bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochromism of Single Transition-Metal Phthalocyanine Thin Films: Effect of Central Metal and Composite Structure
Authors: Toshima Naoki , Tominaga Tsuyoshi 
Published: June 2006

Abstract
Electrochromism of various transition-metal phthalocyanine thin films is studied in a sodium nitrate solution. Copper and nickel phthalocyanine show reversible electrochromism, while, zinc, cobalt, and iron phthalocyanine show the irreversible type. The transition-metal phthalocyanine film, which gives irreversible electrochromism, exhibits a new absorption peak in the NIR region under oxidation. This result indicates that some chemical changes of molecular structure occur with oxidation, and consequently the cyclic voltammograms and the absorbance are diminished with repeated scans, even under the well-designed experimental conditions. As for composite phthalocyanine, the high dispersibility of the phthalocyanine molecules in the codeposited thin film can improve the reversibility in electrochromism. In this case, chemical changes of the molecular structure of metal phthalocyanine with irreversible electrochromism can be prevented to some extents by the codeposition with another phthalocyanine with reversible electrochromism. Sequentially deposited double-layered thin films, in contrast, give completely different results. The electrochromism depends on the order of the oxidation potentials of simple phthalocyanine thin film, and the designed hole transfer compatible with the concept of “sequential potential field” can be accomplished in the double-layered thin film.
Biological Activity of Water-Soluble Fullerenes. Structural Dependence of DNA Cleavage, Cytotoxicity, and Enzyme Inhibitory Activities Including HIV-Protease Inhibition
Authors: Nakamura Eiichi , Tokuyama Hidetoshi , Yamago Shigeru , Shiraki Takashi , Sugiura Yukio 
Published: June 2006

Abstract
Two different classes of water-soluble fullerene derivatives, detergent-type and sphere-type, were synthesized. The derivatives were evaluated for their biological activities including cytotoxicity, DNA cleavage, and inhibition of HIV-protease and other enzymes. Both classes of compounds display generally similar behavior except for their cytotoxicity spectra against several cell lines. The fullerene derivatives bearing N-methylpyrrole were found to be photo-inactive with respect to DNA cleaving activity and cytotoxicity. A study on the kinetics for the inhibition of HIV-protease with detergent type derivative revealed that the compound is a potent fullerene-based HIV protease inhibitor, inhibiting the enzyme activity in a reversible and competitive manner with a Ki value of 0.32 μM.
Analysis of the Excitation and Emission Spectra of Tungstates and Molybdate
Authors: Saito Nobuhiro , Sonoyama Noriyuki , Sakata Tadayoshi 
Published: June 2006

Abstract
The excitation and emission spectra of CaWO4, MgWO4, PbWO4, ZnWO4, and CaMoO4 were analyzed by a configurational coordination model. The spectral line shapes simulated by a configurational coordination model with a singlet ground state and an excited triplet state well explained the line shape of the luminescence spectra and the line shape at the rising part of the excitation spectra of these salts at room temperature. The energy level of the excited triplet state and the reorganization energies at the ground sate and the triplet state were determined. It was concluded that the potential curve at the excited state becomes shallower than that at the ground state for these systems.
Towards a Calculation of the Electronic Structures of Macromolecules. I. Quadratically Convergent Method for a Direct Calculation of Localized Molecular Orbitals
Authors: Sano Tatsuji , Matsuoka Osamu 
Published: June 2006

Abstract
A super configuration–interaction method is applied to a direct calculation of orthogonal localized molecular orbitals (LMO). Its iterative procedure converges quadratically, retaining the initial forms of the LMOs. When the basis sets of large sizes are employed for the calculation, Davidson’s diagonalization method can be adopted beneficially, where the time-consuming four-index transformation of LMO integrals is replaced by simpler two-index transformations. Test calculations using double-zeta basis sets are reported in detail for H2CO (formaldehyde). B2H6 (diborane), C3H4(1-propyne [metylacetylene]), and cytosine. The implication of the method concerning macromolecular calculations is discussed.
Aggregation of Phosphoric Acid, Phenyl Dihydrogenphosphate, and Related Organophosphorus Acids in Conductometric Titration with Triethylamine in DMF
Authors: Hojo Masashi , Hasegawa Hiroshi , Chen Zhidong 
Published: June 2006

Abstract
The conductance increased linearly up to the equivalence point in the conductometric titration of diphenyl hydrogenphosphate ((PhO)2PO(OH)) with triethylamine (Et3N) in DMF at 25 °C. However, it was found that the conductometric titration of phenyl dihydrogenphosphate (PhOPO(OH)2, 1.0 × 10−3—1.0 × 10−2 mol dm−3) gave a maximum at the half-equivalence point (CHA : [Et3N] = 1 : 1/2) and not the linear curve to the equivalence point. Phosphoric (PO(OH)3), phenylphosphonic (PhPO(OH)2), and vinylphosphonic (CH2CHPO(OH)2) acids also gave maxima at the half-equivalence points. The appearance of maxima was explained by homoconjugation between the acid (HA) and the conjugate anion (A−) upon neutralization with the base (B) in DMF : B + 2 HA BH+···HA2−. Dibutyl hydrogenphosphate ((n-BuO)2PO(OH)) of higher concentrations also gave a (small) maximum at the half-equivalence point, while dimethylphosphinic acid ((CH3)2PO(OH)) gave no maximum in DMF. In less basic solvents, acetonitrile and benzonitrile, even diphenyl hydrogenphosphate, gave a maximum. The cause for the appearance of maxima at the half-equivalence point in DMF is discussed from the viewpoint of the basicities of the conjugate anion (A−) and the number of hydrogen bondings involved in the homoconjugation reaction. The ion-pair and quadrupole (the dimer of ion pairs) formation constants of the organophosphorus acids in DMF were obtained by conductometry. The equilibrium concentration of the dimer (H2A2) of PhOPO(OH)2 was found to exceed that of the ion pair (HA) at &gt;1.6 × 10−3 mol dm−3 of the acid.
Binding Data Analysis of the Interaction of Bovine Hemoglobin with Dodecyltrimethylammonium Bromide
Authors: Bordbar Abdul Khalegh , Moosavi-Movahedi Ali Akbar 
Published: June 2006

Abstract
The interaction of dodecyltrimethylammonium bromide, as a cationic surfactant, with bovine hemoglobin, as a biopolymer, has been investigated at different temperatures by an equilibrium dialysis technique. The obtained binding isotherms have been analyzed and interpreted by the Wyman binding potential model and other thermodynamic parameters which have been extracted on the basis of this model. A new method of analysis for evaluating the binding isotherms and estimating the free energy change, ΔGt, per mole of ligand has been proposed.
The unusual behavior of the Scatchard plot at 300 K was analyzed in terms of two sets of binding sites. The first set of binding sites was considered as electrostatic and the second as hydrophobic. The free energy of interaction () from the Wyman model was also resolved according to electrostatic and hydrophobic binding free energies.
A Willgerodt–Kindler Type Selenation of Dihalomethane Derivatives, Chloroform, and Sodium Trichloroacetate by Treating with a Base, Elemental Selenium, and an Amine
Authors: Shimada Kazuaki , Yamaguchi Minoru , Sasaki Tohru , Ohnishi Kenji , Takikawa Yuji 
Published: June 2006

Abstract
Treatment of dihalomethane derivatives, chloroform, or sodium trichloroacetate with elemental selenium in the presence of NaH and an excess amount of an amine gave the corresponding selenoamides, selenoureas, and bis(selenocarbamoyl) triselenides in modest yields. These products were afforded from reactive intermediates related to “selenocarbonyl halides” and “selenophosgenoids” generated by the reaction of dichloromethanide ions and trichloromethanide ion with N-alkylated aminopolyselenide species (R2N–(Se)n−).
Examination of the Conformational Properties of the Prymnesin System : A Computational Chemistry Approach
Authors: Glendenning Lionel , Igarashi Tomoji , Yasumoto Takeshi 
Published: June 2006

Abstract
Prymnesins are potent ichthyotoxic and hemolytic glycoside molecules isolated from the red tide alga Prymnesium parvum. Their unique molecular structure is conformationally rich with a number of key torsional bonds which were probed with contemporary conformational searching techniques in order to describe the three-dimensional structure of the prymnesin molecule. Important topological features include a backbone twist of 60° and an elongation length of 39.5 Å from ring “A” to ring “N” for the prymnesin-2 molecule in the nOe preferred conformation. An appreciation of these and other molecular structural and energetic features determined by computational techniques were examined with the aim of understanding how prymnesin-2 exhibits it’s potent biological activity in relation to these inherent structural traits.
Asymmetric Transformation of Phenylglyoxal into Mandelic Acid Catalyzed by Cyclodextrin-Based Glyoxalase Models
Authors: Tamagaki Seizo , Narikawa Jun , Katayama Atsushi 
Published: June 2006

Abstract
(2-Mercaptoethyl)amino-attached cyclodextrin provides a highly enantioselective environment during the transformation of phenylglyoxal into (S)-mandelic acid, although simple inclusion into native α-,β-, and γ-cyclodextrins and their 2-hydroxypropyl and methyl variants is not sufficient to cause appreciable asymmetric induction.
Enantioselectivity Enhancement of Ester Cleavage by a β-Sheet Polypeptide Containing Catalytic Triads in a Serine Protease
Authors: Fukushima Yasumasa 
Published: June 2006

Abstract
Catalytic activity and enantioselectivity of Poly(Asp–Leu–His–Leu–Ser–Leu) with a β-sheet structure for the hydrolysis of chiral phenylalanine p-nitrophenyl esters were compared with those of the peptide hexamer, under various conditions. The relationship between the β-sheet structure of the polypeptide and the hydrolytic properties was also investigated. Both the activity and the enantioselectivity for the polypeptide were higher than those for the peptide hexamer. The activity increased with pH, but the enantioselectivity was independent of pH. An increase of ethanol content in reaction solution led to a relatively lower rate constant and a higher enantioselectivity. The enantioselectivity decreased with increasing temperature; the activity increased to 25 °C and it reduced above 35 °C. Because the nucleophilicity of the polypeptide and the concentration effect of the substrate reduced by a decrease of the β-sheet content with temperature, the regular secondary structure may play an important role in these hydrolytic reactions. In addition, the efficient hydrolytic activity and the enantioselectivity were derived from activation parameters. The polypeptide may provide a good model for studying the relationship between enzymatic activity and steric structural formation.
Changes of the Aromatic Character of the Ring in Exocyclically Substituted Derivatives of Benzylic Cation as a Result of Varying Charge at the exo-Carbon Atom
Authors: Krygowski Tadeusz Marek , Wisiorowski Marcin , Nakata Kazuhide , Fujio Mizue , Tsuno Yuho 
Published: June 2006

Abstract
Analysis of the molecular geometry of the ring in 18 exocyclically substituted benzylic cation derivatives shows that an increase of delocalization of the positive charge over the ring is associated with a considerable decrease of its aromatic character. Separation of the aromatic character into energetic and geometric terms allows one to conclude that the effect of dearomatization due to delocalization of the positive charge in the ring is mostly reflected in the geometric term, i.e. by an increase of the alternation of bond lengths in the ring.
Dehydrooligopeptides. XIV. Syntheses of 2-[(Z)-1-Amino-1-alken-1-yl]oxazole-4-carboxylic Acid and the Main Common Skeleton of Thiostrepton Peptide Antibiotics, A10255G and J
Authors: Okumura Kazuo , Ito Akio , Saito Hiroyuki , Nakamura Yutaka , Shin Chung-gi 
Published: June 2006

Abstract
The practical synthesis of a unique dehydropentapeptide (2), the common main skeleton of thiostrepton macrocyclic peptide antibiotics, A10255G and J, is described. Peptide 2 is constructed from a novel 2-[(Z)-1-amino-1-propen-1-yl]oxazole-4-carboxylic acid, 2-(1-aminomethyl)- and 2-[(S)-1-aminoethyl]thiazole-4-carboxylic acid residues, besides L-threonine and dehydroalanine residues at the N- and C-termini, respectively. First, the general syntheses of various 2-[(Z)-1-amino-1-alken-1-yl]oxazole-4-carboxylic acid derivatives (11) and preparation of N-terminal dehydrodipeptides (17) containing the acid (11a) were done. Subsequent coupling of 17 with the C-terminal tripeptide comprised of the above two 2-(aminoalkyl)thiazole-4-carboxylic acid moieties (22) and (23) and serine moiety (4), and final β-elimination were tried and gave the desired protected 2 [(P)-2].
Radical Dissociation of 2,2′-Bis(2-aryl-3-benzothiophenonyl)s by Mechanical Energy
Authors: Mori Yukie , Yamada Naho , Kanazawa Miho , Horikoshi Yumiko , Watanabe Yuka , Maeda Koko 
Published: June 2006

Abstract
On applying pressure with a press in the solid state, the title compounds undergo homolysis of the central C–C bond to give green-colored radicals. X-Ray structure analysis for p-chloro derivative showed that the central C(2)–C(2′) bond was not elongated but had a normal distance (1.576 Å) as a hexa-substituted Csp3–Csp3 bond. The amount of the radical formed by mechanical energy depended on the substituents on the 2-phenyl rings and on the solvent of crystallization. As for the crystals containing no solvent, p-bromo and p-chloro derivatives showed higher reactivity than the unsubstituted compound, probably due to smaller dissociation enthalpy. The radical dissociation was suppressed by the presence of some solvent of crystallization. In the solvated crystals, the excess energy supplied by external mechanical energy would be transferred mainly to vibrational modes of the solvent molecules rather than to the substrate.
Cation-Exchanged Montmorillonite (Mn+-Mont)-Catalyzed Prins Reaction
Authors: Tateiwa Jun-ichi , Hashimoto Keiji , Yamauchi Takayoshi , Uemura Sakae 
Published: June 2006

Abstract
The Prins reaction of styrenes with paraformaldehyde or 1,3,5-trioxane in toluene in the presence of cation-exchanged montmorillonite (Mn+-mont), which worked as a Brønsted acid catalyst, at 80 °C produced 4-aryl-1,3-dioxanes selectively in up to 99% isolated yield with a turnover number of up to 5.9 × 102. Among the examined 21 Mn+-monts, Ce3+- and Fe3+-monts were revealed to be quite effective. Regeneration of the catalyst was confirmed with the Ce3+-mont, which could be effectively recycled at least three times. Many lanthanide metal ion-exchanged montmorillonites (Ln3+-monts) were prepared and characterized by X-ray powder diffraction (XRD) and temperature-programmed desorption of ammonia gas (NH3-TPD) methods.
Photomechanical Response of Azobenzene Containing Monolayers on Water Surface
Authors: Seki Takahiro , Fukuda Ryo-ichi , Yokoi Makoto , Tamaki Takashi , Ichimura Kunihiro 
Published: June 2006

Abstract
Monolayers of amphiphilic poly(vinyl alcohol)s and related low-molecular-mass compounds containing photochromic azobenzene (Az) were spread on a water surface. Their photomechanical responses induced by photoirradiation of UV (365 nm) and visible (436 nm) light were investigated. Illumination by UV light induced area expansion of Az monolayers up to ca. three times in magnitude, which strongly depended on the material, monitoring surface pressure, and subphase conditions. The expanded film of these molecular films reverted to the original area upon illumination with visible light. Use of a polymeric material was found to be advantageous to attain sufficient mechanical strength for full reproducibility and faster response. At a fixed area, reversible surface pressure changes were observed upon alternate UV and visible light illumination, and at 10—15 mN m−1 with the 6Az10-PVA monolayer the changes could be visualized plainly by watching motions of camphor grains. In the case of an Az amphiphile having the dissociative carboxylic acid head group, the photoresponsiveness was altered by pH changes and addition of Cd2+ ion in the subphase. Variations in the magnitude and response time of the photoinduced deformation were related to the packing state of Az monolayers evaluated by UV-visible absorption spectroscopy at the air–water interface.
Bioactivity of M2O–TiO2–SiO2 (M = Na, K) Glasses: An In vitro Evaluation
Authors: Kim Hyun-Min , Miyaji Fumiaki , Kokubo Tadashi , Kobayashi Masahiko , Nakamura Takashi 
Published: June 2006

Abstract
The formation of biologically active bonelike apatite on the surfaces of glasses and glass-ceramics is an essential condition for their bonding living bone. In the present study, apatite formation on the surfaces of M2O–TiO2–SiO2 (M = Na, K) glasses was examined in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma in order to evaluate their bioactivity. While none of the Na2O–TiO2–SiO2 ternary glasses formed the surface apatite, K2O–TiO2–SiO2 glasses, not only as SiO2-rich glasses but also as TiO2-rich glasses, formed the apatite. The alkali ions in the glasses exchanged with H3O+ ions in the fluid. The TiO2-rich or SiO2-rich hydrogel which was formed on the surfaces of the glasses induced apatite nucleation. The increased degree of the supersaturation of the fluid with respect to the apatite due to the increase in pH provided favorable conditions for apatite nucleation. This indicates that alkali titanates as well as alkali silicates can be basic components of bioactive glasses.
Multiplex Proton-Transfer and Electron-Transfer Natures Based on the 2,2′-Bi-1H-imidazole System. II. Crystal Structures and Charge-Transfer Complex Formations
Authors: Akutagawa Tomoyuki , Saito Gunzi , Kusunoki Masami , Sakaguchi Ken-ichi 
Published: June 2006

Abstract
Studies of the crystal structures and formation of a charge-transfer (CT) complex proved that 2,2′-bi-1H-imidazole (H2BIM0) forms a new system concerned with the interplay of proton-transfer (PT) and electron-transfer (or charge-transfer (CT)) interactions. X-Ray crystal analyses of newly isolated species, 2-(2-1H-imidazolyl)-1H-imidazolium (H3BIM+) and 2,2′-bi-1H-imidazolium (H4BIM2+), revealed the formation of strong hydrogen bonds along the side-by-side direction of the molecular plane. CT complexes of H3BIM+ and H4BIM2+ with the 7,7,8,8-tetracyanoquinodimethane derivatives (TCNQs) were synthesized by a method metathesis, and the crystal structure of (H3BIM+)2(TCNQ−)2(TCNQ0) was determined. During CT complex formation, the initial simple protonated states of [H3BIM+] or [H4BIM2+] changed to different ones, for example, [H4BIM2+]x[H3BIM+]1−x, [H3BIM+]x[H2BIM0]1−x, and H2BIM0. According to the protonated states of the H2BIM system, the formal charge of the TCNQs in the CT complexes varies from completely ionic, partial CT, to neutral. The mechanism of these complex formations was explained by differences in the acidities between the TCNQ anion radicals (TCNQs−•) and H3BIM+ or H4BIM2+. Higher acidities of H3BIM+ and H4BIM2+ than the TCNQs−• induce the following PT reaction: H3BIM+ (or H4BIM2+) + TCNQs−• → H2BIM0 (or H3BIM+) + HTCNQ•. The isolation of HTCNQ• was a failure due to the following disproportional reaction: 2HTCNQ• → TCNQ0 + H2TCNQ0. However, the formation of the 1,4-benzenedimalononitrile (H2TCNQ0) was confirmed by an analysis of the residual compounds after complex formation. Although the electronic absorptions of TCNQ complexes indicated both the partial CT state of TCNQ and a segregated stacking manner, semiconductive characters were observed. In a crystal of (H3BIM+)2(TCNQ−)2(TCNQ0), the H3BIM+ formed a planar dimer connected by two N–H···N hydrogen bonds, and TCNQ molecules existed as a charge-separated state with segregated trimer stacks. These dimer and TCNQ stacks were tightly connected by both N–H···N≡C hydrogen bonds, which spread into the overall crystal, and by the CT interaction. For the PT and CT system, we propose a synthetic strategy based on the redox potentials and acid dissociation constants.
Solvent-Dependent Photophysical Properties of a Phenothiazone Dye as an Optical Probe
Authors: Otsuki Soichi , Taguchi Takahisa 
Published: June 2006

Abstract
A phenothiazone dye, 7-dimethylamino-3H-phenothiazin-3-one, was investigated as an optical probe in homogeneous media. Two absorption bands appeared in aprotic solvents and dioxane–water and exhibited different dependencies on the solvent polarity/polarizability scale, π*. Both of the bands were quite different from that corresponding to the aggregated molecules or the protonated species of the dye. These results suggest the existence of two ground-state species with non-twisted and twisted conformations of the 7-amino group. The π* dependencies of the fluorescence maxima and the rate constants of the fluorescence decays showed three types of behavior in dioxane–water. The Lippert–Mataga plot of the spectral shift was interpreted by assuming two types of behavior in aprotic solvents. These facts suggest that the fluorescence comes from three emitting states which exist in fast equilibria. The strong polarity dependencies and the long wavelengths of the absorption and fluorescence, the large Stokes shift, and the appreciable fluorescence quantum yield make the dye useful as an optical probe of the polarity of a variety of microenvironments.
Reversal in Solvatochromism: An ET(30) Switch for a New Class of Cyanine Dyes
Authors: Mishra Bijay K , Kuanar Minati , Mishra Amaresh , Behera Gopa B 
Published: June 2006

Abstract
This paper reports the analysis of reversal in solvatochromism of a new class of cyanine dyes by using the ET(30) scale. The point of reversion is defined as a switch that identifies the hydrogen bond donor and hydrogen bond acceptor solvents.
Stereochemical Control in Microbial Reduction. XXVIII. Asymmetric Reduction of α,β-Unsaturated Ketones with Bakers’ Yeast
Authors: Kawai Yasushi , Saitou Kentarou , Hida Kouichi , Dao Duc Hai , Ohno Atsuyoshi 
Published: June 2006

Abstract
Bakers’ yeast reduction of α,β-unsaturated ketones affords optically active saturated ketones contaminated by allylic and saturated alcohols as minor components. Stereoselectivity of the reduction of carbon–carbon double bond strongly depends on the structure of β-aryl substituent. The bakers’ yeast reduction of β-phenyl enones gives saturated ketones in moderate stereoselectivity. Stereoselectivity is not altered by substitution at the para-position, whereas introduction of a substituent at the ortho- or meta-position drastically improves the stereoselectivity. Deuterium-labeling experiments reveal that the enzymatic reduction of carbon–carbon double bond proceeds with formal trans-addition of hydrogens regardless the efficiency of stereoselectivity. The resulting optically active ketone was converted to the precursor of (S)-iopanoic acid, an inhibitor of thyroxine 5′-deiodinase that is a thyroid hormone-converting enzyme and an oral cholecystographic agent.