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排序方式: 共有143条查询结果,搜索用时 31 毫秒
81.
Motoo Tori Kanako Otose Hiroko Fukuyama Junko Murata Yasuko Shiotani Shigeru Takaoka Katsuyuki Nakashima Masakazu Sono Masami Tanaka 《Tetrahedron》2010,66(27-28):5235-5243
Eighteen new eremophilanes (dimeric lactones, lactams, carboxylic acid, methyl ester, tetranor- and dinor-ketones, furanoeremophilane, enoleremophilanolide, epoxyeremophilanolide, and hydroxy- or methoxyeremophilanolides) have been isolated from the methanol extract of fresh rhizomes of Farfugium japonicum (Compositae), and their structures have been determined on the basis of high-resolution 2D NMR and X-ray crystallographic analyses as well as by chemical transformations. 相似文献
82.
Kanako Takada Naoya Nakagawa Kunio Nikki Hiroshi Kimura 《Magnetic resonance in chemistry : MRC》1977,9(2):116-117
Aromatic solvent-induced shifts (ASIS) in 19F n.m.r. spectra of several organic fluoro compounds have been determined in several solvents. 19F n.m.r. signals of unsaturated fluoro compounds in C6F6 and C6H6 show excess high field shifts corresponding to the term σc (solvent shift caused by chemical interactions). The mechanism of this shift is discussed in connection with the presence of an F-π interaction. A thermal study also supports this idea. 相似文献
83.
Chimeric RNA Oligonucleotides with Triazole and Phosphate Linkages: Synthesis and RNA Interference
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Dr. Tomoko Fujino Kanako Kogashi Koudai Okada Dr. Martin Mattarella Takeru Suzuki Dr. Kenichi Yasumoto Prof. Kazuhiro Sogawa Prof. Hiroyuki Isobe 《化学:亚洲杂志》2015,10(12):2683-2688
Chimeric RNA oligonucleotides with an artificial triazole linker were synthesized using solution‐phase click chemistry and solid‐phase automated synthesis. Scalable synthesis methods for jointing units for the chimeric structure have been developed, and after click‐coupling of the jointing units with triazole linkers, a series of chimeric oligonucleotides was prepared by utilizing the well‐established phosphoramidite method for the elongation. The series of chimeric 21‐mer oligonucleotides that possessed the triazole linker at different strands and positions allowed for a screening study of the RNA interference to clarify the preference of the triazole modifications in small‐interfering RNA molecules. 相似文献
84.
Inside Cover: Chimeric RNA Oligonucleotides with Triazole and Phosphate Linkages: Synthesis and RNA Interference (Chem. Asian J. 12/2015)
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85.
Newly developed phosphino-bisphenol 1c was found to be an efficient organocatalyst for the aza-Morita-Baylis-Hillman reaction. High enantioselectivity up to 96% ee was obtained with catalyst loading of 1 mol %. 相似文献
86.
Tom A. J. Welling Sina Sadighikia Kanako Watanabe Albert Grau-Carbonell Maarten Bransen Daisuke Nagao Alfons van Blaaderen Marijn A. van Huis 《Particle & Particle Systems Characterization》2020,37(6):2000003
In theory, liquid-cell (scanning) transmission electron microscopy (LC(S)TEM) is the ideal method to measure 3D diffusion of nanoparticles (NPs) on a single particle level, beyond the capabilities of optical methods. However, particle diffusion experiments have been especially hard to explain in LC(S)TEM as the observed motion thus far has been slower than theoretical predictions by 3–8 orders of magnitude due to electron beam effects. Here, direct experimental evidence of undamped diffusion for two systems is shown; charge-neutral 77 nm gold nanoparticles in glycerol and negatively charged 350 nm titania particles in glycerol carbonate. The high viscosities of the used media and a low electron dose rate allow observation of Brownian motion that is not significantly altered by the electron beam. The resulting diffusion coefficient agrees excellently with a theoretical value assuming free diffusion. It is confirmed that the particles are also moving in the direction parallel to the electron beam by simulating STEM images using Monte Carlo simulations. Simulations and experiments show blurring of the particles when these move out of focus. These results make clear that direct observation of 3D diffusion of NPs is possible, which is of critical importance for the study of interparticle interactions or in situ colloidal self-assembly using LC(S)TEM. 相似文献
87.
Ishii Takahiro Matayoshi Natsuki Taba Kanako Kamada Takashi 《Chemistry of Natural Compounds》2022,58(3):474-477
Chemistry of Natural Compounds - Plectranthus barbatus Andrews is one of the traditional herbs growing in the Okinawa region, Japan. This plant has high nutritional value and is well known... 相似文献
88.
Sekimoto K Sakai M Takayama M 《Journal of the American Society for Mass Spectrometry》2012,23(6):1109-1119
The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric
pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O2–, HCO3–, COO–(COOH), NO2–, NO3–, and NO3–(HNO3) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The
individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric
ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is
most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric
ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric
ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion. 相似文献
89.
Electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years mostly in solvent solution and some in melt form. In this work, near- and supercritical CO2 were used as media for this process. At these conditions, the solubility can be tuned by controlling the temperature and pressure. Therefore, it is possible to form particles and fibers within a thermodynamic window where the biopolymer has been softened, but not dissolved. The experiments were conducted by using electrospinning under pressurized CO2 system at pressures of ~ 8.0 MPa and temperature of 313 K to produce several polymers fibers. Polyvinylpyrrolidone was used as the starting material. During the electrospinning process, the applied voltage was 10–17 kV and the distance of nozzle and collector was 8 cm. The concentration of polymer solution was 4 wt%. The morphology- and structure-produced fibers were observed by scanning electron microscopy. The results showed that temperature and pressure affected the morphology of fibers produced by electrospinning in pressurized CO2. This suggests that the thermal behavior of the polymer can be optimized by adjusting the polymer through the adjustment of pressure and temperature by using CO2 as a solvent. 相似文献
90.
Minakata K Nozawa H Yamagishi I Gonmori K Hasegawa K Suzuki M Watanabe K Suzuki O 《Analytical and bioanalytical chemistry》2012,403(7):1793-1799
A rapid method was developed to identify and quantify the azide ion (N(3)(-)) in gastric fluid and urine. N(3)(-) in diluted biological fluids was reacted with NaAuCl(4) to produce Au(N(3))(2)(-), which was extracted with octanol. Five microliters of the extract were flow-injected into an electrospray ionization tandem mass spectrometric instrument. Quantification of N(3)(-) was performed by selected reaction monitoring of the product ion Au(N)(N(3))(-) at m/z 253, which was derived from the precursor ion Au(N(3))(2)(-) at m/z 281, using 50 μL of aqueous solution within 10 min. This method was found to be linear up to 10(-5) M, to have a limit of quantification of 10(-7) M, a limit of detection of 3.0?×?10(-8) M, and a coefficient of variation of ≦10% at 10(-7) M. In the case of urine, 50 μL of urine were spiked with N(3)(-), this was diluted 10-fold and passed through 1 mL of a resin, and finally diluted to 100-fold of the original. This method was linear up to 10(-3) M, had a limit of quantification of 10(-5) M, a limit of detection of 3.0?×?10(-6) M, and coefficient of variation of ≦8.8% for an original urine concentration of 10(-5) M. The practical applicability of this method was checked by diluting 1 μL of a suspected suicide victim's gastric fluid 20,000-fold and 1 μL of the victim's urine 5,000-fold and then measuring the N(3)(-) levels. These levels were found to be (7.5?±?1.0)?×?10(-2) M and (3.2?±?0.4)?×?10(-3) M, respectively. 相似文献