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11.
The high frequency oscillator provides an excellent means of detecting the end-points of titrations performed with ethylenediaminetetraacetic acid or its salts. The determination of various divalent metals is reported, based on both direct and indirect titrations. Because of the great sensitivity of the method it is possible to determine cobalt, nickel, copper (II), zinc, cadmium, lead and manganese (II) in concentration ranges of 1/1000 to 1/6000M. 相似文献
12.
Tomoya Kinumi Kazuo Tsujimoto Mamoru Ohashi Reiko Hara Tomiyuki Hara Koichi Ozaki Miho Saka Yuko Katsuta Akimori Wada Masayoshi Ito 《Photochemistry and photobiology》1993,58(3):409-412
Abstract— 3, 7-Dimethyl-2, 4, 6, 8, 10-dodecapentaenal was synthesized for reconstitution of the retinochrome analog. Its opsin shift was 1000 cm 1 smaller than that of native retinochrome, whose chromophore contains the same number of double bonds. The conformational change from 6-s-trans to 6-s-cis , as figured in a retinal molecule, plays an important role in the formation of the retinochrome analog, based on the estimation of opsin shifts for retinal analogs locked in the 6-s conformation. Thus the conformation of the 6–7 single bond in the native retinochrome was suggested to be 6 -cis . Analysis of the circular dichroic spectra of retinochrome analogs revealed that the 6-s conformation is independent of the appearance of the β-band. The stereoselectivity in the photoisomerization of the retinal analogs by a retinochrome template depends on the hydrophobic binding in the region of the β-ionone ring. 相似文献
13.
Seiji Shinkai Youichiro Hara Osamu Manabe 《Journal of polymer science. Part A, Polymer chemistry》1982,20(4):1097-1105
Three thiazolium-containing polymers, Th-7, Th-33, and Th-18-Py [where Th-x and Py mean x mol % thiazolium unit and pyridinium unit (54 mol %), respectively], were synthesized from partially p-chloromethylated polystyrene. The catalytic activities of these polymer catalysts in acyloin condensation of aldehydes and decarboxylation of α-keto acids were estimated kinetically by oxidative trapping of the key intermediate by flavin (flavin-trapping technique). In aqueous solution at 30°C, the catalytic activity of Th-18-Py and Th-33 in condensation of p-chlorobenzaldehyde was comparable with that of the cationic-micelle-bound thiazolium ion, whereas Th-7 and a monomeric thiazolium compound (N-benzylthiazolium bromide) scarcely exhibited any catalytic activity. The catalysis of the polymer-bound thiazolium ions was sensitively suppressed by increased ionic strength. These results suggest that the pendent thiazolium ion is activated by the relatively high charge density along the polymer chain: the cationic environment is able to facilitate dissociation of the thiazolium ion to the ylid form and deprotonation of the thiazolium-aldehyde adduct to the key intermediate. 相似文献
14.
-Butyrolactone (hereafter abbreviated GBL) is produced by the two-stage hydrogenation of maleic anhydride(MAH) in the liquid phase: the hydrogenation of MAH to succinic anhydride(SAH) in the first stage and the subsequent hydrogenation of SAH to GBL in the second stage. A novel ruthenium catalyst system consisting of Ru salts, trialkylphosphine and p-toluene sulfonic acid (p-TsOH) was found very effective for the hydrogenation of SAH affording GBL, which exhibited excellent catalyst performance, exceeding 97% selectivity for GBL and high activity. 相似文献
15.
Takeo Katami Tomokuni Hayakawa Masamichi Furukawa Shozo Shibata Tadashi Hara 《Analytica chimica acta》1986
An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 105 l mol?1 cm?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy. 相似文献
16.
Xichen CaiMichihiro Hara Kiyohiko KawaiSachiko Tojo Mamoru FujitsukaTetsuro Majima 《Tetrahedron letters》2003,44(32):6117-6120
Some triplet energy-transfer reactions initiated by photoexcitation of the triplet excited state of dibenz[a,h]anthracene to higher triplet excited states (DBA(Tn)) were observed in the presence of the triplet energy quenchers (Q) such as naphthalene, biphenyl, p-dichlorobenzene, and o-dicyanobenzene. In the case of carbon tetrachloride (CCl4) as Q, DBA(Tn)-sensitized decomposition of CCl4 occurred. 相似文献
17.
Sakamoto M Cai X Hara M Fujitsuka M Majima T 《The journal of physical chemistry. A》2005,109(11):2452-2458
The properties and reactivities of the xanthone (Xn) ketyl radical (XnH*) in the doublet excited state (XnH*(D1)) were examined by using two-color two-laser flash photolysis. The absorption and fluorescence of XnH*(D1) were observed for the first time. Several factors governing the deactivation processes of XnH*(D1) such as interaction and reaction with solvent molecules were discussed. The remarkable change of reactivity of XnH*(D1) compared with that in the ground state (XnH*(D0)) was indicated from the experimental results. The rapid halogen abstraction of XnH*(D1) from some halogen donors such as carbon tetrachloride (CCl4) was found to occur. The halogen abstraction occurred more efficiently in the polar solvents than in the nonpolar solvents. It is suggested that the polar solvents promote the spin distribution of XnH*(D1) of the phenyl ring favorable to the halogen abstraction. 相似文献
18.
Electrochemical and electrocatalytic properties of thin films Au(111-25 nm), which are quasi-single-crystal electrodes 25
nm thick made of gold with the (111) preferential orientation, and same electrodes modified with a monolayer (ML) of palladium
are studied in 0.1 M solutions of HClO4 and H2SO4 employing voltammetric techniques and surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS). Spectroscopic
experiments demonstrate strong adsorption of electrolyte species (H2O, OHads, anions) on the Pd surface. The weak and reversible adsorption of CO on Au(111-25 nm) does not change the interfacial-water
structure. Adsorption of CO on the Pd-modified film results in an irreversibly adsorbed CO adlayer stabilized by co-adsorbed
isolated water species. Various electrooxidation mechanisms are discussed. Electrochemical and spectroscopic investigations
on the adsorption and electrooxidation of HCOOH on bare and 1 ML Pd-Au(111-25 nm) electrodes reveal that electrooxidation
proceeds in both cases via a direct or dehydrogenation pathway. This mechanism involves the formation of formate as intermediate,
which is detected by in situ ATR-SEIRAS. The reactivity on Pd-modified surfaces is higher than on bare gold. The specifically
adsorbed anions (sulfate/bisulfate) and the oxide formation on the substrate surface lower the reactivity for CO and HCOOH
on both surfaces.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 11, pp. 1312–1329.
Based on the report delivered at the 8th International Frumkin Symposium “Kinetics of the Electrode Processes,” October 18–22,
2005, Moscow.
The text was submitted by the authors in English. 相似文献
19.
Murakami K Irie K Ohigashi H Hara H Nagao M Shimizu T Shirasawa T 《Journal of the American Chemical Society》2005,127(43):15168-15174
Amyloid fibrils mainly consist of 40-mer and 42-mer peptides (Abeta40, Abeta42). Abeta42 is believed to play a crucial role in the pathogenesis of Alzheimer's disease because its aggregative ability and neurotoxicity are considerably greater than those of Abeta40. The neurotoxicity of Abeta peptides involving the generation of free radicals is closely related to the S-oxidized radical cation of Met-35. However, the cation's origin and mechanism of stabilization remain unclear. Recently, structural models of fibrillar Abeta42 and Abeta40 based on systematic proline replacement have been proposed by our group [Morimoto, A.; et al. J. Biol. Chem. 2004, 279, 52781] and Wetzel's group [Williams, A. D.; et al. J. Mol. Biol. 2004, 335, 833], respectively. A major difference between these models is that our model of Abeta42 has a C-terminal beta-sheet region. Our biophysical study on Abeta42 using electron spin resonance (ESR) suggests that the S-oxidized radical cation of Met-35 could be generated by the reduction of the tyrosyl radical at Tyr-10 through a turn structure at positions 22 and 23, and stabilized by a C-terminal carboxylate anion through an intramolecular beta-sheet at positions 35-37 and 40-42 to form a C-terminal core that would lead to aggregation. A time-course analysis of the generation of radicals using ESR suggests that stabilization of the radicals by aggregation might be a main reason for the long-lasting oxidative stress of Abeta42. In contrast, the S-oxidized radical cation of Abeta40 is too short-lived to induce potent neurotoxicity because no such stabilization of radicals occurs in Abeta40. 相似文献
20.
T. Suzuki M. Aida Y. Ban Y. Fujii M. Hara T. Mitsugashira 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):581-583
The separation of trivalent actinides and lanthanides was studied by using newly developed tertiary pyridine-type anion-exchange resin embedded in silica beads. Chromatographic elution experiments were carried out by using a packed column of the new resin and methanol-hydrochloric acid solution as an effluent. We confirmed that the actinides were eluted well from the elution bands of lanthanides. Actinides and lanthanides were eluted according to the reverse order of their atomic number. 相似文献