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931.
Oikawa M Shintaku T Fukuda N Sekljic H Fukase Y Yoshizaki H Fukase K Kusumoto S 《Organic & biomolecular chemistry》2004,2(24):3557-3565
The detailed conformational analysis of a single molecule of the tetraacyl biosynthetic precursor-type lipid A and its characteristic supramolecular assembly in aqueous SDS-micelles are described. Regular molecular arrangements were observed by detailed analysis of the NMR spectra of synthetically pure specimens, including regiospecifically 13C-labeled ones. NMR analysis of a biologically inactive precursor-type analogue with four shorter acyl chains demonstrated its conformational flexibility, indicating the importance of hydrophobic interactions for maintaining the conformation of such molecules. 相似文献
932.
Shifts in the optical absorption energy of polymer chains during polymerization of microcrystalline bis(p-toluene sulphonate) diacetylene are shown to be in accord with changes in the strain imposed on the chains by the mismatch of the monomer and polymer crystal lattices. 相似文献
933.
Control of radical polymerization has been one of the most challenging frontiers in polymerization chemistry. This review presents the discovery of metal-catalyzed living radical polymerization and recent developments in the evolution of catalysts in terms of versatility and activity, scope of monomers, controlled polymerization in water, catalyst removal, and precision synthesis of well-controlled polymers such as random, block, end-functionalized, and star polymers. 相似文献
934.
Masayuki Ando Takakazu Goto Mitsuru Tsuchiya Toshiyuki Uryu 《Journal of polymer science. Part A, Polymer chemistry》1989,27(1):317-324
The formation mechanism of microporous film which was obtained by casting a methyl ethyl ketone (MEK)/N,N-dimethlformamide (DMF) solution of an electron beam (EB)-reactive urethane-acrylamide prepolymer was discussed. The porosity and crystallinity increased with increasing DMF content in the solvent mixture. This correlation was explained by a progressive slight coagulation and nucleation of the prepolymer due to the difference in volatility between MEK and DMF. As the result, when the DMF content reached 25 vol%, micropores were formed throughout the film. Such a mechanism was supported by the localization of the acrylamide groups at the surface which was induced by the crystallization and by the interaction of amide groups with DMF. The polymerization of acrylamide groups by EB could fix the microporous morphology. 相似文献
935.
We have synthesized novel axially chiral ligand with two chiral centers, (R)-(R)(2)- and (S)-(S)(2)-2,2'-bis(2,2,2-trifluoro-1-hydroxyethyl)biphenyl (1), which showed a high asymmetric induction when used as ligand. Here, another new approach to 1 by kinetic and thermodynamic resolution is presented which gave these ligands in a much shorter steps, in a higher yield, and in a higher enantiomeric excess. 相似文献
936.
Kaoru Tsuchiya Akihiro Takahashi Naoto Takeda Naoki Asakawa Shigeki Kuroki Isao Ando Akira Shoji Takuo Ozaki 《Journal of Molecular Structure》1995,350(3):233-240
13C cross polarization-magic angle spinning NMR spectra were measured for a series of peptides containing
-valine,
-leucine and
-aspartic acid residues, for which the crystal structures were already determined by X-ray diffraction, in order to investigate the relationship between hydrogen-bond lengths (RN…O) and 13C chemical shifts of amide carbonyl carbons in the peptides. From these experimental results, it was found that the isotropic 13C chemical shifts (δiso) of the amino acid residues move linearly downfield with a decrease in RN…O within the hydrogen-bonded length range considered here and also shown in our previous work on glycine and
-alanine residues as expressed by δiso(ppm) = a − bRN…O(Å) where a and b are 215.4 (ppm) and 14.2 (ppm Å−1) for the
-valine residue, 202.2 (ppm) and 10.0 (ppm Å−1) for the
-leucine residue, and 199.0 (ppm) and 9.6 (ppm Å−1) for the
-aspartic acid residue, respectively. Using these relations, the RN…O values of some polypeptides in the crystalline state were determined through the observation of the amide carbonyl carbon chemical shifts. These values were compared with those determined by the X-ray diffraction method. Furthermore, quantum-chemical calculation of the 13C shielding constant for a model compound was carried out by the finite perturbation theory INDO method in order to ascertain the 13C shielding behavior in the formation of hydrogen bonds. 相似文献
937.
938.
Summary Dielectric constants of O/W emulsions were measured over a wide range of concentration and at frequencies ranging from 20
cps. to 3 mc.
No dielectric dispersion due to the interfacial polarization was observed in the experimental range of frequency, while the
electrode polarization was observed below 100 kc.
Experimental results were compared with theoretical values for spherical dispersions. It was concluded that the dielectric
constants of O/W emulsions were expressed best byBruggeman's equation over the whole range of concentration.
Zusammenfassung Die DK von ?l/Wasser-Emulsionen wurden über einen weiten Konzentrationsbereich und für Frequenzen zwischen 20 Hz und 3 MHz gemessen. Es war keine dielektrische Dispersion verursacht durch Oberfl?chenpolarisation innerhalb des experimentellen Frequenzbereiches zu beobachten. Dagegen wurde unterhalb 100 kHz Elektrodenpolarisation bemerkbar. Die experimentellen Ergebnisse wurden mit den theoretischen Darstellungen der Misch-DK für Dispersionen mit kugligen Teilchen verglichen. Der Verlauf der DK der ?l/Wasser-Emulsion wird am besten und über den ganzen Konzentrationsbereich durch die Gleichung vonBruggeman dargestellt.相似文献
939.
Shigeru Kubota Toshimoto Moriwaki Torahiko Ando Shohei Etoh Akira Fukami 《Journal of polymer science. Part A, Polymer chemistry》1986,24(9):2047-2058
Polyquinazolones containing 4-substituted phenyl groups (H, Cl, CH3, CH3O, NO2) on the quinazolone ring were synthesized in m-cresol and their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss in nitrogen and air. Polyquinazolones were synthesized with intrinsic viscosities in the range of 0.2–0.7 dL/g when phosphorus pentoxide was used as a catalyst. In TGA studies, there was a difference in the initial decomposition temperature of polyquinazolones with varying substituted groups. The introduction of substituted groups reduced oxidative thermal stability of the polymers. Furthermore, the thermal degradation mechanism was investigated by infrared spectrophotometry. 相似文献
940.
Sakamoto M Sano T Fujita S Ando M Yamaguchi K Mino T Fujita T 《The Journal of organic chemistry》2003,68(4):1447-1450
Irradiation of a benzene solution of 3-cyano-2,6-dimethoxypyridine in the presence of ethyl vinyl ether (EVE) gave 1:1 photoadducts, 3-cyano-5-ethoxy-2,8-dimethoxy-4,5-dihydroazocine, in good yields, whose structure was established by X-ray single-crystal analysis. The photoadduct was produced via cycloaddition between the C3-C4 position of the pyridine derivatives and an alkene chromophore. On the other hand, 3-cyano-2,6-dimethoxy-4-methylpyridine cycloadds to EVE at the C2-C3 position of the pyridine ring upon irradiation. The difference is explained on the basis of the steric effect. 相似文献