bluuebunny/crossref_metadata_2025_split huggingface dataset:
CD Spectra and Cyclization of Linear Pentapeptides as Gramicidin S Precursors with a Benzyloxycarbonyl Group on the Side Chain of Orn Residue
Authors: Tamaki Makoto , Akabori Sadatoshi , Muramatsu Ichiro 
Published: August 2006

Abstract
Five pentapeptides related to gramicidin S, H–Val–Orn(Z)–Leu–d-Phe–Pro–OH, H–Orn(Z)–Leu–d-Phe–Pro–Val–OH, H–Leu–d-Phe–Pro–Val–Orn(Z)–OH, H–d-Phe–Pro–Val–Orn(Z)–Leu–OH, and H–Pro–Val–Orn(Z)–Leu–d-Phe–OH, were cyclized with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole. The pentapeptide with a Pro residue at the C-terminal formed predominantly the cyclic dimer (diZ-gramicidin S), while the pentapeptide with an Orn(Z) residue at the C-terminal produced exclusively the cyclic monomer (Z-semigramicidin S). The reaction mode of those pentapeptides was correlated with their CD spectra.
Isolation of (η5-Cyclopentadienyl)(1,2,3,4,5-η6-exo-methoxy-7-oxo-2,4-cycloheptadienyl)ruthenium(II) as a Key Intermediate for the Selective H/D Exchange on Its Coordinated Tropone Moiety by KOH/CD3OD
Authors: Kimura Masaru , Morita Mitsunobu 
Published: August 2006

Abstract
(η5-Cyclopentadienyl)(η5-ligand)ruthenium(II) (ligand = 1,2,3,4,5-η6-exo-methoxy-d3-7-oxo-2,4-cycloheptadienyl-2d 3a, 1,2,3,4,5-η6-exo-methoxy-7-oxo-2,4-cycloheptadienyl-2d, 1,2,3,4,5-η6-exo-methoxy-7-oxo-2,4-cycloheptadienyl, and 1,2,3,4,5-η6-exo-ethoxy-7-oxo-2,4-cycloheptadienyl) was isolated in fairly good yields by treatment of (η5-C5H5)(η6-tropone)ruthenium(II)BF4 with KOH in CD3OD, CH3OD, CH3OH, and ethanol, respectively. The selectively deuterated tropone-2d was readily removed by photolysis of 3a accompanied by demethoxylation with visible light in the presence of large excess of P(OCH3)3.
Emulsion Copolymerization of Styrene with Amphiphilic Poly(2-oxazoline) Macromonomer Bearing Ammonio Group at the Chain End
Authors: Uyama Hiroshi , Sato Masahiro , Matsumoto Yasuhiro , Kobayashi Shiro 
Published: August 2006

Abstract
Emulsion copolymerization of styrene with a block-type amphiphilic poly(2-oxazoline) macromonomer having a quaternary ammonio group at the chain end was performed to produce monodisperse polymer particles in the submicron range. Poly(2-oxazoline) chains and the ammonio group were localized on the particle surface.
The Lowest Lying Singlet and Triplet States of the Halonitrenium Ions NX2+ and NHX+ and a Comparison with the Carbon Analogues CX2 and CHX (X = F, Cl, Br, I). A Theoretical Study
Authors: Gobbi Alberto , Frenking Gernot 
Published: August 2006

Abstract
The equilibrium geometries, energy differences, and vibrational frequencies for the energetically lowest lying 1A1 and 3B1 states of NH2+, NHX+, and NX2+ (X = F, Cl, Br, I) are theoretically predicted using ab initio quantum mechanical methods at the MP4/6-311G(2df)//MP2/6-31G(d) level of theory. Effective core potentials are employed for bromine and iodine. The isoelectronic carbenes CH2, CHX, and CX2 are also calculated. The electronic structure of the molecules is investigated using the topological analysis of the electronic wave function.
Energy Levels and Line Intensities of Diatomic Molecules. Application to Alkali Metal Molecules
Authors: Katô Hajime 
Published: August 2006

Abstract
Calculation of rotational level energies and line intensities of diatomic molecules and its application to alkali metal diatomic molecules are reported. The effects of spin–orbit interaction, rotational interaction, spin–rotation interaction, spin–spin interaction, hyperfine interaction, and Zeeman interaction are considered.
Theoretical Studies of the Aluminum–Water Clusters Al(H2O)n and Their Ions [Al(H2O)n]+
Authors: Watanabe Hidekazu , Aoki Masaharu , Iwata Suehiro 
Published: August 2006

Abstract
With the ab initio molecular orbital calculations, the structures of the neutral clusters Al(H2O)n were optimized, and the vertical ionization energy was evaluated. Two types of the stable clusters are found; the one has a structure [Al(H2O)](H2O)n−1 and the other has [Al(H2O)2](H2O)n−2. The former type of the clusters, in which only one water molecule is directly bonded, is more stable than the latter. The calculated ionization energy with the multi-reference configuration interaction is in very good agreement with the experimental energy determined recently by Fuke’s group, only for the series of the former type of clusters. The structures of the [Al(H2O)n]+ were determined, and the incremental stability energy was evaluated. A very stable ring structure is found in [Al(H2O)4]+. The ring structure persists in [Al(H2O)5]+, but only substantial deformation. The extremely stable structure of [Al(H2O)4]+ explains the observed product distribution of the photo-dissociation recently reported by Fuke’s group.
Structure and Vibrational Analysis of Protonated Ethane C2H7+
Authors: Obata Shigeki , Hirao Kimihiko 
Published: August 2006

Abstract
The stability and vibrational frequencies of protonated ethane, C2H7+, have been studied by ab initio molecular orbital theory. The IR spectra for C2H7+ recorded by Y. T. Lee’s group were interpreted from a theoretical point of view. Ab initio computations predict the existence of two isomers, a bridged structure, and a tight and loose open form. The loose open form is represented as an H2 molecule attached loosely to a classical open C2H5+ ion. The different behavior observed in the IR spectra can be attributed to the changing ratio of the bridged C2H7+ to the open C2H5+ isomers. The final interpretation of these data is that the spectrum at 150 Torr (1 Torr = 133.322 Pa) arises from the bridged structure which is the most stable form of C2H7+. The additional band in the spectrum observed at 60 Torr originates form the weakly bound complex which dissociates upon absorbing a single IR photon.
Formation of the Oxanickelacyclopentene Complex from Nickel(0), Carbon Dioxide, and Alkyne. An ab initio MO/SD-CI Study
Authors: Sakaki Shigeyoshi , Mine Kazuya , Taguchi Daisaku , Arai Toru 
Published: August 2006

Abstract
An ab initio MO/SD-CI study was carried out on the formation reaction of oxanickelacyclopentene, 1, from Ni(PH3), CO2, C2H2. Because C2H2 coordinates to Ni(PH3) more strongly than does CO2 by ca. 11 kcal mol−1 at the SD-CI level, coordination of C2H2 to Ni(PH3) takes place first. The resultant Ni(PH3)(C2H2) reacts with CO2 to yield 1 with no activation barrier and a significant exo-thermicity of 68 kcal mol−1 at the HF level, but a moderate barrier of 30 kcal mol −1 and exo-thermicity of 17 kcal mol−1 at the SD-CI level. 1 takes a three-coordinate T-shaped structure, due to the low-spin d8 electron configuration of Ni(II). Ni(PH3) stabilizes the transition state through a charge-transfer interaction from the occupied d orbital of Ni to the unoccupied π* orbitals of CO2 and C2H2. The electron re-distribution during the reaction is discussed, based on orbital mixing among the d orbital of Ni and the π and π* orbitals of C2H2 and CO2.
An Ab Initio Molecular Orbital Approach to Electronic Structures of the F Center in NaCl. Effects of Basis Set and Cluster Size
Authors: Adachi Jun-ichi , Kosugi Nobuhiro 
Published: August 2006

Abstract
NaCl clusters with a Cl− ion vacancy, Na66+, Na6Cl126−, Na14Cl122+, and Na14Cl184−, are calculated by ab initio molecular orbital calculations to investigate electronic states of F centers in alkali halides. The model clusters are embedded in a point charge field. Description of “1s” ground and “2s” and “2p” excited states of an electron trapped by the vacancy is discussed concerning to basis set and cluster size. The 1s and 2p wave functions of the F-center electron are efficiently described by one s Gaussian-type function placed on the vacancy center and one p Gaussian-type functions placed on the nearest neighbor Na ions when Na 3s is of double ζ quality. The 1s–2p excitation energy is in good agreement with the experimental data. As regards the electron binding energies and the orbital size the 1s wave function almost converges in the cluster Na6Cl126− but the 2p wave function does not converge even in the largest cluster Na14Cl184−.
Synthesis and Structures of Infinite Sheet Copper(I) Complex Polymers with 2,6-Dimethylpyrazine, {[Cu2(C6H8N2)3](ClO4)2(C3H6O)2}∞, and with 2-Chloropyrazine, {[Cu2(C4H3N2Cl)4.5](ClO4)2}∞
Authors: Kitagawa Susumu , Kawata Satoshi , Kondo Mitsuru , Nozaka Youichi , Munakata Megumu 
Published: August 2006

Abstract
The new copper(I) coordination polymers, {[Cu2(2,6-Me2pz)3](ClO4)2(C3H6O)2}∞ (1) and {[Cu2(2-Clpz)4.5](ClO4)2}∞ (2) (2,6–Me2pz = 2,6-dimethylpyrazine; 2–Clpz = 2-chloropyrazine) have been synthesized and their structures have been X-ray crystallographically characterized. 1 crystallizes in the monoclinic, space group P21/a with a = 15.520(5), b = 19.315(2), c = 12.493(2) Å, β = 110.82(2)°, U = 3322(2) Å3, and Z = 4. 2 is orthorhombic, space group Pbca with a = 28.567(6), b = 17.560(9), c = 11.512(9) Å, U = 5774(8) Å3, and Z = 8. These complexes show an infinite sheet structure of macrocations with uninteracting ClO4− anion. 1 shows planar sheets composed of Cu6 hexagons, in which copper atoms are three-coordinate and linked by 2,6-Me2pz molecules. Acetone molecules sit over the cavities of the Cu6 hexagons, resulting in an intercalated layer between the copper sheets. 2 provides the unique polymers having an unprecedented four coordination geometry in binary copper–pyrazine systems. There are terminal and bridging types of 2-Clpz molecules, which produce Cu6 and Cu4 motifs for infinite pleated sheets. The factors governing the mode of polymerization are found by examination of the crystal structures for a series of copper(I) polymers of pyrazine derivatives.
51V NMR Studies of Crystalline Divalent Metal Vanadates and Divanadates
Authors: Hayakawa Satoshi , Yoko Toshinobu , Sakka Sumio 
Published: August 2006

Abstract
51V static and magic-angle spinning (MAS) NMR spectra of crystalline divalent metal vanadates, M3(VO4)2 (M = Mg, Sr, Ba, Zn, Pb) and Mg2M′(VO4)2 (M′ = Sr, Ba, Pb) and divanadates, M2V2O7 (M = Mg, Ca, Sr, Ba, Zn, Pb) have been measured. In vanadates and dichromate-type divanadates, the 51V isotropic chemical shifts decrease linearly with decreasing electronegativity of divalent metal atom adjacent to the VO4-tetrahedron. This was interpreted by considering that the electron density and the symmetry of VO4-tetrahedron increases with decreasing electronegativity of divalent metal atom. This effect was more significant in vanadates than in divanadates. In divanadates the isotropic chemical shifts of the thortveitite-type configuration appeared at lower frequencies than that of the dichromate-type configuration. This was explained by assuming that the degree of s-hybridization of the oxygen orbitals in the V–O–V bonds is higher in the thortveitite-type than in the dichromate-type.
Pressure Effects on the Complexation of t-Butylammonium Perchlorate by Crown Ether
Authors: Yamada Hiroaki , Kazuoka Mayumi , Moriguchi Naoyuki , Sera Akira 
Published: August 2006

Abstract
The effects of hydrostatic pressure on the complexation of t-butylammonium perchlorate by crown ether in methanol were studied by means of a high-pressure high-resolution NMR method at 33.5 °C. The complexation was shown to be promoted upon pressurization.
Intramolecular Charge-Transfer Interaction in 7,12-Epoxy-7,12-dihydrobenz[a]anthracene-8,11-dione and 5,12-Epoxy-5,12-dihydronaphthacene-1,4-dione
Authors: Yamamura Kimiaki , Miyake Hideyoshi 
Published: August 2006

Abstract
7,12-Epoxy-7,12-dihydrobenz[a]anthracene-8,11-dione and 5,12-epoxy-5,12-dihydronaphthacene-1,4-dione have been synthesized. Both of them had pronounced intramolecular charge-transfer bands, although the donor and the acceptor were in unfavorable spatial position and furthermore in one of them its HOMO–LUMO interaction is forbidden.
Detection of Superoxide Ions from Photoexcited Semiconductors in Non-Aqueous Solvents Using the ESR Spin-Trapping Technique
Authors: Noda Hiroyuki , Oikawa Kazuo , Ohya-Nishiguchi Hiroaki , Kamada Hitoshi 
Published: August 2006

Abstract
The ESR spin-trapping technique using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and N-t-butylbenzylideneamine N-oxide (PBN) as spin-trap reagents has been applied to detect active oxygen radicals generated by the photoexcitation of powdery semiconductors (TiO2, WO3, CdS, and Fe2O3) in non-aqueous solvents such as dimethylsulfoxide (DMSO), benzene, ethanol, and acetonitrile. Appreciable amounts of superoxide ion (O2−) were detected from TiO2, WO3, Fe2O3, and CdS suspensions under photoexcitation. The hyperfine splitting constants (hfsc) of the superoxide ion and carbon(C)-centered radical spin adducts for DMPO and PBN could be determined in various non-aqueous solvents. Some characteristic features for the production of the superoxide ion and C-centered radicals are discussed in connection with the energy-level diagrams of the semiconductors and the redox potentials of the superoxide ion and non-aqueous solvents.
Spectroscopic and Structural Characterization of Formazanyl Copper Complexes
Authors: Kawamura Yoshiko , Yamauchi Jun , Ohya-Nishiguchi Hiroaki 
Published: August 2006

Abstract
1-(o-Substituted phenyl)-3,5-diphenyl-5-formazans form various kinds of complexes. The copper(II) complexes of 1,3,5-triphenyl-5-formazan and 1-(p-Cl and o-CH3)-3,5-diphenyl-5-formazans (Group I) showed about 0.012 cm−1 of the parallel component of the copper(II) ESR splitting constant; those of the copper(II) complexes of 1-(o-Cl and o-Br)phenyl-3,5-diphenyl-5-formazans (Group II) were 0.018 cm−1. The f-values in the near-infrared region of the former complexes were almost 10-times larger than those of the latter complexes. The difference was attributed to a tetrahedral distortion of about 65—70 degrees from the planar structure in Group I; the complexes of Group II, however, were almost planar. The complexes of 1-(o-OH and o-COOH)phenyl-3,5-diphenyl-5-formazans (Group III) showed exchange interactions between two copper(II) ions with exchange energies of −375 and +33.5 cm−1 for the former and the latter complexes of Group III, respectively. Referring to the exchange and dipolar interactions, the Cu–Cu distances and the Cu–O–Cu bridging angles are discussed.
Theoretical Studies of the Reactions of Hydrogen Sulfide and Methanethiol with the H, F, and O(3P) Atoms. Possibilities of the Bimolecular Homolytic Substitution (SH2) Reactions
Authors: Takane Shin-ya , Fueno Takayuki 
Published: August 2006

Abstract
Potential energy profiles of the radical substitution reactions of H2S with some atomic radicals X (X = H, O, F) and of CH3SH with the hydrogen atom have been investigated by ab initio molecular orbital calculations employing the 6-31G** basis sets. All the reactions studied have proved to be elementary reactions with no intermediate adducts involved. At the MRD-CI level using the 6-31G** plus the Rydberg s and p orbitals on sulfur, the activation energies of the homolytic substitution reactions H2S + X → H + HSX are calculated to be 50, 127, and 104 kJ mol−1 for X = H, O, and F, respectively, which are uniformly higher than those calculated for the hydrogen abstraction reactions H2S + X → SH + XH. For the substitution reaction CH3SH + H → CH3 + H2S, however, the activation energy calculated is as low as 19 kJ mol−1, which is even slightly lower than that for the abstraction CH3SH + H → CH3S + H2. The predicted prevalence of the homolytic substitution reaction of CH3SH over the hydrogen abstraction is qualitatively in harmony with observations.
Complexation Behavior of Heterocyclic Hydrazones. I. Structure and Acid-Base Equilibria for Heterocyclic Hydrazones
Authors: Taya Toshiki , Sakamoto Tsukasa , Doi Kunio , Otomo Makoto 
Published: August 2006

Abstract
The acid-base equilibria of twenty-one hydrazones substituted by phenyl, pyridyl and/or quinolyl groups have been investigated in aqueous solutions over the region of H− to H0 acidity function by a spectrophotometric method at 25 °C. For 2-pyridinecarbaldehyde 2-(5-substituted)pyridylhydrazones, although the proton dissociation of the neutral species (HL) satisfied a Hammett correlation, those of H2L+ and H3L2+ did not. The thermodynamic parameters for the proton dissociations of H2L+ and H3L2+ of seven representative liqands were determined by a temperature-coefficient method at 25 °C and an ionic strength of 0.1 (KCl). The enthalpy and entropy changes for the proton dissociations of H3L2+ and H2L+ were influenced by the steric effects of the methyl group and/or the introduced quinolyl ring. An analysis of the pH dependence of the 1H NMR signals for three hydrazones in an acetone-d6–D2O solution gave more profitable information concerning the fine structures of HL, H2L+, and H3L2+. Each 1H and 13C NMR chemical shift of some ring-substituted methyl derivatives (HL form) in a dioxane–D2O solution has been briefly assigned. On the other hand, a single-crystal X-ray analysis, 1H NMR data in chloroform-d and thermodynamic data for di-2-pyridyl ketone 2-pyridylhydrazone (DPPH) suggested that the intramolecular hydrogen bond in the DPPH molecule is broken by the addition of a proton to the H2L+ species in an aqueous solution.
Mechanism of Silica Gel Dissolution in Water in the Presence of Pyrocatechol
Authors: Mizutani Tadashi , Takahashi Koji , Kato Tsutomu , Yamamoto Jiro , Ueda Nasuo , Nakashima Ruka 
Published: August 2006

Abstract
The rates of dissolution of silica gel in aqueous alkaline solutions containing pyrocatechol were measured. At pH 10, all of the silica gel was dissolved in the presence of pyrocatechol at 25 °C for 48 h (SiO2 0.3 g and pyrocatechol 0.04 mol in 15 ml of water). The rates of silica-gel dissolution increased with increasing pyrocatechol concentration. Four moles of pyrocatechol were needed to dissolve one mole of SiO2. The rate of dissolution was first order in solid SiO2 concentration. Langmuir-type adsorption of pyrocatechol to the silica-gel surface was assumed to explain the rate dependence on the pyrocatechol concentration.
Preparation and Crystal Structure of Aqua(ethanol)tetrakis(μ-salicylato-O,O′)dicopper(II)–Ethanol–Water (1/1/1)
Authors: Yoneda Kimio , Uchiyama Khoichi , Boettcher Barry , Inouye Yoshinobu 
Published: August 2006

Abstract
A new dinuclear copper(II) salicylate, [Cu2(C7H5O2)4]·2C2H5OH·2H2O, was prepared from copper(II) hydroxide and excess salicyclic acid in 80% ethanol. The structure was clarified by a single crystal X-ray analysis.
Synthesis of 5,15-Diaryl-Substituted Oxochlorins from 5,15-Diaryloctaethylporphyrin
Authors: Osuka Atsuhiro , Marumo Shinji , Maruyama Kazuhiro 
Published: August 2006

Abstract
5,15-Diaryl-substituted oxochlorins were prepared from osmium tetraoxide oxidation of 5,15-diaryloctaethylporphyrin followed by acid-catalyzed pinacol rearrangement. Optical and electrochemical properties of this macrocyclic ring are studied by measuring the absorption and fluorescence spectra, fluorescence lifetimes, and one-electron oxidation and reduction potentials.
Facile Alkoxyl Exchange of 2-Methoxybenzoates via Nucleophilic Aromatic Substitution with Sodium Alkoxides in Dimethylformamide
Authors: Hattori Tetsutaro , Satoh Seiichi , Miyano Sotaro 
Published: August 2006

Abstract
Methyl 2-methoxybenzoate undergoes facile nuclear-methoxyl displacement by treatment with sodium butoxide or isopropoxide in dimethylformamide.
Increased Adverse Drug Reactions to Antimicrobials and Anticonvulsants in Patients with HIV Infection
Authors: Lin Daren , Tucker M Jane , Rieder Michael J 
Published: August 2006

Objective: To review the incidence, signs, symptoms, and mechanisms of adverse drug reactions (ADRs) to sulfonamides, anticonvulsants, and antimycobacterial medications among people with HIV. Data Sources: Searches of MEDLINE/PubMed (1980–November 2005) and National Library of Medicine Meeting Abstracts (1989–November 2005), as well as hand searches of journals and abstracts, were conducted to identify primary literature. Reference lists were reviewed to identify additional relevant reports. Study Selection and Data Extraction: Relevant articles and abstracts, particularly of in vitro experiments and clinical studies, were compiled and reviewed. Data Synthesis: ADRs, especially in HIV-infected patients, are a cause for concern. Sulfonamides, anticonvulsants, and antimycobacterial drugs are commonly used to prevent and treat complications of HIV, including seizures and opportunistic infections. Patients with HIV have a much greater rate of ADRs to these drug classes, including severe and life-threatening hypersensitivity reactions. Several mechanisms of these ADRs have been postulated. Sulfamethoxazole and anticonvulsant hypersensitivity may involve the increased formation and decreased detoxification of reactive metabolites. The mechanisms for the marked increase in hypersensitivity ADRs to antimycobacterial drugs may be related to an altered immune profile in patients infected with both tuberculosis and HIV. Conclusions: ADRs to antimicrobial and anticonvulsant therapy cause markedly increased morbidity and mortality in HIV-positive patients. Further research involving the interaction between HIV and the increased ADRs to these drugs is required.
Choosing the Appropriate Antithrombotic Agent for the Prevention and Treatment of VTE: A Case-Based Approach
Authors: Nutescu Edith A , Wittkowsky Ann K , Dobesh Paul P , Hawkins David W , Dager William E 
Published: August 2006

Objective: To review the risk of venous thromboembolism (VTE) in various patient populations and evaluate the agents available for the prevention and treatment of VTE using a case-based approach. Data Sources: A MEDLINE search (1995–July 2006) was conducted to identify relevant literature. Additional references were reviewed from selected articles. Study Selection and Data Extraction: Articles related to the prevention of VTE in orthopedic surgery, general surgery, and medically ill patients, as well as the treatment of VTE, were reviewed. Data Synthesis: Pharmacologic options for the prevention and treatment of VTE include warfarin, unfractionated heparin (UFH), low-molecular-weight heparins (LMWH), and fondaparinux. Current guidelines support the use of warfarin, LMWH, or fondaparinux for VTE prophylaxis following lower limb major orthopedic surgery. For VTE prophylaxis in hospitalized medical patients or patients undergoing general surgery, use of UFH and LMWH is supported; however, recent data on fondaparinux suggest that it is also effective in these patient populations. The use of UFH or LMWH (both in conjunction with warfarin) for treatment of acute deep venous thrombosis or nonmassive pulmonary embolism is recommended. Recent data suggest that fondaparinux (in conjunction with warfarin) is also effective for the treatment of VTE. A variety of pharmacokinetic, pharmacodynamic, and pharmacoeconomic factors differentiate each agent for the various indications. Conclusions: Currently, a “one-size-fits-all” anticoagulant is not available for treatment of VTE. A variety of patient factors, including type of surgery, medical indication, thrombotic risk factors, bleeding risk, history of heparin-induced thrombocytopenia, and a variety of comorbid conditions can affect the safety, efficacy, and selection of appropriate VTE therapy.