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41.
Lee VY Kato R Ichinohe M Sekiguchi A 《Journal of the American Chemical Society》2005,127(38):13142-13143
Lithium 1,2-disila-3-germacyclopentadienide 2-.Li+ was synthesized by the reduction of 1,2-disila-3-germacyclopenta-2,4-diene 1 with potassium graphite followed by treatment with an excess amount of LiBr. The X-ray analysis of 2-.[Li+(THF)] revealed a delocalized aromatic cyclopentadienide-type structure with the diagnostic eta5-coordination of the Li+ cation to the five-membered ring. Aromaticity of this compound was verified and confirmed by theoretical calculations. The solution behavior of the 2-.Li+ is different in nonpolar and polar solvents; in nonpolar toluene, 2-.Li+ maintained the properties of a delocalized aromatic compound with the characteristically shielded 7Li NMR resonance at -5.4 ppm, whereas in polar THF, 2-.Li+ exhibited the properties of a localized nonaromatic compound with the negative charge situated on the Ge atom. 相似文献
42.
We propose a method for the determination of acid dissociation constants based on the rapid detection of the equivalence point (EP) by feedback-based flow ratiometry and the subsequent estimation of the half equivalence point (EP1/2). The titrant (e.g., NaOH) flow rate FB was varied in response to a control voltage Vc from a controller, while the titrand (e.g., CH3COOH) flow rate FA was held constant. The pH of the mixed solution was monitored downstream from the confluence point of the solutions following a knotted tubular mixer. Initially, Vc was increased linearly. At the instance the detector sensed EP, the ramp direction of Vc changed downward. The pH increased further because of the lag time between the mixing of solutions and the sensing of pH. Following the pH maximum, the pH decreased. The EP was sensed again in this downward scan. The Vc that gives EP1/2 was computed from the Vc just at the time of the EP detection. The Vc was held constant at this level for 18 s, and the plateau pH value thus obtained was taken to be the pKa of the analyte subject to activity corrections. Studies on the dependence of the pKa on the ionic strength or dielectric constant of the solution were conducted in an automated fashion by delivering NaCl solution or acetonitrile through an additional channel. Satisfactory results were obtained with good throughput (53 s per determination) and precision (R.S.D.≈0.3%) for various acids. 相似文献
43.
A planar chiral ferrocene-fused cyclic aldimine was synthesized and a series of iminium salts were divergently prepared from it. The new carbene was generated from a salt by simple deprotonation with a strong base and identified by a carbene trapping experiment with sulfur. The sulfur adduct was fully characterized and its crystal structure implied that the new carbene would create an excellent chiral environment when used as a catalyst or a ligand in catalytic asymmetric synthesis. 相似文献
44.
The ion transfer of creatinine (CRE) at a polarized nitrobenzene (NB)/water (W) interface has been studied. When the pH of the W phase is in the range of 1.2 to 4.0, a well‐defined voltammetric wave is observed for a simple transfer of CRE+ (protonated form) at the NB/W interface. This transfer reaction has been applied to develop an amperometric method for the determination of CRE in urine. In this system, the NB/W interface is covered with a dialysis membrane to prevent possible interference from urine proteins. The concentration of CRE in a urine control has successfully been determined. 相似文献
45.
Shinya Kato Risa Kikuchi Hisae Aoshima Yasukazu Saitoh Nobuhiko Miwa 《Journal of photochemistry and photobiology. B, Biology》2010,98(2):144-151
The UVA-irradiation of 10 J/cm2 on HaCaT keratinocytes increased 59.1% of the intracellular reactive oxygen species (ROS) by NBT assay and the cell viability decreased to 31.5% by WST-1 assay, comparing to the non-irradiated control. In the presence of fullerene-C60 (C60) incorporated in phospholipid membrane vehicle (LiposomeFullerene: Lpsm-Flln) of 250–500 ppm, they were restored to ?9.1% to + 2.3% of the ROS and 83.0–84.8% of the cell viability, but scarcely restored by the liposome without C60 (Lpsm). In HaCaT cells administered with Lpsm-Flln (150 ppm), C60 was ingested at the intracellular concentrations of 1.4–21.9 ppm for 4–24 h, and, intracellular C60 was excreted by 80% at 4 h after rinsing-out, and decreased to 2–10% after 24–48 h. C60 was predominantly distributed around the outside of nuclear membrane without deterioration of intact cell morphology according to fluorescent immunostain. Thus Lpsm-Flln is found to be an effective antioxidant that could preserve HaCaT keratinocytes against UVA-induced cellular injury. Lpsm-Flln has a potential to serve as a cosmetic material for skin protection against UVA. 相似文献
46.
Regulated Incorporation of Two Different Metal Ions into Programmed Sites in a Duplex by DNA Polymerase Catalyzed Primer Extension 下载免费PDF全文
Tatsuya Funai Junko Nakamura Yuki Miyazaki Risa Kiriu Dr. Osamu Nakagawa Dr. Shun‐ichi Wada Prof. Akira Ono Prof. Hidehito Urata 《Angewandte Chemie (International ed. in English)》2014,53(26):6624-6627
Metal‐mediated base pairs formed by the coordination of metal ions to natural or artificial bases impart unique chemical and physical properties to nucleic acids and have attracted considerable interest in the field of nanodevices. AgI ions were found to mediate DNA polymerase catalyzed primer extension through the formation of a C–AgI–T base pair, as well as the previously reported C–AgI–A base pair. The comparative susceptibility of dNTPs to AgI‐mediated enzymatic incorporation into the site opposite cytosine in the template was shown to be dATP>dTTP?dCTP. Furthermore, two kinds of metal ions, AgI and HgII, selectively mediate the incorporation of thymidine 5′‐triphosphate into sites opposite cytosine and thymine in the template, respectively. In other words, the regulated incorporation of different metal ions into programmed sites in the duplex by DNA polymerase was successfully achieved. 相似文献
47.
Back Cover: Regulated Incorporation of Two Different Metal Ions into Programmed Sites in a Duplex by DNA Polymerase Catalyzed Primer Extension (Angew. Chem. Int. Ed. 26/2014) 下载免费PDF全文
48.
Risa Matsumoto 《合成通讯》2013,43(15):1807-1816
The Mn(III)-based oxidation of a tertiary alkylamine, such as nitrilotris(ethane-2,1-diyl) tris(3-oxobutanoate) (1) with 1,1-diphenylethene (2a), effectively proceeded in an acetic acid–formic acid mixed solvent to give nitrilotris(ethane-2,1-diyl) tris(2-methyl-5,5-diphenyl-4,5-dihydrofuran-3-carboxylate) (3). Other typical Mn(III)-based reactions of various β-diketo esters 4a–e, 2,4-pentanedione (6a), malonic acid (6b), and diethyl malonate (6c) with 1,1-diarylthenes 2a–d were also investigated in a similar acetic acid–formic acid mixed solvent and the reaction rate was accelerated and the product yield increased. 相似文献
49.
Here we report the first photochromism of a newly designed [2.2]paracyclophane-bridged imidazole dimer in water. The photochromic dye with a hydrophilic and a hydrophobic substituent forms vesicles in water and shows instantaneous colouration upon UV light irradiation and successive rapid fading in the dark. 相似文献
50.
Asada Y Mutoh R Ishiura M Mino H 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,213(1):200-205
The use of a polychromatic microwave pulse to expand the pumping bandwidth in pulsed electron-electron double resonance (PELDOR) was investigated. The pumping pulse was applied in resonance with the broad (~100 mT) electron paramagnetic resonance (EPR) signal of the manganese cluster of photosystem II in the S2 state. The observation pulses were in resonance with the narrow EPR signal of the tyrosine radical, YD·. It was found that in the case of the polychromatic pumping pulse containing five harmonics with the microwave frequencies between 8.5 and 10.5 GHz the PELDOR effect corresponding to the dipole interaction between the Mn cluster and YD· was about 2.9 times larger than that achieved with a monochromatic pulse. In addition to the dipolar modulation, the nuclear modulation effects were observed. The effects could be suppressed by averaging the PELDOR trace over the time interval between the observation microwave pulses. The polychromatic excitation technique described will be useful for improving the PELDOR sensitivity in the measurements of long distances in biological samples, where the pair consists of a radical with a narrow EPR spectrum and slow phase relaxation, and a metal center that has a broad EPR spectrum and a short phase relaxation time. 相似文献