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31.
In the current studies, we designed a new approach for sizing and isolating chromosomal DNA using coil-globule transition, which avoids fragmentation of giant DNA due to mechanical stress. Although coil-globule transition is reversible and globular DNA is tolerant to mechanical stress, globular DNA cannot be manipulated by an electric field because of the loss of its negative charges. In our system, however, DNA is extracted from an agarose gel in a coiled state into a solution of PEG, and coil-globule transition is induced by cations generated at the anode. This method achieves buffer exchange without stirring, which is the main cause of mechanical stress. Real-time analysis of T4dc viral DNA molecules revealed that they change immediately from a coiled to a globular form when the cation concentration is sufficiently high. This method was used to prepare yeast chromosomal DNA in a globular state without fragmentation. 相似文献
32.
Shigeo Tazuke Michihiko Asai Seizo Okamura 《Journal of polymer science. Part A, Polymer chemistry》1968,6(7):1809-1824
The polymerization of N-vinylcarbazole (VCZ) initiated by sodium chloroaurate (NaAuCl4·2H2O) in nitrobenzene was studied at 30°C. The rate of polymerization (Rp) is proportional to [AuIII] [VCZ] after a short induction period. When reducing agents (ascorbic acid, ferrocene, or mercury metal) are added to the system, the rate of polymerization in the dark increases. The Rp is relatively unaffected by addition of water and N-ethylcarbazole, but the polymerization is completely inhibited in the presence of ammonia. Oxygen and DPPH act as neither inhibitors nor retarders. Kinetic treatments based on the assumption that the active initiating species is AuII produced by reduction of AuIII by VCZ and other reducing agents explain the experimental results very well. 相似文献
33.
Michihiko Noguchi Kazushige Sakamoto Seiji Nagata Shoji Kajigaeshi 《Journal of heterocyclic chemistry》1988,25(1):205-208
6,7-Dihydropyrido[3,4-d]pyrimidine-2,4(1H,3H)-diones were obtained in high yields from the reaction of 5-formyl-1,3,6-trimethylpyrimidine-2,4(1H,3H)-dione ( 1 ) and primary amines. For this pyridopyrimidine synthesis the following reaction pathway is proposed; the [1,5]-hydrogen shift of 1 gives a 5,6-dihydro-5,6-dimethylenepyrimidine-2,4(1H,3H)-dione intermediate. The cycloaddition reaction of the intermediate with aldimines from 1 and the primary amines affords 5,6,7,8-tetrahydropyrido[3,4-d]pyrimidine-2,4(1H,3H)-diones, which are dehydrated to the final products. 相似文献
34.
Satoru Amou Osamu Haba Kaori Shirato Teruaki Hayakawa Mitsuru Ueda Kazuhiko Takeuchi Michihiko Asai 《Journal of polymer science. Part A, Polymer chemistry》1999,37(13):1943-1948
We investigated a head-to-tail regioregularity of poly(3-alkylthiophenes) from 3-alkylthiophene by an oxidative coupling polymerization, which is the simplest and easiest way for the synthesis of polythiophenes. The polymerizations were conducted using ferric chloride (III) as an oxidant in chloroform. Investigating the polymerization conditions, a lower temperature and a lower concentration were effective for increasing the head-to-tail (HT) content. The best HT content of 88% was obtained when the temperature was −45°C and the initial monomer concentration was 0.02 mol L−1. Washing the resulting polymer by n-hexane further increased the content to 91%. Thus, it was found that the high regioselectivity can be achieved by the simple polymerization and the simple operation such as washing. The polymerization mechanism causing the regularity is also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1943–1948, 1999 相似文献
35.
Akinori Nishio Amane Mochizuki Jun‐Ichi Sugiyama Kazuhiko Takeuchi Michihiko Asai Koichiro Yonetake Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》2001,39(3):416-429
An ordered head‐to‐tail (HT) polyurethane was successfully prepared by the polyaddition reaction of p‐isocyanatobenzyl isocyanate with ethylene glycol with dibutyltin dilaurate as a catalyst. Furthermore, the HT regularity of polyurethane was improved to 83% with 1,1,3,3‐tetraphenyl‐1,3‐dichlorodistannoxane. The polymerization was conducted in N,N‐dimethylformamide at 30 °C with both monomers mixed at once. The microstructure of the polymer was investigated by 1H and 13C NMR spectroscopy, and the polymer obtained by the polyaddition reaction had the expected HT linkages. The constitutional regularity of the polymers influenced the thermal properties and crystallinity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 416–429, 2001 相似文献
36.
Sergio Luis L. M. Ramos Michihiko Ogino Masaharu Oguni 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1353-1358
We report molar heat capacities for racemic sec-butylcyclohexane (s-BCH) measured by the adiabatic calorimetric method within the temperature range from 14 to 200 K. In the crystalline state, we identified the presence of a second-order phase transition and a glass transition phenomenon, both originating from the same configurational degree of freedom. The phase and glass transition temperatures T trs and T g were determined to be (136.7 ± 1.0) and (100 ± 1) K, respectively. The entropy of phase transition was estimated to be Δtrs S m = 1.4 J K?1 mol?1 ≈ (1/4) R ln 2. The phase transition was judged to be of an order–disorder type on the basis of the fact that the glass transition occurred in the low-temperature heat-capacity tail. The entropy was interpreted to suggest that four molecules in the crystalline state constitute a unit for producing two distinct configurations in the coexistence of (d)- and (l)-s-BCH. 相似文献
37.
Michihiko Asai Shigeo Tazuke Seizo Okamura 《Journal of polymer science. Part A, Polymer chemistry》1974,12(1):45-56
Further investigations of the photopolymerization of N-vinylcarbazole(VCZ) sensitized by sodium chloroaurate(III) in nitrobenzene were undertaken under irradiation of near-ultraviolet light at 30°C. Copolymerization with isobutyl vinyl ether and the kinetic behavior of polymerization were studied. These propagation and chain-breaking features were discussed in comparison with those obtained in the thermal polymerization. Electron spin resonance spectroscopy was conducted at 77°K in various systems. 相似文献
38.
Michihiko Noguchi Kenjiro Onimura Yuji Isomura Shoji Kajigaeshi 《Journal of heterocyclic chemistry》1991,28(4):885-890
The treatment of (5,5-dimethyl-3-oxo-1-cyclohexenyl)iminotriphenylphosphorane ( 2 ) with phenyl isocyanate ( 3a ) gave N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)-N'-phenylcarbodiimide ( 4a ) in situ. The reaction of 4a with enamines proceeded smoothly to afford the pyridine ring formation with the elimination of amine. This means that 4a is regarded as a new class of 2-aza-1,3-butadiene. The scopes and limitation of this reaction are also discussed. 相似文献
39.
Michihiko Noguchi Masashi ShiraiKuniko Nakashima Ichiro AraiAkiko Nishida Hidetoshi YamamotoAkikazu Kakehi 《Tetrahedron》2003,59(25):4581-4590
The thermal reaction of N-benzyl-N-[3-(N-substituted imino)methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-2-yl]amino acid esters, generated from aldehyde esters and primary amines, provides 2,3-dihydropyrido[1,2-a]pyrrolo[2,3-d]pyrimidin-4(1H)-one derivatives effectively and stereoselectively. Therein, the stereoselective generation of conjugated azomethine ylides from the imine esters and their cyclization is essential for the pyrroline-ring formation. 相似文献
40.
Hoai PM Tsunoi S Ike M Kuratani Y Kudou K Viet PH Fujita M Tanaka M 《Journal of chromatography. A》2003,1020(2):161-171
An efficient method for the simultaneous determination of the degradation products of nonylphenol polyethoxylates (NPnEOs, n = number of ethoxy units), i.e., nonylphenol (NP), NPnEOs (n = 1-3), nonylphenoxy carboxylic acids (NPnECs, n = 1-2, number of ethoxy units plus an acetate) and their halogenated derivatives (XNP, XNP1EO and XNP1EC; X = Br or Cl), in water samples were developed. After trimethylsilylation with N,O-bis(trimethysilyl)acetamide, all the analytes were determined by gas chromatography-tandem mass spectrometry (GC-MS-MS) with electron ionization (EI). The ion peaks of [M - 85]+ of the derivatives were selected as precursor ions and their product ions showing the highest intensities were used for the quantitative analysis. The instrumental detection limits were in the range from 2.1 to 11 pg. The recoveries of the analytes from the water samples were optimized by using solid-phase extraction (SPE). The deuterated reagents of octylphenol, octylphenol monoethoxylate and octylphenoxyacetic acid were used as the surrogates. The method detection limits (500 ml water sample) using C18 SPE were from 2.5 to 18 ng/l. The recoveries from spiked pure water and the environmental water samples were greater than 78%. The method was successfully applied to environmental samples. Remarkably, the concentrations of the halogenated compounds (CINP, CINP1EO and BrNP1EO) were detected at the hundreds of ng/l levels in the Neya river. 相似文献