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51.
52.
Tetsuya Danno Keizo Miyasaka Kinzo Ishikawa 《Journal of Polymer Science.Polymer Physics》1983,21(8):1527-1537
Sorption of iodine by bulk polyacetylene was studied under various I2 gas pressures at 25°C. The sorption dynamics show that the penetration of iodine into PA is not Fickian and the diffusion coefficient increases with time of sorption. A discontinuous increase in the sorption isotherm is observed at P/P0 = 0.25 (P is the pressure of the I2 gas and P0 is the saturation value at 25°C). It is due to iodine penetration into PA crystals, as evidenced by x-ray analysis. The distribution of iodine within crystals is apparently inhomogeneous: some unit cells are changed into “iodine-PA” cells, while others remain unchanged. The electrical conductivity depends not only on the amount of iodine but also on the I2 gas pressure under which sorption is carried out. At given iodine content, the conductivity of a sample doped under higher I2 pressure is greater than that of a sample doped under lower pressure. 相似文献
53.
Anne‐Claire Mitaine‐Offer Tomofumi Miyamoto Vronique Laurens Clment Delaude Marie‐Aleth Lacaille‐Dubois 《Helvetica chimica acta》2003,86(7):2404-2413
Eight new acylated triterpene saponins 1 – 8 were isolated from the roots of Polygala arenaria as four inseparable (E)/(Z) mixtures of the 4‐methoxycinnamoyl and 3,4‐dimethoxycinnamoyl derivatives by repeated MPLC over silica gel. Their structures were established mainly by 600‐MHz 2D‐NMR techniques (1H,1H‐COSY, TOCSY, NOESY, HSQC, HMBC) as 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐(O‐β‐D ‐galactopyranosyl‐(1→4)‐O‐[β‐D ‐glucopyranosyl‐(1→3)]‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐4‐methoxycinnamoyl]}‐β‐D ‐fucopyranosyl) ester and its (Z)‐isomer ( 1 / 2 ), 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐(O‐β‐D ‐galactopyranosyl‐(1→4)‐O‐[β‐D ‐glucopyranosyl‐(1→3)]‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]}‐β‐D ‐fucopyranosyl) ester and its (Z)‐isomer ( 3 / 4 ), 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐(O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐α‐L ‐arabinopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐4‐methoxycinnamoyl]}‐β‐D ‐fucopyranosyl) ester and its (Z)‐isomer ( 5 / 6 ), and 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐(O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐α‐L ‐arabinopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]}‐β‐D ‐fucopyranosyl) ester and its (Z)‐isomer ( 7 / 8 ) (presenegenin=(2β,3β)‐2,3,27‐trihydroxyolean‐12‐ene‐23,28‐dioic acid). In our in vitro lymphocyte proliferation assay (Jurkat T‐leukemia cells), a fraction containing 1 – 4 showed a concentration‐dependent immunomodulatory effect. This effect was not found for the prosapogenin (tenuifolin=3‐O‐(β‐D ‐glucopyranosyl)presenegenin), underlining the importance of the acyl? oligosaccharidic moiety. 相似文献
54.
A hydrophilic fluorescent derivatization reagent for fatty acids, 4-N-(4-N-aminoethyl)piperazino-7-nitro-2,1,3-benzoxadiazole (NBD-PZ-NH(2)), was designed and synthesized. NBD-PZ-NH(2) possesses not only a fluorophore and a reacting group but also a positive charge group and, thus, was hydrophilic and suitable for application to capillary electrophoresis. NBD-PZ-NH(2) reacted with fatty acids in the presence of triphenylphosphine (TPP) and 2,2'-dipyridyl disulfide (DPDS) at room temperature within 10 min. The derivatives were strongly fluoresced and were positively charged at pH below 3. The derivatives of C4-C20 fatty acids were separated within 10 min in 50% acetonitrile in water containing 30 mM ammonium acetate and 1.0 M acetic acid by capillary electrophoresis with laser-induced fluorescence (CE-LIF) detection. The detection limits attained were 6.5 nM (signal-to-noise ratio of 3). It is proposed that NBD-PZ-NH(2) is a prominent derivatization reagent for fatty acids which is suitable for CE-LIF application. 相似文献
55.
Kiyokazu Imai Tomoo Shiomi Yasuyuki Tezuka Toshiaki Kawanishi Tomofumi Jin 《Journal of polymer science. Part A, Polymer chemistry》1988,26(7):1961-1968
Bulk and/or solution polymerizations of a series of vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, and vinyl benzoate were conducted. Iodine-coloration, 1,2-glycol structure, molecular weight, and tacticity (triad and pentad) were measured for the resulting poly(vinyl alcohol)s (PVAs). The iodine-coloration abilities of PVAs, derived from poly(vinyl ester)s that were obtained through bulk polymerization at 60°C, depended on the starting monomer, increasing in the following order: vinyl benzoate < vinyl acetate < vinyl propionate < vinyl butyrate < vinyl pivalate. In solution polymerizations of vinyl propionate and vinyl butyrate, it was revealed that the tacticity of the derived PVAs apparently depended on the type and amount of polymerization solvent employed, as found previously in the case for vinyl acetate. The iodine-coloration of these PVA samples varied in the same order as their syndiotactic content, while no relationship was observed toward their 1,2-glycol content. The probabilities of the syndiotactic propagation at 60°C were estimated as 0.49 (benzoate), 0.54 (acetate), 0.55 (propionate), 0.56 (butyrate), and 0.60 (pivalate), respectively. 相似文献
56.
A ganglioside molecular species, LLG-5 (1), has been obtained from the water soluble lipid fraction of the CHCl3/MeOH extract of the starfish Linckia laevigata. On the basis of chemical and spectroscopic findings, the structure of 1 has been elucidated. Negative ion FAB-MS provided important information both on the structure of the sugar moiety and on the molecular mass of the ganglioside. 1 is a new ganglioside molecular species possessing a 2-->11 linked linear-type trisialosyl moiety. Moreover, 1 exhibited neuritogenic activity in rat pheochromocytoma PC-12 cells in the presence of nerve growth factor. 相似文献
57.
Yamago S Ray B Iida K Yoshida J Tada T Yoshizawa K Kwak Y Goto A Fukuda T 《Journal of the American Chemical Society》2004,126(43):13908-13909
A new versatile method for conducting living radical polymerization has been developed in which organostibines induce consecutive group-transfer radical reactions with alkenes. The method has been successfully applied, for the first time, to the controlled polymerization of both conjugated and unconjugated vinyl monomers, and the desired polymers with predetermined molecular weight and low polydispersity index were obtained in excellent yields. This characteristic feature of this method is exemplified in the first synthesis of block copolymers composed of conjugated and unconjugated monomers, which would be of great importance as functional smart organic nanomaterials. 相似文献
58.
Dalila Smati Anne‐Claire Mitaine‐Offer Tomofumi Miyamoto V. Hammiche Marie‐Aleth Lacaille‐Dubois 《Helvetica chimica acta》2007,90(4):712-719
Four new ursane‐based triterpene glycosides, compounds 1 – 4 , as well as the known glycosides zygophylosides E, G, and H, and 3‐O‐(β‐D ‐quinovopyranosyl)quinovic acid 28‐(O‐β‐D ‐glucopyranosyl) ester, were isolated from the BuOH‐soluble fraction of the MeOH/H2O 7 : 3 extracts of Zygophyllum geslini (roots or aerial parts). Their structures were established mainly by 1D‐ and 2D‐NMR techniques, in combination with HR‐MS analysis and acid hydrolysis. 相似文献
59.
Tada T Nozaki D Kondo M Hamayama S Yoshizawa K 《Journal of the American Chemical Society》2004,126(43):14182-14189
The electrical conductances of dithiolates of polyacene (PA(n)DTs) and polyphenanthrene (PPh(n)DTs), which are typical carbon ladder compounds, are calculated by means of the Landauer formulation combined with density functional theory, where n is the number of benzene rings involved. Surface Green function used in the Landauer formulation is calculated with the Slater-Koster parameters. Attention is turned to the wire-length dependence of the conductances of PA(n)DTs and PPh(n)DTs. The damping of conductance of PA(n)DTs is much smaller than that of PPh(n)DTs because of the small HOMO-LUMO gaps of PA(n)DTs. PA(n)DTs are thus good molecular wires for nanosized electronic devices. Conductance oscillation is found for both molecular wires when n is less than 7. The electrical conductance is enhanced in PA(n)DTs with even-numbered benzene rings, whereas it is enhanced in PPh(n)DTs with odd-numbered benzene rings. The observed conductance oscillation of PA(n)DTs and PPh(n)DTs is due to the oscillation of orbital energy and electron population. Other pi-conjugated oligomers (polyacetylene-DT, oligo(thiophene)-DT, oligo(meso-meso-linked zinc(II) porphyrin-butadiynylene)-DT, oligo(p-phenylethynylene)-DT, and oligo(p-phenylene)-DT) are also studied. In contrast to PA(n)DTs and PPh(n)DTs, the five molecular wires show ordinary exponential decays of conductance. 相似文献
60.
A Green's function formalism incorporating broadened density of states (DOS) is proposed for the calculation of electrical conductance. In cluster-molecule-cluster systems, broadened DOS of the clusters are defined as continuous DOS of electrodes and used to calculate Green's function of electrodes. This approach combined with density functional theory is applied to the electrical transmission of gold atomic wires and molecular wires consisting of benzene-1,4-dithiolate, benzene-1,4-dimethanethiolate, 4,4(')-bipyridine, hexane dithiolate, and octane dithiolate. The B3LYP, B3PW91, MPW1PW91, SVWN, and BPW91 functionals with the LANL2DZ, CEP, and SDD basis sets are employed in the calculation of conductance. The width parameter was successfully determined to reproduce the quantum unit of conductance 2e(2)/h in gold atomic wires. The combination of the B3LYP hybrid functional and the CEP-31G basis set is excellent in reproducing measured conductances of molecular wires by Tao et al. [Science 301, 1221 (2003); J. Am. Chem. Soc. 125, 16164 (2003); Nano Lett. 4, 267 (2004)]. 相似文献