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961.
Styrene-terminated poly(oxyethylene) macromonomers (SOE) with narrow molecular weight distribution and quantitative styrene monofunc-tionality were synthesized. In homopolymerization of SOE, conversion of monomer to polymer was shown to be low in spite of high consumption of the vinyl groups of the SOE molecules. Free-radical copolymer-ization of the macromonomer with methyl methacrylate and styrene occurred smoothly, as opposed to homopolymerization. Cumulative copolymer composition and total conversion were determined from the conversions of macromonomer and comonomer (by weight changes) and by proton NMR of the copolymer. The monomer reactivity ratios were found to be ra = 0.06 and rb = 2.0 for the copolymerization of SOE macromonomer (a) with methyl methacrylate (b). In this case the macromonomer exhibited considerably lower reactivity than predicted from its low molecular weight model compound. The monomer reactivity ratios estimated for SOE and styrene were ra = 0.86 and rb = 1.20. The reactivity of SOE was comparable to, but somewhat lower than, styrene. The graft copolymers were used as activators in the halogen displacement reaction, and it was found that their catalytic activity depends on copolymer composition and chemical structure. 相似文献
962.
Styrene-terminated poly(2-acetoxyethyl methacrylate) macromonomer (EBA), methacrylate-terminated poly(2-acetoxyethyl methacrylate) macromonomer (MPA), and methacrylate-terminated poly(methyl methacrylate) macromonomer (MPM) were synthesized and subjected to polymerization and copolymerization by a free-radical polymerization initiator (AIBN). EBA and MPA were homopolymerized at various concentrations. EBA exhibited higher reactivity than styrene. The reactivity of MPA, however, was almost equal to that of glycidyl methacrylate. Cumulative copolymer compositions were determined by GPC analysis of copolymerization products. The reactivity ratios estimated were ra = 0.95 and rb , = 0.90 for EBA macromonomer (a)-methyl methacrylate (b) copolymerization. These values were not consistent with literature values for the styrene-methyl methacrylate and p-methoxy-styrene-methyl methacrylate systems. The reactivity ratios estimated for MPA and 2-bromoethyl methacrylate were ra - 0.95 and rb , = 0.98; equal to the glycidyl methacrylate-2-bromoethyl methacrylate system. MPA or MPM was also copolymerized with styrene, and the reactivity ratios were ra = 0.40, ra = 0.60 and ra = 0.39, ra = 0.58, respectively. These estimates were in good agreement with the reactivity ratios for glycidyl methacrylate and styrene. Thus, no effect of molecular weight was observed for both copolymerization systems. 相似文献
963.
Shuichi Shimma Yuki Takashima Jun Hashimoto Kan Yonemori Kenji Tamura Akinobu Hamada 《Journal of mass spectrometry : JMS》2013,48(12):1285-1290
Mass spectrometry (MS) was used to measure the concentrations of drug and biological compounds in plasma and tissues. Matrix‐assisted laser desorption/ionization (MALDI) imaging MS (IMS) has recently been applied to the analysis of localized drugs on biological tissue surfaces. In MALDI‐IMS, matrix application process is crucial for successful results. However, it is difficult to obtain homogeneous matrix crystals on the tissue surface due to endogenous salts and tissue surface heterogeneity. Consequently, the non‐uniform crystals degrade the quality of the spectrum and likely cause surface imaging artifacts. Furthermore, the direct application of matrix solution can cause tissue shrinkage due to the organic solvents. Here, we report an alternative two‐step matrix application protocol which combines the vacuum deposition of matrix crystals and the spraying of matrix solution to produce a homogeneous matrix layer on the tissue surface. Our proposed technique can also prevent cracking or shrinking of the tissue samples and improve the ionization efficiency of the distributed exogenous material. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
964.
Takafumi Matsuda Kenichi Yamashita Hideaki Maeda Masahiko Hashimoto Kazuhiko Tsukagoshi 《Journal of separation science》2013,36(5):965-970
A capillary chromatography system has been developed using a ternary mixed‐solvents solution, i.e. water–hydrophilic/hydrophobic organic solvent mixture as a carrier solution. Here, we tried to carry out the chromatographic system on a microchip incorporating the open‐tubular microchannels. A model analyte solution of isoluminol isothiocyanate (ILITC) and ILITC‐labeled biomolecule was injected to the double T‐junction part on the microchip. The analyte solution was delivered in the separation microchannel (40 μm deep, 100 μm wide, and 22 cm long) with the ternary water–ACN–ethyl acetate mixture carrier solution (3:8:4 volume ratio, the organic solvent rich or 15:3:2 volume ratio, the water‐rich). The analyte, free‐ILITC and labeled BSA mixture, was separated through the microchannel, where the carrier solvents were radially distributed in the separation channel generating inner and outer phases. The outer phase acts as a pseudo‐stationary phase under laminar flow conditions in the system. The ILITC and the labeled BSA were eluted and detected with chemiluminescence reaction. 相似文献
965.
m-Nitrostyrene was chemoselectively reduced to m-aminostyrene in an acetonitrile suspension containing a titanium(IV) oxide (TiO2) photocatalyst and a suitable hole scavenger at room temperature under atmospheric pressure without the use of a precious metal or reducing gas. Addition of a small amount of water to acetonitrile increased the reaction rate, and the highest rate was obtained. Moreover, applicability of the photocatalytic system was investigated using various nitro compounds having other reducible groups (chloro, bromo, carboxyl, and acetyl groups), and only the nitro group of these compounds was chemoselectively reduced, resulting in the formation of corresponding amino compounds with high yields. 相似文献
966.
Satoshi Okumura Takayuki Kajikawa Koki Yano Kazuhiko Sakaguchi Daisuke Kosumi Hideki Hashimoto Shigeo Katsumura 《Tetrahedron letters》2014
Fucoxanthin is an essential pigment for the light-harvesting of aquatic algae. It exhibits high energy transfer efficiencies to Chl a (>80%) as well as peridinin (>95%). In order to verify the generality and specificity of the noticeable observation on the ICT excited energy state character, which was found in the study of peridinin, we achieved the straightforward synthesis of a series of fucoxanthin short-chain derivatives via the modified-Julia olefination with the aldehyde half segment possessing a β,γ-epoxyketone function. The established method was successfully applied to the synthesis of the epoxy olefin derivative as an allene modified fucoxanthin analogue. 相似文献
967.
Masahiko Isaka Somporn PalasarnSomjit Komwijit Sayanh SomrithipolSujinda Sommai 《Tetrahedron letters》2014
Cyclodepsipeptides SCH 217048 (1), SCH 218157 (2), and a new analog, pleosporin A (3), were isolated from cultures of an unidentified elephant dung fungus of the family Pleosporaceae. The structure of 3 was elucidated on the basis of detailed spectroscopic interpretation. The absolute configurations of 1–3 were determined by chiral column HPLC analysis and Marfey’s method. Cyclodepsipeptides 1–3 exhibited antimalarial activity against Plasmodium falciparum K1 with respective IC50 values of 1.6, 6.4, and 1.6 μg/mL, while they did not show cytotoxicity against KB, MCF-7 and NCI-H187 cell-lines or non-cancerous Vero cells at 50 μg/mL. 相似文献
968.
Discriminative detection of low‐abundance point mutations using a PCR/ligase detection reaction/capillary gel electrophoresis method and fluorescence dual‐channel monitoring 下载免费PDF全文
Mariko Hamada Koji Shimase Kazuhiko Tsukagoshi Masahiko Hashimoto 《Electrophoresis》2014,35(8):1204-1210
We applied a facile LIF dual‐channel monitoring system recently developed and reported by our group to the polymerase chain reaction/ligase detection reaction/CGE method for detecting low‐abundance point mutations present in a wild‐type sequence‐dominated population. Mutation discrimination limits and signaling fidelity of the analytical system were evaluated using three mutant variations in codon 12 of the K‐ras oncogene that have high diagnostic value for colorectal cancer. We demonstrated the high sensitivity of the present method by detecting rare mutations present among an excess of wild‐type alleles (one mutation among ~100 normal sequences). This method also simultaneously interrogated the allelic compositions of the test samples with high specificity through spectral discrimination of the dye‐tagged ligase detection reaction products using the dual‐channel monitoring system. 相似文献
969.
T. Sato T. Majima Kenro Hashimoto Kouhei Hashimoto Y. Zama J. Matsumoto H. Shiromaru K. Okuno H. Tanuma T. Azuma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(2):189-194
Microhydrated methylene blue cations,
MB+(H2O)
n
, are produced in an
electrospray ion source and their size-distributions are measured as a function of the
source temperature. A series of
MB+(H2O)
n
ions is observed up to
n ≃ 60. A striking feature observed in the mass spectra is that the
series of hydrated ions starts at n = 4; intensities of
n = 1–3 are extremely suppressed. The absence of
n = 1–3 ions is well explained by the energetics concerning evaporation
processes of water molecules, based on stable structures and the binding energies of
MB+(H2O)
n
ions calculated by DFT
calculations up to n = 5.
MB+(H2O)
n
ions for
n > 4 evaporate a single water molecule
sequentially, while MB+(H2O)4 tends to fragment into
MB+ and (H2O)4 rather than
MB+(H2O)3 and an H2O molecule. We have
observed a clear magic peak at n = 24, which strongly suggests that the
MB+(H2O)24 ion is formed by attaching a neutral
(H2O)20 cage onto an MB+(H2O)4
ion. 相似文献
970.
A. Margaryan O. Hashimoto V. Kakoyan S. Knyazyan L. Tang 《Physics of Atomic Nuclei》2011,74(2):216-220
A new “tagged-weak π method” is proposed for determination of electromagnetic transition probabilities B(E2) and B(M1) of the hypernuclear states with lifetimes of ∼10−10 s. With this method, we are planning to measure B(E2) and B(M1) for light hypernuclei at JLab. The results of Monte Carlo simulations for the case of E2(5/2+, 3/2+ → 1/2+) transitions in Λ7He hypernuclei are presented. 相似文献