bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of D-Amino Acid-Containing Basic Peptides with Different Hydrophobicity on the Antimicrobial and Cytotoxic Activity
Authors: Kiyota Taira , Yanagida Ryoko , Oka Masahito , Miyoshi Mie , Lee Sannamu , Sugihara Gohsuke 
Published: September 2002

Abstract
In order to investigate the structure-activity relationships between the hydrophobicity, differences in the number of positive charged amino acids and D-amino acids as well as their action mechanism with different bio-membranes, we designed and synthesized two sets of 12-mer model peptides originating from an amphiphilic antimicrobial model peptide and a D-amino acid-containing non-amphiphilic peptide. The introduction of D-amino acid in peptides led not only to decreases in the hydrophobicity, helical content, and hemolytic activity, but to an increase in the antimicrobial activity against Gram-positive and -negative bacteria. The relative peptide hydrophobicity was estimated in terms of the peptide elution time, expressed by linear trifluoroacetic acid (TFA)-water to TFA-acetonitrile gradients on C18 reverse-phase high-performance liquid chromatography (RP-HPLC). The retention behavior of model peptides on RP-HPLC is correlated with the activity and selectivity for mammalian cells, Gram-positive and -negative bacteria: The α-helical amphiphilic structure is required for cytolytic ability against mammalian cells, but is not necessary for bacterial activity. Additionally, the peptides have different hydrophobicity regions in which they show their optimum activity against both bacteria and erythrocytes. In the highest hydrophobisity region the peptides display high levels of hemolytic activity. At medium hydrophobicity levels, the peptides are able to display to high levels of activity against Gram-positive bacteria. In the lowest hydrophobisity regions the peptides are able to display high levels of activity against Gram-negative bacteria. This may be useful in designing clinically effective antimicrobial peptides with highly potent activity and high bacterial selectivity.
Directive Effect of the 2- and 3-Axial Hydroxy Groups That Appeared in the Complex Metal Hydride Reduction of Cyclohexanones
Authors: Senda Yasuhisa , Kikuchi Nobuhito , Inui Ayuko , Itoh Hiroki 
Published: September 2002

Abstract
A significant directive effect of the 2-axial hydroxy group appeared in the LiAlH4, NaBH4, and Zn(BH4)2 reduction of cyclohexanone, while the 3-axial hydroxy group exhibited a steric hindrance. The distance between the carbonyl carbon and the hydroxy group which interacts with the hydride reagent is mainly responsible for such a difference. In the reduction of Na[B(OAc)3H], both the 2- and 3-axial hydroxycyclohexanones exclusively gave the products which were obtained by the hydride approaching from the side of the hydroxy group. The key point of this stereoselectivity is the formation of Na[B(OAc)2(OR)H], which is far more reactive than the parent hydride, by exchanging the acetate ion with the alkoxide.
Absolute Conformation and Chiroptical Properties. VII. 9(1′)-Msc and Psc Forms of 9-(2-Fluoro-1,1-dimethylethyl)- and 9-(1,1-Dimethylpropyl)-11,12-bis(methoxycarbonyl)-9,10-dihydro-9,10-ethenoanthracenes
Authors: Toyota Shinji , Yoshida Satoshi , Kojima Hiroharu , Oki Michinori 
Published: September 2002

Abstract
The racemic forms of sc-9-(2-fluoro-1,1-dimethylethyl)- and 9-(3-iodo-1,1-dimethylpropyl)-11,12-bis(methoxycarbonyl)-9,10-dihydro-9,10-ethenoanthracene were prepared by treatment of the corresponding carboxylic acid with xenon difluoride and by reduction of 9-(1,1-dimethyl-3-oxopropyl) compound followed by a reaction with iodine in the presence of imidazole, respectively. The fluoro and the iodo compounds were resolved on a chiral column. The absolute conformations of these compounds were determined by deriving them by the same methods from the carboxylic acid and the aldehyde of known absolute conformations. Reduction of the iodo compound with Raney nickel in 1-propanol afforded optically active sc-9-(1,1-dimethylpropyl) compound. In the CD spectrum, the Psc-(-) fluoro compound showed a broad and large trough at ca. 240 nm, similarly with the other halogen compounds, and a stronger Cotton effect at ca. 220 nm than the other halogen compounds. The Psc-(+)-9-(1,1-dimethylpropyl) compound showed a quite different CD spectrum from those of other halogen compounds. Thus the importance of the halogen, though remote from any chromophore, in determining the CD spectra of the title compounds and analogous ones was confirmed.
Radical Cyclization of N-Allyl-2-halo Amide in Water
Authors: Wakabayashi Katsuyu , Yorimitsu Hideki , Shinokubo Hiroshi , Oshima Koichiro 
Published: September 2002

Abstract
Triethylborane-induced radical cyclization of N-allyl-2-iodo amide proceeded smoothly in water to give the corresponding γ-lactam in good yield. Radical cyclization in acidic media was also effective. Chloroacetamide, combined with sodium iodide, was available as a substrate for the atom transfer radical cyclization in water to furnish the iodomethyl-substituted γ-lactam.
Structure and Dynamics of Silica and Acrylamide Gels
Authors: Song Youngjun , Im Seung Soon , Han Yang-Kyoo , Sohn Daewon 
Published: September 2002

Abstract
The structure and dynamics of silica and acrylamide gels were studied using a probe diffusion technique of dynamic light scattering (DLS). Latex particles, diameter = 0.05 μm, embedded in the gel network serve as a probe through their diffusion behavior within the network. A quantitative analysis of the homogeneity of the gel is introduced based on a shift of the correlation function of the dynamic light scattering. The lag time of the particles' correlation function in a completed inorganic silica gel is increased by increasing the contents of the gel network; but the particles' diffusion coefficient in a viscoelastic (acrylamide) gel lowers the f(A)max, the maximum value of the y-axis in the correlation function. The silica gel makes a more homogeneous and compact structure than that of a PAA gel, which has partial heterodyning, by increasing the solid contents of the network density.
Radiation-Induced Coloration of Photochromic Dithienylethene Derivatives in Polymer Matrices
Authors: Irie Setsuko , Irie Masahiro 
Published: September 2002

Abstract
The high-energy radiation-induced coloration of photochromic dithienylethenes was studied in various polymer matrices with the aim of developing a reusable color plastic dosimeter. Upon γ-irradiation, polystyrene films containing 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene 1a and 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene 2a turned red and blue, respectively. The red and blue colors disappeared upon irradiation with visible light, and the films could be reused. In both films the absorption intensities of the colors increased linearly with the absorbed dose. Although radiation-induced coloration was clearly detected in polystyrene films, a color change was scarcely observed in poly(methyl methacrylate) (PMMA) and poly(N-vinyl carbazole) containing 1a and 2a. Excitation energy transfer from polymers to dithienylethenes is considered to play a role in the coloration process in polymer films.
Fatigue Mechanism of Photochromic 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene
Authors: Higashiguchi Kenji , Matsuda Kenji , Kobatake Seiya , Yamada Taro , Kawai Tsuyoshi , Irie Masahiro 
Published: September 2002

Abstract
The fatigue mechanism of photochromic 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied in hexane solution. Upon irradiation with ultraviolet light, two kinds of by-products were produced in addition to normal photochromic reactions. The major by-product was isolated by HPLC, and was characterized by 1H NMR and absorption spectroscopies and X-ray crystallographic analysis. A minor by-product was also isolated and analyzed with a mass spectrometer. Based on the molecular structural analysis a possible photofatigue mechanism of the dithienylethene was proposed.
The Structure of Sulfur Adsorbed on Pt-Na2O/Al2O3 Catalyst and Its Influence on Isobutane Dehydrogenation
Authors: Kobayashi Junya , Shimizu Takashi , Mizushima Takanori 
Published: September 2002

Abstract
The structures of the sulfur species on a sulfurized Pt-Na2O/Al2O3 catalyst were characterized by Extended X-ray Absorption Fine Structure (EXAFS) and temperature-programmed reaction (TPR) experiments. EXAFS indicated that PtS2 is formed on a surface of Pt particles. A TPR experiment using deuterium indicated that HS- is the major species on the catalyst and that the HS- bridges the PtS2 and Na2S particles. This HS- was effective in enhancing the selectivity for isobutane dehydrogenation.
Photo-Induced Electron-Transfer Reactions of Cyclic Organosilanes and Related Compounds
Authors: Kako Masahiro , Nakadaira Yasuhiro 
Published: September 2002

Abstract
Under photo-induced ET conditions in the presence of CCl4 and BF4-, a Si-Si σ-bond readily undergoes chlorinative and fluorinative cleavage, and gives the corresponding chloro- and fluoro-silanes in good yields. In contrast co-photolysis of an aromatic nitrile with a disilane and a tetraalkyl group 14 metal effects selective silylation and alkylation of the nucleus at the position where spin density is high on its radical anion. Chlorination with CCl4 and the intra-molecular trap with the hydroxy group have clarified the radical cationic nature of the intermediate in the photo-induced electron transfer reactions of organooligosilanes. On the other hand, on photo-induced electron transfer, 7-silabicyclo[2.2.1]heptadiene derivatives undergo skeletal rearrangement to give 2-silabicyclo[3.2.0]heptadiene and 1-silabicyclo[2.2.1]heptadiene derivatives which are also the products from the direct photolysis. 7,8-Disilabicyclo[2.2.2]octadiene derivatives afford 1,2-dimethoxydisilane and 1,2-difluorodisilane, respectively on photo-induced electron transfer in the presence of methanol and BF4-. 1,2-Disilacyclohexadiene derivatives undergo ring contraction to give the corresponding silacyclopentadienes under photo-induced electron transfer conditions. Structural and electronic characteristics of the radical cation derived from these cyclic unsaturated organosilanes by MO calculations have been discussed.
Asymmetric Synthesis of β-Amino Acids by Addition of Chiral Enolates to Nitrones via N-Acyloxyiminium Ions
Authors: Kawakami Toru , Ohtake Hiroaki , Arakawa Hiroaki , Okachi Takahiro , Imada Yasushi , Murahashi Shun-Ichi 
Published: September 2002

Abstract
N-Acyloxyiminium ions, generated by the reaction of nitrones with acyl halides, are highly reactive species and undergo facile reaction with a wide range of nucleophiles, such as ketene silyl acetals, titanium(IV) and boron enolates, hydrido- and allyltin(IV) reagents, and alkynyltitanium(IV) reagents, to give α-substituted amine derivatives. Optically active β-amino acids can be prepared by the reaction of N-acyloxyiminium ions with both boron and titanium(IV) enolates bearing chiral auxiliaries. Reversal of diastereoselectivity was observed by the reactions of the boron and titanium(IV) enolates. Using these reactions, all of the four stereoisomers of α-methyl-β-phenylalanines, for example, can be prepared highly diastereoselectively. Cyclic N-acyloxyiminium ions are useful for the asymmetric synthesis of pyrrolidine and piperidine alkaloids; (5R,8R,8aS)-5-cyano-8-methylindolizidine, which is a common key intermediate for synthesis of 5-substituted 8-methylindolizidines, was prepared selectively.
Intramolecular Assistance of Electron Transfer from Heteroatom Compounds. Electrochemical Oxidation of 2-(2-Pyridyl)ethyl-Substituted Ethers, Sulfides, and Selenides
Authors: Watanabe Mitsuru , Suga Seiji , Yoshida Jun-ichi 
Published: September 2002

Abstract
Organoheteroatom compounds having a 2-(2-pyridyl)ethyl group were synthesized and their oxidation potentials were determined by rotating disk electrode voltammetry. The oxidation potentials were found to be less positive than those of the corresponding compounds having a phenyl group in place of the pyridyl group. The dynamic coordination of the pyridyl group to the heteroatom, which stabilizes the cation radical intermediate, seems to be responsible for facilitating the electron transfer. The magnitude of the intramolecular assistance increases along with an increase in the oxidation potential of the parent compounds. This tendency can be explained in terms of the energy match between the nonbonding p orbital of the pyridyl nitrogen and the HOMO of the parent heteroatom compound.
Solubility Prediction Using Statistical Mechanics
Authors: Parsafar Gholamabbas , Keshavarzi Ezat 
Published: September 2002

Abstract
In the present work, a new expression for the chemical potential of a component in its pure and mixed state has been derived using the classical partition function and the Linear Isotherm Regularity, LIR. Using this approach, we are able to interpret all contributions of ideal and non-ideal terms which appear in the chemical potential. The derived chemical potential satisfies Raoult's and Henry's laws. We may also predict the solubility using the chemical potential without any adjustable parameter when the solvent and solute have molecular similarity, like NH3 in H2O. However, for cases in which the solvent and solute molecules are significantly differ, one adjustable parameter must be considered. Success in predicting the solubility in different systems is due to the generality of the used equation of state, LIR.
Accurate Density-Functional Calculation of Core-Electron Binding Energies of Some Substituted Benzenes
Authors: Takahata Yuji , Chong Delano Pun 
Published: September 2002

Abstract
The core electron binding energies (CEBE's) of benzene, seven monosubstituted benzenes (Ph-X) and one disubstituted benzene (p-NH2-C6H4-NO2) were calculated using density-functional theory (DFT). The unrestricted generalized transition-state (uGTS) model was employed. The DeMon DFT program with a combined functional of Becke's exchange (B88) with Perdew's correlation (P86) was used. The average absolute deviation of the calculated CEBE's of the title compounds was 0.3 eV when the cc-pVDZ basis set was used. The ``CEBE shift'' of the ring carbon in Ph-X was calculated while taking the CEBE on the ring carbon in Ph-H as a reference. The thus-calculated CEBE shifts agree with experiment within the value of the average absolute deviation, 0.1 eV. The signs and quantitative numerical values of the CEBE shifts are very close to the corresponding Hammett σ constants.
Computer Simulation Study of Patterns of Copper and Silver Dendrites Grown from Aqueous Solution in High Magnetic Field
Authors: Duan Wenyong , Fujiwara Masao , Tanimoto Yoshifumi 
Published: September 2002

Abstract
The magnetic field effects (MFEs) on the patterns and yields of silver and copper dendrites generated from Cu2+/Zn and Ag+/Cu liquid-solid redox reactions are simulated with the aid of a biased random walk model. In the present model, multi-particles are generated to represent metal ions, and their trajectories walk randomly with superimposed drifts. Comparing the simulation patterns and yields with the experimental ones, it is confirmed that the convection of solution induced by the magnetic force is responsible for the observed MFEs on the dendrites in a high magnetic field gradient (ca. 400 T2 m-1).
X-Ray Crystal Structure Analysis of Silicon Phthalocyanines: Study of the Relationship between Intermolecular Interaction and Photochemical Sensitivity
Authors: Kojima Yuko , Osano Yasuko T , Ohashi Toyoshi 
Published: September 2002

Abstract
This paper reports on the crystal structures of the three silicon phthalocyanines: dichlorosilicon phthalocyanine [SiCl2Pc], dimethoxysilicon phthalocyanine [Si(Ome)2Pc] and bis(tetrahydrofurfuryloxy)silicon phthalocyanine [Si(thff)2Pc]. We found that although Si(Ome)2Pc and Si(thff)2Pc show sensitivity for an electrophotographic photoreceptor, SiCl2Pc doesn't have photosensitivity. It is known that the difference in the photochemical property of phthalocyanines is related to the crystal structures. Although it is difficult for these materials to obtain single crystals with sufficient size for single crystal X-ray analysis, it is very important to determine the crystal structures in order to understand the mechanism concerning the performance of the electrophotographic photoreceptor. In this work we determined the crystal structures from very small (micrometer-sized) single crystals. The compounds crystallized in space group P21/n for SiCl2Pc, Z = 2 with unit-cell parameters a = 10.261(1) Å, b = 14.618(2) Å, c = 9.072(1) Å, β = 98.51(1)°; in space group P1- for Si(Ome)2Pc, Z = 1 with unit-cell parameters a = 11.606(4) Å, b = 7.583(3) Å, c = 8.304(3) Å, α = 96.46(3)°, β = 105.23(3)°, γ = 74.87(3)°; and in space group P1- for Si(thff)2Pc, Z = 1 with unit-cell parameters a = 10.234(6) Å, b = 10.266(7) Å, c = 9.761(6) Å, α = 98.93(2)°, β = 117.94(2)°, γ = 68.83(2)°. All molecules in the three crystals have a symmetry center on Si atom. In the crystal structure, although SiCl2Pc has π-π stacking extended in only one direction (along c-axis), Si(Ome)2Pc and Si(thff)2Pc have intermolecular interactions extended in all directions in the crystals. Si(Ome)2Pc includes water molecules in the crystal, which form hydrogen bonds. We discuss the relationship between the intermolecular interactions and the photochemical property of silicon phthalocyanines.
Polarographic Behavior and Determination of Pendimethalin in Formulations, and Environmental Samples
Authors: Sreedhar Mallipattu , Damodar Janmanchi , Jyothi Nimmagadda Venkata Vijaya , Reddy Srinivasulu Reddy Jayarama 
Published: September 2002

Abstract
A differential pulse polarographic (DPP) method for the determination of pendimethalin is described based on the reduction of a nitro group at a dropping mercury electrode in BR buffers of pH 2.0 to 12.0 using 25% acetone-water mixtures as a solvent. Also, a cyclic voltammetry (CV) technique has been used to study the behavior of pendimethalin at a hanging mercury drop electrode. The differential pulse polarographic method described here has been applied to the determination of pendimethalin in formulations, grains, soils and spiked water samples. Both standard addition and calibration methods were used for the analytical measurements. The lower detection limit was found to be 1.87 × 10-8 M (M = mol dm-3).
Study on an Estimation of the Contributed Energy to the Transfer Free Energies of Complex Ions. Part I. [Fe(CN)2n(phen)(3-n)](2-2n)+ from Water to a Water-ethanol Mixed Solvent
Authors: Tarui Takao 
Published: September 2002

Abstract
The solubilities of [Fe(phen)3](ClO4)2·H2O, [Fe(CN)2(phen)2]·0.5H2O, [Fe(phen)3][Fe(CN)4phen]·8H2O, and [Fe(phen)3]2[Fe(CN)6]·3.5H2O in ethanol-water mixed solvents were measured at 25.0 ± 0.1 °C, and the transfer free energy of each complex ion from water to water-ethanol mixed solvent was calculated. From the obtained data, the transfer free energies were split into contributions from 1,10-phenanthroline-solvent, cyano ligand-solvent interaction energies, and electrostatic energies. The ratio of the contributed energy from 1,10-phenanthroline vs. transfer free energy of free (non-coordinated) 1,10-phenanthroline is almost constant at about 0.6—0.7 over the whole mole-fraction range. There is thus a possibility to estimate the contributed energy from the transfer free energy of the free ligand in the future. On the other hand, the contributed energy from the cyano ligand can not be obtained by multiplying a certain coefficient to the transfer free energy of the free cyanide ion. The contributed energy from electrostatic energy changes in a somewhat different manner, as expected by the Born equation. However, the estimated transfer free energy as the sum of each contributed energy obtained by a least-squares method is in fair agreement with the observed transfer free energy of each complex ion. It has been confirmed that the proposed conception of the contributed energy to the transfer free energy is a useful means to predict the unknown transfer free energy of complex ions.
Magnetic Properties of the Octahedral Chromium Chalcogenide Cluster Complexes [Cr6Se8(PEt3)6], [Cr6Se8(H)(PEt3)6], and [Cr6S8(H)(PEt3)6]
Authors: Kamiguchi Satoshi , Saito Taro , Mori Wasuke 
Published: September 2002

Abstract
The magnetic data of chromium chalcogenide cluster complexes [Cr6Se8(PEt3)6] (1), [Cr6Se8(H)(PEt3)6] (2), and [Cr6S8(H)(PEt3)6] (3) have been analyzed using the Heisenberg-Dirac-Van Vleck Hamiltonian. The analysis has shown that all of these complexes display an antiferromagnetic interaction between chromium atoms and that the coupling constants decrease in the order 2 &gt; 3 &gt; 1. This interaction is mediated by Cr-(μ3-E)-Cr bridges (E = Se, S) and Cr-Cr bonds. In a comparison of the two hydride clusters, the selenide 2 has a larger antiferromagnetic coupling than the sulfide 3. The shorter Cr-Cr distances in 2 (mean 2.66 Å) than those in 1 (mean 2.81 Å) seem to cause larger antiferromagnetic interaction through the Cr-Cr bonds.
Substitution of Five-Membered Heteroarenes and Uracils with Trifluoroacetaldehyde Ethyl Hemiacetal
Authors: Gong Yuefa , Kato Katsuya , Kimoto Hiroshi 
Published: September 2002

Abstract
A number of α-(trifluoromethyl)heteroarylmethanols 2a—c are conveniently obtained in good yields by substitution of pyrole, furan, and thiophene with trifluoroacetaldehyde ethyl hemiacetal (TFAE); 2b and 2c are formed only in the presence of a catalyst such as ZnCl2. Analogous methanols 8a and 8b are also prepared by catalytic substitution of uracils with TFAE in moderate yields.
Antiferromagnetic Adducts of Copper(II) Propionate with Pyridyl Nitronyl Nitroxides
Authors: Mikuriya Masahiro , Azuma Hiroshi , Nukada Ryoji , Sayama Yasuyoshi , Tanaka Katsunori , Lim Jong-Wan , Handa Makoto 
Published: September 2002

Abstract
Copper(II) propionate was reacted with 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (p-nitpy), 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (m-nitpy), and 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide (o-nitpy) to isolate three complexes, which were characterized by measurements of the infrared and electronic spectra, as well as the magnetic susceptibilities. Single-crystal X-ray analyses reveal that the former two complexes are adducts of dimeric copper(II) propionate, [Cu2(pro)4(p-nitpy)2] (1) (Hpro = C2H5COOH) and [Cu2(pro)4(m-nitpy)2] (2), and that the latter complex is bis(picolinato)copper(II) dihydrate (3·2H2O).
Structures and Magnetic Properties of Ruthenium(II,III) Pivalate Cation Dimers Axially Coordinated by Pyridyl Nitronyl Nitroxide Radicals through Their Pyridyl Nitrogen Atoms
Authors: Sayama Yasuyoshi , Handa Makoto , Mikuriya Masahiro , Hiromitsu Ichiro , Kasuga Kuninobu 
Published: September 2002

Abstract
Adduct complexes of ruthenium(II,III) pivalate dimer with pyridyl nitronyl nitroxide radicals, [Ru2(O2CCMe3)4(L)2]X (L = 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide (m-nitpy) and 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide (p-nitpy); X = BF4 and BPh4), have been prepared and characterized. The dimeric cores, which are axially coordinated by the pyridyl nitrogen atoms of the radical ligands, not by the nitroxide oxygen atoms, have been crystallographically confirmed for complexes with m-nitpy (X = BF4) and p-nitpy (X = BPh4) using an X-ray diffraction method. The magnetic interactions between the radical and Ru(II,III) dimer through the pyridyl group and the radicals of the neighboring cation units through the space are weak.