bluuebunny/crossref_metadata_2025_split huggingface dataset:
Association Behavior of 1-Pyrenyl Pendants Introduced into the Papain Active Site
Authors: Sakurai Tadamitsu , Miyata (nee Nojima) Kazue , Watanabe Kenichiro , Kubo Kanji , Inoue Hiroyasu 
Published: December 2003

Abstract
1-(Bromoacetyl)pyrene (BAP) was found to selectively alkylate the cysteine-25 residue (Cys-25) of papain, inactivating the enzyme. A comparison of the spectroscopic behavior of BAP-modified papain with that of the reference compound, 1-{[2-(acetylamino)ethylthio]acetyl}pyrene (TAP), showed that the pyrenecarbonylmethyl pendant (covalently bound to Cys-25 in a 1 : 1 stoichiometric ratio) gives a new absorption around 390 nm and a long-wavelength fluorescence at 465 nm, which are both characteristic of an associated dimer. Effects of solvent and concentration on the absorption and emission spectra of TAP as well as the derivatized enzyme substantiate the dimer formation in the ground state. The finding that the pendant-carbonyl-13C carbon signal undergoes a large upfield shift in the papain active site, as compared to the corresponding signal of 13C-labeled TAP, confirms that the pyrenecarbonyl moiety adopts an enolate-type resonance structure (making the pyrene ring electron-deficient) on formation of a strong hydrogen bond to the neighboring amino acid residue(s). It is proposed that the significant contribution of the enolate-type resonance structure is a driving force for promoting the dimerization of the pyrenecarbonylmethyl reporter group attached to Cys-25 mainly through dipole–dipole and hydrophobic interactions. On the other hand, the introduction of the imino spacer between the 1-pyrenyl carbon and the acetyl carbonyl carbon in BAP-derived pendant greatly weakened a tendency to produce a pendant dimer in the ground state, providing a piece of evidence in support of this proposal.
Reactions of 1,8-Dimethoxy-9-phenylxanthen-9-ol in the Presence of an Acid, and Its Basicity
Authors: Wada Masanori , Kirishima Katsuhiko , Oki Yuichi , Miyamoto Masafumi , Asahara Masahiro , Erabi Tatsuo 
Published: December 2003

Abstract
In the presence of a catalytic amount of acid, the title xanthenol (1) reacted in acetone to give 1,8-dimethoxy-9-phenylxanthen-9-ylmethyl methyl ketone. Analogous reactions were observed for ethyl methyl ketone and acetophenone, but not for diethyl ketone. Propanal and butanal also reacted to give 2-(1,8-dimethoxy-9-phenylxanthen-9-yl)propanal and 2-(1,8-dimethoxy-9-phenylxanthen-9-yl)butanal, respectively. In hot primary and secondary alcohols, 1 was reduced to give 1,8-dimethoxy-9-phenylxanthene. 1 also reacted with methoxybenzenes, phenol, and N-alkylanilines to give 9-aryl-1,8-dimethoxy-9-phenylxanthenes. The basicity of 1, or the stability of the carbenium ion (pKR+ = −0.81), was measured in hydrochloric acid and compared with those of related 9-arylxanthen-9-ols, such as 1,8-dimethoxy-9-(2,6-dimethoxyphenyl)xanthen-9-ol (1.14), 9-(2,6-dimethoxyphenyl)xanthen-9-ol (4.80) (8), and 9-phenylxanthen-9-ol (0.75). The drastic differences in the reactivities and the basicity between 1 and 8 were attributed to a steric effect rather than an electronic effect.
Copper-Mediated Nucleophilic Displacement Reactions of 1-Haloalkynes. Halogen-Halogen Exchange and Sulfonylation
Authors: Abe Hajime , Suzuki Hitomi 
Published: December 2003

Abstract
Some copper(I) and (II) compounds have been found to act as efficient reagents for the nucleophilic displacement of 1-haloalkynes. Copper(I) iodide smoothly transforms 1-bromoalkynes (2) into 1-iodoalkynes (1) which, on further treatment with copper(II) bis(arenesulfinate), are readily converted to the corresponding alkynyl aryl sulfones (4). The kinetic data of the halogen exchange between (4-chlorophenyl)ethynyl bromide (2d) and CuI have shown that the reaction is linearly dependent on the concentrations of both compounds. A mechanistic pathway involving the single electron transfer between 1-haloalkynes and copper(I) salt has been proposed for the present copper-assisted halogen exchange reaction at acetylenic carbon atom.
Synthesis of Disilacycloalkenes by Ruthenium Alkylidene Catalyzed Ring-Closing Metathesis (RCM) Reaction of α,ω-Bis(allyldimethylsilyl)-Substituted Compounds
Authors: Hoshi Takashi , Yasuda Hiroyuki , Sanji Takanobu , Sakurai Hideki 
Published: December 2003

Abstract
Ruthenium-catalyzed ring-closing metathesis (RCM) reactions of various α,ω-bis(allyldimethylsilyl)-, bis(dimethylvinylsilyl)-, and bis(dimethylvinyloxysilyl)-substituted compounds are examined. The steric and electronic influences of the substrates on the RCM reaction were discussed. Although the successful ring-closing reactions are limited to seven- and eight-membered rings, disilacycloalkene derivatives constructed with –SiMe2–CH2–SiMe2–, –SiMe2–(CH2)2–SiMe2–, –SiMe2–O–SiMe2–, –SiMe2–N(Ph)–SiMe2–, and a vinylene unit in the ring system were obtained in good to reasonable yields under the mild reaction conditions. The limitation of the reactions is mainly ascribed to Si–C and Si–Si bonds being longer than the C–C bond in the ring system.
A New Efficient Method for S–CH2–S Bond Formation and Its Application to a Djenkolic Acid-Containing Cyclic Enkephalin Analog
Authors: Ueki Masaaki , Ikeo Takayoshi , Hokari Kumiko , Nakamura Keiko , Saeki Akihiko , Komatsu Hiroshi 
Published: December 2003

Abstract
An efficient methylene insertion reaction to construct an S–CH2–S bridge between two cysteine residues occurred when the thiol-protecting dimethylphosphinothioyl (Mpt) group of Z–Cys(Mpt)–OMe was removed with tetrabutylammonium fluoride hydrate in CH2Cl2. The thiol-free form gave similar results, albeit the yields were somewhat lower. In both cases, the best yields were obtained using 2 molar amounts of the reagent. Higher amounts of the reagent reduced the yield because of dehydroalanine formation. In the case of penicillamine, the thiol-free form was better in reactivity than the S-Mpt form, which required double the amount of the reagent to give the same yield. The reaction was successfully used in a synthesis of a cyclic enkephalin analog with the S–CH2–S bridge.
Photoreactive and Inactive Crystals of 1-Alkylthymine Derivatives
Authors: Tohnai Norimitsu , Inaki Yoshiaki , Miyata Mikiji , Yasui Nobuyoshi , Mochizuki Eiko , Kai Yasushi 
Published: December 2003

Abstract
Two kinds of crystal structures were found for 1-octylthymine from X-ray structure analysis: Structure I was obtained from Crystal I recrystallized from ethyl acetate, and Structure II was obtained from Crystal II recrystallized from ethanol. The thymine bases in Crystal I had high reactivity for photodimerization. Crystal II, however, was inactive for the photodimerization of thymine bases. This paper presents the crystal structure of 1-octylthymine crystallized from ethanol (Crystal II) by X-ray crystal structure analysis. Thymines in Crystal II were concluded to be inactive for photodimerization because of unsuitable orientation of thymine bases in the crystal and because of insufficient space for rotation of thymine during photodimerization.
Thermal Behavior of Diynes with Formally Conjugated Heteroaromatic Sidegroups
Authors: Sarkar Abhijit , Talwar Satya S 
Published: December 2003

Abstract
Diynes with heteroaromatic sidegroups directly linked to the acetylenic backbone were found to show liquid crystalline behaviour upon heating. Thus, 1,4-di(2-thienyl)-1,3-butadiyne, 1,4-di(3-thienyl)-1,3-butadiyne, 1,4-di(3-benzo[b]thienyl)-1,3-butadiyne, 1-(3-quinolyl)-4-(2-thienyl)-1,3-butadiyne, 1-(3-quinolyl)-4-(3-thienyl)-1,3-butadiyne, and 5-(2-thienyl)-2,4-pentadiyne-1-ol were investigated for their thermal behavior. These diynes also underwent polymerization in their liquid crystalline state, although the polymers so formed did not show liquid crystalline behavior. It was found that the S-atom of the heteroaromatic moieties tends to play a role in making the diynes show liquid crystalline behavior. Differential scanning calorimetry, thermogravimetric analysis and hot stage microscopy were used to investigate the liquid crystalline nature of the diynes. All of them showed a nematic liquid crystalline phase upon annealing, whereas smectic phase was totally absent.
Synthesis and Evaluation of Superior Calcium and Mercury Transport by Simple Monocarboxylic Acids of Kemp’s Triacid
Authors: Hirose Takuji , Wang Zhen-He , Baldwin Bruce W , Uchimaru Tadafumi , Kasuga Kazuyuki 
Published: December 2003

Abstract
Transport abilities of alkaline earth, transition, and heavy metal ions were examined for three kinds of disubstituted monoacid derivatives of Kemp’s triacid as transport agents for a liquid membrane system. Diamide derivatives showed high transport ability for CaII over MgII, with selectivity ratios greater than 25. Imide monoacids were also CaII selective. For transition and heavy metal ions, all monoacids including diester monoacid showed very high HgII transport, but with different selectivities depending on the functional group. High HgII/AgI ( = 24), HgII/CuII ( = 194), and HgII/PbII ( = 85) selectivities were observed for diamide, diester, and imide monoacids, respectively. The transport mechanisms are discussed for alkaline earth, transition, and heavy metal ions utilizing ion chromatography analysis of anions co-transported.
Synthesis and Chemical Properties of Metalladithiolene and Metalladithiazole Rings. Unique Reactions Due to Coexistence of Aromaticity and Unsaturation
Authors: Sugimori Akira , Akiyama Takeo , Kajitani Masatsugu , Sugiyama Toru 
Published: December 2003

Abstract
The syntheses and unique chemical properties of metalladithiolene rings (especially in [CpM(S2C2R1R2)]-type complexes) found by our research group are reviewed. The constructions of metalladithiolene rings by one-pot reaction among [CpM(CO)n], alkyne, and elemental sulfur and by the reaction between [CpM(CO)n] and sulfur-containing heterocyclic compounds are described. Several ionic and radical substitution reactions are presented. The substitutions by carbon-centered and sulfur-centered radicals occur in the metalladithiolene rings. Benzoyloxy-substitution by dibenzoyl peroxide (BPO) and succinimido-substitution by N-halosuccinimides (NXS) proceed via ionic mechanisms induced by the heterolysis of BPO and NXS in the interaction with the lone pair electrons at the sulfur atoms. These substitutions are due to the aromatic character of the metalladithiolene rings. The unique addition reactions due to the unsaturated character of the metalladithiolene rings are also described. Diazo compounds and azides react with [CpM(S2C2R1R2)]-type metalladithiolenes to form alkylidene- and imido-bridges between metal and sulfur. Quadricyclane and dimethyl acetylenedicarboxylate add between metal and sulfur. These addition products undergo a variety of types of dissociation: by heating, illumination, or electrochemical redox.
Femtosecond Regular Reflection Spectroscopic Study on Ultrafast Photoinduced Heat Generation in Copper Phthalocyanine Solid
Authors: Hosokawa Yoichiroh , Watanabe Kazuya , Asahi Tsuyoshi , Fukumura Hiroshi , Masuhara Hiroshi 
Published: December 2003

Abstract
A femtosecond regular reflection spectroscopic system was developed and applied to a β-copper phthalocyanine (β-CuPc) pellet. Transient regular reflection spectra were converted into extinction coefficient change (Δk) ones, which correspond to transient absorption spectra, by using Kramers-Kronig transformation. The Δk spectrum observed immediately after excitation was assigned to the excited state of β-CuPc solid, which relaxed by an exciton–exciton annihilation. The spectra remaining over several nanoseconds were assigned to a hot band due to a vibrationally excited state of the electronically ground state. We have clarified that a fast photothermal conversion process is induced by the exciton–exciton annihilation, which was analyzed by a simulation using a time dependent rate (proportional to t−1/2) of the annihilation.
Acid–Base and Monomer–Dimer Equilibria of Methylene Blue in Dip-Coated Thin Films
Authors: Nishikiori Hiromasa , Nagaya Satoshi , Tanaka Nobuaki , Katsuki Akio , Fujii Tsuneo 
Published: December 2003

Abstract
Thin films including Methylene Blue (MB) have been prepared. They were dip-coated using the sol–gel reaction of tetraethyl orthosilicate (TEOS). The absorption spectra of the individual thin films have been observed as a function of time after preparation of the films. The relative contributions of the monomer (MB+), dimer ((MB+)2), and protonated species (MBH2+) existing in the individual thin films to the total absorption spectra were obtained. The acidity in each film was estimated from the relative abundance of the MBH2+. In the case of the system including a large amount of HCl as a catalyst, MB formed MBH2+ in addition to MB+ and (MB+)2 just after preparation of the films. However, MBH2+ in every film disappeared 5—10 min after the preparation. The formation of MBH2+ indicates the very high acidity around MB molecules. In each film just after the preparation, the rate of the hydrolysis became slower and the concentration of the released proton remarkably increased because the polycondensation rapidly proceeded with the contraction in volume. Although growing –SiOSi– networks prevent the evaporation of the acid together with water and ethanol, the decrease of MBH2+ indicates the lowering of acidity in the films due to the evaporation.
Study of a New Crowned Azobenzene: Photochromism and Langmuir?Blodgett Film [Retracted]
Authors: Li Hongqi , Yao Zhongqi , Liu Renhua , Tan Ganzu , Yu Xianda 
Published: December 2003

Abstract
A new crowned azobenzene derivative, 4-[(aza-15-crown-5)-13-yl]-4′-methoxyazobenzene (APCM), was synthesized and incorporated into a β-cyclodextrin derivative, heptakis(6-undecylamino-6-deoxy)-β-cyclodextrin (ACD). The crowned azobenzene showed a large red shift of the maximum UV-vis absorption wavelength upon 254 or 365 nm irradiation. The results from UV-vis and ESR spectral analyses revealed that the photochromic mechanism for the crowned azobenzene was a photoinduced intramolecular charge-transfer (CT) process. APCM/ACD formed a stable Langmuir monolayer at the air–water interface. A multilayer Langmuir–Blodgett (LB) film was constructed from APCM/ACD monolayers, which showed a nonlinear polarisability (β) of 4 × 10−29 esu after one month of storage.
Semi-Empirical Calculations of the Transport Properties of Eight Binary Gas Mixtures at Low Density by the Inversion Method: Part II
Authors: Ghatee Mohammad Hadi , Papari Mohammad Mehdi , Boushehri Ali 
Published: December 2003

Abstract
The viscosities, diffusion coefficients, and thermal diffusion factors for eight binary gas mixtures: He + SF6, He + CO2, He + O2, He + N2O, CH4 + SF6, CH4 + CO2, CH4 + O2, and CH4 + N2O were determined from the extended law of corresponding states for viscosity using the inversion technique for the corresponding interaction potential energies. Lennard–Jones (12-6), (LJ (12-6)), potential function is used as the initial model potential required by the technique. The interaction potential energies from this inversion technique reproduce the viscosities within 1%, the diffusion coefficients within 5%, and the thermal diffusion factors within 25%. The interaction potential energy determined from this inversion method for He + SF6 system is compared with other methods.
Monocyclic Heterocyclic Biomolecules Conform to the Rule of Topological Charge Stabilization
Authors: Aihara Jun-ichi , Ishida Toshimasa 
Published: December 2003

Abstract
Some difficulty is felt in applying the rule of topological charge stabilization (TCS rule) to monocyclic heterocyclic biomolecules, such as substituted pyrroles, furans, thiophenes, imidazoles, and thiazoles. We found that the TCS rule can be reasonably extended to include such heterocycles. We propose that, if all carbon atoms in a hydrocarbon anion are charged uniformly, one or more of them can be replaced by eletronegative heteroatoms to stabilize the π-electron system. Thus, it is still true that the TCS rule dominates general biosynthesis and geochemistry. Coenzyme PQQ (pyrroloquinolinequinone) satisfies the TCS rule in both its oxidized and reduced states. Even apparently antiaromatic 1,2-dithiin seems to conform to the TCS rule.
Phase Transitions of Pure Long-Chain α,ω-Alkanediols from C13 to C24
Authors: Ogawa Yoshihiro , Nakamura Naotake 
Published: December 2003

Abstract
A series of pure α,ω-alkanediols HO-(CH2)n-OH (n = 13—24) was prepared and the effects of chain length and parity on their thermal properties were investigated. Crystal structures of odd α,ω-alkanediols were orthorhombic, while those of even α,ω-alkanediols were monoclinic. α,ω-Alkanediols with n = 13—24 showed solid–solid transitions except for n = 14. The solid–solid transition was found to be reversible. Transition temperatures from the crystal to the high-temperature phase indicated distinctive and regular odd-even effects, while from the high-temperature phase to the liquid, slightly odd–even effects were noted. The average enthalpy increment per methylene unit from the crystal to liquid for odd α,ω-alkanediols was 4.0 kJ mol−1. Enthalpies of transition from crystal to high-temperature phases considerably exceeded those of n-alkanes. HOC13H26OH lost 62% total enthalpy at the solid–solid transition and only 38% at melting. High-temperature phases of α,ω-alkanediols may possibly be liquid crystal phases.
Copper(II) Ion-Catalyzed and Molecular Packing-Dependent Dimerization of Pyridoxal 5-Phosphate–Pyridoxamine 5-Phosphate Schiff Base as a Structural Model for in Vitro Transformation of Amino Acid by Pyridoxal 5-Phosphate: X-Ray Crystal Structural Investigation
Authors: Ishida Toshimasa , Manabe Reijirou , In Yasuko , Takashima Hajime , Kitamura Kunihiro , Wakahara Akio 
Published: December 2003

Abstract
X-Ray crystal structures of the end products, obtained by in vitro Cu(II)-mediated transamination reaction of l-alanine by the vitamin B6 coenzyme, show that the Cu(II) complex of pyridoxal 5-phosphate–pyridoxamine 5-phosphate (PLP–PMP) Schiff base (Cu·C16H18N3O10P2, 1) is spontaneously covalent-bonded between the azomethine carbons of two neighboring Schiff bases with the (R,R)- or (S,S)-configuration, and is led to a dimer structure of the trans (2a) or cis (2b) conformational isomer around the covalent bond, depending on the molecular packing in the crystal. Since crystals of 1 have been obtained, the C–C covalent bond could be formed at the crystalline state. Molecular orbital calculations suggest that the electronic structure of the Schiff base is significantly delocalized by the coordination of the copper(II) ion; also the vertical stacking of 1 aromatic rings, which is suitable for the dimer formation, is promoted by electrostatic interactions between the Pz orbitals of the azomethine nitrogen and carbon atoms. Based on the transformation of 1 to 2a/2b, we propose a transition pathway via the aldimine or ketimine dimer form concerning the metal- and PLP-catalyzed biomimetic transformation of amino acid.
A Reason of Linear Additivity of ‘π Energy’ in Polyenes
Authors: Ichikawa Hiroshi , Yoshida Atsushi , Kagawa Hirotaka , Aihara Jun’ichi 
Published: December 2003

Abstract
The Hückel molecular orbital theory stands on the approximation that a π electron moves in the average field of potentials from other (σ and π) electrons and nuclei, where the nuclear–nuclear repulsion energies are not taken into consideration. A strange property of the Hückel energy is that it has a linear additivity with respect to the ethylene unit in polyenes. Based on the molecular virial theorem and a previous finding that the Hückel energy represents the kinetic energy of π electrons (&lt;T&gt;π), the linearity problem is reduced to two points: (1) why the ratio of &lt;T&gt;π to the total kinetic energy (&lt;T&gt;) is constant in linear polyenes and (2) why &lt;T&gt; is linear with respect to the ethylene unit.
We treated the second problem using a newly developed energy-partitioning technique, and found that the total atomic interactions are well localized around the region between neighboring atoms in spite of strong long-range interactions of the individual potential-energy terms. If we adopt the fact that &lt;T&gt;π/&lt;T&gt; is constant, the riddle of why &lt;T&gt;π or Hückel energy includes the information on the nuclear configuration is also understood through the virial theorem.
Temperature- and Pressure-Induced Phase Transition in Tetrafluoro-1,4-benzoquinone Crystal
Authors: Ikuta Akihiko , Suzuki Yoshio , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi 
Published: December 2003

Abstract
The temperature and pressure effects on the Raman-active inter- and intramolecular vibrations of tetrafluoro-1,4-benzoquinone crystal were studied. The diffuse Raman bands observed in the intermolecular vibrational spectrum could be resolved with decreasing temperature or increasing pressure. The observed spectral structure due to the intermolecular vibrations changed as the temperature fell and also as the pressure increased. The vibrational frequencies of some intramolecular vibrational bands changed discontinuously under a certain pressure when the applied pressure was increased. The calculated pressure-induced frequency shifts for these vibrations deviate from the observed frequency shifts under high pressure. The DSC curve shows no distinct endothermic or exothermic peaks at temperatures between 77 and 520 K. These observations indicate that a displacive phase transition takes place at a temperature of around 180 K under 1 atm or under a pressure of 0.8 GPa at 300 K in a tetrafluoro-1,4-benzoquinone crystal.
The Binding Characteristics of Conventional and α,ω-Type Ionic Surfactant Mixtures to Polyion
Authors: Satake Iwao , Fukunaga Kenichi , Miyazaki Atsuko , Maeda Tamaki , Hayakawa Katumitu 
Published: December 2003

Abstract
The binding isotherms of decyltrimethylammonium bromide (DeTAB) to poly(potassium vinyl sulfate) were determined potentiometrically in mixed solutions with N,N,N,N′,N′,N′-hexamethyl-1,20-icosanediammonium dibromide (ETMAB) and 1,1′-1,20-icosanediylbispyridinium dibromide (EPB). In both systems, an addition of the α,ω-type surfactant causes a remarkable decrease in the slope of the binding isotherm of DeTA+. In addition, the binding isotherm tended to shift regularly to a low concentration range with increasing concentration of the α,ω-type surfactant. A regular solution treatment of the mixed clusters on the polyion chain suggests that substantially all of the added α,ω-type ions bind to the polyion under our experimental conditions. The observed binding isotherms can well be reproduced with interchange energies of −0.6 kT for DeTA+–ETMA2+ and −1.6 kT for DeTA+–EP2+ pairs in the mixed clusters, respectively.
Thermodynamic and Magnetic Studies on the Formation of gem-Diol in an Aldehyde–Water Mixture
Authors: Nakazawa Yoshinori , Takahashi Fujio 
Published: December 2003

Abstract
A thermodynamic study on the formation of gem-diol in an aldehyde–water mixture was carried out by NMR measurements. The equilibrium constants for the formation of gem-diol were determined at 280.3—298.4 K. From the relationship between the equilibrium constant and the temperature, ΔH and ΔS were obtained to be −20.4 kJ mol−1 and −101 J K−1 mol−1 in the case of acetaldehyde, and −22.9 kJ mol−1 and −110 J K−1 mol−1 in the case of propionaldehyde, respectively. It is difficult to isolate the gem-diol from an aldehyde–water mixture. The diamagnetic susceptibility of gem-diol was estimated by measuring the susceptibilities of the aldehyde–water mixture at various molar ratios. The diamagnetic susceptibility was determined using Gouy’s method. The diamagnetic susceptibilities of 1,1-ethanediol and 1,1-propanediol were −39.1 × 10−6 cm3 mol−1 and −51.5 × 10−6 cm3 mol−1 at 287 K, respectively.