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排序方式: 共有208条查询结果,搜索用时 31 毫秒
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Albrecht H Binder U Harder G Lembke-Koppitz I Philipp A Schmidt-Parzefall W Schröder H Schulz HD Wurth R Donker JP Drescher A Matthiesen U Scheck H Spaan B Spengler J Wegener aD Gabriel JC Schubert KR Stiewe J Waldi R Weseler S Brown NN Edwards KW Frisken WR Fukunaga C Gilkinson DJ Gingrich DM Goddard M Kapitza H Kim PC Kutschke R MacFarlane DB McKenna JA McLean KW Nilsson AW Orr RS Padley P Patel PM Prentice JD Seywerd HC Stacey BJ Yoon T Yun JC Ammar R Coppage D Davis R Kanekal S Kwak N 《Physical review letters》1986,56(6):549-552
3.
[reaction: see text]. Phenylalanine-derived B-aryl-N-tosyloxazaborolidinones selectively activate one of two enantiotopic oxygen atoms in prochiral anti dioxane acetals derived from meso-1,3-diols, leading to enantioselective formation of ring-cleavage products. The reaction is utilized as a key step in asymmetric desymmetrization of meso-1,3-diols. 相似文献
4.
Yûetsu Danzaki Kunio Takada Kazuaki Wagatsuma Masaoki Oku 《Analytical and bioanalytical chemistry》1998,361(5):410-418
A practical method to estimate spectral interferences and to select optimum analytical lines in ICP-AES is suggested. Depending on the matrix composition and the amounts of the analyte, the analytical lines suffering from little interferences and the limit of determination can be determined from calculation using spectral interference coefficients. For this calculation, the spectral interference coefficients, which are defined as apparent mass of the analyte equivalent to the spectral interference from unit mass of the interferent, are obtained experimentally for 639 emission lines of 68 elements. There is a good correlation between the coefficients obtained on two spectrometers having different resolutions. 相似文献
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Kiyokawa T Kanaori K Tajima K Kawaguchi M Mizuno T Oku J Tanaka T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(14):3548-3554
The alpha-helical coiled coils have a representative amino acid sequence of (abcdefg)(n) heptad repeats. We previously reported that two peptides named IZ-2A and IZ-2W formed an (IZ-2A)(2)/IZ-2W heterotrimer with an Ala-Ala-Trp interaction in the hydrophobic core. In this paper, we describe the selective formation of AAB- and ABC-type heterotrimers. To increase the selectivity of the AAB-type heterotrimeric formation, Lys residues at the f position were mutated to either an Ala or a Gln residue to form IZ-2A(fA) or IZ-2W(fQ). Separately, both IZ-2A(fA) and IZ-2W(fQ) have a random structure at pH 7 and 20 degrees C. However, together IZ-2A(fA) and IZ-2W(fQ) form a 2:1 complex with a thermal transition midpoint (Tm) of 48 degrees C. This procedure was applied to prepare the ABC-type heterotrimer, in which two sets of Ala-Ala-Trp interactions were designed in the hydrophobic core. Interhelical interaction between the e and g positions and the alpha-helical propensity of the amino acid at the f position were also considered in the design. The resultant three peptides selectively formed the ABC-type heterotrimer with a Tm of 51 degrees C. Other peptide combinations had random coil properties. 相似文献
7.
Morishita H Ohashi S Oku T Nakajima Y Kojima S Ryufuku M Nakamura H Ohmiya Y 《Photochemistry and photobiology》2002,75(3):311-315
Two marine dinoflagellates, Lingulodinium polyedrum and Pyrocystis lunula, emit light in a reaction involving the enzymatic oxidation of its tetrapyrrole luciferin by molecular oxygen. The characteristic properties of P. lunula luciferase have not been clarified, whereas L. polyedrum luciferase, which has three active domains, has been characterized. A cloned partial cDNA of the P. lunula luciferase encodes an active fragment corresponding to part of domain 2 and all of domain 3 of L. polyedrum luciferase. The homology of the amino acid sequence between the two luciferases in domain 3 is about 84.3%. A recombinant His-tagged luciferase fragment containing domain 3 (Mr = 46 kDa) catalyzed the light-emitting oxidation of luciferin (lambdamax = 474 nm). This protein was purified by a single affinity-chromatography procedure. The pH-activity profile and the bioluminescence spectrum of the recombinant enzyme having a third domain are almost identical to those of an extract from P. lunula cultured in vitro. The recombinant enzyme is active at pH 8.0, although the recombinant enzyme derived from the second domain of L. polyedrum luciferase is inactive at pH 8.0. Substitution of Glu-201 by histidine in the third domain of P. lunula luciferase showed a decrease of activity above pH 7.0, suggesting that histidine residues could be responsible for pH-sensitivity in dinoflagellate luciferase. 相似文献
8.
Oku T 《Chemical communications (Cambridge, England)》2002,(4):302-303
The three-dimensional potential map of YB56 was obtained by inverse Fourier transformation of three-dimensional phases and amplitudes in three high-resolution images taken along the [100], [110] and [111] directions of YB56 crystals; the size of the imaging region was 14 nm x 14 nm x approximately 4 nm, and the image directly showed the three-dimensional potential map of the crystal, a useful method for three-dimensional structure analysis in nanoscale regions. 相似文献
9.
A 12M HCl solution of iron oxyhydroxide (a-FeOOH: goethite) was mixed with water glass (18Na2O.36SiO2
.46H2O) at room temperature. The mixture (sol) changed into a dry gel when dried at 25 °C for 120 hours in air. Glass-ceramic and glass samples were prepared when the dry gel was heated for 1-3 hours in an electric furnace at 800 and 900 °C, respectively. The 57Fe Mössbauer spectrum of the dry gel is composed of a magnetic hyperfine structure owing to the formation of g-FeOOH (lepidocrocite). By contrast, the 57Fe Mössbauer spectrum of glass-ceramic and glasses is composed of paramagnetic Fe(III) with distorted tetrahedral symmetry. This proves that Fe(III) atoms occupy network-forming Si(IV) sites in the FeOOH-fixed sodium silicate glass. A leaching test of the silicate glass in the acid rain simulant composed of HNO3 (pH 3.5) and H2SO4 (pH 3.5) revealed high chemical durability, indicating that Fe(III) is firmly fixed in the glass matrix. 相似文献
10.
Masaoki Oku Toetsu Shishido Takeshi Shinohara Qiang Sun Yoshiyuki Kawazoe Kazuo Nakajima Kazuaki Wagatsuma 《Journal of solid state chemistry》2004,177(2):457-460
The solid solutions of ScBRh3-ScRh3 and CeBRh3-CeRh3 are synthesized by the arc melting method, where RBRh3 and RRh3 (R=rare earth element) have perovskite and AuCu3 type structures, respectively. The binding energy of Sc 2p3/2 for ScBxRh3 increases with the boron concentration. The Knight shift of 45Sc observed by nuclear magnetic resonance spectroscopy decreases with increase of boron concentration. The decrement of the Knight shift corresponds the Sc 4s electron density at the Fermi level. The intensity ratio of f2: f1: f0 of Ce 3d XPS spectrum changes with boron concentration of CeBxRh3. It is concluded that in both cases of ScBxRh3 and CeBxRh3 the charge on the atoms on A-site changes with the concentration of the atoms on B-site, where the atoms are not directly bound. 相似文献