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101.
Katsuhiko?Kamio Yoshifumi?Kusumoto Masashi?Sakai Katumitu?HayakawaEmail author 《Colloid and polymer science》2003,281(7):608-613
The conformation of the sodium salt of poly(l-glutamic acid) (P(Glu)) in solutions of the cationic bipolar amphiphile 1, 20-isosanediylbis(alkylammonium chloride) (C 20(RA) 2) with different alkyl head groups as a function of amphiphile concentration was investigated using circular dichroism (CD). RA included methylammonium (MA), ethylammonium (EA), propylammonium (PA), butylammonium (BA), and pentylammonium (PeA) cationic groups. The CD spectrum of each C 20(RA) 2 had a double minima corresponding to the a-helix of P(Glu), which was replaced by CD spectra with a single minimum at wavelengths larger than 222 nm as concentration increased. These changes in the CD spectrum were ascribed to the conformational change from random coil to a-helix and to aggregates of helices. In C 20(EA) 2 solutions, a step-like change in the CD intensity was observed at 222 nm as a function of the ratio of C 20(RA) 2 to P(Glu). At the step, the CD spectrum of the complete a-helix was observed. At 10–35 °C, an a-helix was induced in P(Glu) in the order: C 20(EA) 2>C 20(MA) 2>C 20(PA) 2>C 20(BA) 2>C 20(PeA) 2. This order was ascribed to the best fit of ethylammonium to the P(Glu) side chain. 相似文献
102.
We have prepared polycrystalline samples of Sr3YCo4O10.56, Sr2.4Ca0.6YCo4O10.54, and Sr3YCo3.76Mn0.24O10.59, and found that these materials show unusual impurity effects on their transport and magnetic properties. A tiny amount of impurities such as Mn or Ca suppresses room-temperature ferromagnetism of Sr3YCo4O10.56. With the suppression, their resistivities and thermopowers are also dramatically changed. We propose that the unusual impurity effects are caused by the suppression of orbital ordering. 相似文献
103.
New substrates and reaction conditions which may be expected to yield phenyl cation intermediates have been investigated. The approaches used were: (a) solvolysis of PhX in fluorinated alcohols, where X = ? N (O) = NOTs (tosyloxyazoxy), ? N (O) = NONf (Nf = C4F9SO) and ? OSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document} (CH3)3ōTf (Tf=CF3SO); (b) solvolysis of ArBr, PhOTf and PhOSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}(CH3)3ōTf (phenyl ‘betylate triflate’) in super-acid solvents (FSO3H · SbF5, SbF5, AgSbF6). Analysis of the product mixtures provided no evidence for the intermediacy of phenyl cations as a major pathway in any of the reactions. This result is remarkable, since the ‘betylate’, for example, is a better leaving group by a factor of at least 105 than the ‘super’ leaving group triflate in the solvolysis of alkyl sulfonates. These results are a further indication of the extremely low stability of phenyl cations, as well as of the very special properties of the nitrogen leaving group in arenediazonium ions. 相似文献
104.
105.
S. Kulprecha T. Nihira C. Shimomura K. Yamada N. Nilubol T. Yoshida H. Taguchi 《Tetrahedron》1984,40(15):2843-2846
The microbiological transformation of lithocholic acid (3α-hydroxy-5β-cholanic acid) into 3α, 15β-dihydroxy-5β-cholanic acid by Cunninghamella sp. is Investigated. The structure has been determined on the basis of two-dimensional 1H-NMR. 相似文献
106.
G. Tamai H. Yoshida H. Imai T. Takashina K. Kotoo T. Fuwa Y. Tsuchioka H. Matsuura G. Kajiyama 《Chromatographia》1985,20(11):671-676
Summary New quinidine metabolites, including 10,11-dihydrodiol quinidine N-oxide, 10,11-dihydrodiol quinidine and their glucuronides, were found in human urine. A quinidine monitoring HPLC method including these metabolites, is proposed by the direct injection of body fluid samples onto the precolumn for deproteinization followed by reverse phase separation in the analytical column with a column switching technique. The recovery of spiked quinidine and its metabolites in plasma was quantitative (98–102%) with good reproducibility (C.V.: 1.6–4.0%). Several clinical samples such as whole blood and urine were analyzed by the present method. 相似文献
107.
Qi ZM Matsuda N Santos J Yoshida T Takatsu A Kato K 《Journal of colloid and interface science》2004,271(1):249-253
Broadband, time-resolved optical waveguide (OWG) spectroscopy has been used for in situ, real-time investigation into the self-assembly of metal nanoparticle monolayers. The OWG spectroscopy makes it possible to use the transverse electric (TE) and transverse magnetic (TM) modes to measure surface plasmon absorption of immobilized metal nanoparticles in two directions, parallel and normal to the waveguide surface. Therefore, this technique can provide direction-dependent information on the metal nanoparticles at the interface. In this paper, a 50-microm-thick glass plate was used as a slab waveguide and the kinetics of Au nanoparticle adsorption on a hemoglobin-functionalized glass substrate was examined in the early stage of self-assembly. The findings show that with the TE mode the surface plasmon resonance (SPR) behavior for immobilized Au nanoparticles is different from that with the TM mode. 相似文献
108.
109.
A new pulse sequence is proposed for the determination of scalar coupling correlation in small- and medium-sized organic compounds. The method uses a combination of the double pulsed field gradient spin-echo (DPFGSE) and the selective population transfer (SPT) techniques and is shown to be useful in the analysis of complex spectra with many overlapped signals. The usefulness of this method in the structural elucidation of natural substances is demonstrated using strychnine and digitoxin as examples. 相似文献
110.
Takuma Shinya Nakashima Noriyuki Tantirungkij Manee Kinoshita Shinichi Okada Hirosuke Sew TatsÜji Yoshida Toshiomi 《Applied biochemistry and biotechnology》1991,28(1):327-340
Applied Biochemistry and Biotechnology - A NADPH/NADH-dependent xylose reductase gene was isolated from the xylose-assimilating yeast,Pichia stipitis. DNA sequence analysis showed that the gene... 相似文献