bluuebunny/crossref_metadata_2025 huggingface dataset:
Reseach progress of ferroelectric polymer nanocomposites with high energy storage density
Authors: Shen Zhong-Hui , Jiang Yan-Da , Li Bao-Wen , Zhang Xin ,   Center of Smart Materials and Devices, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China,   International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

Electrostatic capacitors based on dielectrics delivering an ultrahigh power density, low loss and high operating voltage, are widely used in energy storage devices for modern electronic and electrical systems. Dielectric polymers, especially ferroelectric polymers, are preferable for an energy storage medium in film capacitors due to their superiority in ultrahigh breakdown strength, low mass density, flexibility, and easy fabrication process. Ferroelectric polymer nanocomposites combining the advantageous properties of ferroelectric polymer matrix and high dielectric constant of ceramic fillers, show great potential applications in achieving superior energy storage performances and have aroused substantial academic interest. This review focuses on the recent research progress of high-energy-density ferroelectric polymer nanocomposites. First, the synthesis and properties of PVDF-based ferroelectric polymers are introduced. Second, the effects of nanofillers, composite structures and interfaces on the dielectric and energy storage properties of ferroelectric polymer nanocomposites are summarized. Third, the underline mechanism of dielectric and energy storage behaviors in ferroelectric nanocomposites are discussed in the aspect of phase-field simulation. Last, the existing challenges and future directions of ferroelectric polymer nanocomposites with high energy storage density are summarized and prospected.
Ultrafast pulse lasers based on two-dimensional nanomaterial heterostructures as saturable absorber
Authors: Long Hui , Hu Jian-Wei , Wu Fu-Gen , Dong Hua-Feng ,   School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

As the substance carrier of nonlinear optical phenomenon, saturable absorber is an essential material for generating the ultrafast pulse laser. The saturable absorbers based on graphene, transition metal sulfides, topological insulators, black phosphorus and other two-dimensional (2D) materials exhibit different optical advantages. However, limitations of those single 2D materials as saturable absorbers exist. The nanomaterial heterojunction structure can combine the advantages of different 2D materials to achieve optical complementarity, and it also provides new ideas for generating the ultrafast laser with ultrashort pulse duration and high peak power. Here in this paper, the preparation methods, band alignment and the electronic transition mechanism of heterojunction saturable absorbers are summarized, and the recent research progress of ultrafast lasers based on 2D nano-heterostructures are also reviewed, including the wavelength, pulse width, repetition frequency and pulse energy. Therefore, 2D nano-heterostructure exhibits great potential applications in future optical modulator and optical switch.
Fabrication and applications of flexible inorganic ferroelectric thin films
Authors: Lan Shun , Pan Hao , Lin Yuan-Hua ,   State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Inorganic ferroelectric films exhibit excellent electric and optic properties, which have been widely used in dielectrics, memory, piezoelectric, photoelectric devices, etc. However, conventional synthesis strategies based on rigid single-crystal substrates severely limit their applications in flexible electronics. Realization of flexible inorganic ferroelectric films can introduce the excellent properties of inorganic ferroelectric materials into flexible devices, which is the developing trend for the next generation of electronic devices. In this review, the strategies to fabricate flexible inorganic perovskite structures’ ferroelectric films are summarized, including 1) direct growth on flexible substrates, 2) transferring ferroelectric film from a rigid substrate to a flexible one. Subsequently, the applications of flexible inorganic ferroelectric films are briefly introduced. Finally, research status, prospects and future development trend of flexible inorganic ferroelectric films are discussed.
Propagation matrix for electromagnetic interaction through electrostatically and magnetostatically biased graphene sheet
Authors: Wang Fei , Wei Bing ,   School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China,   Collaborative Innovation Center of Information Sensing and Understanding, Xidian University, Xi’an 710071, China
Published: December 2020

The reflection and transmission of plane electromagnetic waves on monolayer graphene are studied theoretically in this paper. From an electromagnetic point of view, monolayer graphene is described as an “infinitely thin” graphene sheet characterized by a surface conductivity, and based on a microscopic quantum dynamical approach, the graphene sheet becomes anisotropic in the presence of both an electrostatic and a magnetic bias. In this work, starting from boundary conditions and phase-matching conditions, the propagation matrix for the analysis of the interaction between an electromagnetic field and thin graphene sheet which is biased electrostatically and magnetostatically, and then characterized by an anisotropic conductivity, is derived. Furthermore, the analytical solutions of co- and cross-polarization reflective and transmittance coefficients through an anisotropic graphene planar surface are obtained from the proposal matrix above, which couples the fundamental transverse electric (TE) polarization and transverse magnetic (TM) polarization and includes the possible effects of electrostatic and/or magnetostatic bias. In conclusion, the cross-polarization reflective coefficient of TE wave and that of TM wave are equal, and their cross-polarization transmittance coefficients have opposite phase. Finally, a new propagation matrix for stratified medium containing anisotropic graphene interfaces is deduced by embedding the matrix across graphene sheet mentioned above into the traditional propagation matrix for isotropic stratified medium. The proposed new matrix can be used to investigate the propagation properties of plane wave in a complex structure of layered medium and anisotropic conductivity interfaces (including graphene sheet) analytically and quickly, and represents a very simple tool for the relevant analysis and design.
Dendritic coincidence detection in Purkinje neurons of awake mice
Authors: Roome Christopher J , Kuhn Bernd
Published: December 2020

Dendritic coincidence detection is fundamental to neuronal processing yet remains largely unexplored in awake animals. Specifically, the underlying dendritic voltage–calcium relationship has not been directly addressed. Here, using simultaneous voltage and calcium two-photon imaging of Purkinje neuron spiny dendrites, we show how coincident synaptic inputs and resulting dendritic spikes modulate dendritic calcium signaling during sensory stimulation in awake mice. Sensory stimulation increased the rate of postsynaptic potentials and dendritic calcium spikes evoked by climbing fiber and parallel fiber synaptic input. These inputs are integrated in a time-dependent and nonlinear fashion to enhance the sensory-evoked dendritic calcium signal. Intrinsic supralinear dendritic mechanisms, including voltage-gated calcium channels and metabotropic glutamate receptors, are recruited cooperatively to expand the dynamic range of sensory-evoked dendritic calcium signals. This establishes how dendrites can use multiple interplaying mechanisms to perform coincidence detection, as a fundamental and ongoing feature of dendritic integration in behaving animals.
Early life imprints the hierarchy of T cell clone sizes
Authors: Gaimann Mario U , Nguyen Maximilian , Desponds Jonathan , Mayer Andreas
Published: December 2020

The adaptive immune system responds to pathogens by selecting clones of cells with specific receptors. While clonal selection in response to particular antigens has been studied in detail, it is unknown how a lifetime of exposures to many antigens collectively shape the immune repertoire. Here, using mathematical modeling and statistical analyses of T cell receptor sequencing data, we develop a quantitative theory of human T cell dynamics compatible with the statistical laws of repertoire organization. We find that clonal expansions during a perinatal time window leave a long-lasting imprint on the human T cell repertoire, which is only slowly reshaped by fluctuating clonal selection during adult life. Our work provides a mechanism for how early clonal dynamics imprint the hierarchy of T cell clone sizes with implications for pathogen defense and autoimmunity.
Distinct temporal difference error signals in dopamine axons in three regions of the striatum in a decision-making task
Authors: Tsutsui-Kimura Iku , Matsumoto Hideyuki , Akiti Korleki , Yamada Melissa M , Uchida Naoshige , Watabe-Uchida Mitsuko
Published: December 2020

Different regions of the striatum regulate different types of behavior. However, how dopamine signals differ across striatal regions and how dopamine regulates different behaviors remain unclear. Here, we compared dopamine axon activity in the ventral, dorsomedial, and dorsolateral striatum, while mice performed a perceptual and value-based decision task. Surprisingly, dopamine axon activity was similar across all three areas. At a glance, the activity multiplexed different variables such as stimulus-associated values, confidence, and reward feedback at different phases of the task. Our modeling demonstrates, however, that these modulations can be inclusively explained by moment-by-moment changes in the expected reward, that is the temporal difference error. A major difference between areas was the overall activity level of reward responses: reward responses in dorsolateral striatum were positively shifted, lacking inhibitory responses to negative prediction errors. The differences in dopamine signals put specific constraints on the properties of behaviors controlled by dopamine in these regions.
Kinesin-4 KIF21B limits microtubule growth to allow rapid centrosome polarization in T cells
Authors: Hooikaas Peter Jan , Damstra Hugo GJ , Gros Oane J , van Riel Wilhelmina E , Martin Maud , Smits Yesper TH , van Loosdregt Jorg , Kapitein Lukas C , Berger Florian , Akhmanova Anna
Published: December 2020

When a T cell and an antigen-presenting cell form an immunological synapse, rapid dynein-driven translocation of the centrosome toward the contact site leads to reorganization of microtubules and associated organelles. Currently, little is known about how the regulation of microtubule dynamics contributes to this process. Here, we show that the knockout of KIF21B, a kinesin-4 linked to autoimmune disorders, causes microtubule overgrowth and perturbs centrosome translocation. KIF21B restricts microtubule length by inducing microtubule pausing typically followed by catastrophe. Catastrophe induction with vinblastine prevented microtubule overgrowth and was sufficient to rescue centrosome polarization in KIF21B-knockout cells. Biophysical simulations showed that a relatively small number of KIF21B molecules can restrict mirotubule length and promote an imbalance of dynein-mediated pulling forces that allows the centrosome to translocate past the nucleus. We conclude that proper control of microtubule length is important for allowing rapid remodeling of the cytoskeleton and efficient T cell polarization.
Uncovering the hidden diversity of Mississippian crinoids (Crinoidea, Echinodermata) from Poland
Authors: Salamon Mariusz A. , Ausich William I. , Brachaniec Tomasz , Płachno Bartosz J. , Gorzelak Przemysław
Published: December 2020

Partial crinoid crowns and aboral cups are reported from the Mississippian of Poland for the first time. Most specimens are partially disarticulated or isolated plates, which prevent identification to genus and species, but regardless these remains indicate a rich diversity of Mississippian crinoids in Poland during the Mississippian, especially during the late Viséan. Lanecrinus? sp. is described from the late Tournaisian of the Dębnik Anticline region. A high crinoid biodiversity occurred during late Viséan of the Holy Cross Mountains, including the camerate crinoids Gilbertsocrinus? sp., Platycrinitidae Indeterminate; one flexible crinoid; and numerous eucladid crinoids, including Cyathocrinites mammillaris (Phillips), three taxa represented by partial cups left in open nomenclature, and numerous additional taxa known only from isolated radial plates, brachial plates, and columnals. To date, the youngest occurrence of Gilbertsocrinus was the early Viséan of the United States, thus the present finding in upper Viséan extends this genus range. Furthermore, the occurrence of Lanecrinus? sp. expands the Western European range of this genus into the Tournaisian. A single partially disarticulated crown, Crinoidea Indeterminate B, is described from the Serpukhovian of the Upper Silesian Coal Basin. In addition, several echinoid test plates and spines are also reported.
The Aichi Biodiversity Targets: achievements for marine conservation and priorities beyond 2020
Authors: Carr Hannah , Abas Marina , Boutahar Loubna , Caretti Olivia N. , Chan Wing Yan , Chapman Abbie S.A. , de Mendonça Sarah N. , Engleman Abigail , Ferrario Filippo , Simmons Kayelyn R. , Verdura Jana , Zivian Anna
Published: December 2020

In 2010 the Conference of the Parties (COP) for the Convention on Biological Diversity revised and updated a Strategic Plan for Biodiversity 2011–2020, which included the Aichi Biodiversity Targets. Here a group of early career researchers mentored by senior scientists, convened as part of the 4th World Conference on Marine Biodiversity, reflects on the accomplishments and shortfalls under four of the Aichi Targets considered highly relevant to marine conservation: target 6 (sustainable fisheries), 11 (protection measures), 15 (ecosystem restoration and resilience) and 19 (knowledge, science and technology). We conclude that although progress has been made towards the targets, these have not been fully achieved for the marine environment by the 2020 deadline. The progress made, however, lays the foundations for further work beyond 2020 to work towards the 2050 Vision for Biodiversity. We identify key priorities that must be addressed to better enable marine biodiversity conservation efforts moving forward.
N‐terminal sequences of pig intestinal sucrase—isomaltase and pro‐sucrase—isomaltase
Authors: Sjöström H. , Norén O. , Christiansen L.A. , Wacker H. , Spiess M. , Bigler-Meier B. , Rickli E.E. , Semenza G.
Published: July 2002

The hog sucrase—isomaltase complex is anchored to the small‐intestinal brush border membrane, as in the rabbit, via a hydrophobic segment located in the N‐terminal region of the isomaltase subunit. The immediate precursor of the ‘final’ sucrase—isomaltase (i.e., pro‐sucrase—isomaltase as prepared from adult hogs whose pancreas had been disconnected from the duodenum) is an amphiphilic single polypeptide chain of M
r 260 000–265 000. Its N‐terminal sequence is virtually identical with (not merely homologous to) the corresponding region of the isomaltase subunit of ‘final’ sucrase‐isomaltase. This shows that the isomaltase portion of pro‐sucrase—isomaltase in the N‐terminal ‘half’ of the precursor polypeptide chain. Thus the succession of domains in pro‐sucrase—isomaltase and its mode of anchoring in the membrane could be deduced. On this basis a likely mechanism of biosynthesis and insertion is proposed.
Binding of actinomycin D to DNA revealed by DNase I footprinting
Authors: Scamrov A.V. , Beabealashvilli R.Sh.
Published: July 2002

We have analyzed the specificity of the actinomycin D—DNA interaction. The ‘footprint’ method has been used in this investigation. It is shown that: (i) The presence of dinucleotide GC or GG is required for binding of a single drug molecule. (ii) The strong binding sites are encoded by tetranucleotide XGCY; where X ≠ G and Y ≠ C in accordance with RNA elongation hindrance sites [1]. (iii) There is a positive cooperativity in binding of actinomycin D with DNA.
Photogeneration of superoxide by adriamycin and daunomycin
Authors: Carmichael Alsdair J. , Mossoba Magdi M. , Riesz Peter
Published: July 2002

The hydroxyl and superoxide anion spin adducts of DMPO and 4‐MePyBN, respectively, were obtained during photoirradiation of adriamycin and daunomycin solutions with visible light. Ethanol and dimethyl sulfoxide did not scavenge hydroxyl radicals in the photoirradiated drug solutions. Furthermore, the hydroxyl‐DMPO spin adduct is not formed in the photolysis of air‐free drug solutions, indicating that hydroxyl radicals are not directly produced in the photochemical reactions. Instead, the observed hydroxyl‐DMPO is formed from the decay of the superoxide anion‐DMPO spin adduct. The mechanism for generating the superoxide anion radical appears to be a direct electron transfer from the photoexcited adriamycin and daunomycin to dissolved oxygen.
Gene duplication in bovine brain myelin proteolipid and homology with related proteins
Authors: Laursen Richard A. , Samiullah Mohammed , Lees Marjorie B.
Published: July 2002

Analysis of the amino acid sequence of bovine brain myelin proteolipid reveals not only extensive internal homology, but also homology with portions of the myelin basic protein, the peripheral nerve myelin protein, Po, and with the small proteolipid subunit of mitochondrial ATP synthase. These results suggest that the myelin proteolipid gene has been constructed from a small number of genetic elements, and that these elements are also found in non‐myelin proteins. Furthermore, the proteolipid appears to have evolved by acquisition of elements from a ‘gene pool’ over a period of time, rather than by a simple duplication mechanism.
In vivo and in vitro catabolism of native and biologically modified LDL
Authors: Nagelkerke J.Fred , Havekes Louis , van Hinsbergh Victor W.M. , van Berkel Theo J.C.
Published: July 2002

Incubation of human low density lipoprotein (LDL) at 37°C in the presence of human umbilical‐vein endothelial cells (EC) causes a time‐dependent shift in the charge and density of LDL. After intravenous injection into rats, native LDL is merely cleared from the circulation by Kupffer cells while EC‐modified LDL is rapidly cleared by endothelial liver cells. The uptake of native LDL by Kupffer cells and EC‐modified LDL by endothelial cells in vivo can be explained by the presence of two different specific receptors on these cell types. It is concluded that the liver endothelial cells form an important protection against a possible atherogenic action of EC‐modified LDL.
The complete nucleotide sequence of the xylanase gene (xynA) of Bacillus pumilus
Authors: Fukusaki Eiichiro , Panbangred Watanalai , Shinmyo Atsuhiko , Okada Hirosuke
Published: July 2002

The complete nucleotide sequence of the xylanase (EC 3.2.1.8) gene (xynA and its flanking regions of Bacillus pumilus IPO, a hyperproducer of xylanase, was determined. A 684 bp open reading frame for xylanase gene was observed. The amino acid sequence of the N‐terminal region of xylanase was determined to be Arg‐Thr‐Ile‐Thr‐, suggesting the processing at Ala27 of pre‐xylanase. The amino acid composition and M
r (22384) of xylanase deduced from DNA sequence agreed with the results obtained with the purified enzyme. The signal sequence consisted of 27 amino acids, of which 3 were basic amino acid residues in the region near the N‐terminus and 15 were hydrophobic amino acid residues. The ribosome binding sequence complementary to the 3′ ‐end of 16 S rRNA of B, subtilis was found 7 bp upstream of the initiation codon, ATG.
Effect of trichothecenes on growth and intracellular pool size of Mycoplasma gallisepticum
Authors: Rottem S. , Yagen B. , Katznell A.
Published: July 2002

T‐2 toxin Mycoplasma gallisepticum Mycoplasma membrane
Trichothecen
Mycotoxin
Intracytoplasmic pool
Isolation of an Mn‐carrying 33‐kDa protein from an oxygen‐evolving photosystem‐II preparation by phase partitioning with butanol
Authors: Yamamoto Yasusi , Shinkai Hiroshi , Isogai Yasuhiro , Matsuura Katsumi , Nishimura Mitsuo
Published: July 2002

An Mn‐containing 33‐kDa protein was isolated by phase partitioning with 50% n‐butanol from an O2‐evolving photosystem‐II preparation. The Mn content in the 33‐kDa protein increased when 1 mM potassium ferricyanide and 0.4 mM diaminodurene were present as oxidants during the butanol treatment and the following dialysis. Under these conditions, 0.1–0.25 atom Mn was detected in one 33‐kDa protein molecule. EPR spectra of the Mn protein showed that the Mn atoms were bound to the protein.
High‐pressure dissociation of the β2‐dimer of tryptophan synthase from Escherichia coli monitored by sucrose gradient centrifugation
Authors: Seifert Thomas , Bartholmes Peter , Jaenicke Rainer
Published: July 2002

High‐pressure dissociation
Sucrose gradient centrifugation
Tryptophan synthase
Ultracentrifugation
Specific labelling by [125I]helodermin of high‐affinity VIP receptors in rat liver membranes
Authors: Robberecht Patrick , Waelbroeck Magali , De Neef Philippe , Camus Jean-Claude , Vandermeers André , Vandermeers-Piret Marie-Claire , Christophe Jean
Published: July 2002

Helodermin, a newly isolated peptide from Gila Monster venom, is structurally related to VIP and secretin. When used as radioligand, [125I]helodermin bound rapidly and reversibly to crude rat liver membranes, the dissociation being accelerated by GTP. Competition binding curves of [125I]helodermin and [125I]VIP with unlabelled peptides showed the following order of decreasing affinity: VIP > helodermin > secretin > hpGRF(1–29)‐NH2. The shape of binding curves and of concurrent adenylate cyclase activation is compatible with the specific labelling, by [125I]helodermin, of a class of high‐affinity VIP receptors that is capable to stimulate adenylate cyclase.
Activation of yeast plasma membrane ATPase by phorbol ester
Authors: Portillo Francisco , Mazón María J.
Published: July 2002

Addition of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) to yeast cells produces a 2‐fold activation of the plasma membrane ATPase. The activation is reversible and time‐ and dose‐dependent. The activated enzyme shows an increased affinity for its substrate, ATP, and its optimum pH is shifted to a more alkaline range. These changes are similar to those observed in the reported activation by glucose. Upon incubation of yeast cells with 32Pi incorporation of radioactivity in a membrane polypeptide of 105 kDa is observed after addition of either glucose or TPA.
On the importance of deoxyribonucleotide pools in the senescence of cultured human diploid fibroblasts
Authors: Dick John E. , Wright Jim A.
Published: July 2002

Previous studies have indicated that ribonucleotide reductase may participate in a mechanism of cellular senescence, which involves modifications in deoxyribonucleotide pools, the products of the reductase reaction. Since very little information about the levels of these pools in senescing cells is currently available, an analysis of deoxyribonucleotide levels was carried out in young, old and very old normal human diploid fibroblasts, as well as in a variant human fibroblast strain with an altered replicative life span. These studies indicated that there are marked age‐related perturbations in these pools which imply that they may be fundamentally important in a process determining the nonproliferative or senescent state.
Tobacco plants transformed with the Agrobacterium T‐DNA gene 1 contain high amounts of indole‐3‐acetamide
Authors: Van Onckelen H. , Rüdelsheim P. , Inzé D. , Follin A. , Messens E. , Horemans S. , Schell J. , Van Montagu M. , De Greef J.
Published: July 2002

The T‐DNA genes 1 and 2 of the Ti plasmid of Agrobacterium tumefaciens are involved in the biosynthesis of IAA in transformed plant cells. Previously, it has been shown that gene 2 codes for an amidohydrolase able to convert IAM into IAA. We have isolated Nicotiana tabacum regenerates transformed with either gene 1 or genes 6a and 6b of the T‐DNA. The tobacco plants transformed with gene 1 contain 500–1000‐times more IAM as compared to plants transformed with genes 6a and 6b, and as compared to untransformed control plants. No drastic differences in endogenous IAA concentrations were observed between the three plant types analyzed.
Distinct structural requirements of Ca2+/phospholipid‐dependent protein kinase (protein kinase C) and cAMP‐dependent protein kinase as evidenced by synthetic peptide substrates
Authors: Ferrari Stefano , Marchiori Fernando , Borin Gianfranco , Pinna Lorenzo A.
Published: July 2002

Protein kinase C, purified to near homogeneity from the brain, has been tested toward a variety of synthetic peptide substrates including different phosphorylatable residues. While it proved totally inactive toward the tyrosyi peptide Asp‐Ala‐Glu‐Tyr‐Ala‐Ala‐Arg‐Arg‐Arg‐Gly, as well as toward several more or less acidic seryl peptides, it phosphorylates with a Ca2+/phospholipid‐dependent mechanism, at seryl and/or threonyl residues, many basic peptides, some of which are also good substrates for cAMP‐dependent protein kinase (A‐kinase). Among the peptides tested, however, the best substrate for protein kinase C, with kinetic constants comparable to those of histones, is the nonapeptide Gly‐Ser‐Arg6‐Tyr, which is not a substrate for A‐kinase. Moreover, although the peptide Pro‐Arg5‐Ser‐Ser‐Arg‐Pro‐Val‐Arg is a good substrate for both kinases, its derivative with ornitines replacing arginines is phosphorylated only by protein kinase C. Some typical substrates of A‐kinase on the other hand, like the peptides Phe‐Arg2‐Leu‐Ser‐Ile‐Ser‐Thr‐Glu‐Ser and Arg2‐Ala‐Ser‐Val‐Ala, are phosphorylated by protein kinase C rather slowly and with unfavourable kinetic constants. It is concluded that, while both protein kinase C and A‐kinase need basic groups close to the phosphorylatable residues, their primary structure determinants are quite distinct.
Transient transcriptional inhibition of the transferrin gene by cyclic AMP
Authors: Tuil David , Vaulont Sophie , Levin Mariano J. , Munnich Arnold , Moguilewsky Martine , Bouton Marie M. , Brissot Pierre , Dreyfus Jean-Claude , Kahn Axel
Published: July 2002

Transferrin mRNA content and gene transcription rate were measured in the liver of rats submitted to iron overload or depletion, castration, treatment with sexual steroid hormones, glucagon and cyclic AMP. The influence of puberty in males and females and of pregnancy was also analysed. Glucagon and cyclic AMP reduced mRNA level by about 50% at the 12th hour of treatment and transferrin gene transcription by as muchas 95% at the 30th minute of drug infusion, with a secondary increase of the transcription rate for a protracted treatment. None of the other hormones tested had any detectable effect on transferrin gene expression, the same being true for iron overload or depletion.
Isolation and structural characterization of the smaller‐size oligosaccharides from desialylated human κ‐casein
Authors: van Halbeek H. , Vliegenthart J.F.G. , Fiat A.-M. , Jollès P.
Published: July 2002

Alkaline borohydride reductive cleavage (β‐elimination) of desialylated human κ‐caseinoglycopeptide resulted in the release of a series of oligosaccharides. The smaller‐size compounds among them were purified to virtual homogeneity by gel filtration followed by high‐performance liquid chromatography. The structures of 9 oligosaccharides were determined by 1H‐NMR spectroscopy in conjunction with sugar analysis. The tetrasaccharide Galβ(1→3)[Galβ(1→4)GlcNAcβ(1→6)]GalNAc‐ol and various partial structures thereof were characterized. Notably, the disaccharide GlcNAcβ(1→6)GalNAc‐ol and the trisaccharide Galβ(1→4)GlcNAcβ(1→6)GalNAc‐ol were identified; they represent a novel type of core structure for mucin‐type carbohydrate chains, namely a peptide‐linked GalNAc that is mono‐substituted at C‐6. In addition, some oligosaccharides ending in GlcNAc‐ol could be characterized. Their possible origin is discussed.
Spermine antagonises the effects of dexamethasone, glucagon and cyclic AMP in increasing the activity of phosphatidate phosphohydrolase in isolated rat hepatocytes
Authors: Pittner Richard A. , Bracken Paul , Fears Robin , Brindley David N.
Published: July 2002

Rat hepatocytes were incubated in monolayer culture, under serum free conditions, for 8 h. Glucagon (10 nM), 8‐(4‐chlorophenylthio)adenosine 3',5'‐cyclic monophosphate (100 μM) and dexamethasone (100 nM) increased the activity of phosphatidate phosphohydrolase by approx. 2‐, 3.6‐ and 3.3‐fold, respectively. Spermine alone had no significant effect. Spermine (2.5 mM) almost completely inhibited the glucagon induced increase in phosphohydrolase activity. It only partially inhibited the dexamethasone and cyclic AMP mediated inductions. Spermidine had no significant effect in this respect. The results are discussed in relation to the known effects of polyamines on glycerolipid synthesis, in particular, and on intermediary metabolism.
Primary structure of the α‐subunit of bovine adenylate cyclase‐stimulating G‐protein deduced from the cDNA sequence
Authors: Nukada Toshihide , Tanabe Tsutomu , Takahashi Hideo , Noda Masaharu , Hirose Tadaaki , Inayama Seiichi , Numa Shosaku
Published: July 2002

The primary structure of the α‐subunit of the adenylate cyclase‐stimulating G‐protein (Gs) has been deduced from the nucleotide sequence of cloned DNA complementary to the bovine cerebral mRNA encoding the polypeptide. Comparison of the amino acid sequences of the α‐subunits of Gs and transducin reveals that some of the highly conserved regions show sequence homology with elongation factor‐Tu and ras p21 proteins and correspond to functional regions of guanine nucleotide‐binding proteins.
Stimulation of estrogen receptor accumulation by estradiol in primary cultures of salmon hepatocytes
Authors: Mommsen Thomas P. , Lazier Catherine B.
Published: July 2002

Hepatocytes of Salmo salar in primary culture form confluent monolayers and can be maintained at 11 °C in serum‐free medium for 8 days with minimal cell loss. Cultured hepatocytes from immature male salmon contain estrogen receptor both in nuclear and cytosol fractions (2000 and 2400 sites/cell, respectively). A single addition of estradiol results in an increase in the nuclear receptor to a level of 23 000 sites/cell after 24 h. This nuclear receptor concentration is similar to that in liver of estrogen‐treated salmon in vivo, and is much higher than has been found for any other egg‐laying vertebrate. The cultured salmon hepatocytes thus represent a highly sensitive system for the study of estrogen receptor dynamics and vitellogenesis in vitro.
Proline isomerization during refolding of ribonuclease A is accelerated by the presence of folding intermediates
Authors: Schmid Franz X.
Published: July 2002

The trans → cis isomerization of Pro 93 was measured during refolding of bovine ribonuclease A. This isomerization is slow (τ = 500s) under marginally stable folding conditions of 2.0 M GdmCl, pH 6, at 10°C. However, it is strongly accelerated (τ = 100 s) in samples which, prior to isomerization, had been converted to a folding intermediate by a 15s refolding pulse under strongly native conditions (0.8 M ammonium sulfate, 0°C). The results demonstrate that extensive folding is possible before Pro 93 isomerizes to its native cis state and that the presence of structural folding intermediates leads to a marked increase in the rate of subsequent proline isomerization.
Effect of ionic strength on production of cAMP‐ and Ca2+ ‐independent protein kinase from rat liver plasma membrane
Authors: Hashimoto Eikichi , Sakanoue Youichirou , Mizuta Keiko , Yamamura Hirohei
Published: July 2002

Production of cAMP‐ and Ca2+‐independent protein kinase was stimulated when rat liver plasma membrane was incubated with increasing concentrations of NaCl. This protein kinase release was diminished by addition of protease inhibitor. The molecular mass of this enzyme was approx. 50 kDa and a high concentration of Mg2+ was required for whole histone phosphorylation. These properties are similar to those of the protease‐activated form of protein kinase C. The NaCl effect could be replaced by other salts such as LiCl and NaHCO3. These results suggest that membrane‐bound protein kinase C is activated by limited proteolysis corresponding to an increase in ionic strength.
Does intrinsic fluorescence reflect conformational changes in the Ca2+‐ATPase of sarcoplasmic reticulum?
Authors: Champeil Philippe , Le Maire Marc , Moller Jesper V. , Riollet Sylvie , Guillain Florent , Green N.Michael
Published: July 2002

We have investigated the kinetics of the intrinsic fluorescence drop observed when ATP is added to purified sarcoplasmic reticulum ATPase in a potassium‐free medium containing magnesium and calcium, at pH 6 and 20°C. Under these conditions, analysis of the fluorescence drop is complex. Several events contributed to the rate of the fluorescence drop initiated by turnover, including phosphorylation, conformational transition of the phosphorylated complex, and dephosphorylation. On the other hand, when 75% of total fluorescence was quenched by energy transfer to the membrane‐bound ionophore A23187, the observed turnoverdependent drop in residual fluorescence mainly reflected the conformational transition of the phosphorylated ATPase. Combination of fast kinetics with the quenching of selected tryptophan residues is suggested to be a promising tool for the study of proteins containing many of these residues.
Identification of the plasma membrane receptor for interleukin‐1 on mouse thymoma cells
Authors: Bron C. , MacDonald H.R.
Published: July 2002

The plasma membrane receptor for interleukin‐1 (IL‐1) has been characterized from mouse EL4‐6.1 thymoma cells. Following binding of IL‐1 to surface labeled EL4‐6.1 cells, the IL‐1 binding molecule was immunoprecipitated using a rabbit antiserum against the hormone. The putative IL‐1 receptor is a membrane‐associated glycopeptide of Mr
= 82000 containing probably two or three N‐linked glycan units as indicated by its conversion into a Mr
= 60 000 polypeptide upon deglycosylation with endo‐β‐N‐glycosidase F.
The precursor of barley plastocyanin Sequence of cDNA clones and gene expression in different tissues
Authors: Nielsen P.S. , Gausing K.
Published: July 2002

Full length cDNA clones encoding the precursor of plastocyanin have been isolated from a leaf cDNA library from barley (a monocotyledon). The deduced amino acid sequence comprises an N‐terminal transit peptide of 58 amino acids and a mature plastocyanin sequence of 97 amino acids (M
r, 10 185) which is two amino acids shorter than the sequence of plastocyanin from dicotyledons. Northern hybridization experiments show that the level of plastocyanin messenger increases greatly in older leaf cells and that the level is 8–20‐fold higher in green leaves than in etiolated leaves. Plastocyanin messenger could not be detected in coleoptiles and roots.
Calcium ionophore A23187 enhances human neutrophil superoxide release, stimulated by phorbol dibutyrate, by converting phorbol ester receptors from a low‐ to high‐affinity state
Authors: French J.K. , Hurst N.P. , Zaiewski P.D. , Valente L. , Forbes I.J.
Published: July 2002

The calcium ionophore A23187 acted synergistically with phorbol dibutyrate (PDBu) to stimulate human neutrophil superoxide production. A23187 shortened the lag period and markedly increased the initial rate of neutrophil superoxide production induced by suboptimal concentrations of PDBu. l μM A23187 reduced the EC50 value for superoxide release from 56 to 8 nM PDBu. This effect of A23187 was correlated with enhanced binding of [3H]PDBu to its receptor and a reduction in the dissociation constant (K
d) from 27 to 10 nM, without altering the apparent total number of phorbol dibutyrate receptors. These actions of A23187 were abolished in the presence of EGTA or TMB‐8, confirming a dependence on Ca2+.
Primary and post‐irradiation inactivation of the sulfhydryl enzyme malate synthase: correlation of protective effects of additives
Authors: Durchschlag Helmut , Zipper Peter
Published: July 2002

The presence of additives during X‐irradiation of malate synthase led to radioprotective effects against primary and post‐irradiation inactivation. Pronounced effects were provided by typical scavengers, sulfhydryl reagents and specific ligands (substrates, products, analogues). The results show that scavenging and specific protection are responsible for the protective efficiency of additives. Scavengers delete noxious species formed during irradiation or post‐radiationem. Sulfhydryl reagents may act as repair substances. Specific ligands protect the active site of the enzyme and the essential sulfhydryls; specific protection is more pronounced post‐radiationem. Ligands and sulfhydryl reagents may additionally act as scavengers. A cumulative index for the protective power of additives against both sorts of inactivation was established.
Conserved and variable elements in RNA genomes of potexviruses
Authors: Skryabin K.G. , Morozov S.Yu. , Kraev A.S. , Rozanov M.N. , Chernov B.K. , Lukasheva L.I. , Atabekov J.G.
Published: July 2002

The nucleotide sequences of genomic RNAs and predicted amino acid sequences of two strains of potato virus X and white clover mosaic potexvirus were compared to each other, and the proteins of different plus‐RNA‐containing plant viruses. The predicted non‐virion proteins of potexviruses have direct sequence homology and common structural peculiarities with those of several ‘Sindbis‐like’ plant viruses. The most conserved amino acid sequences were found to be located in the polypeptide encoded by the long 5′‐proximal open reading frame (ORF1). The putative polypeptide encoded by the ORF2 starting beyond the ORF1 stop codon is clearly related to the presumptive NTP‐binding domain of the ORF1‐coded polypeptide. These results suggest possible functions for all of the potexvirus proteins and also indicate that potexviruses have a genome organization which is considerably different from that of other plant viruses.
Affinity labeling of forskolin‐binding proteins comparison between glucose carrier and adenylate cyclase
Authors: Pfeuffer Elke , Pfeuffer Thomas
Published: July 2002

An [125I]iodoazidosalicylic acid derivative of forskolin was synthesized for identification of the diterpene's binding sites on the catalytic subunit of adenylate cyclase and on glucose transport proteins. The affinity label was selectively incorporated into proteins of M
r 40 000–60 000 in membranes from human erythrocytes and from various other tissues. The iodoazidosalicylic acid derivative also specifically labeled the catalytic moiety of adenylate cyclase from rabbit myocardial membranes. However, the structural requirements of the two forskolin‐binding sites must be different, since the affinity of the photolabel for the glucose carriers is much higher than that for the cyclase catalyst. Furthermore, the label is readily competed with by D‐glucose and cytochalasin B for its binding site on the glucose carrier but not on adenylate cyclase.
Signal peptidase can cleave inside a polytopic membrane protein
Authors: Beltzer James P. , Wessels Hans Peter , Spiess Martin
Published: July 2002

The signal peptides of most proteins targeted to the endoplasmic reticulum are specifically cleaved by signal peptidase. Although potential cleavage sites occur frequently in polytopic proteins after membrane‐spanning segments, processing is restricted to the first hydrophobic domain, suggesting that signal peptidase might not have access to subsequently translocated, internal domains. To test this hypothesis, we replaced the third transmembrane segment of an artificial threefold membrane‐spanning protein by a sequence which is normally an amino‐terminal signal. Upon in vitro translation and insertion into microsomes, efficient cleavage at this sequence was observed, thus demonstrating the ability of signal peptidase to cleave within polytopic membrane proteins.
Catalytic properties of the heterodisulfide reductase involved in the final step of methanogenesis
Authors: Hedderich R. , Berkessel A. , Thauer R.K.
Published: July 2002

Reduction of the heterodisulfide of coenzyme M (H‐S‐CoM) and 7‐mercaptoheptanoyl(L)threonine phosphate (H‐S‐HTP) is a partial reaction in methanogenesis. The CoM‐S‐S‐HTP reductase mediating this reaction has thus far not been studied. We report here that the enzyme from Methanobacterium thermoautotrophicum and Methanosarcina barkeri catalyzes the reduction of CoM‐S‐S‐HTP with reduced viologen dyes and, in the reverse direction, the oxidation of H‐S‐CoM plus H‐S‐HTP to the heterodisulfide by methylene blue. The CoM‐S‐S‐HTP reductase from M. thermoautotrophicum (strain Marburg) was partially purified (30‐fold) to a specific activity of 10 μmol·min−1·mg protein−1. The enzyme was highly substrate specific: e.g. neither the heterodisulfide derived from 6‐mercaptohexanoylthreonine phosphate nor the homodisulfide of H‐SCoM or of HSHTP was reduced. The D‐enantiomer of CoM‐S‐S‐HTP was, however, converted at 35% of the specific rate of the L‐form. Apparent Km and apparent Vmax values for substrates and products were determined.
Archaebacterial malate dehydrogenase: The amino‐terminal sequence of the enzyme from Sulfolobus acidocaldarius is homologous to the eubacterial and eukaryotic malate dehydrogenases
Authors: Görisch Helmut , Jany Klaus-Dieter
Published: July 2002

42 residues of the N‐terminal amino acid sequence of malate dehydrogenase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius have been determined as VKVAFIGVGRGVGQTIAYNTIVNGYADEVMLYDVVPELPTKK. In eubacterial and eukaryotic enzymes this region is known to encompass residues involved in pyridine nucleotide binding. In the archaebacterial enzyme the residues Gly‐7, Gly‐ 11 and Asp‐33 are also present. The data suggest that in the enzyme from S. acidocaldarius like in the other malate dehydrogenases the binding domain for NAD(H) is localized at the N‐terminal part of the polypeptide chain. The archaebacterial enzyme is homologous to the other malate dehydrogenases, of which the amino acid sequences are known, however, it is only distantly related to the mitochondrial/E. coli group and the cytosolic/Thermus flavus group.
Location of the calmodulin‐ and actin‐binding domains at the C‐terminus of caldesmon
Authors: Makuch Robert , Walsh Michael P. , Dabrowska Renata
Published: July 2002

Digestion of caldesmon with carboxypeptidase Y is accompanied by loss of its ability to inhibit actomyosin ATPase activity and to bind actin and calmodulin. Similarly, carboxypeptidase Y digestion of a terminal 40 kDa chymotryptic fragment of caldesmon abolishes its inhibition of the actomyosin ATPase and binding to actin and calmodulin. This represents the first direct demonstration that these functional domains of caldesmon are located close to the carboxy‐terminus of the molecule.
Identification in human erythrocytes of mono(ADP‐ribosyl) protein hydrolase that cleaves a mono(ADP‐ribosyl) Gi linkage
Authors: Tanuma Sei-ichi , Endo Hiroyoshi
Published: July 2002

A novel enzymatic activity, the hydrolysis of linkages between mono(ADP‐ribose) and cysteine residues in Gi prepared by eukaryotic ADP‐ribosyl‐transferase C [(1988) J. Biol. Chem. 263, 5485‐5489] was found in the cytosol of human erythrocytes. The mono(ADP‐ribosyl) Gi hydrolase, tentatively named ADP‐ribosyI protein hydrolase C was partially purified by sequential chromatographies on DEAE‐cellulose and Blue Sepharose. This enzyme catalyzes the release of ADP‐ribose from mono(ADP‐ribosyl) Gi Its activity was enhanced by Ca2+ and inhibited by ADP‐ribose. The presence of this enzyme in eukaryotic cells suggests that endogenous mono(ADP‐ribosyl)ation of Gi is a reversible post‐translational modification.
Change in α‐ketoglutarate dehydrogenase cooperative properties due to dihydrolipoate and NADH
Authors: Bunik V.I. , Buneeva O.A. , Gomazkova V.S.
Published: July 2002

Reducing 2 SH‐groups of KGD by dihydrolipoate leads to cooperativity in substrate binding. Cooperative properties of KGD in the KGD complex are modulated by NADH. Physiological significance of these observations is discussed.
An X‐ray solution scattering study of the cofactor and activator induced structural changes in yeast pyruvate decarboxylase (PDC)
Authors: Hübner G. , König S. , Schellenberger A. , Koch M.H.J.
Published: July 2002

Structure and activation pattern of pyruvate decarboxylase (PDC) from yeast was studied by synchrotron radiation X‐ray solution scattering. The results give a direct proof that the reversible deactivation of PDC at pH 8.0 is accompanied by the dissociation of the tetrameric holoenzyme into dimeric halves. The kinetics of this process was followed. At pH 6.5 the dimeric halves reassociate to a tetramer even in the absence of cofactors. The changes of the scattering pattern upon binding of the substrate‐like activator pyruvamide indicate that the structure expands in the course of the enzyme activation.
Immunological studies of the toxic site in ammodytoxin A
Authors: Čurin-Šerbec Vladka , Novak Djurdja , Babnik Joža , Turk Dušan , Gubenšek Franc
Published: July 2002

Two monoclonal antibodies against the native ammodytoxin A and four site‐directed polyclonal antibodies against synthetic peptides derived from the primary structure of the toxin were prepared in order to estimate the localization of its toxic site. Some of the antibodies neutralized the lethal toxicity of the toxin, thus indicating an approximate position of the toxic or receptor binding site on the molecule that is different from those predicted by comparison with a number of known sequences.
Expression and purification of plasmid‐encoded Thermoplasma acidophilum citrate synthase from Escherichia coli
Authors: Sutherland Katharine J. , Danson Michael J. , Hough David W. , Towner Paul
Published: July 2002

The citrate synthase gene from the thermophilic archaebacterium. Thermoplasma acidophilum was expressed in Escherichia coli, yielding an active product of the expected molecular weight. Manipulation of the citrate synthase gene in a series of pUC19 constructs showed that the presumed Thermoplasma ribosome binding site is recognized by the E. coli ribosome. A rapid purification of the expression of the expression product to homogeneity was achieved, based on the thermostability of Thermoplasma citrate synthase.
Modulation of cofactor requirement for the activation of protein kinase C by heparin Possible effect at the regulatory domain
Authors: Goueli Said A. , Hanten John A. , Ahmed Khalil
Published: July 2002

Heparin was found to stimulate the phosphorylation of histone H1 but not protamine sulfate catalyzed by Ca2+/phospholipid‐dependent protein kinase (protein kinase C or PKC). The effect of heparin on histone H1 phosphorylation appeared to be due to an increase in phosphatidylserine affinity for PKC activation in the presence of heparin. This effect of heparin was abolisched when trypsinized, cofactor‐independent, PKC was employed to phosphorylate histone H1. These studies suggest that heparin acts at the regulatory domain of PKC, and emphasize the importance of the negative charge in influencing the accessibility of the substrate to PKC action
Crystal organization in rat bone lamellae
Authors: Weiner Stephen , Arad Talmon , Traub Wolfie
Published: July 2002

The plate‐shaped crystals of rat bone are arranged in parallel layers that form coherent structures up to the level of individual lamellae. The crystal layers of the thin lamellae are parallel to the lamellar boundary, whereas those of the thicker lamellae are oblique to the boundary. The basic structure of rat bone can be described as ‘rotated plywood’; a structure hitherto unrecognized in either biologic or synthetic materials.