bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term expansion of human functional epidermal precursor cells: promotion of extensive amplification by low TGF-β1 concentrations
Authors: Fortunel Nicolas O. , Hatzfeld Jacques A. , Rosemary Pierre-Antoine , Ferraris Corinne , Monier Marie-Noëlle , Haydont Valérie , Longuet Joanna , Brethon Benoit , Lim Bing , Castiel Isabelle , Schmidt Rainer , Hatzfeld Antoinette
Published: September 2003

We have previously introduced the concept of high proliferative potential-quiescent (HPP-Q) cells to refer to primitive human hematopoietic progenitors, on which transforming growth factor-β1 (TGF-β1) exerts a pleiotropic effect. TGF-β1 confers to these slow-dividing cells a mitogenic receptorlow phenotype and maintains immature properties by preventing differentiation and apoptosis. However, the effect of TGF-β1 on long-term expansion has not yet been clearly demonstrated. Here, we describe the characterization of a human skin keratinocyte subpopulation, highly enriched for primitive epidermal precursors, on the basis of high adhesion capacity (Adh+++) and low expression of the epidermal growth factor receptor (Adh+++EGF-Rlow). In our standard culture condition without feeder cells, the mean estimated output for cells from an unfractionated population of primary foreskin keratinocytes was 107-108, increasing to 1012-1013 in cultures initiated with selected Adh+++EGF-Rlow precursors. Characterization of these cells revealed a hitherto unknown property of TGF-β1: its addition at a very low concentration (10 pg/ml) in long-term cultures induces a very significant additional increase of expansion. In this optimized system, outputs obtained in cultures initiated with Adh+++EGF-Rlow cells repeatedly reached 1016-1017 (∼60 population doublings, ∼4×1018 keratinocytes produced per clonogenic cell present in the initial population). At the molecular level, this effect is associated with an increase in Smad1, Smad2 and Smad3 phosphorylation and an increase in α6 and β1 integrin expression. No such effect could be observed on mature keratinocytes with low adhesion capacity (Adh-/+). We finally demonstrated that the progeny of Adh+++EGF-Rlow precursors after long-term expansion is still capable of generating a pluristratified epidermis in a model for skin reconstruction. In conclusion, after further characterizing the phenotype of primitive epidermal precursors, we demonstrated a new function of TGF-β1, which is to promote undifferentiated keratinocyte amplification.
The junctional adhesion molecule (JAM) family members JAM-2 and JAM-3 associate with the cell polarity protein PAR-3: a possible role for JAMs in endothelial cell polarity
Authors: Ebnet Klaus , Aurrand-Lions Michel , Kuhn Annegret , Kiefer Friedemann , Butz Stefan , Zander Kerstin , Brickwedde Maria-Katharina Meyer zu , Suzuki Atsushi , Imhof Beat A. , Vestweber Dietmar
Published: September 2003

Tight junctions play a central role in the establishment of cell polarity in vertebrate endothelial and epithelial cells. A ternary protein complex consisting of the cell polarity proteins PAR-3 and PAR-6 and the atypical protein kinase C localizes at tight junctions and is crucial for tight junction formation. We have recently shown that PAR-3 directly associates with the junctional adhesion molecule (JAM), which suggests that the ternary complex is targeted to tight junctions of epithelial cells through PAR-3 binding to JAM. The expression of JAM-related proteins by endothelial cells prompted us to test whether recruitment of the ternary complex in endothelial cells can occur through binding to JAM-2, JAM-3, endothelial cell-selective adhesion molecule (ESAM) or coxsackie- and adenovirus receptor (CAR). Here we show that the two JAM-related proteins JAM-2 and JAM-3 directly associate with PAR-3. The association between PAR-3 and JAM-2/-3 is mediated through the first PDZ domain of PAR-3. In agreement with the predominant expression of JAM-2 and JAM-3 in endothelial cells, we found that PAR-3 is expressed by endothelial cells in vivo and is localized at cell contacts of cultured endothelial cells. PAR-3 associates with JAM-2/-3 but not with the JAM-related Ig-superfamily members ESAM or CAR. In addition, we show that the tight junction-associated protein ZO-1 associates with JAM-2/-3 in a PDZ domain-dependent manner. Using ectopic expression of JAM-2 in CHO cells, we show that the junctional localization of JAM-2 is regulated by serine phosphorylation and that its clustering at cell-cell contacts recruits endogenous PAR-3 and ZO-1. Our findings suggest that JAM-2 affects endothelial cell junctions by its regulated clustering at intercellular contacts, and they support a role for JAM-2, and possibly JAM-3, in tight junction formation of endothelial cells.
Complex protein-DNA dynamics at the latent origin of DNA replication of Epstein-Barr virus
Authors: Ritzi Marion , Tillack Kristina , Gerhardt Jeannine , Ott Elisabeth , Humme Sibille , Kremmer Elisabeth , Hammerschmidt Wolfgang , Schepers Aloys
Published: September 2003

The sequential binding of the origin recognition complex (ORC), Cdc6p and the minichromosome maintenance proteins (MCM2-7) mediates replication competence at eukaryotic origins of DNA replication. The latent origin of Epstein-Barr virus, oriP, is a viral origin known to recruit ORC. OriP also binds EBNA1, a virally encoded protein that lacks any activity predicted to be required for replication initiation. Here, we used chromatin immunoprecipitation and chromatin binding to compare the cell-cycle-dependent binding of pre-RC components and EBNA1 to oriP and to global cellular chromatin. Prereplicative-complex components such as the Mcm2p-Mcm7p proteins and HsOrc1p are regulated in a cell-cycle-dependent fashion, whereas other HsOrc subunits and EBNA1 remain constantly bound. In addition, HsOrc1p becomes sensitive to the 26S proteasome after release from DNA during S phase. These results show that the complex protein-DNA dynamics at the viral oriP are synchronized with the cell division cycle. Chromatin-binding and chromatin-immunoprecipitation experiments on G0 arrested cells indicated that the ORC core complex (ORC2-5) and EBNA1 remain bound to chromatin and oriP. HsOrc6p and the MCM2-7 complex are released in resting cells. HsOrc1p is partly liberated from chromatin. Our data suggest that origins remain marked in resting cells by the ORC core complex to ensure a rapid and regulated reentry into the cell cycle. These findings indicate that HsOrc is a dynamic complex and that its DNA binding activity is regulated differently in the various stages of the cell cycle.
Ligand-receptor pairs in plant peptide signaling
Authors: Matsubayashi Yoshikatsu
Published: September 2003

Extensive studies on plant signaling molecules over the past decade indicate that plant cell-to-cell communication, as is the case with animal systems, makes use of small peptide signals and specific receptors. To date, four peptide-ligand-receptor pairs have been identified and shown to be involved in a variety of processes. Systemin and phytosulfokine (PSK), the first and second signaling peptides identified in plants, were isolated by biochemical purification based on their biological activities. Furthermore, their receptors have been biochemically purified from plasma membranes on the basis of specific ligand-receptor interactions. By contrast, the two other peptide signals, CLAVATA3 (CLV3) and the pollen S determinant SCR/SP11, were genetically identified during searches for specific ligands for receptors that had already been cloned. Systemin functions in the plant wound response, whereas PSK appears to cooperate with auxin and cytokinin to regulate cellular dedifferentiation and redifferentiation. CLV3 is important for meristem organization, binding to a heterodimeric receptor comprising the CLV1 and CLV2 proteins. SCR/SP11 instead plays a role in self-incompatibility, where it activates a signalling cascade that leads to rejection of pollen with the same S haplotype. These ligands all seem to bind to receptors that possess intrinsic kinase activity, and al least two of them are generated by proteolytic processing of larger precursor proteins.
Vps20p and Vta1p interact with Vps4p and function in multivesicular body sorting and endosomal transport inSaccharomyces cerevisiae
Authors: Yeo Sebastian C. L. , Xu Linghui , Ren Jihui , Boulton Victoria J. , Wagle Mahendra D. , Liu Cong , Ren Gang , Wong Peisze , Zahn Regina , Sasajala Piriya , Yang Hongyuan , Piper Robert C. , Munn Alan L.
Published: September 2003

Vps4p (End13p) is an AAA-family ATPase that functions in membrane transport through endosomes, sorting of soluble vacuolar proteins to the vacuole, and multivesicular body (MVB) sorting of membrane proteins to the vacuole lumen. In a yeast two-hybrid screen with Vps4p as bait we isolated VPS20 (YMR077c) and the novel open reading frame YLR181c, for which the name VTA1 has recently been assigned (Saccharomyces Genome Database). Vps4p directly binds Vps20p and Vta1p in vitro and binding is not dependent on ATP - conversely, Vps4p binding to Vps20p is partially sensitive to ATP hydrolysis. Both ATP binding [Vps4p-(K179A)] and ATP hydrolysis [Vps4p-(E233Q)] mutant proteins exhibit enhanced binding to Vps20p and Vta1p in vitro. The Vps4p-Vps20p interaction involves the coiled-coil domain of each protein, whereas the Vps4p-Vta1p interaction involves the (non-coiled-coil) C-terminus of each protein. Deletion of either VPS20 (vps20Δ) or VTA1 (vta1Δ) leads to similar class E Vps- phenotypes resembling those of vps4Δ, including carboxypeptidase Y (CPY) secretion, a block in ubiquitin-dependent MVB sorting, and a delay in both post-internalisation endocytic transport and biosynthetic transport to the vacuole. The vacuole resident membrane protein Sna3p (whose MVB sorting is ubiquitin-independent) does not appear to exit the class E compartment or reach the vacuole in cells lacking Vps20p, Vta1p or Vps4p, in contrast to other proteins whose delivery to the vacuole is only delayed. We propose that Vps20p and Vta1p regulate Vps4p function in vivo.
Novel functions and signalling pathways for GDNF
Authors: Sariola Hannu , Saarma Mart
Published: September 2003

Glial-cell-line-derived neurotrophic factor (GDNF) was originally identified as a survival factor for midbrain dopaminergic neurons. GDNF and related ligands, neurturin (NRTN), artemin (ARTN) and persephin (PSPN), maintain several neuronal populations in the central nervous systems, including midbrain dopamine neurons and motoneurons. In addition, GDNF, NRTN and ARTN support the survival and regulate the differentiation of many peripheral neurons, including sympathetic, parasympathetic, sensory and enteric neurons. GDNF has further critical roles outside the nervous system in the regulation of kidney morphogenesis and spermatogenesis. GDNF family ligands bind to specific GDNF family receptor α (GFRα) proteins, all of which form receptor complexes and signal through the RET receptor tyrosine kinase. The biology of GDNF signalling is much more complex than originally assumed. The neurotrophic effect of GDNF, except in motoneurons, requires the presence of transforming growth factor β, which activates the transport of GFRα1 to the cell membrane. GDNF can also signal RET independently through GFR1α. Upon ligand binding, GDNF in complex with GFRα1 may interact with heparan sulphate glycosaminoglycans to activate the Met receptor tyrosine kinase through cytoplasmic Src-family kinases. GDNF family ligands also signal through the neural cell adhesion molecule NCAM. In cells lacking RET, GDNF binds with high affinity to the NCAM and GFRα1 complex, which activates Fyn and FAK.
Kinetics of the Photobromination of Dichloro- and Dibromoethane. Estimate of the C–H Bond Dissociation Energies and the Heats of Formation of the CH3CCl2 and CH3CBr2 Radicals
Authors: Miyokawa Kikuo , Tschuikow-Roux Eugene
Published: September 2003

The kinetics of the α-H abstraction reaction RH + Br → R + HBr, RH = 1,1-dichloro (1) and 1,1-dibromoethane (2) was investigated in the temperature range 308—368 K using chloroethane and ethane as an external competitor, respectively. The relative rates were combined with the known rate parameters for chloroethane and ethane to obtain the absolute rate constants (cm3 mol−1 s−1): k1 = [6.9 ± 3.8(σ)] × 1011exp[(−7300 ± 360 cal mol−1)/RT] and k2 = [2.2 ± 1.2(σ)] × 1011exp[(−7110 ± 360 cal mol−1)/RT]. Using a justifiable approximation concerning the magnitude of the activation energies for the reverse reaction, the following thermochemical quantities (kcal mol−1) were derived: ΔH°f(CH3CCl2) = 11.9 ± 1.2, D°(CH3CCl2-H) = 95.1 ± 1.2, ΔH°f(CH3CBr2) = 33.5 ± 1.3, D°(CH3CBr2-H) = 94.9 ± 1.2. The relation between the reaction thermochemistry and the reactivity in chlorination and bromination of haloethanes is discussed.
Behavior of Biradicals Generated from a Norrish Type-I Reaction of 2,2-Diphenylcycloalkanones. Chain-Length Dependence and Magnetic Field Effects
Authors: Suzuki Itsuko , Tanaka Ryoko , Yamaguchi Akinori , Maki Shin-ichiro , Misawa Hiroaki , Tokumaru Katsumi , Nakagaki Ryoichi , Sakuragi Hirochika
Published: September 2003

The reaction course of acyl-diphenylmethyl biradicals (α-oxo-ω,ω-diphenyl-α,ω-alkanediyl biradicals), O=C↑–(CH2)n−2–C↑Ph2 (3BR-n), generated from the Norrish type-I reaction of 2,2-diphenylcycloalkanones (CK-n) with various ring sizes in methanol, is switched from intramolecular disproportionation (n = 6, 7), giving a diphenylalkenal, to acyl-phenyl recombination (n ≥ 9), affording a cyclophane derivative. The behavior of 3BR-9 derived from CK-9 was studied in detail; the photolysis of CK-9 afforded an open-chain and a cyclic decarbonylation product together with an unsaturated aldehyde and a 4-methylene-2,5-cyclohexadienyl ketone (a pre-cyclophane). The photolysis of this ketone gave the same products that arose from the photolysis of CK-9, presenting the possibility that the decarbonylation products and a part of the aldehyde are formed as secondary products during irradiation.

The magnetic field dependence of the lifetimes of 3BR-n (n = 12 and 13) generated from CK-12 and 13, respectively, was measured in methanol by means of a pulsed-laser excitation technique. The rate constants for intersystem crossing showed a maximum at a relatively low field strength, which decreased with increasing the field strength to level off to an asymptotic value at > 1.5 kG. The results show that the role of hyperfine coupling in intersystem crossing is less important in these systems, presumably because of the presence of a carbonyl oxygen and the absence of a hydrogen atom at the radical center.
Oxidative Iodination of Arenes with Manganese(IV) Oxide or Potassium Permanganate as the Oxidants
Authors: Lulinski Piotr , Skulski Lech
Published: September 2003

Novel and easy laboratory methods (novel Procedures 1—4) are presented for the oxidative mono- and diiodination of both activated and deactivated arenes, which gave the pure iodinated products in 62—89% yields. The reactions were carried out in the anhydrous, strongly acidic system, I2/activated MnO2/AcOH/Ac2O/concd H2SO4, firstly at r.t. for 2 h, then at 45—55 °C for 2—9 h. The resulting mixtures were poured into excess aq Na2SO3 solution buffered with (NH4)2CO3 to neutralize H2SO4. The following workups are given. Similarly, on carrying out the iodination reactions (at 35 °C, for one hour) in the anhydrous, strongly acidic system, I2/KMnO4/AcOH/Ac2O/concd H2SO4, it was possible to mono- or diiodinate several deactivated arenes in 73—87% yields (improved Procedures 5 and 6).
Properties and Application Feasibility of an Osmium-Oxygen Thin Film Prepared by DC-Glow-Discharge Deposition from Osmium Tetraoxide
Authors: Inoue Hitoshi , Satoh Kazuyuki
Published: September 2003

An osmium-oxygen thin film was prepared by d.c.-glow-discharge deposition from osmium tetraoxide with a filming rate of 1 nm s−1. The fundamental properties of the films were investigated. The prepared films had a homogeneous amorphous structure and 10−4 Ω cm order of resistivity. Since the transparency of a 20 nm thick film was about 80% for visible light, a transparent conductive film could be obtained on glass or plastic substrates. X-Ray photoelectron spectroscopy measurements showed that the film contained 30 at.% of osmium and 70 at.% of oxygen, which might make the film be easily etched by an oxygen-plasma, or be electrically oxidized. Since the osmium film could be patterned by oxygen-plasma etching or by a lift-off method, which are familiar lithography techniques in the field of semiconductor devices, it is expected to be used as micro-electrode or micro-wiring materials. Low-temperature film preparation also makes it possible to be applied as an X-ray mask material for X-ray lithography.
Second-Order Optical Nonlinearity of In Situ Prepared Polyurethanes Having Thiazolylazo Chromophores
Authors: Matsui Masaki , Kushida Mitsugu , Funabiki Kazumasa , Muramatsu Hiroshige , Shibata Katsuyoshi , Hirota Kazuo , Hosoda Masahiro , Tai Kazuo
Published: September 2003

The in situ prepared polyurethane films of the thiazolylazo NLOphores showed d33values of 38—49 pm V−1. The temporal stability of the poled NLOphore was in the following order of the polymers: network > side chain > main chain.
Characteristic Monomial Tables for Enumeration of Achiral and Chiral Isomers
Authors: Fujita Shinsaku
Published: September 2003

The characteristic monomial table of an achiral group is applied to combinatorial enumeration of the following types: (1) achiral isomers and enantiomeric pairs, (2) achiral isomers and chiral isomers, (3) enantiomeric pairs, and (4) achiral isomers. The cycle index of each case is obtained by using the same set of subduced cycle indices derived from characteristic monomials, where the coefficients of the subduced cycle indices are given in advance.
Identification of Active Crystalline Phase in La-K-Cu-V Mixed Oxide for the Simultaneous Removal of Nitrogen Oxides and Diesel Soot
Authors: Teraoka Yasutake , Shangguan Wengfeng , Jansson Kjell , Nygren Mats , Kagawa Shuichi
Published: September 2003

The oxide catalyst having an overall metal composition of La/K/Cu/V = 9/1/7/3 (denoted as LKCVO) showed an excellent selectivity to NOx reduction into N2 in the simultaneous NOx-soot removal reaction, though it was a mixture of several crystalline phases. In order to identify the real active phase, LKCVO was characterized by X-ray diffraction (XRD) and by elemental analysis of individual grains in a transmission electron microscope (TEM) equipped with an energy dispersive spectrometer (EDS). LKCVO was found to be composed of CuO and mixed metal oxides analogous to La2CuO4, LaVO4, and La3VO7. By comparing the catalytic activity of LKCVO with those of single-phase oxides synthesized according to the results of XRD and TEM/EDS, (La2−xKx)(Cu0.95V0.05)O4 with 0.05 ≤ x ≤ 0.1 was identified to be the real active phase in LKCVO for the simultaneous NOx-soot removal reaction.
Syntheses, Characterizations, and Redox Behavior of Optically Active Viologens and Bisviologens
Authors: Tsukahara Keiichi , Kaneko Junko , Miyaji Tomoko , Abe Kaya , Matsuoka Maki , Hara Tomoko , Tanase Tomoaki , Yano Shigenobu
Published: September 2003

Optically active viologens, containing [1-(1-naphthyl)-, 1-phenyl-, and 1-cyclohexylethyl]carbamoylmethyl groups, have been synthesized and characterized. The redox behavior of the chiral viologens was studied compared with achiral viologens. The monoviologens containing naphthyl groups show an intermolecular charge-transfer interaction between the bipyridinium and naphthyl groups in aqueous solution. The association constants are dependent on the chirality of the viologens and larger in the (S,S)- and (R,R)-isomers than in the (R,S)-one. Chiral bisviologens, in which two viologen units are linked with a trimethylene chain, have also been synthesized and characterized. Although the intermolecular charge-transfer interaction between the bipyridinium and viologen units of bisviologens was very weak in solution, such an interaction was appreciably observed in a solid state, which was confirmed by X-ray crystallography. Monoradical trications produced by a one-electron reduction of bisviologens disproportionate more easily in the (R,S)-isomers than in the (S,S)- and (R,R)-ones. The disproportionation is controlled by the steric bulk of the chiral substituents in intramolecular association between two viologen radical units of diradical dications.
Unusual Electrical Properties of Neutral Mixed-Stack Charge-Transfer Complexes of DAP–BRL (DAP = 1,6-Diaminopyrene, BRL = p-Bromanil)
Authors: Fujinawa Tasuku , Goto Hirotoshi , Naito Toshio , Inabe Tamotsu , Akutagawa Tomoyuki , Nakamura Takayoshi
Published: September 2003

Two polymorphs of 1 : 1 charge-transfer complexes of DAP–BRL were grown from a benzene solution. The γ-form is triclinic, space group P1-, a = 16.53(1), b = 17.80(1), c = 8.235(5) Å, α = 96.42(7), β = 97.76(6), γ = 120.79(5)°, V = 2015(3) Å3, and Z = 4; the δ-form is monoclinic, space group Pn, a = 6.862(3), b = 9.891(2), c = 15.246(2) Å, β = 101.78(2)°, V = 1012.9(5) Å3, and Z = 2. Both crystals comprise mixed stacks of donors and acceptors. The molecular geometry, the CO stretching frequencies, and the EPR spectra indicate that most of the component molecules in both crystals are in the neutral state. The electrical conductivity is, however, found to be high; especially the value for γ-DAP–BRL (10−1Ω−1 cm−1) is unusually high as a neutral mixed-stack complex.
A Pulse-Product-Yield-Detected ESR Study on the Photolysis of Nitronaphthalene–Aniline Bifunctional Chain Molecule
Authors: Konishi Yoshinari , Maruthamuthu Pichai , Okazaki Masaharu , Arakawa Youko , Nakagaki Ryoichi
Published: September 2003

The effects of microwaves (MW) on the photolysis of a benzene solution of N-[12-(4-nitro-1-naphthyloxy)dodecyl]aniline under a magnetic field were investigated. The reaction intermediate was identified as a biradical the ESR spectrum of which was recorded by plotting the MW effect as a function of the magnetic field under which the reaction proceeds. The kinetic parameters of the reaction system were estimated from the MW effects observed as functions of the delay period from the laser pulse for putting on/off the MW pulse.
Formation of a Trinuclear Mercury(II) Complex Mediated by a Phosphorane: Molecular Structure of [Hg{Hg(I)(Ph3PCHCOPh)(μ-I)2}2]
Authors: Kalyanasundari Balasubramanian , Panchanatheswaran Krishnaswamy , Parthasarathi Viraraghavan , Robinson Ward T
Published: September 2003

Phenacylidenetriphenylphosphorane reacts with HgI2 in 2 : 3 molar ratio to form a novel trinuclear iodobridged symmetrical complex whose structure has been elucidated by IR, multinuclear NMR, and X-ray crystallography. The Hg···Hg distance [3.648(1) Å] indicates a negligible bonding interaction between the mercury atoms.
Colloidal Titration of Chitosan and Critical Unit of Chitosan to the Potentiometric Colloidal Titration with Poly(vinyl sulfate) Using Toluidine Blue as Indicator
Authors: Hattori Toshiaki , Katai Kazuhito , Kato Masanao , Izume Masato , Mizuta Youichi
Published: September 2003

Three sorts of characterized chitosan were measured by visual titration and potentiometric titration with poly(vinyl sulfate) using Toluidine Blue as the indicator, to evaluate the stoichiometry and the accuracy. The measurement values for two dialyzed chitosans by both colloidal titration methods agreed with the values obtained by the acid-base titration. The relative differences between the acid-base titration and the colloidal titration were < 2%, and the relative standard deviation of the potentiometric colloidal titration was < 1%. For a oligo-chitosan (ChO) which consisted of several d-glucosamine oligosaccharides, the value obtained by the potentiometric colloidal titration was much smaller than the value from the acid-base titration. The inadequate result was due to the low stability constant of ChO–PVS. The observed values in the colloidal titration of ChO were evaluated for the content of each d-glucosamine oligosaccharide, and a critical unit that indicated the least unit of d-glucosamine oligosaccharide that contributed to the measurement value was estimated. The critical unit was four, tetra(d-glucosamine saccharide).
Determination of Trace Molybdenum in Water Samples by Electrothermal Atomic Absorption Spectrometry after Preconcentration with Miniaturized Coprecipitation
Authors: Shimizu Tokuo , Ito Hirobumi , Kawaguchi Hiroshi , Shijo Yoshio
Published: September 2003

Miniaturized coprecipitation with hydrous manganese(IV) oxide was studied for the preconcentration of sub μg dm−3 levels of molybdenum in water samples. Manganese(IV) oxide was produced by a reaction of permanganate ion with ethanol in the presence of 0.1 mol dm−3 hydrochloric acid. A nanogram amount of molybdenum in a 10 cm3 sample was quantitatively coprecipitated. The amount of manganese required was 0.1—0.40 mg for a 10 cm3 sample. The precipitate was collected on a 10 μm membrane filter, and then dissolved in 50 mm3 of 5.6 mol dm−3 nitric acid and 75 mm3 of 1% hydrogen peroxide. An 80-fold preconcentration factor was obtained by this procedure. The molybdenum concentration was determined by electrothermal atomic absorption spectrometry using a pyrolytic graphite coated cuvette. The detection limit (3σ) was found to be 8.9 ng dm−3. The proposed method was successfully applied to river water and snow samples.
Correlation of Exciplex Formation with Ground State Conformations in Flexible Bichromophoric Esters: 2-(1-Pyrenyl)ethyl p-Cyanobenzoate and Its Model Compounds
Authors: Kawakami Jun , Furuta Toshiaki , Nakamura Junko , Uchida Akira , Iwamura Michiko
Published: September 2003

Two kinds of model compounds for a bichromophoric ester, 2-(1-pyrenyl)ethyl p-cyanobenzoate (P2CN), were synthesized: 1-substituted 2-(1-pyrenyl)ethyl p-cyanobenzoates (RP2CN, R = Me, Et, and Ph) as flexible model compounds and trans-2-(1-pyrenyl)cyclohexyl p-cyanobenzoate (cyclo-P2CN) as a rigid model compound. P2CN and all the model compounds had an intramolecular exciplex emission (φEX ≈ 0.010) and efficient quenching of fluorescence from the locally excited pyrene part (φLE ≈ 0.001). The decay lifetimes of the locally excited pyrene were 365 ps for P2CN and 66 ps for cyclo-P2CN, which were respectively identical with the risetime for the exciplex formation. The 1H NMR of both P2CN and RP2CN showed the shifts of H2″ and H3″ of the p-cyanobenzoyl to the higher and H10′ of 1-pyrenyl signals to the lower magnetic field compared with those of the reference compounds, approaching towards those of cyclo-P2CN. NOE was observed between H10′ and H2″ of cyclo-P2CN, and, although very weak, between H2′ and H3″ of MeP2CN. In the solid state, P2CN adopts a folded conformation, which is roughly close to the gauche conformation, with the dihedral angle of 57.5° between p-cyanophenyl ring and pyrenyl ring based on X-ray crystallographic analysis on a leaflet monoclinic crystal, suggesting the exciplex formation from this conformation in P2CN.
Effects of N-Terminal l-Amino Acid Residues on Helical Screw Sense in Achiral Peptides
Authors: Inai Yoshihito , Kurokawa Yuji , Ida Atushi , Hirabayashi Tadamichi
Published: September 2003

To understand the effects of N-terminal l-residues on dominating helical screw sense in achiral peptides, we adopted six kinds of peptides Boc–X–(Aib–ΔPhe)2–Aib–OMe (Boc, t-butoxycarbonyl; OMe, methoxy), in which the X residue is an l-amino acid of alanine (Ala), leucine (Leu), valine (Val), phenylalanine (Phe), 1-naphthylalanine (Nap), or proline (Pro). The segment –(Aib–ΔPhe)2– was used for a backbone composed of two “enantiomeric” (left-/right-handed) helices. Actually, this could be confirmed by 1H NMR and CD spectroscopy on Boc–(Aib–ΔPhe)2–Aib–OMe, which took left- and right-handed 310-helices with the same content. All peptides were also found to take 310-type helical conformations in CDCl3 from solvent accessibility of NH resonances. Chloroform, acetonitrile, methanol, and tetrahydrofuran were used for solvents in CD measurement. All peptides in all solvents showed marked exciton couplets around 280 nm with a positive peak at longer wavelengths. Consequently, when an N-terminal l-residue, irrespective of types of l-residues, is introduced into a helical segment of achiral peptide, its main chain prefers the left-handed screw sense. The peptide with X = Alashowed the smallest amplitude of exciton couplets in each solvent, meaning that the Ala residue with the smallest side chain (methyl group) had the least effective chirality for taking a one-side helical screw sense preferentially, compared with the other residues used here.
Reactivities of Stable Rotamers. XLI. Reactions of 1-(9-Fluorenyl)-2-(1-methylethenyl)naphthalene Rotamers with Chalcogenyl Halides and Observation of Coloration During the Reaction of Methanesulfenyl Chloride and the ap-Rotamer
Authors: Oki Michinori , Hirose Takanori , Kataoka Yasukazu , Ogata Taisuke , Toyota Shinji , Matsuo Takashi , Kawai Yasushi , Ohno Atsuyoshi
Published: September 2003

Reactions of p-toluenesulfenyl chloride with the title olefins in carbon tetrachloride afforded an addition product and sp-1-(9-fluorenyl)-2-[1-(p-tolylthiomethyl)ethenyl]naphthalene in the case of ap, whereas the only product was ap-1-(9-fluorenyl)-2-[1-(p-tolylthiomethyl)ethenyl]naphthalene in the case of sp. No cyclized compounds, which are commonly observed in the reactions of the sp-isomer with halogens or halogen chloride, were detected. Various unsuccessful attempts, including use of methanesulfenyl chloride to take advantage of different sulfur acidity, use of a soft anion to retard deprotonation or a polar solvent to accelerate cyclization by stabilizing the intervening cations, have been made to find conditions for formation of the cyclized compound. Similar unsuccessful results were obtained with benzeneselenenyl halides. Such results are attributed to the effective participation of a chalcogen atom in stabilizing a β-carbocation, which opens momentarily but is less vulnerable to the SN2 type attack of the existing nucleophile. Coloration was observed in the reaction of the sp form with methanesulfenyl chloride.
Theoretical Prediction of Isolable Fullerene Isomers
Authors: Aihara Jun-ichi
Published: September 2003

Isolable fullerene isomers must be kinetically very or fairly stable. It was found that both the minimum bond resonance energy (min BRE) and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy separation are useful for estimating the kinetic stability of fullerene molecules. A fullerene isomer must be difficult to isolate from the arc-produced soot if it has a min BRE of less than −0.100 |β| and/or a HOMO-LUMO energy separation smaller than 0.130 |β|. All fullerene isomers so far isolated are kinetically stable in this sense. Candidates for isolable fullerene isomers were chosen by evaluating these two indices.
Facile Synthesis of the Fused 6-6-5 Ring System Containing Chroman Ring from 2-(1-Hydroxy-5-alkenyl)phenol Derivatives via Intramolecular Inverse-Electron-Demand Diels–Alder Reaction
Authors: Shrestha Kedar Shanker , Honda Kiyoshi , Asami Masatoshi , Inoue Seiichi
Published: September 2003

A simple and facile synthesis of the fused 6-6-5 ring system, i.e., 1,2,3,3a,4,9b-hexahydrocyclopenta[c][1]benzopyrans, was achieved through the intramolecular [4+2] cycloaddition of o-quinonemethides generated from 2-(1-hydroxy-5-alkenyl)phenol derivatives under acidic conditions. In general, cis-fused tricyclic compounds of 6-6-5 ring system were obtained as the major products. Reactivity and selectivity of the cycloaddition reaction depended on the substituents on the aromatic ring and in the dienophilic olefin moiety.
Synthesis of Medium-Sized Bicyclic Compounds by Intramolecular Cyclization of Cyclic β-Keto Radicals Generated from Cyclopropanols Using Manganese(III) Tris(pyridine-2-carboxylate) and Its Application to Total Synthesis of 10-Isothiocyanatoguaia-6-ene
Authors: Iwasawa Nobuharu , Funahashi Masahiro , Hayakawa Satoshi , Ikeno Taketo , Narasaka Koichi
Published: September 2003

Bicyclic cyclopropanols having an olefinic side chain are oxidized with manganese(III) tris(pyridine-2-carboxylate) to generate cyclic β-keto radicals with ring-expansion. These cyclize intramolecularly, affording bicyclic radical intermediates. The cyclized radicals are trapped with various radical-trapping reagents such as electron-rich or -deficient olefins, tributylstannane and diphenyl diselenide to give the corresponding functionalized products. Stereochemistries of the bicyclic products are well predicted by MM2 force field calculation. A stereoselective total synthesis of an isothiocyano sesquiterpene, 10-isothiocyanatoguaia-6-ene, is achieved using this reaction.
Asymmetric Reduction of α-Keto Esters and α-Diketones with a Bakers’ Yeast Keto Ester Reductase
Authors: Kawai Yasushi , Hida Kouichi , Tsujimoto Munekazu , Kondo Shin-ichi , Kitano Kazutada , Nakamura Kaoru , Ohno Atsuyoshi
Published: September 2003

Optically pure α-hydroxy esters and α-hydroxy ketones have been synthesized by the reduction of the corresponding ketones with a keto ester reductase isolated from bakers’ yeast (YKER-I). The reduction of α-keto esters affords the corresponding (S)- or (R)-hydroxy esters selectively, where the stereochemical course depends on the chain length of the alkyl substituent on the carbonyl group. An α-keto short alkanoic ester affords the corresponding (S)-hydroxy ester, whereas a long alkanoate yields the corresponding (R)-hydroxy ester. The reduction of α-diketones affords the corresponding (S)-2-hydroxy ketones regio- and stereoselectively.
The Synthesis, Molecular Structure and Selectivity of Macrotricyclic Ammonium-ion Receptor for Bromide Ion
Authors: Ito Naohito , Izumi Mitsunori , Ichikawa Kazuhiko , Shiro Motoo
Published: September 2003

The cage receptor [R4N4(C5H10)2(C6H12)4]4+ ([566]RMQA4+) was designed and synthesized. X-ray crystallography, 1H-NMR and molecular mechanics calculation revealed the complexibility and selectivity toward Br−. In the presence of both Cl− and Br−, [566]RMQA4+ shows the higher selectivity toward Br− in aqueous solution.
Diastereoselection in Crystalline State Photochromism of a Diarylethene Having a Chiral Substituent
Authors: Kodani Tetsuhiro , Matsuda Kenji , Yamada Taro , Irie Masahiro
Published: September 2003

A diarylethene having a chiral substituent underwent a diastereoselective photocyclization reaction in the crystalline phase, while the selectivity was not observed in solution.
Effect of Hydrothermal Treatment of Titania-pillared Montmorillonite for Photocatalytic Degradation of Dibutyl Phthalate in Water
Authors: Yoshida Hisao , Kawase Tomomi , Miyashita Yoshinori , Murata Chizu , Ooka Chihiro , Hattori Tadashi
Published: September 2003

Titania-pillared clay could adsorb dibutyl phthalate (DBP), one of endocrine disruptors, and degrade it photocatalytically. Hydrothermal treatment of this material, which increased the crystallinity of titania pillars, enhanced the photocatalytic activity without losing the adsorption ability and reduced the elution of titania pillars.
Reactions of Vinyldisilanes with Ruthenium Carbonyl
Authors: Dai Xiaosu , Kano Naokazu , Kako Masahiro , Nakadaira Yasuhiro
Published: September 2003

Reaction of β-styrylpentamethyldisilane (1a) with Ru3(CO)12 afforded β-styryltrimethylsilane (2a) with elimination of a dimethylsilylene unit, while under similar conditions α-isomer 1b yielded 2a together with 1a. Studies on these reactions suggest the formation of silapropenyl and silylene ruthenium complexes as key intermediates.
Optically Active Aldiminato Cobalt(II) Complexes as Efficient Catalysts for Enantioselective Cyclopropanation of Styrenes with Diazoacetates
Authors: Yamada Tohru , Ikeno Taketo , Sekino Hiroyuki , Sato Mitsuo
Published: September 2003

The optically active cobalt(II) complex, MPAC, has proved to be efficient enantioselective catalyst for the cyclopropanation of styrenes with diazoacetates. The addition of a catalytic amount of N-methylimidazole remarkably accelerated the cyclopropanation reaction to improve both the chemical and optical yields of the product.
Long-Lived Charge Separation with High Quantum Yield in a Ferrocene-Porphyrin-Fullerene Triad
Authors: Fujitsuka Mamoru , Ito Osamu , Imahori Hiroshi , Yamada Koji , Yamada Hiroko , Sakata Yoshiteru
Published: September 2003

A ferrocene-porphyrin-C60 triad was prepared to mimic efficient photosynthetic multistep electron transfer system. Upon irradiation, the triad produced a long-lived charge-separated state with a high quantum yield, compared with the previously reported artificial photosynthetic triads. The lifetime of the charge separated state increased with increasing the solvent polarity. These results indicate that C60 is an excellent building block as an acceptor in light energy conversion systems.
Formation and Stability of New Hybrid Dichalcogena Dications(S-Se, S-Te and Se-Te) Bearing (2-Methylchalcogenomethyl)phenyl Skeleton
Authors: Naka Hiroyuki , Shindo Masayo , Maruyama Tetsushi , Sato Soichi , Furukawa Naomichi
Published: September 2003

Ethyl 2-(methylthiomethyl)phenyl selenide 1a, telluride 1b and ethyl 2-(methylselanylmethyl)phenyl telluride 1c were prepared and treated with 1 equivalent of triflic anhydride (Tf2O) or 2 equivalents of nitrosonium salts (NOBF4 or NOPF6) at low temperature to generate the corresponding selenathia, tellurathia and telluraselena dications(2a, 2b and 2c), the structures of which were determined by NMR spectroscopy and 2b was successfully isolated.
Electrochemical Evaluation of Interaction between Avidin and Biotin Self-assembled Using Marker Ions
Authors: Kuramitz Hideki , Sugawara Kazuharu , Nakamura Hiroshi , Tanaka Shunitz
Published: September 2003

The interaction between avidin and biotin as self-assembled monolayer on a gold electrode surface was electrochemically evaluated by monitoring the changes in the electrode response of the ferrocyanide ion as redox-marker. It was clarified that the permeability changes of avidin membrane introduced onto the biotin self-assembled monolayer against ferrocyanide ion were ascribed to electrostatic interaction between avidin and marker ion.
Synthesis and Crystal Structure of New Sulfate-Bridged Coordination Polymer, {(4,4′-bpyH2)[Fe3(4,4′-bpy)3(SO4)4(H2O)6]·10H2O}n (4,4′-bpy = 4,4′-Bipyridine). Three-Dimensional Network with Microporous Channels
Authors: Noro Shin-ichiro , Kondo Mitsuru , Kitagawa Susumu , Ishii Tomohiko , Matsuzaka Hiroyuki
Published: September 2003

A new sulfate-bridged coordination polymer, {(4,4′-bpyH2)[Fe3(4,4′-bpy)3(SO4)4(H2O)6]·10H2O}n, was synthesized and crystallographically characterized. This complex shows a novel three-dimensional (3-D) log-cabin type structure constructed from one-dimensional (1-D) [Fe(4,4′-bpy)(H2O)2]n cationic chain, free protonated 4,4′-bpy, and sulfate dianion. This structure shows channel-like cavities with dimensions of about 3 Å × 4 Å.
Synthesis and Characterization of an Iron Porphyrin with a Thiolate Axial Ligand and Its Dioxygen Adduct as a Model for the Active Center of Cytochrome P-450
Authors: Tani Fumito , Nakayama Shinya , Ichimura Mari , Nakamura Nobuhumi , Naruta Yoshinori
Published: September 2003

Synthesis and characterization of an iron porphyrin axially-coordinated by thiolate were carried out in order to mimic the active center of cytochrome P-450. O2 binds reversibly to the ferrous form at −80 °C. The oxygenated complex showed a ν(Fe-O2) band at 578 cm−1 in the resonance Raman spectrum.
Synthesis of Cyclic Oligomer Having a Low Ionization Potential
Authors: Maruyama Sumio , Hokari Hirofumi , Tao Xu-tang , Gunji Atsushi , Wada Tatsuo , Sasabe Hiroyuki
Published: September 2003

Synthesis of cyclic oligomer having a low ionization potential (Ip) is described. Ip of this cyclic oligomer was determined as 5.05 eV, which is lowered than that of corresponding poly(3,6-ethynyl-9-tetradecylcarbazole) (5.24 eV). This result indicated that the cyclic oligomer would be new candidate for hole injection and/or transport material in organic light-emitting diodes.
Crystal Structure and Electrochemical Behavior of an Unusual Nitrosyl-Ru Complex Obtained by a Reaction of Ru2(Me COO)4 Cl with 2-Pyridinecarboxylic Acid
Authors: Yukawa Yasuhiko , Igarashi Satoshi , Horiike Hideki , Nagao Hirotaka , Howell F Scott , Mukaida Masao
Published: September 2003

The crystal structure and the electrochemical behavior of a Ru-complex, which was obtained from a reaction of [Ru2(MeCOO)4Cl] with 2-pyridinecarboxylic acid and NO2−, were investigated: the complex consists of nitrosyl, 2-pyridinecarboxylato, and acetato ligands. The cyclic voltammogram showed no redox wave in the region of the potential window, unlike common Ru(NO)-complexes.
Excitation-Polarization Effects on Single-Molecule Fluorescence on Quartz Surfaces
Authors: Yamauchi Masayo , Ye Jing Yong , Yogi Osamu , Ishikawa Mitsuru
Published: September 2003

The single-molecule fluorescence of dye molecules on quartz surfaces was studied by using a photon-counting video microscopy. We observed fluorescent spots including a countable number of molecules. The orientation of the transition dipole of the molecules on quartz surfaces was found to vary widely in contrast to that observed on Si surfaces where the transition dipole was highly ordered.
Production of Polyester Blend of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and Poly(3-hydroxyalkanoate) with Saturated and Unsaturated Monomers from 4-Hydroxybutyric Acid by Chromobacterium sp.
Authors: Kimura Hiroshi , Iwama Masanobu , Sasaki Shintaro , Takeishi Makoto
Published: September 2003

Chromobacterium sp. isolated from a river soil produced a polyester blend of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P(3HB-co-4HB)) and poly(3-hydroxyalkanoate) (P(3HA)) consisting of both saturated 3-hydroxyalkanoic acid(3HA) units of even carbon number from C4 to C14 and unsaturated 3HA units of carbon number C12 and C14, when 4-hydroxybutyric acid(4HBA) was fed as the sole carbon sources.
Synthesis, Structure and Reactivity of Phenoxo Copper(II) Complexes, Cu(OAr)(HB(3,5-Pri2pz)3) (Ar = C6H4-4-F, 2,6-Me2C6H3, 2,6-But2C6H3)
Authors: Fujisawa Kiyoshi , Iwata Yusaku , Kitajima Nobumasa , Higashimura Hideyuki , Kubota Masaaki , Miyashita Yoshitaro , Yamada Yasunori , Okamoto Ken-ichi , Moro-oka Yoshihiko
Published: September 2003

Structure and reactivity of novel tetrahedral phenoxo copper(II) complexes have been reported as models for the reaction intermediates of tyrosinase catalyzed oxidation of phenols.
Effect of Vapor Adsorption on the Photoelectron Emission from Gold in Ambient Atmosphere
Authors: Inumaru Kei , Okubo Yasuo , Fujii Toshiaki , Yamanaka Shoji
Published: September 2003

Photoelectron emission from Au was measured in ambient atmosphere under irradiation of ultraviolet light from a Hg lamp. The emission was greatly influenced by the adsorption of organic and inorganic vapors. The adsorption of cyclohexene showed a significant, but gradual increase of photoelectron emission. On the other hand, the adsorption of acetone reduced photoelectron emission irreversibly to near zero. The change of the photoelectron emission could be interpreted in terms of the change of the work function.
Electrocatalytic Oxidation of Cysteine on a Nafion-Ruthenium Oxide Pyrochlore Chemically Modified Electrode
Authors: Zen Jyh-Myng , Kumar Annamalai Senthil , Chen Jyh-Cheng
Published: September 2003

The electrocatalytic oxidation of cysteine (CySH) to cystine (CyS-SCy) was noticed on the Nafion-ruthenium oxide pyrochlore chemically modified electrode. The electrocatalytic oxidation was mediated by the RuVI/IV redox sites in the oxide pyrochlore network in terms of the Michaelis-Menten kinetics. The obtained heterogeneous catalytic rate constant (kc) and transfer coefficient (α) are 6.33 s−1 and 0.99, respectively.
8,16,24,32-Tetramethoxy[2.2.2.2]metacyclophane-1,9,17,25-tetrayne: A Novel Ionophore Having a Preorganized but Unexpectedly Flexible Cavity
Authors: Kawase Takeshi , Hosokawa Youichi , Kurata Hiroyuki , Oda Masaji
Published: September 2003

The title cyclophane has a preorganized cavity with about 1.2 Å in diameter surrounded by four oxygen atoms (X-ray analysis); however, solvent extraction experiments using alkali metal picrates revealed the unexpectedly flexible nature of the cavity that forms 1:1 complexes with various alkali metal ions with considerably large association constants.
Preparation of Dialkoxyborylbis(bromozincio)methane and Its Reaction with Electrophiles
Authors: Matsubara Seijiro , Otake Yasuyuki , Hashimoto Yuko , Utimoto Kiitiro
Published: September 2003

Dialkoxyborylbis(bromozincio)methane was prepared from dialkoxyboryldibromomethane by the Pb-catalyzed reaction with zinc. The dialkoxyborylbis(bromozincio)methane afforded vinylboranes by TiCl4-mediated reaction with aldehydes or ketones. The reagent also coupled doubly with an equivalent organic halide under an influence of transition metal salts.
Dibenzoannulated 3,5,3″,5″-Tetra(t-butyl)-p-terphenoquinone. A Reversible, Photochemical-Thermal Switching System Involving Restricted Conformational Change
Authors: Kurata Hiroyuki , Tanaka Tomomi , Oda Masaji
Published: September 2003

The title compound, a new terphenoquinone derivative, shows a dynamic redox behavior upon cyclic voltammetry and a reversible, photochemical-thermal isomerization between the quinone and diradical forms, both phenomena involving restricted conformational change.
Visual Drop Test of Hemoglobin in Whole Blood by Using Ring-like Concentration of Rhodamine B onto Octadecylsilanized Silica Plate
Authors: Kaneko Emiko , Yoshimoto Keitaro , Yotsuyanagi Takao
Published: September 2003

It has been found that some dye solutes become concentrated along the perimeter of an aqueous drop sitting on an octadecylsilanized silica plate. The fluorescent ring of Rhodamine B was applied to a visual test of hemoglobin in whole blood. When a drop of diluted blood and the dye is set on the plate, the resulting fluorescent ring can be observed through the drop with an ultraviolet lamp in the dark only for the samples of low hemoglobin content.
Phase Separation of an Unsymmetrical Disulfide SAM at an Evaporated Au(111) Electrode Monitored by Reductive Desorption and the Electrochemical Response of Cytochrome c
Authors: Nishiyama Katsuhiko , Kie Tan Tjang , Taniguchi Isao
Published: September 2003

The surface structure of an unsymmetrical disulfide (hexadecyl 4-pyridyl disulfide) modified Au(111) evaporated electrode has been evaluated using the redox behavior of cytochrome c and the electrochemical reductive desorption reaction. Controlling the modification time, either a homogeneous SAM or a phase-separated SAM was prepared.
Preparation of Functionalized Unsymmetrical Disulfides by a Base-induced Crossed Reaction of Symmetrical Disulfides
Authors: Kamiyama Hiroaki , Noguchi Toshiya , Onodera Akira , Yokomori Sadakazu , Nakayama Juzo
Published: September 2003

Highly functionalized, unsymmetrical disulfides (presumed metabolites of a bioactive sulfide) were synthesized by a base-induced, crossed reaction of two different symmetrical disulfides. The reaction was also applied to the preparation of a vitamin B1 derivative, Prosultiamine.
Uniform-sized Molecularly Imprinted Polymers for Bisphenol A
Authors: Haginaka Jun , Sanbe Haruyo
Published: September 2003

A uniform-sized molecularly imprinted polymer for bisphenol A (1) has been prepared by a multi-step swelling and thermal polymerization method using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate (EDMA) as a functional monomer and cross-linker, respectively. Hydrophobic and hydrogen bonding interactions between 1 and 4-VPY-EDMA materials could play an important role in the recognition of 1. The 1-imprinted 4-VPY-EDMA materials selectively recognized the template molecule among the phenolic estrogenic and xenoestrogenic compounds tested.