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81.
Andrei V. Afonin Dmitry V. Pavlov Igor A. Ushakov Natalia A. Keiko 《Magnetic resonance in chemistry : MRC》2012,50(7):502-510
In the 13C NMR spectra of methylglyoxal bisdimethylhydrazone, the 13C‐5 signal is shifted to higher frequencies, while the 13C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the 1H‐6 chemical shift and 1J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(1H‐6) and 1J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the 1H shielding and one‐bond 13C–1H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The 1H, 13C and 15N chemical shifts of the 2‐ and 8‐(CH3)2N groups attached to the –C(CH3)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH3)2N group conjugate effectively with the π‐framework, and the 2‐(CH3)2N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the 1H, 13C and 15N shieldings. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
82.
Keiko Doi-Kawano Etsuko Nishimoto Yoshiaki Kouzuma Daisuke Takahashi Shoji Yamashita Makoto Kimura 《Journal of fluorescence》2009,19(4):631-639
The steady-state and time-resolved fluorescece spectroscopy is one of the most powerful method to detect and analyze subtle
conformation change and interaction between peptide elements in protein. Phytocystatin Scb isolated from sunflower seeds includes
a single Trp residue at position 85. In an attempt to investigate the interaction of the N-terminal region of Scb with the
first and second hairpin loops by fluorescence spectroscopy of Trp residue, two Scb mutants in which single Trp locates at
position 52 and 58, respectively, and their N-terminal removed mutants were generated. The N-terminal truncation changed the
fluorescence decay kinetics of Trp52 from the triple exponential to double. Furthermore, the time-resolved fluorescence anisotropy
residue indicated that the segmental motion of Trp52 was significantly enhanced by its N-terminal truncation. In contrast,
Trp58 and Trp85 had little influence. The N-terminal successive truncations of Scb and its mutants resulted in the weaken
inhibitors to papain. These results suggested that the N-terminal region of Scb interacts with the peptide segment preceding
the first hairpin loop, thereby stabilizing the conformation of the hairpin loop structure. 相似文献
83.
H. Matsumura T. Miura S. Ishihama N. Matsuda T. Aze K. Masumoto T. Suzuki 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):423-428
Gold activation detectors were placed at nine positions on the inner wall of the KEK neutrino target station, and were exposed
to secondary particles during approximately one month of machine operation. After exposure, the production rates of 19 spallation
nuclides, which were produced in the Au activation detectors by nuclear reactions with different threshold energies, were
determined by γ-ray spectrometry. Thus, it was indicated that the Au activation detector is a novel tool for obtaining the
distribution of various secondary particles with high intensity and high energy. 相似文献
84.
The persistent spectral hole burning (PSHB) phenomenon was found to occur in many kinds of nanocrystalline semiconductors, such as CdSe, CdS, CuCl, CuBr and CuI, embedded in crystals, glass or polymers. In inhomogeneously broadened exciton absorption spectra of these nanocrystals, the spectral hole and its associated structure were created by the narrow-band laser excitation and were conserved for more than several hours at 2 K. Hole depth grew in proportion to the logarithm of the burning fluence. Thermally-annealing and light-induced hole-filling phenomena were observed. The hole burning takes place by the tunneling process through potential barriers with broadly distributed barrier height and thickness. Unusual luminescence behaviors related to the PSHB phenomena were also observed. They are luminescence elongation with increase of the light exposure and hole burning in the luminescence spectrum. The observed PSHB phenomena are explained by the exciton localization and the succeeding ionization of nanocrystals. The energy of the photoionized nanocrystal is released from the original energy and the new energies depend on the spatial arrangement of the trapped carriers. Quantum confinement of carriers and resulting strong Coulomb interaction between confined carriers and trapped carriers are essential for the energy change. Possible applications of the PSHB phenomenon is discussed. 相似文献
85.
Atsuko Ito Keiko Iwai Chiyuki Oyama Setsu Morimoto Hiroaki Kato 《Hyperfine Interactions》1992,71(1-4):1371-1374
Magnetization and Mössbauer measurements have been made on a diluted antiferromagnets FexMg1?xTiO3 with x=0.2, 0.3 and 0.7. It has been demonstrated that this system exhibits a spin glass or a reentrant spin glass like behavior in the samples with x around the percolation concenrration xc≈0.25. It has been shown that various sizes of magnetic clusters are formed well above the transition temperatures determined by the magnetization measurements in the samples with x near xc. The behavior of Fe0.2Mg0.8TiO3 is discussed as a typical cluster glass. 相似文献
86.
Coherent spectroscopy of semiconductor quantum dots, such as photon echo, accumulated photon echo, interferometric coherency measurement, quantum beat and coherent phonon measurement, are reviewed in relation to the historical progress in the coherent spectroscopy of semiconductors. 相似文献
87.
88.
Sumitomo K Mayumi K Minamikawa H Masuda M Asahi T Shimizu T Ito K Yamaguchi Y 《Electrophoresis》2011,32(3-4):448-454
Although polyethylene oxide (PEO) offers several advantages as a sieving polymer in SDS capillary polymer electrophoresis (SDS-CPE), solution properties of PEO cause deterioration in the electrophoresis because PEO in solution aggregates itself, degrades into smaller pieces, and forms polymer-micelle complexes with SDS. We examined protein separation on SDS-CPE with PEO as a sieving matrix in four individual buffer solutions: Tris-CHES, Tris-Gly, Tris-Tricine, and Tris-HCl buffers. The solution properties of PEO as a sieving matrix in those buffers were examined by dynamic light scattering (DLS) and by surface tension. Preferential SDS adsorption onto PEO disturbed protein-SDS complexation and impaired the protein separation efficiency. Substantial adsorption of SDS to PEO was particularly observed in Tris-Gly buffer. The Tris-CHES buffer prevented SDS from adsorbing onto the PEO. Only Tris-CHES buffer achieved separation of six proteins. This study demonstrated efficient protein separation on SDS-CPE with PEO. 相似文献
89.
Matsumoto J Sugiura Y Yuki D Hayasaka T Goto-Inoue N Zaima N Kunii Y Wada A Yang Q Nishiura K Akatsu H Hori A Hashizume Y Yamamoto T Ikemoto K Setou M Niwa S 《Analytical and bioanalytical chemistry》2011,400(7):1933-1943
Schizophrenia is one of the major psychiatric disorders, and lipids have focused on the important roles in this disorder. In fact, lipids related to various functions in the brain. Previous studies have indicated that phospholipids, particularly ones containing polyunsaturated fatty acyl residues, are deficient in postmortem brains from patients with schizophrenia. However, due to the difficulties in handling human postmortem brains, particularly the large size and complex structures of the human brain, there is little agreement regarding the qualitative and quantitative abnormalities of phospholipids in brains from patients with schizophrenia, particularly if corresponding brain regions are not used. In this study, to overcome these problems, we employed matrix-assisted laser desorption/ionization imaging mass spectrometry (IMS), enabling direct microregion analysis of phospholipids in the postmortem brain of a patient with schizophrenia via brain sections prepared on glass slides. With integration of traditional histochemical examination, we could analyze regions of interest in the brain at the micrometric level. We found abnormal phospholipid distributions within internal brain structures, namely, the frontal cortex and occipital cortex. IMS revealed abnormal distributions of phosphatidylcholine molecular species particularly in the cortical layer of frontal cortex region. In addition, the combined use of liquid chromatography/electrospray ionization tandem mass spectrometry strengthened the capability for identification of numerous lipid molecular species. Our results are expected to further elucidate various metabolic processes in the neural system. 相似文献
90.
Eiichi Masumoto Hiroshi Maruoka Fumi Okabe Sho Nishida Yuki Yoshimura Toshihiro Fujioka Kenji Yamagata 《Journal of heterocyclic chemistry》2011,48(1):96-104
Dihydropyridazinones 4a , 4b , N‐substituted dihydropyrazoles 5b , 5c , 5d , and O‐substituted pyrazoles 6a , 6b , 6c , 6d have been synthesized starting from spirocyclopropanepyrazole derivative 2 . Treatment of 2 with α‐chloro esters, e.g., methyl chloroacetate, ethyl chloroacetate, isopropyl chloroacetate, and tert‐butyl chloroacetate, in potassium carbonate/sodium iodide system caused ring opening and subsequent C‐ or N‐attack nucleophilic substitution to give the corresponding dihydropyridazinones 4a , 4b and N‐substituted dihydropyrazoles 5b , 5c , 5d . On the other hand, in the absence of sodium iodide, O‐substituted pyrazoles 6a , 6b , 6c , 6d were obtained from 2 via an O‐attack nucleophilic substitution. J. Heterocyclic Chem., 2011. 相似文献