Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 76 , Issue 9
Showing 1-23 articles out of 23 articles from the selected issue
  • Shinzaburo Ito, Hiroyuki Aoki
    Type: Accounts
    Subject area: AI
    2003 Volume 76 Issue 9 Pages 1693-1705
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The applications of the optical methods using fluorescent probes for investigating polymer structure and dynamics at a molecular level are reviewed. The versatile and particular abilities of the fluorescence method have been exemplified using ultrathin films made of polymer monolayers, which provided fine model systems designed with a nanometer precision. In the latter part of this article, the emerging research field of scanning near-field optical microscopy (SNOM) is introduced. This novel microscopic technique enabled us to carry out spectroscopic and time-resolved measurements with a lateral resolution of 100 nm, which is obviously beyond the diffraction limit of light. We applied SNOM to study various nanometer-scale structures of polymer assemblies, such as the two-dimensional phase separation structure, morphology of single polymer chains, and structural inhomogeneity of polymer networks. These results showed that the combination of the fluorescence method and SNOM technique will open a new field of research on polymeric materials by providing molecular information on the basis of real optical images on a nanometric scale.
  • Ryoji Miyata, Masahide Terazima
    Type: Headline
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1707-1712
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The energy releasing process from a photo-excited chromophore embedded in a protein structure to the surrounding protein matrix and to the solvent is studied for deoxymyoglobin by the acoustic peak delay method with the transient grating technique. The acoustic peak delay time is usually a good indicator of the solvent heating time by the nonradiative transition after the photoexcitation and should be a positive value. However, the peak delay after the photoexcitation of deoxymyoglobin was found to be −15 ps. The observed negative peak delay was interpreted in terms of interference between two acoustic waves: an acoustic wave due to the thermal expansion of the protein and a wave of the medium. A theoretical calculation suggests that most of the energy of the heme is first transferred to the protein part and subsequently dissipates into the solvent. During this energy-releasing process, the protein experiences the transient thermal expansion and it creates an acoustic wave.
  • Yuko Wasada-Tsutsui, Hiroaki Wasada, Shigenobu Funahashi
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 9 Pages 1713-1722
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The stability of divalent cations (M(II)) of the first transition series, penta-, hexa-, and heptasolvated by hydrogen cyanide was studied in order to clarify the reaction mechanisms of nitrile-exchange reactions. The structural stabilities of the [M(NCH)7]2+s depend on the d-electron configurations, though all of the [M(NCH)5]2+s and [M(NCH)6]2+s are located at the local minima. The [M(NCH)7]2+s are structurally more stable than the heptahydrated analogues. Successive binding energies show that it is difficult for an incoming ligand to penetrate the first solvation shells of cations in the later members. Thus, the associative mechanism of solvent-exchange reactions is favorable for cations in the earlier members resulting from energetics as well as structural stability. The symmetry of the imaginary vibrational mode along the reaction path corresponds to that of the transition density induced by one-electron excitation from the antibonding orbital occupied in the d3 ion to the 4s orbital. The stable [M(NCH)7]2+s arise from the large excitation energies sufficient to reduce the second term (see Eq. 4 in the text) of Bader–Pearson’s second-order perturbation expansion.
  • Kazuma Gotoh, Shin’ichi Ishimaru, Ryuichi Ikeda
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 9 Pages 1723-1727
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The 1H NMR spin-lattice relaxation times (T1) of triethylamine (TEA) molecules included in five kinds of AFI crystals with different concentrations of Si atoms in the wall were measured. The temperature and Larmor frequency dependences of T1 were well explained by introducing a distributed motional correlation time (τ) for the pseudo-C3 TEA reorientation. An obtained linear decrease in the τ distribution width with an increase of the Si concentration, i.e., the number of Brønsted acid sites, was shown to be related to the orientations of TEA molecules in channels.
  • Silpi Datta, Chaitali Mukhopadhyay, Swapan Kumar Bose
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1729-1734
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Evidence for an intermolecular interaction of riboflavin and sodium salicylate in an aqueous medium was obtained from the presence of isosbestic points in the absorption spectra and an isoemissive point in the emission spectra. The equilibrium constant was estimated from absorption and emission studies, and also from the solubility of riboflavin in an aqueous solution of sodium salicylate, and was found to be in the range of 10–14 mol dm−3. Lifetime measurements indicate a predominantly static mechanism of quenching. The Stern–Volmer constant for the quenching of riboflavin by sodium salicylate was significantly reduced upon the addition of urea. An MD simulation study on the system revealed a stacked conformation, which is probably due to a hydrophobic interaction of the two components.
  • Hajime Tanida, Ken-ichi Kato, Iwao Watanabe
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1735-1740
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Hydrogen atom position in the hydrated iodide anion complex is determined from X-ray Absorption Near Edge Structure (XANES) of an aqueous iodide solution at both the K- and L-edges. The spectra are compared with the theoretical ones calculated by using the FEFF method for several model geometries having hydrogen atoms at different positions. Satisfactory agreements are obtained from models with an almost linear alignment of iodine–hydrogen–oxygen atoms, indicating the capability of the XANES analysis when it is combined with the multiple scattering calculations as a method to detect the positions of hydrogen atoms in the first coordination sphere.
  • Neera Sharma, Sapan K. Jain, Ramesh C. Rastogi
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1741-1746
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The electronic absorption and fluorescence spectra of some indoles were recorded at room temperature in solvents of different polarities. In order to elucidate the solvent band shifts during relaxation of the excited states, the dipole moments of the excited singlet states were estimated from solvent-dependent Stokes shift data using a solvatochromic method based on a microscopic solvent polarity parameter (ETN). All indoles show a substantial increase in the dipole moment upon excitation to the emitting state. These results are generally consistent with the Austin model 1 (AM1) calculations, and are found to be quite reliable in view of the fact that the correlation of the solvatochromic Stokes shifts with the microscopic solvent polarity parameter (ETN) is superior to that obtained using bulk solvent polarity functions in almost all the systems studied here.
  • Akira Hanaki, Manabu Hiraoka, Toshikazu Abe, Yasuhiro Funahashi, Akira ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 9 Pages 1747-1755
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Cu(II) complexes of glycine-peptides, abbreviated as Cu(HiL): L = glycylglycine, triglycine, tetraglycine, and pentaglycine (i = 1–3), react with cysteine to form ternary complexes, Cu(H−1L)(Cys), as first intermediates. The spectral parameters of the ternary complexes, which were similar irrespective of the peptides, were as follows: λmax = 332 ± 1 nm (ε = 4250 ± 50 M−1 cm−1), g|| = 2.170 ± 0.005, g = 2.00 ± 0.05, and A|| = (2.05 ± 0.01) × 10−4 cm−1, indicating that the ternary complexes have identical coordination structures: the Cu(II) coordinates with the peptides via the nitrogens from the terminal amino and the neighboring deprotonated-amide group, and with cysteine via the amino nitrogen and the thiolate sulfur. Based on the absorbance-time curves, the concentrations of each Cu(II) and Cu(I) species during the reaction were calculated. The species distribution curve clearly visualized the pathway of the Cu(II) transport from Cu(HiL) to Cu(Cys)2 via Cu(H−1L)(Cys). The rate of Cu(H−1L)(Cys) formation, which was evaluated from the initial increase in the species distribution curve, depended on the coordination modes of the Cu(HiL) complexes. Both the Cu(H−1L), involving N,N,O,O* donors, and the Cu(H−2L), involving N,N,N,O−* donors, rapidly formed Cu(H−1L)(Cys) complexes, where the donors asterisked represent the fourth ligand in the Cu(HiL) complexes. The second-order rate constant, k1+, was on the order of 106 M−1 s−1, or bigger. The Cu(H−3L), involving N,N,N,N−* donors, reacted relatively slowly; k1+ was on the order of 104 M−1 s−1. Those results indicate that the affinity of the Cu(II) for the fourth donor in Cu(HiL) determines the rate of metal-transport.
  • Huafang Zhou, Shigenobu Kasai, Hiroyuki Noda, Hiroaki Ohya-Nishiguchi, ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 9 Pages 1757-1762
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The peroxidase activity in a single protoplast of alga Bryopsis plumosa is quantitatively characterized by scanning electrochemical microscopy. The generation of ferriceniummethanol (FMA+) at the protoplast surface is directly detected by the microelectrode tip scanned close to the sample surface in seawater containing ferrocenemethanol (FMA) and hydrogen peroxide, an electron mediator and an enzyme-substrate, respectively. The oxidation reaction requires hydrogen peroxide, which clearly shows FMA+ generation due to the peroxidase (POD) catalytic reaction occurring in the protoplast. The FMA+ generation and the FMA accumulation rates at a single alga protoplast were equivalent. A plot of the FMA+ generation rates according to the hydrogen peroxide concentrations was well allowed with a Michaelis–Menten-type reaction. An estimation of the mass-transfer rate and a determination of the Km are quite important advantages of the SECM technique that cannot be realized using other techniques. The POD activity has been further investigated from the viewpoint of the size of the protoplast. The POD activity of the alga in the adult stage is also visualized by SECM. The noninvasive nature of the SECM technique has been confirmed by observing the developmental process after measurements.
  • Nobuhiko Iki, Naoya Morohashi, Yusuke Yamane, Sotaro Miyano
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 9 Pages 1763-1768
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The solvent-extraction behavior of 2,8,14,20-tetrathiacalix[4]arene 2 was compared with those of 2-monothiacalix[4]arene 3 as well as linear tetramer (4) and dimer (5) of p-tert-butylphenol linked by sulfide bonds at the ortho positions in order to clarify the effect of the cyclic and acyclic structure and the number of sulfide bonds. The linear tetramer 4 showed almost the same extraction behavior as that of the cyclic counterpart 2, showing the dependence on the pH for the extraction of Co(II), Ni(II), Cu(II), and Zn(II) ions. On the other hand, monothiacalix[4]arene 3 and acyclic dimer 5 showed far inferior extractability as compared to the former two, suggesting that the number of sulfide linkages, rather than the cyclic/acyclic structure, is predominant to determine the extractability. An equilibrium study on the extraction behavior of open-chain 4 (H4L) toward Co(II), Cu(II), and Zn(II) ions revealed that the composition of the extracted species can be written as [Mi(H2L)i] (i: integer), as was the case obtained by cyclic 2. Furthermore, the extraction constants of 4 for those metal ions were almost the same as those obtained by 2. The similarity of the extraction behavior between 2 and 4 suggests that the acyclic tetramer 4 may act as a pseudo-thiacalix[4]arene to have the same complexation manner as cyclic 2 by the O,S,O-donor set, in which the presence of a phenol unit flanked by sulfide bonds at the both ortho positions is essential. In other words, the effect of the bridging sulfide in the phenol oligomers may be reasonably explained by the electron-withdrawing effect of the sulfide moiety to provide the phenol unit with a higher acidity to form [M2(H2L)2]-type complexes having a double-cone structure stabilized by two sets of O,S,O-ligated metal bridges.
  • Kazutoshi Danjobara, Yuko Mitsuka, Yuji Miyasato, Masaaki Ohba, Hisash ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 9 Pages 1769-1773
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The dinucleating compartmental ligand (L2,3)2−, derived from the [2:1:1] cyclic condensation of 2,6-diformyl-4-methylphenol, ethylenediamine and 1,3-trimethylenediamine, has formed heterodinuclear CoIIMII complexes, [CoM(L2,3)](ClO4)2·H2O·0.5CH3CN (M = Ni (1), Zn (2)). Crystallographic studies for [CoNi(L2,3)(CH3CN)3](ClO4)2·2MeOH·0.5H2O (1′) indicate that the CoII is bound to the N2O2 site formed with ethylenediamine and has a square-pyramidal geometry with one acetonitrile molecule at the apex. The Ni is bound to the N2O2 site formed with 1,3-trimethylenediamine and has a pseudo octahedral geometry with two acetonitrile molecules at the axial sites. Complex 1 shows a ferromagnetic interaction between the CoII (S = 1/2) and NiII (S = 1) ions and a frozen DMF solution of 1 at liquid nitrogen temperature exhibits EPR signals attributable to the ST = 3/2 ground state with a zero-field splitting of D = 0.095 cm−1. The cryomagnetic property is simulated, based on isotropic model (H = −2JS1S2) and by taking into consideration the zero-field splitting, to give an exchange integral of J = +22 cm−1.
  • Hiroshi Kimura, Kiminari Mouri, Makoto Takeishi, Takeshi Endo
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1775-1781
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    The biosynthesis of polyesters from different L-amino acids was investigated by wild-type Ralstonia eutropha (formerly Alcaligenes eutrophus). The accumulation and degradation of the polyesters was found to occur during the cultivation time from 6 h to 48 h, when R. eutropha was cultivated on nitrogen-poor medium containing 1% (w/v) of each L-amino acid as the sole carbon source by two-step batch fermentation. L-Valine was best among different L-amino acids used for the polyester productivity. The polyester content in dried cells produced from L-valine as the sole carbon source was up to 36 wt % during the cultivation time from 24 h to 36 h in a two-step fermentation and up to 27 wt % during 120 h of culture time in a one-step fermentation, respectively. The compositions and molecular weights of the polyesters produced from L-valine were ca. 90 mol% of 3-hydroxybutyric acid (3HB) and ca. 10 mol% of 3-hydroxyvaleric acid (3HV) units and up to 5 × 105–8 × 105 g mol−1, respectively. As-biosynthesized P(3HB-co-ca. 10 mol% 3HV) was shown to have a random sequence distribution of 3HB and 3HV units by analysis of the 13C NMR spectra and have a very narrow comonomer compositional distribution by the fractionation method with chloroform/heptane mixed solvent.
  • Masashi Ikegami, Tatsuo Arai
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1783-1792
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Intramolecularly hydrogen bonded hemiindigo compounds 24 were prepared and their photochemical behavior was investigated. Z-2 did not undergo isomerization, while 3 underwent isomerization mutually between the Z-isomer and E-isomer in solution to exhibit a color change between greenish yellow and reddish orange in benzene. Introduction of a formyl group at the 2-position of the pyrrole ring of 3 brought about the increase in the fluorescence quantum yield and fluorescence lifetime by a factor of 10, and the decrease of the quantum yield of isomerization of 4 in benzene. In addition, introduction of the formyl group affects the thermal stability. The intramolecular hydrogen bonding can be used to construct a novel photochromic molecule.
  • Takeshi Kawase, Tomoaki Okada, Tetsuya Enomoto, Takayuki Kikuchi, Yoji ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1793-1799
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Upon heating at 200 °C in o-dichlorobenzene, 2,5-bis(dicyanomethylene)bicyclo[4.2.0]octa-3,7-diene gave rise to 2,6-bis(dicyanomethylene)bicyclo[3.3.0]octa-3,7-diene by a rearrangement as a sole isolable product in modest yield, and no trace of 5,8-bis(dicyanomethylene)cycloocta-1,3,6-triene, the expected product, was detected. On the other hand, 2,5-bis(dicyanomethylene)bicyclo[4.2.0]octa-7-ene underwent a thermal reaction at lower temperature (110 °C in toluene) to give 5,8-bis(dicyanomethylene)-1,3-cyclooctadiene, the normal ring-opened product, and 2,6-bis(dicyanomethylene)bicyclo[3.3.0]octa-1(5)-ene, a rearranged product, in about 1:1 ratio. The rearranged product has a planar 1,1,6,6-tetracyanohexatriene structure (X-ray analysis), and shows a considerably lower electron affinity than that of tetracyanoethylene and 7,7,8,8-tetracyano-p-quinodimethane. The electron acceptor also formed a crystalline 1:1 charge transfer complex with tetrathiafulvalene, of which electronic conductivity was near insulating (1.1 × 10−7 S cm−1). We have proposed a possible mechanism for the rearangements involving the zwitterionic intermediates.
  • Gaku Yamamoto, Chiharu Agawa, Takahiro Ohno, Mao Minoura, Yasuhiro Maz ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1801-1811
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Static and dynamic stereochemistry of N-alkyl, O-alkyl, and N,O-dialkyl derivatives of N-(1,4-dimethyl-9-triptycyl)hydroxylamine were studied. X-ray crystallographic analysis revealed that an N-alkyl derivative adopts R*-(−sc)* conformation while N,O-dialkyl derivatives adopt R*-ap conformation. In solution, stereomutation was almost frozen on the NMR timescale at ca. −60 °C. The same conformer as found in the crystal was the major conformer in solution in each compound, and a small amount of a second conformer was found in equilibrium with the major one for the N-alkyl and N,O-dialkyl derivatives. The stereomutation was interpreted in terms of diastereomerization and enantiomerization, and the 1H NMR lineshape analysis afforded the activation parameters for these processes.
  • Morio Yashiro, Maiko Higuchi, Makoto Komiyama, Youichi Ishii
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1813-1817
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    An Mn2+ complex with 2,2′:6′,2″-terpyridine (terpy) was found to promote the hydrolysis of NpN (NpN = diribonucleoside monophosphate diester) efficiently at pH 7.0 and 50 °C under ambient conditions. The structure of the Mn2+ complex involving a phosphodiester molecule, [(terpy)(dpp)MnII(μ-dpp)2MnII(dpp)(terpy)], dpp = diphenyl phosphate anion, was established by X-ray crystallography, and the coordination mode of Mn2+ to a phosphodiester molecule was considered.
  • Takashi Sakai, Akiko Matsuda, Toshinobu Korenaga, Tadashi Ema
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1819-1821
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    A synthetically useful primary alcohol, 3-phenyl-2H-azirine-2-methanol, was resolved efficiently by a reaction at −40 °C with a lipase immobilized on the porous ceramic (Toyonite) and vinyl butanoate in ether (E value of 130 and TTN/h value of 7800).
  • Toshiyuki Ohe, Takuya Ohse, Kenji Mori, Seiji Ohtaka, Sakae Uemura
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1823-1827
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Cross-coupling reactions between α,β-unsaturated carbonyl compounds and aromatic aldehydes have been achieved in tetrahydrofuran (THF) at 25 °C under N2 using a catalytic amount of InCl3 (0.05 molar amount to the substrate) in the presence of both chlorotrimethylsilane (TMSCl) and aluminum foil (Al). These reactions provide the corresponding β,γ-unsaturated ketones in moderate yields, together with pinacol-coupling products of aldehydes as side products. Chlorides other than TMSCl and AlCl3, such as LiCl, CaCl2, MgCl2, and SOCl2, are not effective at all. Without either TMSCl or Al, no reaction proceeds even in the presence of the catalyst.
  • Takashi Hashihayata, Kazuhiro Ikegai, Kazuya Takeuchi, Hideki Jona, Te ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1829-1848
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    A convergent total synthesis of F1α antigen, a member of the tumor-associated O-linked mucin glycosyl amino acid, was tried by one-pot sequential glycosylation. Highly α-selective glycosylation of amino acid 7 with thioglycoside 6 was successfully carried out by combining trityl trifluoromethanesulfonate (TrOTf) and N-iodosuccimide (NIS) which gave glycosyl amino acid 21 in high yield (97%, α/β = 83⁄17). Next, the glycosylation of thioglycoside 4 with galactosyl phenyl carbonate 2 or fluoride 3 was tried by the promotion of trityl tetrakis(pentafluorophenyl)borate [TrB(C6F5)4] or trifluoromethanesulfonic acid (TfOH); protected F1α 25 was afforded in 80 or 89% overall yield, respectively, by the further addition of glycosyl amino acid 5 and NIS. The desired trisaccharide was obtained in high yield after removal of the protecting groups. Next, a convergent total synthesis of branched hepta-β-glucoside 30 having phytoalexin-elicitor activity was efficiently performed by way of two one-pot sequential glycosylation reactions: that is, trisaccharide 34 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three given monosaccharides (31, 35, and 36) as shown in Scheme 12 and by subsequent selective deprotection of 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 34 with three monosaccharides (31, 32, and 33d) also proceeded smoothly to afford heptaglucoside 43 stereoselectively in 48% total yield based on monosaccharide 32. Phytoalexin-elicitor active branched hepta-β-glucoside 30 was afforded by the sequential deprotection.
  • Morifumi Fujita, Kenji Ihara, Wan Hyeok Kim, Tadashi Okuyama
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1849-1855
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Solvolysis of 4-methylcyclohexylidenemethyl(phenyl)iodonium tetrafluoroborate (1) and its R isomer (69% ee) was carried out in 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) in the presence of bases such as acetate, pyridine, triethylamine, and alkoxide. The reaction is much faster in TFE than in HFP. Products in TFE include solely un-rearranged (racemized) enol ether 2 together with iodobenzene, while the main product in HFP is ring-expanded (partially racemized) 1-alkoxycycloheptene 3. Results show that 2 is formed via α-elimination with alkylidenecarbene as an intermediate, while the reaction in HFP to give 3 involves a cycloheptyne intermediate that is mostly derived from an intermediate cyclohept-1-enyl cation via the E1-type pathway.
  • Yumika Fukuoka, Yuko Matsushita, Sachi Furukawa, Takuro Niidome, Tomom ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1857-1861
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Pleurocidin (Ple) isolated from the skin of the winter flounder is a cationic amphiphilic peptide with antibacterial activity. To search for a simple peptide with strong antibacterial activity but no hemolytic activity, we designed three model peptides based on Ple, Ple I, Ple II, and Ple III. In the model peptides, Leu or Ala, and Lys were used instead of some hydrophobic amino acids and hydrophilic ones in Ple, respectively, to simplify the amino acid composition. The order of their α-helicity and hydrophobicity is Ple I > Ple II > Ple III. Ple I and Ple II showed antibacterial activity similar to Ple amide (Ple-NH2). However, Ple I had very strong hemolytic activity. Ple III exhibited negligible biological activity. Ple II was found to be a desirable candidate to promote the study of the structure-activity relationship.
  • Peyman Salehi, Mohammad Mehdi Khodaei, Mohammad Ali Zolfigol, Sara Sir ...
    Type: Short Articles
    Subject area: OB
    2003 Volume 76 Issue 9 Pages 1863-1864
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Friedel–Crafts acylation of alkoxybenzenes was achieved efficiently by a reaction with aliphatic acid anhydrides in the presence of catalytic amounts of aluminum hydrogensulfate, Al(HSO4)3, in nitromethane and under solvent-free conditions. Alkylbenzenes and aryl halides, as well as aromatic anhydrides, remained intact under these conditions.
  • Tomoki Ogoshi, Yoshiki Chujo
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 9 Pages 1865-1871
    Published: 2003
    Released: September 15, 2003
    JOURNALS RESTRICTED ACCESS
    Transparent organic–inorganic polymer hybrids with various organic polymers (polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and poly(acrylic acid) (PAA)) that are soluble in amphiphilic solvents such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc), could be easily synthesized by the sol–gel reaction of tetramethoxysilane (TMOS) in an amphiphilic solvent. It is because DMF and DMAc form strong hydrogen bonds with the silanol groups of the silica gel and have a high compatibility with organic polymers. DMF and DMAc play a role as compatibilizers between the organic polymer and silica gel. The hydrogen bonding interaction was confirmed by FT-IR spectra. The compatibility of the organic polymer with the amphiphilic solvent was explained by the solubility of the polymer in an amphiphilic solvent. The thermal stability of the polymer hybrids obtained was increased compared to that of bulk polymer by post-treatment. The homogeneity of the obtained polymer hybrids was confirmed by SEM and nitrogen porosimetry studies.
feedback
Top