bluuebunny/crossref_metadata_2025 huggingface dataset:
Replacement of the Sox10 transcription factor by Sox8 reveals incomplete functional equivalence
Authors: Kellerer Susanne , Schreiner Silke , Stolt C. Claus , Scholz Stefanie , Bösl Michael R. , Wegner Michael
Published: June 2006

Sox8 and Sox10 are two closely related transcription factors of the Sox protein family with overlapping expression patterns during development. They are believed to perform very similar functions because several developmental processes, including enteric nervous system development and oligodendrocyte differentiation, are regulated by both Sox proteins. To analyze the extent of functional equivalence between the two Sox proteins, we employed targeted mutagenesis to replace Sox10 with Sox8 in the mouse. In mice that expressed Sox8 instead of Sox10, Sox10 deficiency was phenotypically rescued to different extents in affected tissues. Whereas development of glial cells and neurons in the sensory and sympathetic parts of the peripheral nervous system was almost normal when Sox10 was replaced by Sox8, melanocyte development was as defective as in Sox10-deficient mice. The ability of Sox8 to rescue the defects in enteric nervous system development and oligodendrocyte differentiation of Sox10-deficient mice was limited. We conclude that the extent of functional equivalence depends on the tissue and that, despite their relatedness, Sox8 and Sox10 have more unique functions than previously appreciated.
The function of growth/differentiation factor 11 (Gdf11) in rostrocaudal patterning of the developing spinal cord
Authors: Liu Jeh-Ping
Published: June 2006

Hoxc family transcription factors are expressed in different domains along the rostrocaudal (RC) axis of the developing spinal cord and they define RC identities of spinal neurons. Our previous study using an in vitro assay system demonstrated that Fgf and Gdf11 signals located around Hensen's node of chick embryos have the ability to induce profiled Hoxc protein expression. To investigate the function of Gdf11 in RC patterning of the spinal cord in vivo,we expressed Gdf11 in chick embryonic spinal cord by in ovo electroporation and found that ectopic expression of Gdf11 in the neural tissue causes a rostral displacement of Hoxc protein expression domains,accompanied by rostral shifts in the positions of motoneuron columns and pools. Moreover, ectopic expression of follistatin (Fst), an antagonist of Gdf11, has a converse effect and causes caudal displacement of Hox protein expression domains, as well as motoneuron columns and pools. Mouse mutants lacking Gdf11 function exhibit a similar caudal displacement of Hox expression domains, but the severity of phenotype increases towards the caudal end of the spinal cord, indicating that the function of Gdf11 is more important in the caudal spinal cord. We also provide evidence that Gdf11 induces Smad2 phosphorylation and activated Smad2 is able to induce caudal Hox gene expression. These results demonstrate that Gdf11 has an important function in determining Hox gene expression domains and RC identity in the caudal spinal cord.
Supramolecular Self-Assembly of Macrocycles, Catenanes, and Cages through Coordination of Pyridine-Based Ligands to Transition Metals
Authors: Fujita Makoto , Ogura Katsuyuki
Published: June 2006

Recent developments in the study of the transition-metal mediated supramolecular self-assembly are reviewed. Focus is on the self-assembly of macrocycles, catenanes, and cages from (en)Pd(NO3)2 (1) and pyridine-based bridging ligands. Coordination of linear 4,4′-bipyridine on the cis coordination site of palladium complex gives a macrocyclic square supramolecule, whereas macrocyclic dinuclear Pd(II) complexes self-assemble from 1 and flexible bridging ligands. Unprecedented formation of catenanes through rapid slippage of two preformed molecular rings can be achieved by exploiting the labile character of a Pd(II)-linked macrocycle: i.e., a macrocycle assembling from 1 and PyCH2C6H4CH2Py exists in rapid equilibrium with its catenated dimer and the equilibrium is strongly pushed toward the catenane (> 99 : 1) in a polar media. The combination of 1 with tridentate ligands gives three-dimensional cagelike hosts. A spherical M3L2 complex organizes from 1 and a flexible tridentate ligand only in the presence of specific guests providing a model for induced fit. On the other hand, a nanometer-sized hollow supramolecule self-assembles from four rigid tridentate ligands held together by six protected Pd complex 1.
Toward Dendritic Two-Dimensional Polycarbenes: Syntheses of ‘Starburst’-Type Nona- and Dodecadiazo Compounds and Magnetic Study of Their Photoproducts
Authors: Matsuda Kenji , Nakamura Nobuo , Inoue Katsuya , Koga Noboru , Iwamura Hiizu
Published: June 2006

‘Starburst’-type nona- and dodecadiazo compounds were designed and synthesized by using the cyclotrimerization of ethynyl ketones as a key step. Construction of the larger dodecadiazo compounds was facilitated by using a trimethylsilyl protecting group for an acetylenic moiety. The diazo compounds were photolyzed in MTHF solid solution at cryogenic temperatures and analyzed by means of Faraday magnetometry and ESR spectroscopy. From the field dependence of the magnetization, the nonacarbene, the photoproduct of nonadiazo compound, was evidenced to have a nonadecet (S = 9) ground state. This spin multiplicity is the highest value ever reported for purely organic materials. On the other hand, the spin multiplicity was low and antiferromagnetic interaction operated in the photoproduct of the dodecadiazo compound. This result was interpreted not in terms of the intermolecular antiferromagnetic interaction but of the intramolecular cross-linking between the carbene centers. In the ‘Starburst’-type polycarbenes with extended branching, the reactive carbene centers can become mutually too close to each other in space and so appear to recombine readily. This study showed one of the limitations of the extension of the carbene network by way of flexible ‘Starburst’-type structures.
Partial Molar Fluctuations in Aqueous 2-Butoxyethanol
Authors: Koga Yoshikata , Westh Peter
Published: June 2006

The normalized fluctuations were reformulated in a unified manner, keeping the number of molecules in each coarse grain fixed. The normalized fluctuations were evaluated for aqueous 2-butoxyethanol using the existing data of κT, Cp, αp, and Vm. The partial molar fluctuations of 2-butoxyethanol were then calculated. These quantities added some more evidences to the mixing schemes in aqueous 2-butoxyethanol conjectured earlier in this laboratory.
Fischer–Tropsch Synthesis with Supported Cobalt Catalyst. Promoting Effects of Lanthanum Oxide for Cobalt/Silica Catalyst
Authors: Adachi Michiaki , Yoshii Kiyotaka , Han Yi Zhuo , Fujimoto Kaoru
Published: June 2006

The promotional effects of metal oxides for a silica-supported cobalt catalyst were investigated by using X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Temperature Programmed Reaction (TPR), and Fourier Transform-Infrared Spectroscopy (FT-IR) techniques. The La-modified cobalt catalyst with 3% La loading which was prepared by simultaneous impregnation showed higher catalytic activity while keeping slightly higher selectivity of C2+ hydrocarbons. TPR, FT-IR, and TEM studies revealed that CO is adsorbed on the La-modified cobalt catalyst in a more active state compared to the monometallic cobalt catalyst, which was caused by the agglomeration of cobalt.
An Analysis of the CIDEP Mechanisms in the Hydrogen Abstraction Reactions of Excited Quinoxaline and Related Compounds
Authors: Ohara Keishi , Hirota Noboru
Published: June 2006

The Chemically Induced Dynamic Electron Polarization (CIDEP) mechanisms in the hydrogen abstraction reactions of excited azaaromatic compounds; quinoxaline, phenazine, and quinoline are investigated in detail. It is shown that several polarization mechanisms are involved and the observed CIDEP spectra vary strongly depending on various factors such as the concentration, the temperature, the delay time, and the excitation light intensity. The net emissive spin polarization is ascribed mainly to the radical–triplet pair mechanism (RTPM), which is strongly dependent on the concentrations of the radical and triplet molecules. It is shown that the triplet molecules are long-lived and the condition to produce the RTPM polarization is satisfied. The observed time evolutions of the transient EPR signals are qualitatively explained on the basis of the rate equations, which include the RTPM polarization and the relaxation.
X-Ray Diffraction and 35Cl NQR Studies of Bis-2-picolinium Hexachlorostannate
Authors: Horiuchi Keizo , Fukami Takanori
Published: June 2006

The crystal structure of bis-2-picolinium hexachlorostannate (CH3C5H4NH)2SnCl6 was determined at room temperature by a single-crystal X-ray diffraction method. This crystal forms triclinic with space group and Z = 1. The temperature dependence of the 35Cl NQR spectrum was investigated at between 77 K and around 340 K, at which temperatures the signals faded out. Three signals with an equal intensity were observed with no anomaly in their temperature variation over the entire temperature region investigated. DTA measurements were carried out at between 140 and 430 K, and no heat anomaly was observed.
1D and 2D FT-EPR Studies on the Photoinduced Electron Transfer Reaction from Zn Porphyrin to Duroquinone in CTAC Micellar Solution
Authors: Hanaishi Ryuji , Ohba Yasunori , Yamauchi Seigo , Iwaizumi Masamoto
Published: June 2006

A photoinduced electron transfer reaction in a model system of the photosynthesis was investigated by means of pulsed EPR in one (1D)- and two-dimensions (2D). EPR spectra of a spin correlated radical ion pair(SCRP) and a spin polarized radical anion were observed in the system of tetrakis(4-sulfonatophenyl) porphyrinozinc(II) (ZnTPPS)/duroquinone (DQ)/cetyltrimethylammonium chloride micellar solution. In order to investigate the dynamics and structures of the intermediate species, a non-linear least square fitting (NLLSQ), instead of linear prediction (LP), was examined for analyses of free induction decays (FID’s) in a 1D experiment. FID’s were fairly well reproduced with the NLLSQ method as a sum of the signals of the DQ anion and the SCRP. For the DQ anion, the linewidth gradually decreased indicating movement of the anion across the micelle/water interface.

For a definitive assignment of the SCRP, a 2D nutation experiment was performed. Different flip angle dependences were observed for the SCRP and the free anion. Under an assumption of an average exchange interaction (J), the 2D spectra of the SCRP were simulated, including an off-resonance effect on the basis of density matrix formalism. Comparison of the calculated and observed spectra indicated that the upper limit of the average |J| was 0.3 MHz (J < 0).
Metal Complexes of Peptides. VI. Di-μ-hydroxo–Dicobalt(III) Complexes Containing Peptides
Authors: Ama Tomoharu , Yonemura Toshiaki , Kawaguchi Hiroshi , Yasui Takaji
Published: June 2006

Two isomers of the dinuclear complex with β-alanyl-l-aspartate (β-ad), glycinate (gly), and ethylenediamine (en), [Co(β-ad)Co(gly)(en)(μ-OH)2]+, were prepared by treating an aqueous solution containing [Co(β-ad)(OH2)2] and [Co(gly)(en)(OH2)2]2+ under basic conditions. The geometrical structures and absolute configurations of these isomers were assigned on the basis of the NMR, UV, and CD spectral data; the assignments were confirmed on the basis of the spectral data of the mononuclear species that were obtained by the acid hydrolysis of the isomers. The faster eluted isomer (eluted with H2O on an SP-Sephadex (K+ form) column) consists of [Co(β-ad)(μ-OH)2] (β-ad coordinates to cobalt(III) as a tetradentate) and Δ-fac(O)-[Co(gly)(en)(μ-OH)2] moieties, and the later consists of [Co(β-ad)(μ-OH)2] and Λ-fac(O)-[Co(gly)(en)(μ-OH)2]. Another di-μ-hydroxo–dicobalt(III) complex containing β-alanyl-l-histidinate (car), [Co2(car)2(μ-OH)2], was also prepared by treating an aqueous solution containing [Co(car)(OH2)2]+ under basic conditions. The dinuclear structures of these complexes are stable for several days in the neutral aqueous solutions.
Colorimetric Determination of Ascorbic Acid in Pharmaceuticals and Fruits Using a Chromium(VI)–Diphenylcarbazide Complex
Authors: Arya Satya Prakash , Mahajan Meenakshi
Published: June 2006

A simple and rapid method is presented for the determination of ascorbic acid. This method is based on the reducing action of ascorbic acid, which proportionately decreases the color intensity of the Cr(VI)–diphenylcarbazide complex. The absorbance of the complex was measured at 540 nm. A linear relationship between the absorbance and concentration of ascorbic acid was found to hold well up to 3.2 μg ml−1. Most of the common ingredients present in pharmaceutical preparations were found to be tolerated. The method has been successfully applied to the determination of vitamin C in the pure state, dosage forms and citrus fruits.
Reduction of Manganese(III) in Tris(benzoyltrifluoroacetonato)Mn(III) in Carbon Tetrachloride in the Presence of Trioctylphosphine Oxide
Authors: Sekine Tatsuya , Osada Kazuhiro , Hokura Akiko
Published: June 2006

An addition of trioctylphosphine oxide (TOPO) enhanced the rate of back extraction of manganese in tris(benzoyltrifluoroacetonato)Mn(III) from carbon tetrachloride containing benzoyltrifluoroacetone (4,4,4-trifluoro-1-phenyl-1,3-butanedione, Hbfa) into acid aqueous solutions due to reduction of manganese(III) in this complex in the organic phase. It was found by spectrometry that manganese(III) in this complex in water- and air-saturated carbon tetrachloride was stable for a long time in the absence of TOPO but its reduction occurred in the presence of TOPO. The rate of reduction was first order with respect to the TOPO concentration and inverse first order with respect to the Hbfa concentration. This was explained as follows: An addition of TOPO to the metal ion in the complex promoted the dissociation of one of the bfa− ions in the complex and the leaving bfa− ion gave an electron to the manganese(III). On the other hand, a bfa− ion from the coexisting Hbfa in the solution should exchange with the bfa− in the MnIII(bfa)3 complex but it does not cause reduction of manganese(III) and this was assumed to compete with the addition of TOPO and to cause the inverse first order dependence of the rate of reduction on the Hbfa concentration.
Synthesis and Characterization of Manganese(III) Complexes with 2-{N-[2-(4-Imidazolyl)ethyl]iminomethyl}phenol or 2-{N-[2-(2-Pyridyl)ethyl]iminomethyl}phenol
Authors: Mikuriya Masahiro , Nukada Ryoji , Tokami Wataru , Hashimoto Youichi , Fujii Toshinori
Published: June 2006

Manganese(III) complexes with 2-{N-[2-(4-imidazolyl)ethyl]iminomethyl}phenol (HL1) or 2-{N-[2-(2-pyridyl)ethyl]iminomethyl}phenol (HL2), [MnL12]ClO4·CH3OH (1) and [MnL22]ClO4 (2), have been synthesized and characterized by infrared and electronic spectra, cyclic voltammetry, and temperature dependence of magnetic susceptibilities (80—300 K). The molecular structures of 1 and 2 were determined by single-crystal X-ray structure analysis. The manganese atom adopts an elongated octahedral geometry with two phenolic oxygen atoms, two imine nitrogen atoms, and two imidazolyl or pyridyl nitrogen atoms.
Structural Analysis of Cadmium–Glycylglycine Complexes Studied by X-Ray Diffraction and High Resolution 113Cd and 13C Solid State NMR
Authors: Takayama Toshio , Ohuchida Shirabe , Koike Yoshio , Watanabe Masanobu , Hashizume Daisuke , Ohashi Yuji
Published: June 2006

Structural analysis of bis(glycylglycinato)cadmium(II) complexes prepared to adjust the pH to 6 (A) and 9 (C), were studied by X-ray diffraction and high resolution 113Cd and 13C solid state NMR. In order to compare with the structure of A, structural analysis of bis(glycylglycinato)zinc(II) complexes (B) prepared to adjust the pH to 6 was also performed by the same methods. The structure of A was six coordinate; a five-membered chelate ring was formed between the terminal amino-group and the adjacent O (peptide) and the terminal carboxygroups of the dipeptide ligands were involved in Cd binding in the complex. The structure of B was similar to A, indicating that the Cd nucleus was better suited for probing the Zn nucleus-ligand structure. The structure of C was six coordinate; the four terminal carboxygroups (O) and the two terminal aminogroups (N) of the dipeptide ligands were involved in Cd binding in the complex. High-resolution 113Cd and 13C CP/MAS NMR spectra have been measured in order to obtain detailed information about the structures. The 113Cd signal of A showed a low field chemical shift compared with the peak of C. This means that the chelate ring shows decreased shielding. From the 13C spectra of A and C, it was seen that the Cd nucleus of A is bonded to a carbonyl oxygen (peptide) and the terminal carboxyl group of the dipeptide, but that for C is not bonded to a carbonyl oxygen (peptide).
Reaction Mechanism of Mercury(II) with Protonated N-Substituted Porphyrin
Authors: Nahar Nurun , Tabata Masaaki , Kaneko Kentaro
Published: June 2006

Kinetic and equilibrium studies on the complexation of mercury(II) ion with N-p-nitrobenzyl-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, (NO2Bz(Htpps)4−; HP4−) were carried out. The equilibrium constant, defined as KHgP = [HgP3−][H+][Hg2+]−1[HP4−]−1, was determined spectrophotometrically in the pH range 2—3 and at temperatures of between 15 and 35 °C. The value of KHgP was found to be 106.28 ± 0.04; and ΔH° and ΔS° values were 4.5 ± 0.7 kJ mol−1 and 134 ± 2 J mol−1 K−1, respectively at 25 °C. The kinetic studies were carried out under a pseudo-first order condition in an aqueous medium at 10—35 °C, I = 0.1(NaNO3), [HP4−] = 3 × 10−6, [Hg(II)] = 4.74 × 10−5 to 2.84 × 10−4, [acetate buffer] = 5 × 10−3 to 1 × 10−1 mol dm−3, and pH 4.2 to 5.6. The observed rate constant of the reaction was dependent of the total concentrations of mercury(II) and acetate buffer, but independent of the pH and ionic strength. The overall reaction was first order with respect to the total [Hg(II)] and [HP4−]. The rate expression of the reaction is d[HgP3−]/dt = (k1[Hg(OH)2] + k2[Hg(oac)2])[H2P3−]. The k1 and k2 values were found to be (1.26 ± 0.19) × 106 and (1.87 ± 0.01) × 106 mol−1 dm3 s−1 (25.0 °C), and the activation enthalpies and entropyies were ΔH‡ = 24.8 ± 3.8 kJ mol−1and ΔS‡ = −46 ± 13 J mol−1 K−1 for the k1, and ΔH‡ = 45.0 ± 2.1 kJ mol−1, ΔS‡ = 25.4 ± 7.4 J mol−1 K−1 for the k2. The kinetic data revealed that dihydroxomercury(II) directly reacts with the protonated porphyrin with a small activation enthalpy and a negative activation entropy.
Different Electrochemical Behavior of Complexes Having the Identical Nitroso Ligand in cis-[Ru(N,O-hia)(bpy)2]+ and cis-[Ru(N,O-hia)(bpy)(py)2]+ (hia: Hydroxyiminoacetylacetonato, CH3COC(NO)COCH3−)
Authors: Ooyama Dai , Nagao Noriharu , Kuroda Hiroshi , Satoh Utako , Howell F Scott , Mukaida Masao , Nagao Hirotaka , Tanaka Koji
Published: June 2006

[Ru(N,O-hia)(bpy)2]+ (I) and [Ru(N,O-hia)(bpy)(py)2]+ (II) (hia: CH3COC(NO)COCH3−) were prepared by the reactions of cis-[Ru(NO)(OH2)(bpy)2]3+ and cis-[Ru(NO)(OH)(bpy)(py)2]2+ with acetylacetone(Hacac) respectively. An X-ray structure analysis shows that the products have the identical nitroso ligand. Electrochemical behaviors of the complexes differ dramatically: I underwent an ECEC reaction, which could be illustrated as involving a structural rearrangement of the Ru-hia bonding, but II did not show such behavior and a typical reversible one-electron redox nature was found.
Hydrogenation of Biphenyl Using a Hydrogen Storage Alloy as a Hydrogenation Reagent
Authors: Nakagawa Shin-ichi , Murata Satoru , Nomura Masakatsu , Sakai Tetsuo
Published: June 2006

A detailed investigation of the hydrogenation reaction of biphenyl with MmNi3.5Co0.7Al0.8H4.2 [Mm: mixture of La, Ce, Pr, and Nd (30 : 52 : 5 : 13 wt ratio)] to give either cyclohexylbenzene or bicyclohexyl was performed. Time profiles of the amounts of hydrogen evolved from the alloy and that introduced into biphenyl during the reaction were measured; it was suggested that the hydrogen absorbed by the alloy could predominantly react with the substrate, and the hydrogen released into the gas phase played only a minor role in the reaction. The deuteration of biphenyl with the deuterated alloy, MmNi3.5Co0.7Al0.8D3.5, was also examined; a GC-MS analysis of the reaction mixture indicated that a H–D exchange between the hydrogen in the substrate and the deuterium in the alloy took place as a parallel reaction to hydrogenation of the aromatic rings, and, as a result, the product cyclohexylbenzene appeared to contain 3-9 deuterium atoms.
Synthesis and Reactions of Titanacycles Containing Group 14 Elements and Their Zirconium Analogues
Authors: Choi Nami , Morino Satoshi , Sugi Shin-ichiro , Ando Wataru
Published: June 2006

Lithium dimesitylgermanedithiolate reacted with titanocene or zirconocene dichloride to give 2,2-dimesityl-1,3-dithia-2-germa-4-titanacycle (3a) and its zirconocene analogue (3b), which afforded a stable 2,3,4,5-tetrathiagermolane (4) in treatment with S2Cl2. The reaction of 3b with Ph2GeCl2 gave unsymmetric 1,3,2,4-dithiadigermetane (5). The bis(η5-cyclopentadienyl) derivative of cis-2,3-di-t-butyl-2,3-diphenyl-1,4-dithia-2,3-disila-5-titanacyclopentane (7a) obtained from lithium 1,2-di-t-butyl-1,2-diphenyldisilane-1,2-dithiolate reacted with electrophilic reagents (SCl2, S2Cl2, Se2Cl2, R2GeCl2) to give the corresponding heterocycles.
The Synthesis, Antileukemic Activity, and Crystal Structures of Indirubin Derivatives
Authors: Li Chunmin , Go Yunhong , Mao Zihua , Koyano Kazuo , Kai Yasushi , Kanehisa Nobuko , Zhu Qingtai , Zhou Zhonghua , Wu Souyu
Published: June 2006

In order to search for a new kind of antileukemic drug, we synthesized four indirubin derivatives, including indirubin monooxime (IM), indirubin monooxime O-methyl ether (IMME), N1-methylindirubin monooxime O-methyl ether (MIMME), and indirubin monooxime O-ethyl ether (IMEE). Their antileukemic activities in vivo and in vitro were tested; some of these compounds showed good activities. Their molecular and crystal structures were determined by an X-ray diffraction method. The results revealed that all four indirubin derivatives are planar, and have a tendency to form a big π-system. The molecular structures also showed that oximation of indirubin resulted in only a slight change in the antileukemic activity. On the other hand, the amido moiety in the compounds may play an important role in the activity of the indirubin monooxime derivatives. This conclusion was supported by the calculation results of the electrostatic-potential (esp) derived charge distribution of the indirubin derivatives, which were obtained using an ab initio molecular orbital of the basis set (3-21G), taking the electronic correlation into account at the MP2 level.
Palladium-Catalyzed Acylcyanation of Terminal Arylacetylenes. Synthesis of 1,3-Diaryl-3-cyano-2-propen-1-ones and Tetrasubstituted Furans
Authors: Nozaki Kyoko , Sato Naomasa , Takaya Hidemasa
Published: June 2006

(Z)-1,3-Diaryl-3-cyano-2-propen-1-ones ((Z)-1) are prepared from arenecarbonyl cyanide and terminal arylacetylene in the presence of Pd(OAc)2–PPh3 (1 mol amt. to Pd)–0.5dppb (1,4-bis(diphenylphosphino)butane) (0.5 mol amt. to Pd). The reaction proceeded via the formation of acetylenic ketone 3, followed by the palladium-catalyzed addition of HCN, and isomerization of the resulting (E)-1 to (Z)-1. Oxidative addition of arenecarbonyl cyanide to zero-valent palladium metal has been observed by admixture of 4-MeOC6H4COCN to Pd2(dba)3 · CHCl3–PPh3–0.5dppb oxide (dppb oxide = Ph2P(O)(CH2)4P(O)Ph2). The resulting Pd(4-MeOC6H4CO)(CN)(PPh3)(ligand) afforded (Z)-1c by reaction with phenylacetylene. Thus, the role of two kinds of phosphine, PPh3 and dppb, suggests that the former acts as a ligand and the latter works as a reductant of Pd(II). The product (Z)-1 can be photoisomerized to (E)-1 under room light in CDCl3. The product (Z)-1 was obtained by a four-component coupling reaction of 4-iodotoluene, phenylacetylene, KCN, and carbon monoxide. A new synthesis of tetrasubstituted furans is also mentioned.
Production of Hydroxy Unsaturated Fatty Acids Using Crude Lipoxygenase Obtained from Infected Rice Plants
Authors: Kato Tadahiro , Watanabe Tsutomu , Hirukawa Toshifumi , Tomita Norihiro , Namai Tsuneo
Published: June 2006

In order to explore the oxidation mode of lipoxygenase (LOX) obtained from infected rice plants, typical unsaturated fatty acids (3—8) were treated with LOX and oxygen. It was observed that ω-10 and ω-6 positions of unsaturated fatty acids were oxidized predominantly in the cases of exotic ω-6 (4 and 5) and ω-3 (7 and 8) series, respectively. In the case of endogenous fatty acids (3 and 6), oxidation at ω-6 position predominated. All the allylic alcohols obtained by reduction of the oxidation products with NaBH4 possess S-configuration.
Synthesis of β-Lactams from Isocyanates and Vinyl Ethers under High Pressure
Authors: Taguchi Yoichi , Tsuchiya Tohru , Oishi Akihiro , Shibuya Isao
Published: June 2006

The [2 + 2]cycloaddition of phenyl isocyanate to 2,3-dihydrofuran was appreciably accelerated by compression to produce a β-lactam ring; its apparent activation volume was estimated to be −28 ml mol−1. Similar β-lactams were obtained under high pressure in the reaction of phenyl isocyanate with various vinyl ethers. Although the [2 + 2]cycloaddition of alkyl isocyanates to 2,3-dihydrofuran was also accelerated under high pressure to give β-lactams with good yields; the reactions of alkyl isocyanates with ethyl vinyl ether were slow, even at high pressure.
Preparation and Properties of 1,1′-Disubstituted Trichotomine Derivatives with a Twisted C=C Bond
Authors: Irikawa Hajime , Kanke Satoru , Mito Kousuke , Kobayashi Yasuhiro , Akasaka Tomoko , Atsumi Tadashi , Arimoto Hirokazu , Okumura Yasuaki
Published: June 2006

Green trichotomine derivatives bearing alkyl groups on C1 and C1′ were prepared. In their absorption spectra, the λmax shifted to longer wavelengths as the 1,1′-substituents became bulkier, and the bathochromism indicated twisting of the central C2=C2′ double bond. A 1,1′ -dimethyltrichotomine derivative underwent autooxidation to give orange-red 1,11b-dihydroxylated and 1,11b-seco-dicarbonyl compounds, in which twisting of the central C2=C2′ double bond might be relieved by the decreasing steric interactions between the substituents on C1 and the C3′ carbonyl groups.
NAD(P)+–NAD(P)H Models. 87. Nonsteric Stereochemistry Controlled by a Carbonyl Dipole
Authors: Ohno Atsuyoshi , Tsutsumi Akihiro , Yamazaki Norimasa , Okamura Mutsuo , Mikata Yuji , Fujii Masayuki
Published: June 2006

6,7-Dihydro-1,6,11-trimethyl-5-oxo-5H-benzo[c]pyrido[2,3-e]azepin-1-ium iodide (11-Me-MMPA+I−) was synthesized, and it was confirmed that the axial chirality in the salt is stable at room temperature. Upon the reduction of 11-Me-MMPA+ with a pair of diastereomeric dihydropyridine derivatives, the reacting face is always that in which the carbonyl dipole in the cation is included (i.e., syn selectivity), regardless the configuration of the reducing agent. A steric hindrance, in a classical sense, and other factors contribute to the stereochemistry of the reaction only in a minor part. Plausible intermolecular arrangements at the transition state of the reaction are discussed in order to understand the mechanism of this nonsteric stereochemistry.
Conformational Study on 2-Acyl-1-alkylidene-1,2,3,4-tetrahydroisoquinolines
Authors: Kitamura Masato , Tsukamoto Masaki , Takaya Hidemasa , Noyori Ryoji
Published: June 2006

The title enamide compounds can exist in either a sickle or U conformation with respect to the C=C–N–C=O conjugated moiety, where the sickle form is greatly favored. The sickle rotamers are chiral in nature in both solution and crystalline states, as proved by 1H NMR and a single-crystal X-ray analyses. The molecular distortion from the standard structure occurs in such a way as to retain the amide planarity, indicating a higher significance of the orbital interaction compared to the overlapping. The pathway and interconversion rate between the rotational stereoisomers are highly dependent on the nature of the 1-alkylidene and N-acyl groups. The energy barrier for the stereomutation of (Z)-2-(p-bromobenzoyl)-1-(3,4-dimethoxyphenylmethylene)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline has been determined by a lineshape analysis of the 1H NMR spectra.
Lanthanide Ion as a Catalyst for Internucleotide Bond Formation
Authors: Sawai Hiroaki , Yamamoto Kenji
Published: June 2006

The lanthanide ion-catalyzed oligomerization of adenosine 5′-(1-imidazolylphosphate) was performed to yield short-chained oligoriboadenylates. The effect of lanthanide ions on the synthesis of oligoriboadenylates increased nearly in the order of the atomic number: None < Nd3+   La3+   Ce3+   Pr3+   Sm3+   Eu3+   Gd3+ < Tb3+ < Dy3+   Ho3+ < Er3+ < Yb3+ < Lu3+. The total yield of the oligoriboadenylates was 49% when Lu3+ was used as a catalyst. The linkage in the resulting oligoribadenylate was mainly 2′–5′.
A Fast Procedure for the Preparation of Amides/Peptides from Carboxylic Acids and Azides via Two Redox Reactions: Application to the Synthesis of Methionine Enkephalin
Authors: Ghosh Sunil K , Verma Rekha , Ghosh Usha , Mamdapur Vasant R
Published: June 2006

A one-pot self regulated approach for the synthesis of amides/peptides based on two reduction–oxidation (redox) reactions has been described. The primary and secondary amides/peptides are made by using azidotrimethylsilane and alkyl azides/α-azido acid derivatives respectively as the direct source of amine components. Benzeneselenol, generated in the reaction medium during carboxyl activation, has been found to be an effective reducing agent for the conversion of azides to primary amines. The methodology has been applied to the synthesis of methionine enkephalin.
Salt Effect on the Interaction of 22,24-Diprotonated 5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin with a β-Sheet Structure of a Zwitterionic Polypeptide
Authors: Fukushima Yasumasa
Published: June 2006

The effect of sodium chloride on the absorption and CD spectra of the β-sheet structure of a zwitterionic poly(Glu–Val–Lys–Val)/22,24-diprotonated 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin system in aqueous solution was studied under various conditions. The monomeric TPPS was aggregated by the addition of the polypeptide and/or NaCl; at least four kinds of TPPS aggregation were observed. Although the aggregated species with an absorption band at around 489 nm formed an S-chiral conformation at [P]/[D] from 1 to 5 below 100 mM NaCl, the S-chirality changed to R-chirality by increasing to 500 mM NaCl or above. These results may indicate that an increase in the ionic strength induces a chiral conformational transition due to the prevention of electrostatic interactions between TPPS and the polypeptide; also the S-and R-chiralities could be caused by the secondary structure of the polypeptide and original property of TPPS, respectively. It is presumed that the electrostatic interactions play an important role in binding TPPS with the polypeptide as a major driving force. However, even 1000 mM NaCl could not completely shield the electrostatic interactions.
Rearrangement Approaches to Cyclic Skeletons. X. Pinacol-Type Rearrangement of 2-Substituted 1-Methoxybicyclo[2.2.2]oct-5-en-2-ols into Bicyclo[3.2.1]oct-6-en-2-ones. Remarkable Substituent Effects on Predominant Migration of the Unsaturated Bridge
Authors: Uyehara Tadao , Inayama Toshihiro , Furuta Toshiaki , Kato Tadahiro , Yamamoto Yoshinori , Ueno Masako , Sato Toshio
Published: June 2006

Pinacol-type rearrangement of 2-substituted 1-methoxybicyclo[2.2.2]oct-5-en-exo-2-ols (1) by treatment with p-toluenesulfonic acid in boiling benzene gave bicyclo[3.2.1]oct-6-en-2ones (2) and -3en-2-ones (4) in a ratio of ≥ 10 to 1 along with small amounts of dehydration products. Treatment of the endo isomers (3) under the same conditions gave 2, 4, and the dehydration products. The ratios of 2 to 4, in this case were within a certain range and were influenced by the substituent at the C-2 position. The ratio of the relative disappearance rate constant of 1 to that of the corresponding 3 was less than 10. This observation suggests that the unsaturated bridge does not offer remarkable anchimeric assistance in the reaction of 1. A similar acid treatment of the dehydration products gave 2 and 4 and their ratio was somewhat affected by the substituent. A mechanism is proposed for the pinacol-type rearrangement.
Synthesis of (3S,4S)-Statine and a Related Compound, (3S,4S)-AHPPA, from d-Glucosamine as a Chiral Pool
Authors: Shinozaki Katsuo , Mizuno Kazuhiro , Oda Hirohisa , Masaki Yukio
Published: June 2006

Biologically important threo-β-hydroxy-γ-amino acids, (3S,4S)-statine ((3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid) (1) and (3S,4S)-AHPPA (3S,4S)-4-amino-3-hydroxy-5-phenylpentanoic acid) (2), were synthesized starting from d-glucosamine (3) as a chiral pool. Two routes for the transformation of d-glucosamine to key intermediates, which are applicable to the synthesis of threo-β-hydroxy-γ-amino acids, were investigated. The successful route involved C(6)-carbon degradation and elimination of the C(4)-hydroxy group of d-glucosamine in 8 steps and 30% overall yield to furnish (4R,5S)-2-oxo-5-vinyloxazolidine-4-carbaldehyde dimethyl acetal (17), which has been utilized as a versatile intermediate for synthesizing the target compounds.
Intermediate Formation Process in Thermolysin Catalysis Observed Using a Fluorescent Displacement Probe in the Stopped-Flow Method
Authors: Kunugi Shigeru , Yokoyama Masahito , Kuroda Yasue , Yoshida Masumi , Koyasu Akira , Yamada Takashi , Sakamoto Akira
Published: June 2006

The thermolysin-catalyzed hydrolysis of N-Cbz-tripeptides was studied by means of a fluorescence stopped-flow method using N-dansyl-l-phenylalanine (Dns–Phe) as a displacement probe at lower pH.

To determine the probe features of Dns–Phe, the equilibrium and kinetics of the binary interaction between Dns–Phe and the enzyme were studied by means of static differential fluorescence and by fluorescence temperature-jump methods in the pH range 4.5—5.6.

The dissociation constant (Kd) increased along with an increase in pH. Both the decreasing (apparent) binding rate and the increasing (apparent) dissociation rate with increasing pH were attributed to this decline of complex formation at higher pH.

The pre-steady state process in the substrate hydrolytic reaction was studied with this displacement probe, and the observed rate constant for the four tripeptide substrates had saturation kinetics that indicated the existence of a new intermediate during the sequence of the enzyme reaction. Four tripeptide substrates had comparable k2 values (rate constant of intermediate formation), whereas the KS value of Cbz–Phe–Leu–Ala was about twice that of the others.
A Novel Trimerization of 1-Phenylsulfanyl-2,2,2-trifluoroethyl Isocyanide Giving a Dihydropyrimidine Derivative
Authors: Uno Hidemitsu , Oka Kenji , Tani Hiroyuki , Kawada Yoshihiro , Ono Noboru
Published: June 2006

1-Phenylsulfanyl-2,2,2-trifluoroethyl isocyanide (2a) readily and selectively trimerized to 4,6-bis(phenylsulfanyl)-1-(1-phenylsulfanyl-2,2,2-trifluoroethyl)-5-(2,2,2-trifluoroethylideneamino)-2-trifluoromethyl-1,2-dihydropyrimidine (5) at room temperature, while other α-phenylsulfanyl isocyanides such as phenyl(phenylsulfanyl)methyl isocyanide (2b) are stable. Heating of 2b resulted in formation of the corresponding nitrile as well as diphenyl disulfide and [bis(phenylsulfanyl)methyl]benzene.
Preparation of New Nitrogen-Bridged Heterocycles. 42. Synthesis and the Reaction of Pyridinium N-Ylides Using Bifunctional Ethyl Thiocyanatoacetates
Authors: Kakehi Akikazu , Ito Suketaka , Hashimoto Yasunobu
Published: June 2006

Various pyridinium (monosubstituted methylide)s were smoothly attacked to the cyano group in ethyl thiocyanatoacetate or ethyl 2-thiocyanatopropionate to afford the corresponding pyridinium (substituted cyanomethylide)s in low-to-moderate yields, while pyridinium (unsubstituted amidate)s reacted with the ester carbonyl group in the same reagents to give pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates in considerable yields. The 1,3-dipolar cycloadditions of some pyridinium (unsymmetrically substituted cyanomethylide)s with dimethyl acetylenedicarboxylate (DMAD) in various solvents afforded only dimethyl 3-cyanoindolizine-1,2-dicarboxylate, except a few examples. On the other hand, the treatment of pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates with a strong base, such as potassium t-butoxide, gave new bicyclic mesoionic compounds, N-[2-(1,3,4-thiadiazolo[3,2-a]pyridinio)]acetamidate derivatives, in moderate yields. The intermediacy of N-[1-(2-thiocyanatopyridinio)]acetamidates in the formation reactions of the latter compounds was also proven by independent syntheses.
Photodimerizations and Crystal Structures of Thymine Derivatives Having a Long Alkyl Chain Connected with a Carbamate Bond
Authors: Sugiki Takanori , Tohnai Norimitu , Wang Yuhua , Wada Takehiko , Inaki Yoshiaki
Published: June 2006

Photodimerizations of thymine derivatives having a long alkyl chain on a carbamate bond were investigated by irradiation of UV light at 280 nm in amorphous and crystalline film states. The amorphous films obtained by spin-coating from chloroform solution had higher initial rate constants for photodimerization relative to those of the crystalline films after annealing. X-Ray crystal structure analysis showed that the thymine derivatives had intermolecular hydrogen bonds that led to disadvantageous molecular orientation for the photodimerization. The photodimerization, however, is preferred in the localized layer structures of thymine units and alkyl chain.
A Molecular Theory of Tacky Adhesion
Authors: Furukawa Junji
Published: June 2006

Adhesive force fa acts on the adherend surface through pseudo links and is given by a product of wetting force W/l and the fraction of links of about 10−2. W is a wetting energy of about 101—2 cgs-unit and l is a length of a segment of 1 nm in the adhesives polymer and fa is about 106—7 cgs-unit or 1—10 kg cm−2. On peeling a tape of pressure-sensitive adhesives, the adhesives layer is expanded and voids and fibrils are often formed. The shear forces in fibrils are integrated to give the peeing force P. The layer is deformed to give a concaved shape expressed with a catenary curve. In this model, P increases with increasing the relaxation time τ, thickness h, velocity v, and decreasing the peeling angle θ. P is expressed as P = (0.7 fa/sin/θ)/(1/h + 1/τv). For the tensile test in parallel plates, the thickness is expanded uniformly and P = fa(1 + τv/h). For the shear test, the cohesive rupture occurs and P = ηv/h, η being viscosity.
Uptake of HIV testing in a busy South London GU medicine clinic – will we reach targets set in the National Strategy and are we testing those at risk?
Authors: Tipnis S R , Fox E F
Published: June 2006

We audited the practice of offering, and the uptake of, an HIV antibody test in new genitourinary medicine clinic attenders. We aimed to determine if we have reached targets set in the National Strategy for Sexual Health and HIV for 2006. We also aimed to determine whether patients at higher risk of acquiring HIV infection reached these targets. We found that nearly all patients were offered an HIV test (94.7%) and uptake was 60.5%, demonstrating that we have already reached our target. However, in this audit, the 60% uptake targets were not met by patients at increased risk of HIV, with 52.9% uptake in men who have sex with men and 50% uptake in Black Africans.
Distal sensory polyneuropathy in HIV-positive patients in the HAART era: an entity underestimated by clinical examination
Authors: Skopelitis E E , Kokotis P I , Kontos A N , Panayiotakopoulos G D , Konstantinou K , Kordossis T , Karandreas N
Published: June 2006

The aim of this study was to determine the prevalence of distal sensory polyneuropathy (DSP) in our HIV-positive patients under highly active antiretroviral therapy (HAART) and to investigate correlations with clinical, laboratory and demographic factors. One hundred consecutive HIV-positive patients underwent clinical and electrophysiological evaluation for DSP. Correlations with HIV stage, CD4 count, nadir CD4 count, viral load (VL), disease duration, age, sex and type of antiretrovirals were examined. Thirty-six percent of the patients had DSP (13% clinical, 23% subclinical diagnosed by electrophysiology). The prevalence of DSP was affected in a statistically significant manner by the diagnosis of AIDS ( P = 0.00033), age ( P = 0.0102), nadir CD4 count ( P = 0.0087) and exposure to two neurotoxic antiretrovirals ( P = 0.0189). Advanced HIV stage, sex, time from diagnosis, current CD4 count and VL did not seem to affect the prevalence of DSP. Clinical examination plus electrophysiology reveals that DSP affects 36% of patients under HAART, although subclinical in 2/3 of cases. Age, severe prior immunosuppression and the combined use of zalcitabine (ddC), stavudine (d4T) and didanosine (ddI) are important risk factors.
Assessing sexually transmitted infections in a cohort of women living with HIV/AIDS, in Rio de Janeiro, Brazil
Authors: Grinsztejn Beatriz , Bastos Francisco Inácio , Veloso Valdiléa G , Friedman Ruth Khalili , Pilotto José Henrique , Schechter Mauro , Derrico Monica , Andrade Angela , Lourenço Maria Cristina , Moreira Ronaldo Ismério , Russomano Fabio , Morgado Mariza , Currier Judith S
Published: June 2006

A cohort of 458 HIV-positive women under antiretroviral therapy has been followed at a reference hospital in Rio de Janeiro, Brazil. Most of them belong to impoverished social strata. Patients were screened for sexually transmitted infections (STIs) and gynaecologic conditions. Some STIs were found to be uncommon (e.g. chlamydial and gonococcal infections), while some conditions (bacterial vaginosis) and STIs, e.g. hepatitis B and human papilloma virus (HPV) infection, were found to be quite prevalent. The latter is of special concern, due to the high prevalence of HIV/HPV co-infection (∼51%) and its association with severe immunodeficiency, in a context of unacceptable high levels of uterine cancer and uneven gynaecological care. HIV-positive women are in need of comprehensive health services, including high-quality, regular, gynaecologic care in order to diagnose and treat lower genital tract infections and prevent the evolution of HPV-related lesions. Reproductive counselling should be a part of this approach.
Haemorrhagic acute disseminated encephalomyelitis: an unusual case of blindness in an HIV-infected patient
Authors: Raychaudhuri Malini , de Silva Thushan , Connor Stephen , Poulton Mary
Published: June 2006

Acute disseminated encephalomyelitis (ADEM) is a monophasic, polysymptomatic, immune-mediated demyelinating disorder involving central nervous system (CNS) white matter. It is usually seen in association with exanthematous viral illnesses, systemic infections or vaccinations. The haemorrhagic form of ADEM is rarer and follows a more fulminant course. We describe a case of haemorrhagic ADEM in an HIV-infected patient presenting solely with acute onset bilateral blindness and normal retina. ADEM was diagnosed from clinical, laboratory and radiological findings. Although ADEM has been seen with HIV seroconversion illness and in chronic infection, the haemorrhagic form has never been reported in association with HIV. Acute onset blindness is extremely rare in HIV-positive patients. A Medline search revealed very few reports. The importance of considering haemorrhagic ADEM as aetiology of blindness in such a scenario is discussed.
Prediction of RNA binding sites in proteins from amino acid sequence
Authors: Terribilini Michael , Lee Jae-Hyung , Yan Changhui , Jernigan Robert L. , Honavar Vasant , Dobbs Drena
Published: June 2006

RNA–protein interactions are vitally important in a wide range of biological processes, including regulation of gene expression, protein synthesis, and replication and assembly of many viruses. We have developed a computational tool for predicting which amino acids of an RNA binding protein participate in RNA–protein interactions, using only the protein sequence as input. RNABindR was developed using machine learning on a validated nonredundant data set of interfaces from known RNA–protein complexes in the Protein Data Bank. It generates a classifier that captures primary sequence signals sufficient for predicting which amino acids in a given protein are located in the RNA–protein interface. In leave-one-out cross-validation experiments, RNABindR identifies interface residues with >85% overall accuracy. It can be calibrated by the user to obtain either high specificity or high sensitivity for interface residues. RNABindR, implementing a Naive Bayes classifier, performs as well as a more complex neural network classifier (to our knowledge, the only previously published sequence-based method for RNA binding site prediction) and offers the advantages of speed, simplicity and interpretability of results. RNABindR predictions on the human telomerase protein hTERT are in good agreement with experimental data. The availability of computational tools for predicting which residues in an RNA binding protein are likely to contact RNA should facilitate design of experiments to directly test RNA binding function and contribute to our understanding of the diversity, mechanisms, and regulation of RNA–protein complexes in biological systems. (RNABindR is available as a Web tool from http://bindr.gdcb.iastate.edu.)
Identification, cloning, and functional analysis of the human U6 snRNA-specific terminal uridylyl transferase
Authors: Trippe Ralf , Guschina Elena , Hossbach Markus , Urlaub Henning , Lührmann Reinhard , Benecke Bernd-Joachim
Published: June 2006

Mammalian cells contain a highly specific terminal uridylyl transferase (TUTase) that exclusively accepts U6 snRNA as substrate. This enzyme, termed U6-TUTase, was purified from HeLa cell extracts and analyzed by microsequencing. All sequenced peptides matched a unique human cDNA coding for a previously unknown protein. Domain structure analysis revealed that the U6-TUTase also belongs to the well-characterized poly(A) polymerase protein superfamily. However, by amino acid sequence as well as RNA-binding motifs, human U6-TUTase is highly divergent from both the poly(A) polymerases and from the TUTases identified within the editing complexes of trypanosomes. After cloning, the recombinant U6-TUTase was expressed in HeLa cells. Analysis of its catalytical activity confirmed the identity of the cloned protein as U6-TUTase, exhibiting the same exclusive substrate specificity for U6 snRNA as the endogenous enzyme. That unique selectivity even excluded as substrate U6atac RNA, the functional homolog of the minor spliceosome. Finally, RNAi knockdown experiments revealed that U6-TUTase is essential for cell proliferation. Surprisingly, large amounts of the recombinant enzyme were found to accumulate within nucleoli.
The fragile X mental retardation protein interacts with a distinct mRNA nuclear export factor NXF2
Authors: Lai Dongmei , Sakkas Denny , Huang Yingqun
Published: June 2006

Loss of fragile X mental retardation protein, FMRP, causes the fragile X syndrome. Highly expressed in the brain and testis, FMRP has been implicated in the transport and translation of specific mRNAs. Here we show that FMRP and the mRNA nuclear export factor NXF2 co-express in the mouse male germ cells and hippocampal neurons and that FMRP associates with NXF2 but not with its close relative NXF1. We thus hypothesize that FMRP and NXF2 may act in concert to promote the nucleocytoplasmic transport of specific mRNAs in male germ cells and neurons.