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排序方式: 共有141条查询结果,搜索用时 15 毫秒
111.
Makoto Oba Naomi Kawabe Hiroomi Takazaki Yosuke Demizu Mitsunobu Doi Masaaki Kurihara Hiroshi Suemune Masakazu Tanaka 《Tetrahedron》2014
The chiral cyclic α,α-disubstituted α-amino acid, (3R,4R)-1-amino-3,4-diazido-1-cyclopentanecarboxylic acid [(R,R)-Ac5cdN3], was introduced into achiral α-aminoisobutyric acid (Aib) peptides. The azido groups of (R,R)-Ac5cdN3 in the peptides were efficiently converted into 1,2,3-triazole functional groups. FTIR, 1H NMR, and CD spectra revealed that the dominant conformations of all peptides in solution were 310-helical structures without controlling the helical-screw sense. X-ray crystallographic analyses of peptides containing (R,R)-Ac5cdN3 showed that both the right-handed (P) and left-handed (M) 310-helical structures were present in the crystal state. 相似文献
112.
Hitoshi Soyama Yoshiaki Yanauchi Kazunori Sato Toshiaki Ikohagi Risaburo Oba Ryoichiro Oshima 《Experimental Thermal and Fluid Science》1996,12(4):411-416
Some peculiar phenomena occur around ultrahigh-speed submerged water jets accompanied by very severe cavitation erosion. Using the flow visualization technique with a xenon flash, the water jets were carefully observed, and the spatial distributions of highly erosive impulsive pressures around the jets were measured by means of a pressure-sensitive film technique. The effects of the injection pressure and the nozzle configuration are systematically clarified. Thus, the characteristics and structures of ultrahigh-speed submerged water jets are clearly shown. 相似文献
113.
Naoya Shibata Fumiyasu Oba Takahisa Yamamoto Taketo Sakuma Yuichi Ikuhara 《哲学杂志》2013,93(19):2221-2246
The atomic structure of a = 3, [110]/{112} grain boundary in a yttria-stabilized cubic zirconia bicrystal has been investigated by high-resolution transmission electron microscopy (HRTEM). It was found that the grain boundary migrated to form periodic facets, although the bicrystal was initially joined so as to have the symmetric boundary plane of {112}. The faceted boundary planes were indexed as {111}/{115}. The structure of the {111}/{115} grain boundary was composed of an alternate array of two types of structure unit: {112}- and {111}-type structure units. HRTEM observations combined with lattice statics calculations verified that both crystals were relatively shifted by (α/4)[110] along the rotation axis to form a stable grain-boundary structure. A weak-beam dark-field image revealed that there was a periodic array of dislocations along the grain boundary. The grain-boundary dislocations were considered to be introduced by the slight misorientation from the perfect = 3 orientation. The fact that the periodicity of the facets corresponded to that of the grain-boundary dislocations must indicate that the introduction of the grain-boundary dislocations is closely related to the periodicity of the facets. An atomic flipping model has been proposed for the facet growth from the initial = 3, {112} grain boundary. 相似文献
114.
Uchida H Miyata K Oba M Ishii T Suma T Itaka K Nishiyama N Kataoka K 《Journal of the American Chemical Society》2011,133(39):15524-15532
A series of the N-substituted polyaspartamides possessing repeating aminoethylene units in the side chain was prepared in this study to identify polyplexes with effective endosomal escape and low cytotoxicity. All cationic N-substituted polyaspartamides showed appreciably lower cytotoxicity than that of commercial transfection reagents. Interestingly, a distinctive odd-even effect of the repeating aminoethylene units in the polymer side chain on the efficiencies of endosomal escape and transfection to several cell lines was observed. The polyplexes from the polymers with an even number of repeating aminoethylene units (PA-Es) achieved an order of magnitude higher transfection efficiency, without marked cytotoxicity, than those of the polymers with an odd number of repeating aminoethylene units (PA-Os). This odd-even effect agreed well with the buffering capacity of these polymers as well as their capability to disrupt membrane integrity selectively at endosomal pH, leading to highly effective endosomal escape of the PA-E polyplexes. Furthermore, the formation of a polyvalent charged array with precise spacing between protonated amino groups in the polymer side chain was shown to be essential for effective disruption of the endosomal membrane, thus facilitating transport of the polyplex into the cytoplasm. These data provide useful knowledge for designing polycations to construct safe and efficient nonviral gene carriers. 相似文献
115.
Oba M Okada Y Nishiyama K Shimada S Ando W 《Chemical communications (Cambridge, England)》2008,(42):5378-5380
Bis(2,4,6-triisopropylphenyl) tellurone (Tip(2)TeO(2)) was prepared, fully characterized by spectroscopic and X-ray crystallographic analyses, as well as theoretical calculations, and found to be an effective oxidizing agent that was capable of converting alcohols into carbonyl compounds under mild reaction conditions. 相似文献
116.
Four amidecrownophanes 3a-d, including three new compounds 3a, 3c and 3d, were readily prepared through amidation of dicarbonyl dichloride with diamine derivatives without using high-dilution or template conditions and then the tandem Claisen rearrangement. At the macrocyclization step the intramolecular hydrogen bonding of the intermediate might play an important role to give high yields of 1:1 macrocycles. 相似文献
117.
Dr. Konstantin V. Purtov Dr. Valentin N. Petushkov Dr. Mikhail S. Baranov Dr. Konstantin S. Mineev Dr. Natalja S. Rodionova Zinaida M. Kaskova Aleksandra S. Tsarkova Dr. Alexei I. Petunin Dr. Vladimir S. Bondar Dr. Emma K. Rodicheva Dr. Svetlana E. Medvedeva Prof. Yuichi Oba Yumiko Oba Prof. Alexander S. Arseniev Prof. Sergey Lukyanov Prof. Josef I. Gitelson Dr. Ilia V. Yampolsky 《Angewandte Chemie (International ed. in English)》2015,54(28):8124-8128
Many species of fungi naturally produce light, a phenomenon known as bioluminescence, however, the fungal substrates used in the chemical reactions that produce light have not been reported. We identified the fungal compound luciferin 3‐hydroxyhispidin, which is biosynthesized by oxidation of the precursor hispidin, a known fungal and plant secondary metabolite. The fungal luciferin does not share structural similarity with the other eight known luciferins. Furthermore, it was shown that 3‐hydroxyhispidin leads to bioluminescence in extracts from four diverse genera of luminous fungi, thus suggesting a common biochemical mechanism for fungal bioluminescence. 相似文献
118.
Kosuke Okuma Akira M. Ono Makoto Oba Masatsune Kainosho Tsutomu Terauchi 《Tetrahedron letters》2009,50(13):1482-163
We have developed a synthetic route for (2S,3R)- and (2S,3S)-[2-13C;3-2H] glutamic acids with high enantioselectivity. The key reactions in this synthesis are the asymmetric reduction of the 2,3-didehydroornithine derivative using the (S,S)-Et-DuPHOS-Rh catalyst and the oxidation of the δ-position by ruthenium catalysis. 相似文献
119.
Stereoselective synthesis of non-proteinogenic amino acids via Michael addition to 3,4-didehydropyroglutamate derivative in which the carboxyl function is protected as a 2,7,8-trioxabicyclo[3.2.1]octane (ABO ester) group is described. The obtained 3-substituted pyroglutamic ABO ester was directly converted to 3-substituted glutamic acids such as chlorpheg by acidic hydrolysis, whereas 3-substituted proline derivatives were obtained by chemoselective reduction of the lactam carbonyl group. A formal total synthesis of baclofen, a γ-aminobutyric acid (GABA) analogue, is also described. 相似文献
120.