bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Aspect of Organobismuth Chemistry: Synthesis, Properties, and Reactions of Bismuthonium Compounds
Authors: Matano Yoshihiro , Suzuki Hitomi
Published: June 2006

This article is intended to describe recent progress in the chemistry of bismuthonium compounds, represented by onium salts, ylides, and imides, that have long been left untouched within the frame of heteroatom chemistry mainly because of limited access. However, the recent development of methodologies for the preparation of bismuthonium compounds has enabled us to unveil their properties as well as their chemistry. The article is comprised of three sections that mainly deal with: bismuthonium salts synthesized from triphenylbismuth difluoride and organo-silanes or -stannanes; stabilized and moderately stabilized bismuthonium ylides synthesized from triphenylbismuth(V) compounds and bismuthonium salts; and bismuthane imides prepared by oxidative imination of bismuthanes and by reaction between triphenylbismuth(V) dihalides and sulfonamides. Synthesis, X-ray structures, and typical reaction modes of these bismuthonium compounds are delineated in the order in which they appear.
Crystal and Molecular Structures of Novel Metal–Carbene Complexes IV. Effect of Carbonyl Groups and Formation Mechanism
Authors: Manabe Noriko , Yasui Masanori , Nishiyama Hideyuki , Shimamoto Souichi , Matsumura Noboru , Iwasaki Fujiko
Published: June 2006

X-Ray structure analyses were carried out for the metal complexes obtained from 2,3,4,5-tetrahydro-1,6-dialkyl-3,4-trimethylene-5-thioxo-6aλ4-thia-1,3,4,6-tetraazapentalene-2-ones (8) and 2,3,4,5-tetrahydro-1,6-diphenyl-3,4-trimethylene-6aλ4-thia-1,3,4,6-tetraazapentalene-2,5-dione (9), in order to investigate the effect of the carbonyl groups on the formation of the metal–carbene complexes instead of thiocarbonyl groups. The structure analyses revealed that the Pt complex 10, {[3-(methylcarbamoyl-κN) perhydropyrimidine-1-yl-κC2] (methyliminomethanethiolato-κS)}(triphenylphosphine)platinum (II), and the Rh complex 11, trans(P,P′)-(chloro) {[3-(ethylcarbamoyl-κN)perhydropyrimidine-1-yl-κC2] (ethyliminomethanethiolato-κS)}bis(triphenylphosphine)rhodium(III), were obtained from the mono-carbonyl derivative 8. They are metal–carbene complexes coordinated with S and N atoms; the oxygen atoms of the carbonyl groups remained without coordinating to a metal atom. Treating a bis-carbonyl derivative 9 with a Rh reagent, the resultant complex was a Rh complex, 12, trans(P,P′)-dichlorobis(triphenylphosphine) [1,4,5,6-tetrahydro-1-(phenylcarbamoyl)-2-pyrimidinethiolato-κN,κS]rhodium(III), which was not a metal–carbene complex. The formation of the metal–carbene complexes required at least one thiocarbonyl group; the central metal was coordinated by at least one S atom. The formation mechanism of the metal–carbene complexes was proposed from the results of the structures of carbene complexes and MO calculations.
Dependency of Phosphorescence Energy Transfer Rate on Distance between a Cationic Donor and a Cationic Acceptor and on Temperature
Authors: Yoshimura Akio , Nozaki Koichi , Ikeda Noriaki , Ohno Takeshi
Published: June 2006

Phosphorescence energy transfer within ligand bridged diruthenium(II) compounds of the form [(bpy)2Ru(II)(B)Ru(II)(becbpy)2]4+, where bpy, becbpy, and B are 2,2′-bipyridine, 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine, and a bridging ligand, respectively, was investigated in butyronitrile solution in the temperature range 77—330 K. Excitation energy transfer occurs from the Ru(bpy)22+ moiety to the Ru(becbpy)22+ moiety. The energy transfer rate (kEN = (0.4—7.4) × 106 s−1) at 77 K is weakly dependent on the Ru2+–Ru2+ distance (r), which is estimated for the extended conformer of the bridging ligand. A linear plot of log kEN vs. log (1/r6) shows that energy transfer occurs via the dipole–dipole interaction. The weak temperature-dependence of the energy transfer rate in the temperature range 77—110 K is explained in terms of the absorption-emission coupling integral. The fast energy transfer (55 × 106 s−1) within [(bpy)2Ru(bpbimH2)Ru(becbpy)2]4+ (bpbimH2 = 2,2′-di-(2-pyridyl)-6,6′-bibenzimidazole) at 77 K is ascribed to the substantial exchange interaction between the Ru(bpy)2(bpbimH2)2+ moiety in the excited state and the Ru(becbpy)22+ moiety in the ground state.
Magnetic Field Effects on Intramolecular Exciplex Fluorescence of Chain-Linked Phenanthrene and N,N-Dimethylaniline: Influence of Chain Length, Solvent, and Temperature
Authors: Cao Hong , Fujiwara Yoshihisa , Haino Takeharu , Fukazawa Yoshimasa , Tung Chen-Ho , Tanimoto Yoshifumi
Published: June 2006

Magnetic field effects (MFEs) on the intramolecular exciplex fluorescence of a chain-linked phenanthrene (Phen)/N,N-dimethylaniline (DMA) system, Phen–(CH2)n–O–(CH2)2–DMA, have been studied in the magnetic fields (≤0.62 T) as functions of (1) solvent polarity (ε = 7.6—36.7), (2) chain length (n = 4—12), and (3) temperature (223—333 K). The MFEs on the exciplex fluorescence are attributable to the singlet–triplet intersystem crossing in the intramolecular radical ion pair which is in dynamic equilibrium with the exciplex. (1) Solvent polarity increases significantly the MFEs on the exciplex fluorescence of Phen–(CH2)10–O–(CH2)2–DMA. This is attributable to the stability of the intramolecular radical ion pair relative to the exciplex. (2) A remarkable influence of chain length on MFEs in the exciplex fluorescence in N,N-dimethylformamide (DMF) was observed. The results were discussed in connection with the edge-to-edge distances  of two radicals obtained from molecular dynamics calculation for model compounds. (3) The temperature-induced high-field shift of the exchange energies |2J| for Phen–(CH2)4–O–(CH2)2–DMA in DMF was discussed in connection with .
Branching Ratios of Excited Sn I States Produced by Collisions of He(23S) Atom with SnCl4 and Sn(CH3)4
Authors: Tokue Ikuo , Sakai Yuko , Kobayashi Masaaki , Yamasaki Katsuyoshi
Published: June 2006

Fluorescence in the 200—600 nm range from excited fragments produced by collision of He(23S) with SnCl4 and Sn(CH3)4 has been studied in the relative collision energy of 135—210 meV. Emission cross sections for Sn I atomic resonance lines from SnCl4 slightly decrease with increasing collision energy. This originates from the fact that the effective potential between He(23S) and SnCl4 is slightly attractive. The branching ratio of Sn I states observed from SnCl4 is consistent with a simple dissociation model assuming equipartition of the available energy. These results are compatible with the harpoon mechanism as an initial step for formation of Sn I from SnCl4. On the other hand, the effective potential between He(23S) and Sn(CH3)4 is found to be repulsive, and the branching ratio of Sn I is increased to much more than that estimated from the statistical model. Excited Sn I states seem to be produced directly from Sn(CH3)4 by an excitation transfer mechanism via superexcited states, which mainly decay by Penning ionization.
Organic Radicals Exhibiting Intermolecular Ferromagnetic Interactions with High Probability: 4-Arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls and Related Compounds
Authors: Togashi Kensuke , Imachi Ron , Tomioka Katsuyuki , Tsuboi Hidenori , Ishida Takayuki , Nogami Takashi , Takeda Naoya , Ishikawa Masayasu
Published: June 2006

A series of 4-arylmethyleneamino-2,2,6,6-tetramethylpiperidin-1-yloxyls (4-arylmethyleneamino-TEMPO) and related compounds were synthesized, and their magnetic susceptibilities were measured by a SQUID magnetometer in the temperature range of 1.8—100 K. Of 165 radicals investigated, 52 kinds of radicals exhibited intermolecular ferromagnetic interactions. These were confirmed by the increase of effective magnetic moments in low-temperature regions. Positive Weiss temperatures (θ), ranging from +0.03 to +0.75 K, were found for these materials. Over 100 kinds of radicals exhibited antiferromagnetic interactions with θ ranging from −0.01 to −24 K. The surprisingly high probability of finding organic radicals with intermolecular ferromagnetic interaction may be understood by the characteristic molecular arrangements in the crystals. An oxygen atom of an NO radical site of a piperidin-1-yloxyl moiety is apt to locate near methyl- and/or methylene-hydrogens of β-positions of the adjacent molecules, and the resultant spin polarization gives rise to parallel spin alignments of nearest NO sites in the crystals. 4-(4-Iodophenylmethyleneamino)-TEMPO exhibited a bulk ferromagnetic transition at 0.4 K. Six radicals exhibited metamagnetic transitions at magnetic fields lower than 200 Oe below 0.1 K.
Amorphous State of Vacuum-Deposited Benzene and Its Crystallization
Authors: Ishii Kikujiro , Nakayama Hideyuki , Yoshida Tomohiro , Usui Hiroyuki , Koyama Kei
Published: June 2006

The structure of benzene films that were vacuum-deposited on cold-metal substrates to be 5—20 μm in thickness was studied with Raman spectroscopy and X-ray diffraction. Films deposited below 30 K were amorphous. They crystallized when the temperature was raised to about 60 K. If the substrate temperature at sample deposition was set above 45 K, films including crystalline particles were obtained. Structural relaxation in the amorphous state did not take place in an appreciable manner before the crystallization. Only an increase in intramolecular Raman-band intensities was observed during the relaxation in the amorphous state. Such behavior of amorphous benzene is compared with that of amorphous states of other simple organic compounds. The above crystallization temperature is discussed in relation to the previously estimated glass-transition temperature of benzene by referring to NMR data.
m
j
-Resolved Doppler Spectroscopy of Cs(6p2P3/2,m
j) Atoms Predissociated from a Single Level Cs2D1Σu+ (v = 46, J = 54)
Authors: Matsubara Kensuke , Tajima Yumi , Baba Masaaki , Kawai Jun , Katô Hajime
Published: June 2006

In a plane perpendicular to a magnetic field a collimated cesium beam was crossed at right angles by a pump laser beam. Cs2 molecules were excited to the D1Σu+ (v = 46, J = 54) level, which predissociated selectively to Cs(6s2S1/2) + Cs(6p2P3/2) atoms. The mj-resolved excitation spectra of the Cs(8s2S1/2,m′j ← 6p2P3/2,mj) transitions at a magnetic field of 1.91 kG were measured using a probe laser beam propagated either along the magnetic field or along the pump beam. The population of Cs(6p2P3/2,mj) atoms was found to be in the ratio 77 : 136 : 100 : 46 for mj = 3/2, 1/2, −1/2, and −3/2 based on an analysis of the line intensities. From the line shapes of the excitation spectra, Cs(6p2P3/2,±1/2) atoms were found to recoil predominantly parallel to the magnetic field H, and Cs(6p2P3/2,±3/2) atoms were found to recoil predominantly perpendicular to H.
Extraction Behavior of Silver Ion with Open-Chain S,S′-α,ω-Alkanediyl O,O′-Bis[2-(ethylthio)ethyl]dithiocarbonates
Authors: Mendoza Concepcion S , Kamata Satsuo
Published: June 2006

The S,S′-α,ω-alkanediyl O,O′-bis[2-(ethylthio)ethyl]dithiocarbonates, which are easily accessible by synthesis, have been used in solvent extraction studies of precious metal ions. Taking S,S′-1,3-propanediyl O,O′-bis[2-(ethylthio)ethyl]dithiocarbonate (PbETEdTC) as the representative of this group, the compound appears to have promising efficiency for the extraction of silver from perchlorate media, where the silver ion forms a 1 : 1 extractable complex with PbETEdTC. A quantitative back-extraction process from the organic phase is possible with 5 M HCl. From extraction studies, PbETEdTC proved to be a good extractant for silver in a perchlorate medium. The important role played by structural modifications of the bis(dithiocarbonate) molecule is evidenced by the differences in the silver extractabilities and silver-ligand stoichiometries.
Reduction and Oxidation Processes of Blue Copper Proteins, Azurin, Pseudoazurin, Umecyanin, Stellacyanin, Plantacyanin, and Plastocyanin Approached by Cyclic and Potential Step Voltammetries
Authors: Sakurai Takeshi , Nose Fumitaka , Fujiki Takayuki , Suzuki Shinnichiro
Published: June 2006

Direct electrochemistry of a series of blue copper proteins: azurin, pseudoazurin, umecyanin, stellacyanin, plantacyanin, and plastocyanin has been performed at a gold electrode modified with di-4-pyridyl disulfide and/or at a bare glassy carbon electrode. Well-resolved cyclic voltammograms with peak separation, ΔEp = 55—100 mV were obtained, allowing the facile determination of the redox potential of blue copper proteins. Protein molecules associate with the electrode surface through both electrostatic and hydrophobic interactions, of which the predominant one differs according to the combination of protein and electrode. Double-step voltammetry showed that redox processes of blue copper proteins depend profoundly on the translocation of the molecules (diffusion and/or change of orientation) at the electrode surface. The heterogeneous rate constants at pH 6.0 and 25 °C for both reduction and oxidation processes were independently determined to be the order of 10−3 to 10−4 cm s−1 by single-step voltammetry and were compared with those determined by cyclic voltammetry. Further, activation parameters for redox processes of some blue copper proteins have been determined from temperature dependence studies. The reaction pathway of blue copper proteins was discussed.
Crystal Structure of the Pentamolybdate Complex Coordinated by Adenosine-5′-monophosphoric Acid
Authors: Inoue Miyao , Yamase Toshihiro
Published: June 2006

Na2[(Hamp)2Mo5O15]·6H2O (where amp is adenosine-5′-monophosphate) has been crystallized by acidifying a solution containing Na2MoO4·2H2O and adenosine-5′-monophosphoric acid (AMP = H2amp) to pH 3—4. A single-crystal X-ray structural analysis of a colorless crystal of Na2[(Hamp)2Mo5O15]·6H2O [space group P3121, a = 27.494(2), c = 10.165(1) Å, V = 6654.5(9) Å3, Z = 3, R = 0.086, and Rw = 0.073 for 1087 independent data with I < 3σ(I)] showed that the anion is coordinated by two amp-phosphate-O atoms. [(Hamp)2Mo5O15]2− is isostructural with [(OPO3)2Mo5O15]6−, in which two PO4 tetrahedra span either side of a ring of edge- and corner-linked MoO6 octahedra. Two [(Hamp)2Mo5O15]2− anions are connected with ionic bondings of the Oanion–Na–Owater–Na–Oanion linkage, to be oriented parallel to the c-axis. The adenine-base ring of the amp ligand is stacked by that of the neighboring anion at a distance of 3.4 Å along the c-axis. The 13C and 31P NMR spectra of a solution containing Na2MoO4·2H2O and AMP at different pH levels indicate the formation of the pentamolybdate complex at pH > 6.
Photolysis of Cobalt(III) Complexes Containing Sulfinate-S Ligands. Formation of Organic Peroxide Complexes through Desulfurization
Authors: Kojima Masaaki , Akhter Farooque MD , Nakajima Kiyohiko , Yoshikawa Yuzo
Published: June 2006

The photolysis of trans(t-N,S)-[Co{S(O)2CH(CH3)COO-S,O}(tren)]+ (t-N = tertiary amine nitrogen; tren = tris(2-aminoethyl)amine) with visible light yielded three complexes: pink, red-1, and red-2. The molecular structure of the pink complex tetraphenylborate was determined by the X-ray method to be trans(t-N,O(C))-[Co{OOCH(CH3)COO-O,O}(tren)][B(C6H5)4]·CH3OH·H2O (O(C) = oxygen of carboxylate group); irradiation induced desulfurization and yielded an organic peroxide complex. Crystal data: C34H48BCoN4O6, FW 678.52, triclinic, (No. 2), a = 19.583(3), b = 19.838(4), c = 9.996(1) Å, α = 103.60(1), β = 102.13(1), γ = 70.29(1)°, V = 3517(1) Å3, Z = 4, Dx = 1.29 g cm−3, μ = 0.533 mm−1 for Mo Kα radiation (λ = 0.71073 Å). The red-2 complex is thermally stable, while the red-1 one thermally reverts to the starting complex. The red-1 and red-2 complexes were assigned as linkage isomerized sulfinato-O complexes, trans(t-N,O(S))- and cis(t-N,O(S))-[Co{OS(O)CH(CH3)COO-O,O}(tren)]+ (O(S) = oxygen of sulfinate group), respectively, on the basis of the UV-vis and IR spectra and thermal stability. The irradiation of trans(t-N,S)-[Co{S(O)2CH2COO-S,O}(tren)]+ and [Co{S(O)2CH(CH3)COO-S,O}(en)2]+ also yielded both peroxide complexes and linkage isomerized sulfinato-O complexes.
Difference in the Kinetic Behavior on the AC-Catalyzed Decomposition (AC = Activated Carbon) of [Co(C2O4)3]3− and [Co(NH3)5(H2O)]3+, and on the AC-Catalyzed Ligand-Substitution Reactions between Each Complex and EDTA in an Aqueous Solution
Authors: Kimura Masaru , Miyamoto Ikuko , Fujita Syouko , Kumashiro Sachiko
Published: June 2006

The decomposition reaction of tris(oxalato)cobaltate(III) ion, [Co(ox)3]3−, occurred to produce cobalt(II) ion and carbon dioxide by adding activated carbon (AC) in an aqueous solution, taking a rate law of the first order with respect to the concentrations of not only [Co(ox)3]3−, but also AC. The rate of decomposition was independent of the pH values over a wide range of 2—8. On the contrary, the pentaammineaquacobalt(III) ion, [Co(NH3)5(H2O)]3+, did not decompose at all under the same conditions. When the same reaction mixtures as mentioned above contained ethylenediaminetetraacetate (EDTA), which denotes all forms of H4edta, H3edta−, H2edta2− etc., both of the complexes, [Co(ox)3]3− and [Co(NH3)5(H2O)]3+, converted quantitatively to [Co(edta)]−, taking a first-order rate law with respect to the concentration of either [Co(ox)3]3− or [Co(NH3)5(H2O)]3+. The rate was proportional to the added AC amounts, and was extremely inhibited by adding 8-quinolinol (oxine), methanol, or ethanol. The pH dependence on the reaction rates was extremely different in [Co(ox)3]3− and [Co(NH3)5(H2O)]3+; the rate in the former case was independent of the pH in the 2—5, and decreased at less than 2 and at larger than 5; that in the latter case was maximum at around pH 6, and decreased accordingly to pH’s less or larger than ca. 6, and became almost zero at pH 2. Such differences in the kinetic behavior are discussed.
Heptacoordinate Vanadium(III) Complexes Containing a Didentate Sulfate Ligand. X-Ray Structures of [V2(SO4)3{N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine}2] and [V(SO4){N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-ethanediamine}]+ and Their Solution Properties
Authors: Kanamori Kan , Kameda Eiji , Okamoto Ken-ichi
Published: June 2006

Several vanadium(III) complexes with a tetradentate N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen) or a hexadentate N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) ligand were prepared and characterized by UV-vis and Raman spectroscopy. Of these complexes, the structures of two vanadium(III) complexes with a didentate sulfate were determined by X-ray crystallography. [V2(SO4)3(bispicen)2] crystallizes in the monoclinic space group C2/c with a = 25.083(7), b = 24.236(5), c = 15.708(5) Å, β = 114.96(2)°, Z = 8, and R = 0.087. The complex containing the [V(SO4)(tpen)]+ cation crystallizes in the orthorhombic space group Aba2 with a = 20.1836(8), b = 19.793(1), c = 15.6107(7) Å, Z = 8, and R = 0.069. Both complexes adopt a heptacoordinate pentagonal bipyramidal structure in which the didentate sulfate is situated in the pentagonal plane. The heptacoordinate structure of the tpen-SO42− complex is stable in an aqueous solution, whereas the bispicen-SO42− complex is easily aquated to yield a hexacoordinate oxo-bridged dinuclear species.
Cytosine-Carboxylate Interactions: Crystal Structure of Cytosinium Hydrogen Maleate
Authors: Balasubramanian Thailampillai , Muthiah Packianathan Thomas , Robinson Ward Thomas
Published: June 2006

Interactions of carboxylate groups of proteins with nucleobases are some of the important stereochemical patterns involved in protein-nucleic acid recognition. The title compound serves as a model for such interactions, involving constrained carboxyl groups. Space group: , a = 7.424(1), b = 7.952(2), c = 8.248(2) Å, α = 106.61(3)°, β = 94.97(3)°, and γ = 91.26(3)°. The structure was solved by direct methods. Cytosine is protonated at N(3). The usual fork-like interaction of the carboxylate groups with cytosine is absent and a network of hydrogen bonding involving the cytosine moiety and hydrogen maleate is present. The interaction of carboxylate group and the amino group of cytosine observed here is reminiscent of the carboxylate–GC pair interaction observed in a protein–DNA complex (DNA repressor of phage 434 complex). There is also a C(6)–H···O (of maleate) interaction.
Synthesis of Ring-Fluorinated Porphyrins and Reconstitutional Myoglobins with Their Iron Complexes
Authors: Suzuki Akihiro , Tomizawa Tadashi , Hayashi Takashi , Mizutani Tadashi , Ogoshi Hisanobu
Published: June 2006

The total syntheses of monofluoroporphyrin derivatives from monofluoropyrroles and the reconstitution of synthetic heme into sperm-whale myoglobin are described. The heme orientation in a cavity of the protein was determined by 1H and 19F NMR studies. It is noted that a fluoro substituent was found to be a useful probe for studying the heme-protein interaction.
1H NMR Study of the Heme Molecular Structure in Sperm Whale Met-Aquo and Met-Imidazole Myoglobins
Authors: Yamamoto Yasuhiko
Published: June 2006

The resolved heme peripheral side-chain proton resonances of sperm whale met-aquo myoglobin have been connected to the corresponding resonances in met-imidazole myoglobin by the magnetization transfer through the external ligand exchange. From the signal assignments in met-imidazole myoglobin, which have been independently obtained using conventional two-dimensional NMR and one-dimensional nuclear Overhauser effect difference spectroscopies, the observed connectivities unambiguously identified the corresponding resonances of met-aquo myoglobin. The calculation of the pseudo-contact shifts for the resonances of met-aquo myoglobin from the reported zero-field splitting constant [Y. -H. Kao, and J. T. J. Lecomte, J. Am. Chem. Soc., 115, 9754—9762 (1993) and J. Am. Chem. Soc., 116, 6991 (1994)] together with the diamagnetic shifts observed for carbonmonoxy myoglobin [B. C. Mabbutt, and P. E. Wright, Biochim. Biophys. Acta, 832, 175—185 (1985)], allowed the extraction of the contact shifts from their paramagnetic shifts. The heme peripheral propionate conformation in met-aquo myoglobin has been determined from the analysis of the contact shifts for the CαH2 proton resonances. The obtained conformations agreed well with those described by the X-ray study [T. Takano, J. Mol. Biol., 110, 537—568 (1977)]. The thermal spin equilibrium in met-imidazole myoglobin has been analyzed using the mean heme methyl proton shift as an indicator for the spin state of the protein. The equilibrium populations determined from the analysis of the NMR shift data did not agree with those determined from the magnetic susceptibility measurements [T. Iizuka, and M. Kotani, Biochim. Biophys. Acta,181, 275—286 (1969)], indicating that the heme methyl proton shifts cannot be used as quantitative probe for the thermal spin equilibrium in met-imidazole myoglobin. This would be attributed to the temperature-dependent delocalization of the unpaired electron density from the heme iron to the porphyrin π system and the axial ligands due to the perturbation on the coordination structure around the iron, exerted by the steric repulsion between the bound imidazole and the imidazole side-chain of the distal His residue, as revealed by the X-ray study [C. Lionetti, M. G. Guanziroli, F. Frigerio, P. Ascenzi, and M. Bolognesi, J. Mol. Biol., 217, 409—412 (1991)].
Preparation of Branched Oligogermynes and Their Micropatterning by Ultraviolet Irradiation
Authors: Mochida Kunio , Ohkawa Tomoharu , Kawata Hiroki , Watanabe Akira , Ito Osamu , Matsuda Minoru
Published: June 2006

Branced oligogermynes were prepared both by Wurtz coupling reactions of alkyl- and phenyl-trichlorogermanes with sodium metal and by the reaction of alkyltrichlorogermanes using of samarium(II) diiodide. Upon ultraviolet irradiation of oligo(phenylgermyne) in air, the germanium–germanium bond in an oligo(phenylgermyne) film changed into a digermoxane chain. The laser flash photolysis of the oligo(phenylgermyne) film showed the formation of a germyl radical as a reactive intermediate during photodegradation. The formation of germanium carbide (Ge–C) and germanium dioxide (GeO2) was observed upon a heat treatment of unirradiated and irradiated oligo(phenylgermyne) films, respectively. A relatively high-resolution GeC/GeO2 micropatterning was obtained by combining the photochemical and thermal properties of branced oligogermynes.
Chemical Aspects Concerning the Friction and Abrasion of Rubber
Authors: Furukawa Junji
Published: June 2006

The frictional force (fF) is proportional to the normal force; for rubber it is corrected by a factor involving the pressure and elasticity due to a change of the contact surface. During friction induced by a slider, fF fluctuates, which is conventionally explained by a stick-slip mechanics. However, the effect of the temperature and velocity on fF as well as the frequencies of vibration and pattern abrasion producing worn products of various size, are not studied using mechanical model.

On the contrary, the author discusses here the chemical mechanism of stick-peeling based on a model involving pseudo crosslinks of multi-sizes. The frictional force (fF) is taken to be equal to the peeling force (fP), For adhesives, fP is proportional to the adhesion force (fA) affected by such rheological factors as the peeling velocity (v), the thickness (h), and the relaxation time (τ); fP = fA(τvh)0.5. Here, fA is proportional to the fraction of the pseudo link (ν) and the wetting energy (W) divided by the peeling distance, which is almost equal to the bond length (l) and fA is expressed as fA = (ν/N)2/3(W/l). ν is the number of links formed on the surface of the rubber, and is varied with the sizes of the links 4 (link A) and 16 (link B) and their relaxation times of 10−3.4 s (τA) and 10−1 s (τB).

Also, for the frictional force (fF) the same equation is obtained when v and h are taken to be the velocity of the slider and the thickness of the rubber layer deformed by the slider, respectively. Friction produces two kinds of vibrations by the dissociation of links A and B; their frequencies are given by the reciprocal of τA and τB, respectively.

Abrasion is caused by the scission of rubber chains connected with links A and B in the peeling process. The former abrasion yields powdery wear products by crazing, whereas in the latter the scission of chemical bonds of the energy (D) develops to give crest-shape tearing i.e. so-called pattern abrasion. The sizes of wear products are proportional to the relaxation distances corresponding to τA and τB. The resistance to abrasion of rubber is expressed by a ratio of the force at a break (fB) to fF, fB/fF = (ν/N)1/3(D/Wl2)(vτh)−0.5. Carbon black improves the abrasion resistance due to its reinforcing ability, and the resistance is enhanced by increasing the content, specific surface area and adhesion ability of carbon black. Their optimum values were also estimated theoretically.
A previously unidentified activity of yeast and mouse RNA:pseudouridine synthases 1 (Pus1p) on tRNAs
Authors: Behm-Ansmant Isabelle , Massenet Séverine , Immel FranÇoise , Patton Jeffrey R. , Motorin Yuri , Branlant Christiane
Published: June 2006

Mouse pseudouridine synthase 1 (mPus1p) was the first vertebrate RNA:pseudouridine synthase that was cloned and characterized biochemically. The mPus1p was previously found to catalyze Ψ formation at positions 27, 28, 34, and 36 in in vitro produced yeast and human tRNAs. On the other hand, the homologousSaccharomyces cerevisiaescPus1p protein was shown to modify seven uridine residues in tRNAs (26, 27, 28, 34, 36, 65, and 67) and U44 in U2 snRNA. In this work, we expressed mPus1p in yeast cells lacking scPus1p and studied modification of U2 snRNA and several yeast tRNAs. Our data showed that, in these in vivo conditions, the mouse enzyme efficiently modifies yeast U2 snRNA at position 44 and tRNAs at positions 27, 28, 34, and 36. However, a tRNA:Ψ26-synthase activity of mPus1p was not observed. Furthermore, we found that both scPus1p and mPus1p, in vivo and in vitro, have a previously unidentified activity at position 1 in cytoplasmic tRNAArg(ACG). This modification can take place in mature tRNA, as well as in pre-tRNAs with 5′ and/or 3′ extensions. Thus, we identified the protein carrying one of the last missing yeast tRNA:Ψ synthase activities. In addition, our results reveal an additional activity of mPus1p at position 30 in tRNA that scPus1p does not possess.
Professional Negligence: When Practice Goes Wrong
Authors: Harris Curtis E , Richards Warren , Fincham Jack E
Published: June 2006

Objective:

TO review the practice and legal principles of negligence law.

Case Summary:

An illustrative, fictional case is presented, based in part on facts gleaned from actual case law. A respected pharmacist, faced with the financial loss of his business, decided to engage in 2 creative but unethical schemes to increase his profit margin. In doing so, he violated federal Medicare law and placed a number of the patients who used his services at significant risk for medical complications.

Discussion:

Negligence law has evolved over the past 30 years in a manner that significantly increases the liability of the practicing pharmacist for both ordinary negligence actions and criminal negligence actions. In addition, the past decade has seen the expansion of Medicare Fraud and Abuse law such that it now represents an increasingly high risk area for every medical service provider, including the pharmacist.

Conclusions:

Professional practice in the US is highly regulated, governed by both case law and statutory law. Every practicing pharmacist should be aware of the law that governs his or her behavior to avoid both civil and criminal liability.
Pharmacist Critique Was Ill-Informed
Authors: Karpa Kelly Dowhower
Published: June 2006

Pharmacists’ ability to exercise “professional right of conscience” in dispensing emergency contraception, as well as the professionalism of pharmacists, has fallen under attack recently by the media, by state governments, and even by other healthcare professionals in published commentaries. This editorial discusses the controversy surrounding emergency contraceptives, the right of pharmacists to refuse to fill prescriptions that they consider morally objectionable, and the responsibility of pharmacists to provide medications in a timely and professional manner. The professionalism of pharmacy is also examined in light of the expanded scope of practice in which pharmacists increasingly find themselves practicing.
Interpersonal Precipitants and Suicide Attempts in Borderline Personality Disorder
Authors: Brodsky Beth S. , Groves Shelly A. , Oquendo Maria A. , Mann J. John , Stanley Barbara
Published: June 2006

Borderline personality disorder (BPD) is often characterized by multiple low lethality suicide attempts triggered by seemingly minor incidents, and less commonly by high lethality attempts that are attributed to impulsiveness or comorbid major depression. The relationships among life events, impulsiveness, and type of suicidal behavior has hardly been studied in BPD and mood disorders. This study compared depressed attempters with and without BPD to identify specific suicide precipitants and risk factors in BPD and their relationship to severity of suicidal behavior. Attempters with comorbid BPD and major depressive disorder (MDD) had a higher number of lifetime suicide attempts; made their first attempt at a younger age; reported more interpersonal triggers; and had higher levels of lifetime aggression, hostility, and impulsivity, compared with attempters with major depression only. Environmental triggers of attempts in BPD are more likely to be interpersonal stressors. Lethality of attempts in BPD plus MDD is equal to that in MDD only, indicating that the seriousness of precipitants is unrelated to the lethality of the suicidal behavior. The differences between groups suggest that risk assessment and treatment should target both depression and personality disorder in those with combined illness.
Predictors of Suicidal Ideation Among “At Risk” Cocaine‐Using African American Women
Authors: Klein Hugh , Elifson Kirk W. , Sterk Claire E.
Published: June 2006

The focus of this study was to identify factors that differentiate women drug abusers who had experienced suicidal ideation from those who did not. Face‐to‐face interviews were conducted with 221 cocaine‐using women in Atlanta, GA, 88 (39.8%) of whom reported thinking about committing suicide at least once during the 90 days prior to interview and 133 (60.2%) of whom did not. Multivariate logistic regression was used to identify predictors of suicidal ideation, and post hoc goodness‐of‐fit tests were conducted to assess the robustness of final models derived. Model 1 excluded all psychosocial functioning measures and Model 2 included these items. Both models showed that suicidal ideation was more common among women who were unemployed, had been abused sexually, engaged in sexual relations to cope with stresses, or had less helpful relatives. In addition, Model 1 revealed a heightened risk for women experiencing financial problems and those who had a previous mental health diagnosis, whereas Model 2 showed an elevated risk among women who experienced anxiety and those who had lower levels of self‐esteem. These findings suggest the need for prevention and intervention programs that target at‐risk women, and for such programs to include an emphasis on suicidal ideation in addition to focusing on risk factors that are addressed more commonly.
Panic-Prone State Induced in Rats with GABA Dysfunction in the Dorsomedial Hypothalamus Is Mediated by NMDA Receptors
Authors: Johnson Philip L. , Shekhar Anantha
Published: June 2006

Rats with chronic inhibition of GABA synthesis and consequently enhanced glutamatergic excitation in the dorsomedial hypothalamus (DMH) develop panic-like responses, defined as tachycardia, tachypnea, hypertension, and increased anxiety as measured by a social interaction (SI) test, after intravenous sodium lactate infusions, a phenomenon similar to patients with panic disorder. Therefore, the present studies tested the role of the postsynaptic NMDA and AMPA type glutamatergic receptors in the lactate-induced panic-like responses in these rats. Rats were fit with femoral arterial and venous catheters and Alzet pumps [filled with the GABA synthesis inhibitorl-allylglycine (l-AG; 3.5 nmol/0.5 μl per hour) or its inactive isomerd-AG] into the DMH. After 4–5 d of recovery only those rats withl-AG pumps exhibited panic-like responses to lactate infusions. Using double immunocytochemistry, we found that rats exhibiting panic-like responses (e.g.,l-AG plus lactate) had increased c-Fos immunoreactivity in DMH neurons expressing the NMDA receptor 1 (NR1) subunit, but not those expressing the glutamate receptor 2 and 3 subunits of the AMPA receptors. To confirm this pharmacologically, we tested another group of rats implanted withl-AG pumps with intravenous lactate infusions preceded by injections of either NMDA [aminophosphonopentanoic acid (AP-5) or (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine maleate (MK-801)] or non-NMDA [CNQX or 4-(8-methyl-9H-1,3-dioxolo[4,5-h][2,3]benzodazepin-5-yl)-benzenamine dihydrochloride (GYKI52466)] antagonists into the DMH. Injections of NMDA, but not non-NMDA, antagonists into the DMH resulted in dose-dependent blockade of the tachycardia, tachypnea, hypertension, and SI responses after lactate infusions. These results suggest that NMDA, and not non-NMDA, type glutamate receptors regulate lactate-induced panic-like responses in rats with GABA dysfunction in the DMH.
Heparan Sulphation Patterns Generated by Specific Heparan Sulfotransferase Enzymes Direct Distinct Aspects of Retinal Axon Guidance at the Optic Chiasm
Authors: Pratt Thomas , Conway Christopher D. , Tian Natasha M. M.-L. , Price David J. , Mason John O.
Published: June 2006

Retinal ganglion cell (RGC) axons from each eye execute a series of maneuvers as they converge on the ventral surface of the brain at the optic chiasm for sorting into the optic tracts. Heparan sulfate proteoglycans (HSPGs) are extracellular glycoproteins involved in cell-surface interactions. HSPGs exhibit massive structural diversity, conferred partly by extensive post-translational modification including differential sulfation. Here we examine the roles of HSPG sulfation in RGC axon guidance at the chiasm. We identified different axon navigation phenotypes in twoheparan sulfate sulfotransferase(Hst) mutant embryos,Hs2st−/−andHs6st1−/−, each lacking an enzyme that catalyzes a particular HSPG modification.Hs2st−/−embryos display axon disorganization at the chiasm.Hs6st1−/−embryos exhibit prolific inter-retinal innervation. We show that RGCs expressHs2standHs6st1and that navigation errors made by their axons coincide with regions of highHs2stand/orHs6st1expression at the chiasm. Slit proteins are expressed at particular locations in the retina and around the chiasm and are normally deployed to prevent axons entering inappropriate territories. We show thatHs2stand/orHs6st1expression coincides with Slit expression domains at locations where RGC axons make navigation errors inHs2st−/−andHs6st1−/−mutants and thatHs6st1−/−RGC axons are less sensitive to Slit2 repulsion than their wild-type counterpartsin vitro. We suggest that (1) Hs2st and Hs6st1 are each deployed to generate distinct patterns of heparan sulfation on RGCs and at the optic chiasm and (2) this differential sulfation directs retinal axons through the chiasm, at least in part by modulating the response of the navigating growth cone to Slit proteins.
Long-Term Depression at the Mossy Fiber–Deep Cerebellar Nucleus Synapse
Authors: Zhang Wei , Linden David J.
Published: June 2006

Several lines of evidence have indicated that the deep cerebellar nuclei (DCN) are a site of memory storage for certain forms of motor learning, most notably associative eyelid conditioning. In particular, these experiments, together with network models, have implicated the excitatory glutamatergic synapse between mossy fibers and DCN neurons in this memory trace. However, to date, evidence for persistent use-dependent change in the strength of this synapse has been almost entirely absent. Here, we report that high-frequency burst stimulation of mossy fibers, either alone or paired with postsynaptic depolarization, gives rise to long-term depression (LTD) of the mossy fiber–DCN synapse. This form of LTD is not associated with changes in the paired-pulse ratio and is blocked by loading with a postsynaptic Ca2+chelator but not by bath application of an NMDA receptor antagonist. Mossy fiber–DCN LTD requires activation of a group I metabotropic glutamate receptor (mGluR) and protein translation. Unlike mGluR/translation-dependent LTD in other brain regions, this form of LTD requires mGluR1 and is mGluR5 independent.
The Tip-Link Antigen, a Protein Associated with the Transduction Complex of Sensory Hair Cells, Is Protocadherin-15
Authors: Ahmed Zubair M. , Goodyear Richard , Riazuddin Saima , Lagziel Ayala , Legan P. Kevin , Behra Martine , Burgess Shawn M. , Lilley Kathryn S. , Wilcox Edward R. , Riazuddin Sheikh , Griffith Andrew J. , Frolenkov Gregory I. , Belyantseva Inna A. , Richardson Guy P. , Friedman Thomas B.
Published: June 2006

Sound and acceleration are detected by hair bundles, mechanosensory structures located at the apical pole of hair cells in the inner ear. The different elements of the hair bundle, the stereocilia and a kinocilium, are interconnected by a variety of link types. One of these links, the tip link, connects the top of a shorter stereocilium with the lateral membrane of an adjacent taller stereocilium and may gate the mechanotransducer channel of the hair cell. Mass spectrometric and Western blot analyses identify the tip-link antigen, a hitherto unidentified antigen specifically associated with the tip and kinocilial links of sensory hair bundles in the inner ear and the ciliary calyx of photoreceptors in the eye, as an avian ortholog of human protocadherin-15, a product of the gene for the deaf/blindness Usher syndrome type 1F/DFNB23locus. Multiple protocadherin-15 transcripts are shown to be expressed in the mouse inner ear, and these define four major isoform classes, two with entirely novel, previously unidentified cytoplasmic domains. Antibodies to the three cytoplasmic domain-containing isoform classes reveal that each has a different spatiotemporal expression pattern in the developing and mature inner ear. Two isoforms are distributed in a manner compatible for association with the tip-link complex. An isoform located at the tips of stereocilia is sensitive to calcium chelation and proteolysis with subtilisin and reappears at the tips of stereocilia as transduction recovers after the removal of calcium chelators. Protocadherin-15 is therefore associated with the tip-link complex and may be an integral component of this structure and/or required for its formation.
Lateral Diffusion Drives Constitutive Exchange of AMPA Receptors at Dendritic Spines and Is Regulated by Spine Morphology
Authors: Ashby Michael C. , Maier Susie R. , Nishimune Atsushi , Henley Jeremy M.
Published: June 2006

Synapse specificity is a basic feature of synaptic plasticity, but it remains unclear how synapse-specific signaling is achieved if postsynaptic membrane proteins can diffuse laterally between synapses. We monitored movements of AMPA receptors (AMPARs) on the surface of mature neurons to investigate the role of lateral diffusion in constitutive AMPAR trafficking and to assess the influence of membrane architecture on the surface distribution of synaptic proteins. Our data show that lateral diffusion is responsible for the continual exchange of a substantial pool of AMPARs at the spine surface. Furthermore, we found that a general characteristic of membrane proteins is that their movement into and out of spines is slow compared with that in nonspiny membrane. This shows that lateral diffusion is dependent on spine morphology and is restricted at the spine neck. These results demonstrate the importance of lateral diffusion in trafficking of AMPAR protein population and provide new insight into how spine structure can maintain synapse specificity by compartmentalizing lateral diffusion and therefore increasing the residence time of membrane proteins near individual synapses.
Temperature-Dependent Shift of Balance among the Components of Short-Term Plasticity in Hippocampal Synapses
Authors: Klyachko Vitaly A. , Stevens Charles F.
Published: June 2006

Studies of short-term plasticity (STP) in the hippocampus, performed mostly at room temperature, have shown that small central synapses rapidly depress in response to high-frequency stimulation. This decrease in synaptic strength with synapse use places constraints on the use of STP as a dynamic filter for processing of natural high-frequency input. Here we report that, because of a strong but differential temperature dependence of STP components, the properties of STP in excitatory hippocampal synapses change dramatically with temperature. By separating the contributions of various STP processes during spike trains at different temperatures, we found a shift from dominating depression at 23°C to prevailing facilitation and augmentation at 33−38°C. This shift of balance among STP components resulted from a large increase in amplitudes of facilitation and augmentation (Q10∼2.6 and ∼5.1, respectively) and little change in the amplitude of depression (Q10∼1.1) with temperature. These changes were accompanied by the accelerated decay of all three processes (Q10= 3.2, 6.6, and 2.1, respectively). The balance of STP components achieved at higher temperatures greatly improved the maintenance of synaptic strength during prolonged synaptic use and had a strong effect on the processing of natural spike trains: a variable mixture of facilitated and depressed responses at 23°C changed into a significantly more reproducible and depression-free filtering pattern at 33−38°C. This filtering pattern was highly conserved among cells, slices, and animals, and under various physiological conditions, arguing for its physiological significance. Therefore, the fine balance among STP components, achieved only at near body temperatures, is required for the robust function of STP as a dynamic filter during natural stimulation.
GABA Transporters Regulate a Standing GABACReceptor-Mediated Current at a Retinal Presynaptic Terminal
Authors: Hull Court , Li Geng-Lin , von Gersdorff Henrique
Published: June 2006

At the axon terminal of goldfish retinal bipolar cells, GABACreceptors have been shown to mediate inhibitory reciprocal synaptic currents. Here, we demonstrate a novel standing GABAergic current mediated exclusively by GABACreceptors. Selective inhibition of GAT-1 GABA transporters on amacrine cells increases this tonic current and reveals a specific functional coupling between GAT-1 transporters and GABACreceptors. We propose that this GABACreceptor-mediated standing current serves to regulate synaptic gain by shunting depolarizing potentials that can produce Ca2+-dependent action potentials at the bipolar cell terminal. Furthermore, we find that the amount of GABACreceptor-mediated reciprocal feedback between bipolar cell terminals and amacrine cells is greatly increased when GAT-1 transporters are specifically blocked by NO-711 (1-[2-[[(diphenylmethylene)imino]oxy]ethyl]-1,2,5,6-tetrahydro-3-pyridinecarboxylic acid hydrochloride). The involvement of GAT-1 transporters in regulating this standing (or tonic) GABACcurrent implicates them in a novel role as major determinants of presynaptic excitability.
Ongoing Epileptiform Activity in the Post-Ischemic Hippocampus Is Associated with a Permanent Shift of the Excitatory–Inhibitory Synaptic Balance in CA3 Pyramidal Neurons
Authors: Epsztein Jérôme , Milh Mathieu , Id Bihi Rachid , Jorquera Isabel , Ben-Ari Yehezkel , Represa Alfonso , Crépel Valérie
Published: June 2006

Ischemic strokes are often associated with late-onset epilepsy, but the underlying mechanisms are poorly understood. In the hippocampus, which is one of the regions most sensitive to ischemic challenge, global ischemia induces a complete loss of CA1 pyramidal neurons, whereas the resistant CA3 pyramidal neurons display a long-term hyperexcitability several months after the insult. The mechanisms of this long-term hyperexcitability remain unknown despite its clinical implication. Using chronicin vivoEEG recordings andin vitrofield recordings in slices, we now report spontaneous interictal epileptiform discharges in the CA3 area of the hippocampus from post-ischemic rats several months after the insult. Whole-cell recordings from CA3 pyramidal neurons, revealed a permanent reduction in the frequency of spontaneous and miniature GABAergic IPSCs and a parallel increase in the frequency of spontaneous and miniature glutamatergic postsynaptic currents. Global ischemia also induced a dramatic loss of GABAergic interneurons and terminals together with an increase in glutamatergic terminals in the CA3 area of the hippocampus. Altogether, our results show a morpho-functional reorganization in the CA3 network several months after global ischemia, resulting in a net shift in the excitatory–inhibitory balance toward excitation that may constitute a substrate for the generation of epileptiform discharges in the post-ischemic hippocampus.