigated. A cross‐sectional design was employed in this study. Participants were workers in a telecommunications enterprise who had received annual health check‐ups from 1995 to 1997 and were between 20 and 59 years of age. A self‐administered questionnaire survey obtaining information about sex, age, past history of disease, present illness, working conditions, lifestyle and subjective mental symptoms was conducted once a year. Workers with a past history of disease or present illness were excluded from the analysis. In total, 66 004 questionnaires were analysed in this study. Favourable lifestyles and working conditions were enumerated; Healthy Work and Lifestyle Scores were totalled, and their influence on mental symptoms was also investigated. It was found that for every year, the result of ANCOVA suggested that the lower the Healthy Work and Lifestyle Scores, the higher the age‐adjusted mean number of perceived mental symptoms. The results of multiple comparisons revealed significant deterioration in the number of perceived mental symptoms in the groups whose Healthy Work and Lifestyle Scores were 0–4‐, 5‐ and 6‐point. This comprehensive score suggested that working conditions and lifestyle correlated with the mental health of Japanese workers. Copyright © 2003 John Wiley & Sons, Ltd.
Modal identification of Di Wang Building under Typhoon York using the Hilbert–Huang transform method
Authors: Xu Y. L. , Chen S. W. , Zhang R. C.
Published: April 2003

The Di Wang Building is one of the tallest composite buildings in the world, located in downtown Shenzhen City of China about 2 km from the Hong Kong border. On 16 September 1999, Typhoon York – that is the strongest typhoon since 1983 and the typhoon of longest duration on record – attacked Hong Kong and Shenzhen. The wind and structural monitoring system installed in the Di Wang Building timely recorded wind and structural response data. The newly emerged Hilbert–Huang transform (HHT) method in conjunction with the random decrement technique (RDT) is applied to the measured data in this paper to identify dynamic characteristics of the building. A series of natural frequencies and modal damping ratios of the building under different wind speeds in different directions are identified and compared with those from the fast Fourier transform (FFT)‐based method. The variations of natural frequency, total modal damping ratio and net structural modal damping ratio with wind speed and vibration amplitude are also investigated. The results show that the natural frequencies identified by the HHT method are almost the same as those obtained by the FFT‐based method. The first two modal damping ratios given by the HHT method are, however, lower than those by the FFT‐based method, which may indicate that the FFT‐based method overestimates the modal damping ratios. Both the total and the net structural modal damping ratios increase with increasing wind speed and vibration amplitude but the situation is reversed for the natural frequency. Copyright © 2003 John Wiley & Sons, Ltd.
Stable Isotope Stratigraphy of a Late Last Interglacial Speleothem from Rana, Northern Norway
Authors: Linge Henriette , Lauritzen Stein-Erik , Lundberg Joyce
Published: April 2003

A stalagmite from Rana, northern Norway, dated by the TIMS uranium-series technique, yields records of stable oxygen and carbon isotopes covering the period from late marine oxygen isotope substages (MIS) 5e to 5a, that is, 123,350 to 73,300 yr ago. Rapid growth (∼46 μm/yr) between 123,350 and 119,500 yr ago reflects climatic conditions favorable for speleothem growth. This period is characterized by century- to millennial-scale oscillations in both stable isotope records, where both the absolute values and the isotope ranges are similar to Holocene and older samples from the region. From 119,500 to 107,700 yr ago, speleothem growth was slow (∼0.7 μm/yr), and between 107,700 and 73,300 yr ago growth is barely noticeable (0.07 μm/yr). During the period of slow growth the stable isotope records show an overall enrichment trend. The transition between rapid and slow growth rate occurring sometime between 119,500 and 107,700 yr ago is believed to reflect the termination of interglacial climate in this region. The absence of detritus and corrosion features in the slowly deposited calcite suggests that the valley outside the cave remained sufficiently ice free for speleothem growth to occur until at least 73,300 yr ago.
230Th/U Dating of Frozen Peat, Bol'shoy Lyakhovsky Island (Northern Siberia)
Authors: Schirrmeister Lutz , Oezen Deniz , Geyh Mebus A
Published: April 2003

The chronology of Quaternary paleoenvironment and climate in northeastern Siberia is poorly understood due to a lack of reliable numerical age determinations. The best climatic archives are ice-rich permafrost sequences, which are widely distributed in northeastern Siberia. For this study, 230Th/U-ages were determined by thermal ionization mass spectrometry (TIMS) from frozen peat in a permafrost deposit at the southern cliff of the Bol'shoy Lyakhovsky Island (New Siberian Archipelago), west of the Zimov'e River. These yielded a Pre-Eemian “isochron”-corrected 230Th/U-age of 200,900±3400 yr. This result is reliable because permafrost deposits behave as closed systems with respect to uranium and thorium. Our findings suggest that 230Th/U dating of frozen peat in permafrost deposits is a useful tool for the reconstruction of the Middle Quaternary environment of northern Siberia and of the whole Arctic.
The membrane distal half of gp130 is responsible for the formation of a ternary complex with IL‐6 and the IL‐6 receptor
Authors: Horsten Ursula , Schmitz-Van de Leur Hildegard , Müllberg Jürgen , Heinrich Peter C. , Rose-John Stefan
Published: April 2003

Gp130 is the signal transducing subunit of the interleukin‐6 receptor. Signaling is initiated by the complex formation of gp130 with IL‐6 bound to the IL‐6 receptor (IL‐6R). We have subdivided the extracellular domain of gp130 in two parts and expressed the mutant proteins as soluble IgG fusion proteins in COS‐7 cells. By studying the formation of the ternary complex we show that the membrane distal half of gp130 which contains a cytokine receptor domain is responsible for the interaction with the IL‐6/IL‐6R complex. Interestingly this is the same region which is believed to be involved in specific recognition of the related cytokines LIF, OM, and probably also of CNTF and IL‐11.
Evidence for a monooxygenase‐catalyzed primary process in the catabolism of chlorophyll
Authors: Curty Christophe , Engel Norbert , Gossauer Albert
Published: April 2003

Only recently have products of the enzymatic breakdown of the chlorophylls been characterized for the first time. All catabolites isolated until now from a chlorophyte and from angiosperms have in common the position at which the primary oxygenative ring cleavage occurs, yielding linear tetrapyrroles (19‐formyl‐1[21H,22H]bilinones). In vivo studies of 18,18O2 incorporation in one of the chlorophyll catabolites isolated from Chlorella protothecoides show unequivocally that of the two oxygen atoms inserted into the pigment, only the formyl oxygen originates from dioxygen whereas the other one, the lactamic oxygen atom, derives from water. These findings suggest a monooxygenase‐catalyzed primary process in the catabolism of chlorophyll.
Rev‐dependency of expression of human immunodeficiency virus type 1 gag and env genes
Authors: Sakai Hiroyuki , Furuta Rika A. , Tokunaga Kenzo , Kawamura Meiko , Hatanaka Masakazu , Adachi Akio
Published: April 2003

Structural gene expression of human immunodeficiency virus type 1 (HIV‐1) requires a viral regulatory protein, Rev transactivator. We investigated Rev‐dependency of HIV‐1 gene expression by various reporter systems. Expression of unspliced and singly‐spliced viral mRNAs was demonstrated to be differentially dependent on the Rev function. This difference of Rev‐dependency was found not to be determined by cis‐elements in gag, pol, and env coding sequences reported so far, and was lost when the reporter constructs containing minimum elements for Rev‐responsiveness such as splice signals and rev responsive element were used for experiments. These findings indicated that fundamental structure of HIV‐1 mRNA was critical for the differential regulation of gene expression by Rev transactivator.
Human thrombin variable region 1, including E39, is involved in interactions with α1‐antitrypsin M358R and protein C
Authors: Gaussem Pascale , Picard Véronique , Chadeuf Gilliane , Arnaud Emmanuel , Aiach Martine
Published: April 2003

We used an antithrombin autoantibody (IgG D), the epitope of which encompasses ABE1 and amino acids located within variable region 1, to study thrombin interactions with R358 α1‐AT and protein C. IgG D inhibited the thrombin interaction with R358 α1‐AT, while hirugen had no effect, indicating that the interaction of R358 α1‐AT with thrombin may involve the VR1 subsite. We also obtained evidence that VR1 may be involved in the activation of protein C by thrombin in the absence of thrombomodulin. Moreover, IgG D attenuated the inhibitory effect of calcium ions during protein C activation by thrombin, probably by masking E 39 within the VR1 site.
Nucleotide sequence encoding the di‐haem cytochrome c551 peroxidase from Pseudomonas aeruginosa
Authors: Ridout Christopher J. , James Richard , Greenwood Colin
Published: April 2003

The nucleotide sequence of the gene encoding cytochrome c
551 peroxidase from Pseudomonas aeruginosa is reported. The translated amino acid sequence differs from the sequence reported earlier by peptide mapping most significantly by the presence of a section containing an additional 20 residues. A number of minor differences are also evident. The new sequence translates to a protein containing 346 amino acids, the first 23 being typical of a hydrophobic leader peptide with a characteristic protease cleavage site.
AP‐1 DNA‐binding activity is inhibited by selenite and selenodiglutathione
Authors: Spyrou Giannis , Björnstedt Mikael , Kumar Sushil , Holmgren Arne
Published: April 2003

The binding of the transcription factor AP‐1 to DNA has been shown to be modulated by redox control mechanisms. Selenite and selenodiglutathione (GS‐Se‐SG), inhibit mammalian cell growth and are efficient oxidants of reduced thioredoxin and reduced thioredoxin reductase. Here, we report that selenite and GS‐Se‐SG efficiently inhibited AP‐1 DNA‐binding in nuclear extracts from 3B6 lymphocytes. A GS‐Se‐SG concentration of 0.75 μM resulted in 50% inhibition of AP‐1 DNA‐binding, whereas the same effect was achieved with 7.5 μM selenite. Nuclear extracts prepared from human 3B6 lymphocytes exposed for 4 h to 10 μM selenite showed a 50% reduction of AP‐1 binding. These data suggest that selenite and selenodiglutathione inactivate the AP‐1 factor and provide a mechanism by which selenium compounds inhibit cell growth.
A novel 6Fe (2 × [3Fe‐4S]) ferredoxin from Mycobacterium smegmatis
Authors: Imai Takeo , Urushiyama Akio , Saito Hiroshi , Sakamoto Yuki , Ota Katsuya , Ohmori Daijiro
Published: April 2003

A novel ferredoxin was purified from Mycobacterium smegmatis by a series of hydrophobic chromatographies in the presence of high concentrations of ammonium sulfate and sodium chloride. The ferredoxin exhibited the same peptide map and N‐terminal amino acid sequence as the known 7Fe ferredoxin from the same bacterium. On the other hand, this ferredoxin was found to contain ∼6 Fe/mol ferredoxin and was also shown to contain only [3Fe‐4S] clusters by resonance Raman spectroscopy, indicating that it is a novel 6Fe ferredoxin which contains two [3Fe‐4S] clusters.
Inhibition of apoptosis by the expression of antisense Nedd2
Authors: Kumar Sharad
Published: April 2003

Nedd2 belongs to a family of mammalian cysteine proteases which share similarity with the Caenorhabditis elegans cell death protein, Ced‐3. Overexpression of Nedd2 has been shown to induce apoptosis in mammalian cells but in the absence of a specific known inhibitor, it remains to be seen whether this represents cytotoxic effects of the Nedd2 protease or the specific activation of an apoptotic pathway. The present work shows that the factor‐dependent cell line FDC‐P1 expressing mouse antisense Nedd2 mRNA, exhibits significant inhibition of cell death upon removal of the cytokines, thus providing evidence for a direct role of Nedd2 in mediating apoptosis.
Identification of additional homologues of subunits VII and VIII of the ubiquinol‐cytochrome c oxidoreductase enables definition of consensus sequences
Authors: Boumans Hans , Berden Jan A. , Grivell Leslie A.
Published: April 2003

The Candida utilis QCR7 gene encoding subunit VII of the ubiquinol‐cytochrome c oxidoreductase was isolated by functional complementation of the Saccharomyces cerevisiae subunit VII‐null mutant. Several other subunit VII homologues as well as homologues for subunit VIII were identified by screening the GenBank database. Some of these homologues for subunit VII could only be identified as such using a consensus sequence that was derived from the multiple sequence alignment. Definition of the consensus should facilitate further analysis of structure/function relationships in this protein.
The presence of H+ and Na+‐translocating ATPases in Methanobacterium thermoautotrophicum and their possible function under alkaline conditions
Authors: Šmigáň Peter , Majerník Alan , Polák Peter , Hapala Ivan , Greksák Miloslav
Published: April 2003

Two ATPases with different apparent molecular masses of approx. 500 kDa and 400 kDa were identified in the EDTA extract of the cell membranes of Methanobacterium thermoautotrophicum. Western blotting with polyclonal antiserum reactive with β‐subunit of mitochondrial ATPase from rat liver and yeast was used for further analysis of these ATPases. A strong crossreactivity with a single protein band with an apparent molecular weight of about 53 kDa (similar to β‐subunit of F‐type ATPase from other sources) was found in protein extracts of whole cells of Methanobacterium thermoautotrophicum strains ΔH and Marburg, as well as of Methanospirillum hungatei. This indicates the presence of F‐type ATPase in methanogens. ATP synthesis driven by membrane potential which was generated by artificially‐imposed ΔpH in the presence of protonophorous uncoupler and sodium ions was stimulated by bafilomycin A1, an inhibitor of V‐ and A‐type ATPases, as well as by harmaline, an inhibitor of Na+/H+ antiporter. These results indicate that cells of Methanobacterium thermoautotrophicum strain ΔH contain the F‐type ATP synthase which is Na+‐translocating in addition to V‐ or A‐type ATP synthase which is H+‐translocating.
Inhibition of liver microsomal carnitine acyltransferases by sulphonylurea drugs
Authors: Broadway Neil M. , Saggerson E.David
Published: April 2003

The sulphonylureas glibenclamide and tolbutamide inhibited carnitine acyltransferase activities in rat liver microsomes. Glibenclamide was a more potent inhibitor than tolbutamide. The effect of tolbutamide on the malonyl‐CoA‐inhibitable transferase was influenced by the phospholipid/detergent environment whereas the effect of glibenclamide was not. Glibenclamide was a more potent inhibitor of the malonyl‐CoA‐inhibitable transferase than of the malonyl‐CoA‐insensitive enzyme. The extent of inhibition of the malonyl‐CoA‐inhibitable transferase by tolbutamide was similar to its effect on VLDL triacylglycerol secretion as reported by Wiggins and Gibbons [Biochem. J. 284 (1992) 457–462] possibly supporting the suggestion that microsomal carnitine acyltransferases are involved in VLDL triacylglycerol assembly/secretion.
Rat renin gene transcription is initiated at a single start site
Authors: Della Bruna Roberto , Schricker Karin , Holmer Stephen , Kurtz Armin
Published: April 2003

The promoter region of the renin gene in man, mouse and rat contains several putative transcription start sites, which in mouse have been shown to be tissue specific and differently regulated. To investigate which of these start sites are used during stimulation of renin gene transcription by the major physiological control factors, we determined the transcription start sites of rat renin in the kidney and adrenal glands by RNase protection using a cRNA probe spanning 387 bases upstream and 121 bases downstream from the canonical transcription initiation site. To stimulate renin gene expression, we used renal artery stenosis, angiotensin II antagonists, furosemide and isoprenaline infusions and low sodium diet. Our results suggest that only one TATA box is functional in rat kidney and adrenal.
Heat shock activation of NFkB in rat liver is mediated by interleukin‐1
Authors: Pogliaghi Giovanna , Tacchini Lorenza , Anzon Elena , Radice Laura , Bernelli-Zazzera Aldo
Published: April 2003

Exposure to high temperature (heat shock) activates the transcription factor NFkB in the liver of the living rat, but is not effective in hepatoblastoma cells in culture: on the contrary, activation of the heat shock transcription factor (HSF) occurs under both conditions. Pre‐treatment of the rat with IL‐1 receptor antagonist suppresses the activation of NFkB, which seems to be mediated by the release of this cytokine, but does not hamper the activation of HSF and the concurrent induction of hsp 70 mRNA. IL‐1 activity actually shows a strong, albeit transient, increase in the blood of heat shocked rats.
Molecular cloning and functional expression in E. coli of a novel plant enzyme mediating ξ‐carotene desaturation
Authors: Albrecht Manuela , Klein Annelyse , Hugueney Philippe , Sandmann Gerhard , Kuntz Marcel
Published: April 2003

We have cloned a cDNA from the plant Capsicum annuum which encodes a novel enzyme mediating the dehydrogenation of ξ‐carotene and neurosporene to lycopene when expressed in E. coli cells accumulating ξ‐carotene or neurosporene. This enzyme is unable to dehydrogenate either phytoene or lycopene. The deduced amino acid sequence suggests that this cDNA encodes a polypeptide whose mature size is ca. 59 kDa and which is synthesized as a precursor with a NH2‐terminal extension resembling transit peptides for plastid targeting. Sequence comparison reveals 33–35% similarity with previously cloned plant or cyanobacterial phytoene desaturases. In contrast, only limited sequence similarity is found with a ξ‐carotene desaturase from the cyanobacterium Anabaena.
Human colon produces fully processed glucagon‐like peptide‐1 (7–36) amide
Authors: Deacon Carolyn F. , Johnsen Anders H. , Holst Jens J.
Published: April 2003

The human colon contains many open‐type endocrine cells which express the preproglucagon gene and possess glucagon‐like peptide‐1 (GLP‐1) immunoreactivity, but the molecular form of the peptide is unknown. Acid ethanol extracts of human colon (n = 4) were subjected to gel filtration and successive purification by high‐pressure liquid chromatography, monitored by specific RIAs. A single GLP‐1‐immunoreactive peak was isolated and identified as GLP‐1 (7–36)amide by amino acid sequence analysis and mass spectrometry. We conclude that proglucagon is processed in the large intestine in the same manner as in the small intestine, and results in the formation of fully processed biologically active GLP‐1.
Peroxynitrite‐mediated oxidation of dihydrorhodamine 123 occurs in early stages of endotoxic and hemorrhagic shock and ischemia‐reperfusion injury
Authors: Szabó Csaba , Salzman Andrew L. , Ischiropoulos Harry
Published: April 2003

To quantify peroxynitrite production during shock, we measured oxidation of dihydrorhodamine 123 in rats. In endotoxic and hemorrhagic shock and splanchic ischemia‐reperfusion, dihydrorhodamine oxidation rapidly increased, which was prevented by inhibition of endothelial nitric oxide (·NO) synthase (ecNOS). Thus, peroxynitrite is already formed at early stages of shock from ecNOS‐derived ·NO. Overproduction of ·NO by the inducible NOS at late shock was not associated with additional increases in dihydrorhodamine oxidation. ecNOS inhibition enhanced dihydrorhodamine oxidation in control rats. These latter findings may be explained by ·NO‐mediated inhibition of peroxynitrite‐induced dihydrorhodamine oxidation, a phenomenon also observed in vitro.
Cross‐linking of at least three binding sites mediates signal transduction in a CR2‐positive Burkitt lymphoma derived cell line (Raji)
Authors: Barile Guiseppe , Pernozzoli Barbara , Tiracchia Valentina , Ioppolo Salvatore , De Cristofaro Maria , Mattei Elisabetta , Faggioni Alberto
Published: April 2003

In this study we demonstrate that Raji cells, a CR2‐positive Burkitt lymphoma‐derived cell line, during cell growth, need the cross‐linking of multiple OKB7 binding sites or C3d determinants to mediate signal transduction. The loss of one of these affects the cellular response. Moreover, OKB7, the anti‐CR2 MoAb, recognizes C3d determinants on the cell surface and inhibits signal transduction induced by anti‐C3d polyclonal antibody. Since Raji cells are always CR2 positive during cell growth, we suppose that at least another protein, along with CR2, may be involved in setting up a cell surface complex able to receive and transduce the signal triggered by OKB7. In our experimental system the protein that offers a third binding site to OKB7, may be represented by a 33 kDa protein bearing C3d determinants.
δ‐l‐(α‐Aminoadipoyl)‐l‐cysteinyl‐d‐valine synthetase: isolation of l‐cysteinyl‐d‐valine, a ‘shunt’ product, and implications for the order of peptide bond formation
Authors: Shiau Chia-Yang , Baldwin Jack E. , Byford Michael F. , Schofield Christopher J.
Published: April 2003

l‐Cysteinyl‐d‐valine was isolated from incubations of l‐glutamate, l‐cysteine and l‐valine with δ‐l‐(α‐aminoadipoyl)‐l‐cysteinyl‐d‐valine synthetase and identified by 1H NMR and electrospray ionization MS. This is entirely consistent with our prior proposal (Shiau, C.‐Y., Baldwin, J.E., Byford, M.F., Sobey, W.J. and Schofield, C.J. (1995) FEBS Lett. 358, 97–100) that the α‐peptide bond between cysteine and valine is formed before the δ‐peptide bond between α‐aminoadipate and cysteine. The inclusion of l‐glutamate, an analogue of l‐α‐aminoadipate, did not result in a detectable amount of tripeptide product, but did increase apparent yields of l‐cysteinyl‐d‐valine. Conceivably, formation of the l‐glutamyladenylate stimulates synthesis of the cysteinyl‐valine dipeptide indirectly via a conformational change in the enzyme.
DNA synthesis primed by mononucleotides (de novo synthesis) catalyzed by HIV‐1 reverse transcriptase: tRNALys,3 activation
Authors: Zakharova Ol'ga D. , Tarrago-Litvak Laura , Fournier Michel , Litvak Simon , Nevinsky Georgyi A.
Published: April 2003

HIV‐1 RT is able to catalyze DNA synthesis starting from mononucleotides used both as minimal primers and as nucleotide substrates (de novo synthesis) in the presence of a complementary template. The rate of this process is rather slow when compared to the polymerization primed by an oligonucleotide. The addition of tRNALys,3 to this system increased the de novo synthesis rate by 2‐fold. Addition of low concentrations of agents able to modify protein conformation, such as urea, dimethylsulfoxide and Triton X‐100, can activate the de novo synthesis by a factor 2 to 5. A dramatic synergy is observed in the presence of the three compounds since the stimulating effect of tRNA increases 10–15 times. These results suggest that compounds activating RT are able to induce a conformational change of the enzyme which results in a higher specific activity. Primer tRNA seems to play an important role in HIV‐1 RT modification(s) leading to a polymerase having a higher affinity for the primer or the dTTP, but not for the template. The specificity of RT for the template is not influenced by changes in the kinetics or in the thermodynamic parameters of the polymerization reaction.
Functional expression of the human CHIP28 water channel in a yeast secretory mutant
Authors: Laizé Vincent , Rousselet Germain , Verbavatz Jean-Marc , Berthonaud Véronique , Gobin Renée , Roudier Nathalie , Abrami Laurence , Ripoche Pierre , Tacnet Frédérique
Published: April 2003

The temperature‐sensitive Saccharomyces cerevisiae mutant strain NY17, deficient in the secretory pathway (sec6‐4 mutation), is used for the heterologous expression of the human CHIP28 water channel. After a heat‐shock, the protein is present in partially purified post‐golgi secretory vesicles. Immunodetection and water transport studies, directly made on the vesicles, showed that CHIP28 is highly expressed and active in the yeast membranes.
A novel gene family encoding proteins with highly differing structure because of a rapidly evolving exon
Authors: Lundwall Åke , Lazure Claude
Published: April 2003

Despite vast differences in primary structure, it is here shown that several predominant semen proteins are encoded by genes that belongs to a common family. Members have their transcription unit split into three exons: the first encoding the signal peptide, the second the secreted protein, while the third exon solely consists of 3′ non‐translated nucleotides. The first and and the third exon are conserved between members, but the second exon is not. The genes for human semenogelins I and II, rat SVSII, SVSIV, SVSV and guinea pig GP1 and GP2 belong to this gene family.
Changes in the histidine residues of Cu/Zn superoxide dismutase during aging
Authors: Santa Maria Consuelo , Revilla Elisa , Ayala Antonio , de la Cruz Cristina P. , Machado Alberto
Published: April 2003

Cu/Zn‐Superoxide dismutase activity (Cu/Zn‐SOD) was studied in liver from 3‐ and 24‐month‐old rat. A significant decrease of enzyme activity in liver of the aged rat was found. Various amino acid residues and protein carbonyl groups (CO) were measured in purified young and old enzyme. It was found that the ‘old’ enzyme had one histidine fewer and higher CO content than the ‘young’ Cu/Zn‐SOD. Inactivation ‘in vitro’ of purified commercial bovine erythrocyte Cu/Zn‐SOD led to a decrease in the enzymatic activity, an increase in the CO and one histidine residue modified. A similar behavior between aging and oxidation was suggested.
Determination and cellular localization of adenylyl cyclase isozymes expressed in embryonic chick heart
Authors: Hai Jing Yu  , Unnerstall James R. , Green Richard D.
Published: April 2003

Mammalian heart has been reported to express AC isozymes (types V and VI) that are inhibited by < μM [Ca2+]; avian heart has been reported to express adenylyl cyclase activity that is inhibited by < μM [Ca2+]. We have used reverse transcription polymerase chain reaction (RT‐PCR) to determine that type V and VI AC mRNAs are present in freshly isolated ventricular myocytes. Subsequent RNase protection assays revealed that that the type V signal is 4–5 times that for the type VI isozyme. In situ hybridization with high specific activity cRNA probes combined with immunocytochemistry with a chick anti‐myosin antibody was used to probe the cellular origins of type V and type VI AC signals. These studies show that myocytes contain messages for both the type V and VI isozymes but that AC V is the major isoform. Interestingly, while the type V AC mRNA appears to be localized primarily, if not exclusively, in myocytes, the signal for type AC VI mRNA in non‐myocytes is stronger than in myocytes.
Cloning and expression in Escherichia coli of cDNA encoding house dust mite allergen Der f 3, serine protease from Dermatophagoides farinae
Authors: Nishiyama Chiharu , Yasuhara Takaomi , Yuuki Toshifumi , Okumura Yasushi
Published: April 2003

Der f 3 is one of the allergens produced by house dust mite Dermatophagoides farinae showing serine protease activity. Based on its amino acid sequence, a cDNA clone encoding Der f 3 was isolated from a cDNA library of D. farinae. Sequencing analysis of the clone revealed the presence of an open reading frame of 780 bp, which encodes a mature protein of 232 amino acids with 27 amino acids of pre‐pro sequence at the N‐terminus. When proDer f 3 was produced in Escherichia coli as a fused protein with glutathione‐S‐transferase, the fused protein was accumulated as inclusion bodies. The protein purified with 8 M urea and glutathione‐affinity column chromatography, however, did not show protease activity. When an arginine residue was introduced at the C‐terminus of the pro‐region in place of threonine, removal of the pro‐region to produce an active mature protease was observed. The specificity and the activity of this recombinant protease were almost the same as those of native Der f 3.
Degradation of cartilage aggrecan by collagenase‐3 (MMP‐13)
Authors: Fosang Amanda J. , Last Karena , Knäuper Vera , Murphy Gillian , Neame Peter J.
Published: April 2003

Degradation of the large cartilage proteoglycan aggrecan in arthritis involves an unidentified enzyme aggrecanase, and at least one of the matrix metalloproteinases. Proteinase‐sensitive cleavage sites in the aggrecan interglobular domain (IGD) have been identified for many of the human MMPs, as well as for aggrecanase and other proteinases. The major MMP expressed by chondrocytes stimulated with retinoic acid to degrade their matrix is collagenase‐3 or MMP‐13. Because of its potential role in aggrecan degradation we examined the specificity of MMP‐13 for an aggrecan substrate. The results show that MMP‐13 cleaves aggrecan in the IGD at the same site (..PEN341‐FFG..) identified for other members of the MMP family, and also at a novel site ..VKP384‐VFE.. not previously observed for other proteinases.