bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Morphology-Controlled Poly(aniline) Synthesis Using Anionic Porphyrin Aggregate as a Template and Proton-Driven Structural Changes in the Porphyrin Aggregate
Authors: Hatano Tsukasa , Bae Ah-Hyun , Takeuchi Masayuki , Ikeda Atsushi , Shinkai Seiji 
Published: October 2004

Abstract
It was found that 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS), which is known to aggregate in a one-dimensional fashion in water, acts as a template for the electropolymerization of aniline on an ITO electrode. Examinations using cyclic voltammetry (CV) and UV–vis spectroscopy established that J-aggregated TPPS molecules are entrapped in the resultant poly(aniline). Scanning electron microscopy (SEM) observations established that poly(aniline) grows to a nanosized rod-like structure, reflecting the aggregation structure of TPPS. The chemical oxidative polymerization of aniline in the presence of TPPS also gave a poly(aniline) rod-like structure containing the TPPS J-aggregate. It was found that the J-aggregation mode in the poly(aniline)/TPPS composite disappears when the medium pH is shifted from acidic to basic, but is regenerated when the medium pH is shifted from basic to acidic. This interconversion could be visually recognized by changes in the color and the fluorescence intensity.
Investigations of Phase Structure Transformation and VUV Excitation of YPO4:Tb Synthesized by Solution Precipitation Route
Authors: Di Weihua , Chen Jianyong , Wang Xiaojun , Chen Baojiu 
Published: October 2004

Abstract
Tb-doped YPO4 has been synthesized by a mild and simple solution precipitation approach. pH value of synthesis has a significant influence on the formation and crystallinity of YPO4:Tb. Phase transformation occurs in the annealing process. Vacuum ultraviolet (VUV) excitation of Tb-doped YPO4 is investigated and possible luminescence mechanism under VUV excitation is illustrated.
Synthesis and Spectral Property of Novel Phthalocyanines Substituted with Four Azo Group Moieties on Periphery of Phthalocyanine Ring
Authors: Li Ying-Feng , Li Shao-Lu , Jiang Ke Jian , Yang Lian-Ming 
Published: October 2004

Abstract
A novel class of phthalocyanines substituted with azo group moieties on the periphery of phthalocyanine ring was synthesized, and they show obvious, broad uncommon absorption band in the visible region compared to those normal phthalocyanines.
An Efficient Synthesis of 3,4-Dihydropyran-2-one Derivatives by Lewis Base-catalyzed Tandem Michael Addition and Lactonization
Authors: Tozawa Takashi , Fujisawa Hidehiko , Mukaiyama Teruaki 
Published: October 2004

Abstract
A convenient one-pot preparation of 3,4-dihydropyran-2-one derivatives by Michael addition of silyl enolate derived from phenyl ester with α,β-unsaturated ketones in the presence of a Lewis base catalyst such as tetrabutylammonium phenoxide was developed. In this catalytic cycle, 3,4-dihydropyran-2-ones were produced in good to excellent yields via intramolecular cyclization of in situ formed Michael-adducts.
An Effective Catalyst for Syngas-to-Dimethyl Ether Process with Steamed Zeolite HMCM-49 as Dehydration Component
Authors: Xia Jianchao , Mao Dongsen , Xu Ning , Chen Qingling , Zhang Yahong , Tang Yi 
Published: October 2004

Abstract
The HMCM-49 zeolites before and after steam treatment were commingled with methanol synthesis catalyst to perform the single-step syngas-to-dimethyl ether process. The high temperature steam treatment meliorated the acidity of HMCM-49 zeolite, and consequently enhanced the selectivity to dimethyl ether significantly by reducing the formation of by-products like carbon dioxide and hydrocarbons.
Synthesis of Wollastonite Single Crystal Nanowires by a Novel Hydrothermal Route
Authors: Li Xiaoke , Chang Jiang 
Published: October 2004

Abstract
This article firstly reports the successful synthesis of wollastonite single crystal nanowires by hydrothermal route. We obtained xonotlite nanowires on hydrothermal condition at a lower temperature (180 °C) using cationic surfactant as template. The nanowires have high aspect ratios more than 100 with diameters of 50–100 nm. After calcination at 800 °C for 2 h, xonotlite nanowires transformed to wollastonite and the fibrous structure was preserved. They were characterized by powder X-ray diffractometry (XRD), transmission electron microscopy (TEM). The mechanism of wollastonite nanowires formation was also discussed.
Synthesis, Structure, and Magnetic Property of Organic-radical Labeled Carborane
Authors: Iwahori Fumiyasu , Kamibayashi Kengo , Nishikawa Yoshikazu , Yamashita Masahiro , Abe Jiro 
Published: October 2004

Abstract
A carborane derivative containing nitronyl nitroxide group was synthesized and was crystallographically and magnetically characterized. The X-ray structure analysis revealed that the molecules were crystallized in a head-to-tail dimer fashion. The intradimer ferromagnetic interaction (J/kB = +4.26(2) K) was observed.
Formation of Stable Molecular Glasses of Yttrium(III) Acyl-Dl-Alaninate Complexes
Authors: Iida Masayasu , Masuda Rie , Naren Gerile , Bin Yuezhen , Kajiwara Kazuhito 
Published: October 2004

Abstract
Yttrium(III) acylalaninate complexes such as tris(N-hexanoyl-Dl-alaninato)yttrium(III) (=Y(hex-Dl-ala)3) and tris(N-octanoyl-Dl-alaninato)yttrium(III) (=Y(oct-Dl-ala)3) form stable glassy states by an evaporation of solvent from the methanol solution. The trend of formation of the stable glassy state is sensitive to a difference in the acylalaninate ligands.
Polarity of Room-Temperature Ionic Liquid as Examined by EPR Spectroscopy
Authors: Kawai Akio , Hidemori Takehiro , Shibuya Kazuhiko 
Published: October 2004

Abstract
Polarity of several ionic liquids was examined by 14N hyperfine coupling constant of nitroxide radical measured by EPR method. Polarity judged from EPR agrees well with those by solvatochromic dyes, suggesting that EPR is another valuable probe for polarity of ionic liquids.
A Synthetic Peptide Derived from the Non-Structural Protein 3 of Hepatitis C Virus Serves as a Specific Substrate for PKC
Authors: Borowski Peter , Resch Kerstin , Schmitz Herbert , Heiland Max 
Published: October 2004

AbstractA synthetic peptide corresponding to the amino acid sequence Arg1487-Arg-Gly-Arg-Thr-Gly-Arg-Gly-Arg-Arg-Gly-Ile-Tyr-Arg1500of the hepatitis C virus (HCV) polyprotein was found to be a selective substrate for protein kinase C (PKC). In the presence of Ca2+, TPA and phospholipid, PKC phosphorylates the peptide [termed HCV(1487–1500)] with aKmof 11μM andVmaxof 24 μmol × min−1× mg−1. HCV(1487–1500) acts as a competitive inhibitor of PKC towards other peptide or protein substrates and inhibits the kinase activity with an IC50corresponding to theKmvalues measured for the substrates. N- or C-terminally deleted analogs of HCV(1487–1500) did not show inhibitory effects and were only marginally or not phosphorylatable.We designed an additional peptide in which the tyrosine residue was replaced by phenylalanine ([Phe1499]HCV(1487–1500)). This peptide was neither phosphorylated by other serine/threonine kinases tested nor by whole cell extracts prepared from PKC-depleted cells. [Phe1499]HCV(1487–1500) was used to monitor the TPA-induced translocation of PKC activity to the particulate fraction in JB6 cells. The use of SDS/PAGE to separate the peptide from ATP and Piallowed to monitor simultaneously PKC autophosphorylation and phosphorylation of the peptide. The data presented here show that [Phe1499]HCV(1487–1500) can serve as a convenient tool for investigations of PKC activity also in the presence of other kinases in tissues or in crude cell extracts.
Activation of Progelatinase B by Membranes of Human Polymorphonuclear Granulocytes
Authors: Kolkenbrock Hansjörg , Zimmermann Jürgen , Burmester Gerd-R. , Ulbrich Norbert 
Published: October 2004

AbstractIsolated human granulocyte plasma membranes contain progelatinase B. The binding of progelatinase B to the membrane, however, is relatively weak, and a considerable part of progelatinase B can be removed by simply washing the membrane with buffer. This detachment does not depend on the ionic strength of the buffer, indicating that electrostatic forces do not play an important role in the binding of progelatinase B to the membrane. A complete removal of progelatinase B is achieved by chromatography of neutrophil membranes on gelatin-agarose.The plasma membrane of human granulocytes activates added progelatinase B. This activation is inhibited by soybean trypsin inhibitor and is thus performed by membrane bound serine proteinases. In contrast to other reports that claimed an important role of elastase in activating progelatinase B, we found that this activation is mostly inhibited by chymostatin and not by elastatinal and is thus primarily due to cathepsin G. Proteinase 3 was shown to activate progelatinase B as efficient as neutrophil elastase, i. e. much weaker than cathepsin G. Binding of cathepsin G and elastase to the neutrophil membrane does not change their ability to activate progelatinase B. However, cathepsin G , the most potent activator of the three neutrophil serine proteinases, is only a weak activator, when compared to stromelysin-1. This, as well as only a weak binding of progelatinase B, make it doubtful that activation of membrane-bound progelatinase B by membrane-bound serine proteinases is of significant physiological importance.
Tissue-Specific Regulation of IRS-2/PI 3-Kinase Association in Aged Rats
Authors: Carvalho Carla R.O. , Maeda Lucimara , Brenelli Sigisfredo L. , Saad Mario J.A. 
Published: October 2004

AbstractWe have examined the insulin-stimulated IRS-2 association with PI 3-kinase and the phosphorylation of AKT/PKB, which is functionally located downstream of the PI 3-kinase, in aged (obese) rats. The IRS-2 protein levels were similar in 2 and 20 month-old rats in both tissues, liver and muscle. There were reductions in insulin-induced IRS-2 tyrosine phosphorylation in liver and muscle, accompanied by a decrease in IRS-2/PI 3-kinase association and in AKT/PKB phosphorylation only in muscle tissue of aged rats. This regulation may be important in the altered glucose metabolism observed in aged (obese) rats.
Investigation of the Effect of Freezing on Protease-Catalyzed Peptide Synthesis Using Cryoprotectants and Frozen Organic Solvent
Authors: Haensler Marion , Arnold Klaus 
Published: October 2004

Abstract
In order to investigate the effect of freezing on aqueous protease-catalyzed peptide synthesis systems, the influence of polyethylene glycols as cryoprotecting substances on α-chymotrypsin-catalyzed coupling of a N-protected acyl donor ester and various nucleophilic amino components was studied. Changes in S'-specificity of α-chymotrypsin in frozen aqueous systems were suppressed by polyethylene glycols even at concentrations below 1% (w/v). Furthermore, the influence of freeze-concentration in organic solvents on protease-catalyzed peptide synthesis was investigated for the first time. In frozen tert-butanol, α-chymotrypsin-catalyzed peptide synthesis took advantage from freeze-concentration, but in contrast to frozen aqueous systems, no changes in S'-specificity of the biocatalyst were observed. The results suggest that freeze-concentration is not the only cause of freezing-induced yield improvement in aqueous peptide synthesis systems, but interactions between enzyme and ice structures strongly contribute to the observed effects.
The Twin-Arginine Translocation System: A Novel Means of Transporting Folded Proteins in Chloroplasts and Bacteria
Authors: Robinson C. 
Published: October 2004

AbstractProtein translocases have been characterised in several membrane systems and the translocation mechanisms have been shown to differ in critical respects. Nevertheless, the majority were believed to transport proteins only in a largely unfolded state, and this widespread characteristic was viewed as a likely evolutionary effort to minimise the diameter of translocation pore required. Within the last few years, however, studies on the chloroplast thylakoid membrane have revealed a novel class of protein translocase which possesses the apparently unique ability to transport fullyfolded proteins across a tightly sealed energytransducing membrane. A related system, (the twinarginine translocation, or Tat system) has now been characterised in the Escherichia coli plasma membrane and considerations of its substrate specificity again point to its involvement in the transport of folded proteins. The emerging data suggest a critical involvement in many membranes for the biogenesis of two types of globular protein: those that are obliged to fold prior to translocation, and those that fold too tightly or rapidly for other types of protein translocase to handle.
Responses to Peroxynitrite in Yeast: Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) as a Sensitive Intracellular Target for Nitration and Enhancement of Chaperone Expression and Ubiquitination
Authors: Buchczyk Darius P. , Briviba Karlis , Hartl F. Ulrich , Sies Helmut 
Published: October 2004

AbstractPeroxynitrite (ONOO−), a potent oxidizing and nitrating species, has been linked to covalent modifications of biomolecules in a number of pathological conditions. InS. cerevisiae, a model eukaryotic cell system, ONOO−was found to be more potent than hydrogen peroxide in oxidizing thiols, inducing heat shock proteins (Hsp70) and enhancing the ubiquitination of proteins. As identified by microsequence analysis following immunoprecipitation with anti-nitrotyrosine antibodies, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was especially susceptible to nitration by ONOO−in yeast cells. The activity of this enzyme was strongly inhibited upon steady-state exposure of the cells to low doses of ONOO−in yeast and in cultured rat astrocytes. Thus, ONOO−is a potent stressor in yeast capable of inducing oxidative damage and protein nitration, with GAPDH being a preferential target protein that is efficiently inactivated.
Enhancing the T R Transition of Insulin by Helix-Promoting Sequence Modifications at the N-Terminal B-Chain
Authors: Shneine Jewad , Voswinkel Marc , Federwisch Matthias , Wollmer Axel 
Published: October 2004

AbstractStructurally, the T→R transition of insulin mainly consists of a rearrangement of the N-terminal B-chain (residues B1–B8) from extended to helical in one or both of the trimers of the hexamer. The dependence of the transition on the nature of the ligands inducing it, such as inorganic anions or phenolic compounds, as well as of the metal ions complexing the hexamer, has been the subject of extensive investigations. This study explores the effect of helix-enhancing modifications of the N-terminal B-chain sequence where the transition actually occurs, with special emphasis on N-capping. In total 15 different analogues were prepared by semisynthesis. 80% of the hexamers of the most successful analogues with zinc were found to adopt the T3R3state in the absence of any transforming ligands, as compared to only 4% of wild-type insulin. Transformation with SCN−ions can exceed the T3R3state where it stops in the case of wild-type insulin. Full transformation to the R6state can be achieved by only one-tenth the phenol concentration required for wild-type insulin, i. e. almost at the stoichiometric ratio of 6 phenols per hexamer.
3-Hydroxybenzoate:Coenzyme A Ligase from Cell Cultures of Centaurium erythraea: Isolation and Characterization
Authors: Barillas Wagner , Beerhues Ludger 
Published: October 2004

Abstract
In xanthone biosynthesis, 3-hydroxybenzoate:coenzyme
A ligase (3HBL) supplies the starter substrate for
the formation of an intermediate benzophenone. 3HBL
from cell cultures of the medicinal plant Centaurium
erythraea was purified to apparent homogeneity using
a sevenstepprocedure. The enzyme was an AMPforming CoA ligase with a K = 14.7 for 3-hydroxybenzoic acid, 8.5 for coenzyme A and 229 for ATP. The pH and temperature optima were 7.5 and 35C, respectively. In SDSPAGE, two polypeptides of M 41500 and 40500 were detected. Both proteins were structurally related to each other as shown by tryptic digestion. Their Ntermini were blocked. The difference in their apparent molecular masses could
not be attributed to glycosylation. 3HBL had a native
M of approx. 50000 and is thus active as a monomer.
Permutation of the Active Site Motif of Tryparedoxin 2
Authors: Steinert Peter , Plank-Schumacher Karin , Montemartini Marisa , Hecht Hans-Jürgen , Flohé Leopold 
Published: October 2004

AbstractTryparedoxins (TXN) are thioredoxinrelated proteins which, as trypanothione:peroxiredoxin oxidoreductases, constitute the trypanothionedependent antioxidant defense and may also serve as substrates for ribonucleotide reductase in trypanosomatids. The active site motif of TXN2, [40]WCPPCR[45], of Crithidia fasciculata was mutated by sitedirected mutagenesis and eight corresponding muteins were expressed in E. coli as terminally Histagged proteins, purified to homogeneity by nickel chelate chromatography, and characterized in terms of specific activity, specificity and, if possible, kinetics. Exchange of Cys41 and Cys44 by serine yielded inactive products confirming their presumed involvement in catalysis. Exchange of Arg45 by aspartate resulted in loss of activity, suggesting an activation of active site cysteines by the positive charge of Arg45. Substitution of Trp40 by phenylalanine or tyrosine resulted in moderate decrease of specific activity, as did exchange of Pro42 by glycine. Kinetic analysis of these three muteins revealed that primarily the reaction with trypanothione is affected by the mutations. Simulation of thioredoxin or glutaredoxin like active sites in TXN2 (P42G and W40T/P43Y, respectively) did not result in thioredoxin or glutaredoxin like activities. These data underscore that TXNs, although belonging to the thioredoxin superfamily, represent a group of enzymes distinct from thioredoxins and glutaredoxins in terms of specificity, and appear attractive as molecular targets for the design of trypanocidal compounds.
In Vitro Evolution of Ligands for HCV-Specific Serum Antibodies
Authors: Zhu Zong Yu , Minenkova Olga , Bellintani Francesca , Tomassi Amedeo De , Urbanelli Lorena , Felici Franco , Monaci Paolo 
Published: October 2004

AbstractWe developed a strategy to improve the properties of ligands selected from phagedisplayed random peptide libraries. A sitedirected mutagenesis protocol that introduces mutations and extends the size of a target sequence has been set up to generate diversity in a single or in a population of clones. The pool of mutants thus created is screened to identify variants with the desired properties. We refer to this strategy as in vitro evolution of ligands. Here we report the application of this in vitro evolution protocol to the identification of improved ligands for HCVspecific serum antibodies. A single clone or population of clones were processed to generate a secondary library. Screening of these libraries with sera from HCVinfected patients identified peptides with an enhanced and broadened ability to detect HCVspecific serum antibodies.
Stability of Bacteriophage T4 Short Tail Fiber
Authors: Burda Martin R. , Hindennach Ingrid , Miller Stefan 
Published: October 2004

Abstract
Adsorption of Teven bacteriophages to the E. coli
host cell is mediated by long and short tail fibers. Bacteriophage T4 short tail fiber protein p12 was used to
investigate the stability against thermal and chemical
denaturation. Purified p12 is thermostable with a melting
point of 78C. Guanidinium chlorideinduced denaturation
displayed strong hysteresis and an intermediate
between 2 and 3 denaturant. The transitions
occur at 1.5 and 3.2 denaturant as revealed by fluorescence spectroscopy and circular dichroism. The
data suggest an equilibrium unfolding intermediate
with a separate unfolding of the Cterminal knob domain
and the shaft region.
Guanosine Nucleotides Regulate B2 Kinin Receptor Affinity of Agonists But Not of Antagonists: Discussion of a Model Proposing Receptor Precoupling to G Protein
Authors: Faussner Alexander , Roscher Adelbert A. 
Published: October 2004

AbstractThe effect of nucleotides on binding of the B2 kinin (BK) receptor agonist [[3]H]BK and the antagonist [[3]H]NPC17731 to particulate fractions of human foreskin fibroblasts was studied. At 0C, particulate fractions exhibited a single class of binding sites with a K of 2.3n for [[3]H]BK and a K of 3.8n for the antagonist [[3]H]NPC17731. Incubation with radioligands at 37C for 5 min gave a reduction of agonist, as well as antagonist, binding that was between 0 40% depending on the preparation, even in the absence of guanosine nucleotides. As shown by Scatchard analysis, this reduction in specific binding was due to a shift in the affinity of at least a fraction of the receptors. The presence at 37C of the guanine nucleotides GTP, GDP and their poorly hydrolyzable analogs left [[3]H] NPC17731 binding unaffected, but reduced the receptor affinity for [[3]H]BK to a K of about 15 n. The maximal number of receptors, however, was unchanged. This affinity change was strongly dependent on the presence of bivalent cations, in particular Mg[2+]. It was reversed by incubation at 0C. The rank order of the guanosine nucleotides for [[3]H]BK binding reduction was GTP[γS] = Gppp [greater than] GTP = GDP [greater than] GDP[βS]. GMP, ATP, ADP and AMP showed no influence on agonist binding. A model for the interaction of the B2 kinin receptor with G proteins is discussed.
Regulation of PTHrP and PTH/PTHrP Receptor by Extracellular Ca2+Concentration and Hormones in the Breast Cancer Cell Line 8701-BC
Authors: Luparello Claudio , Santamaria Francesca , Schilling Tobias 
Published: October 2004

AbstractIt was previously reported that 8701-BC breast tumour cells express the gene for parathyroid hormonerelated peptide (PTHrP) and PTH/PTHrP receptor (PTHrPR) and release immunoreactive PTHrP (iPTHrP) into the extracellular medium. Since the regulation of PTHrP and PTHrPR by breast cancer cells has been poorly investigated so far, we have chosen the 8701- BC cell line as a model system to investigate whether alterations in the extracellular Ca[2+] concentration ([Ca[2+]]) and treatment with some wellknown differentiation agents for breast cells, such as dimethyl sulfoxide, hydrocortisone, progesterone, prolactin, alltrans retinoic acid and transforming growth factorβ1 might (i) modulate quantitatively the release of iPTHrP, (ii) affect the PTHrP promoter usage and mRNA splicing patterns, and (iii) modify the expression of PTHrPR. The data obtained indicate that 8701-BC cells are potentially able to utilise different start sites and mRNA splicing patterns for PTHrP transcription, and respond to variations of [Ca[2+]] and to the addition of two hormones, hydrocortisone and progesterone, with modifications in the extracellular amount of iPTHrP. Moreover, expression of PTHrPR is also modulated by changes of [Ca[2+]] or treatment with hydrocortisone. This indicates that the 8701-BC cell line is a suitable in vitro model for further studies on the complex molecular regulation of the PTHrP/PTHrPR pair in breast cancer.