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971.
Yukio Yokoyama Natsuko Wakabayashi Yuki Furugaki Hisakuni Sato 《Analytical sciences》2004,20(8):1189-1192
This paper describes a versatile technique for amino-acid separation using a novel low-capacity sulfoacylated macroreticular polystyrene-divinylbenzene cation-exchange column with a simple binary high-pressure pH gradient elution. Proteinic 16 amino acids were well separated within 50 min using a H3PO4/Na2HPO4-CH3CN eluent system, and the cycle time was about 70 min. The chromatography with postcolumn OPA fluorescent detection was reproducible with RSDs less than 1% for retention times, and was quantitative with RSDs less than 5% for area responses. A linear regression line with an r2 value above 0.9990 was obtained for each analyte in concentration from 0.1 to 10 microM by 20 microL injection. The method was applicable to the separation and detection of urinary diagnostic amino acid due to inborn errors of metabolism, such as phenylketonuria. The analytical costs would be decreased by using the proposed method. 相似文献
972.
Shusuke Yamanaka Yuki Mitsuta Mitsutaka Okumura Kizashi Yamaguchi Haruki Nakamura 《Molecular physics》2015,113(3-4):336-341
We here formulate and implement linear response function (LRF) of the Mayer bond order (MBO), which is expected to be a new indicator to describe intrinsic chemical reactivity of molecules. We calculate LRFs of the MBOs of para-substituted benzoic acids, and compare the results with the Hammett substituent constants and computational results of acid dissociation constants that were previously reported. The results are discussed from the viewpoint of the applicability of LRF of the MBO to estimate the relative reactivity of the substituted benzoic acids. 相似文献
973.
The mechanism of imperfection sensitivity of elastic-plastic plates under compression is complex as they undergo elastic and/or plastic buckling, dependent on their width-thickness ratio. For elastic buckling, the Koiter power law is an established means to describe the imperfection sensitivity. Yet, for plastic buckling, there is no such an established way to describe it. In this paper, the quadratic power law is advanced to describe imperfection-insensitive plastic buckling behavior. The Koiter power law is extended by implementing the quadratic law so as to describe the elastic and plastic buckling in a synthetic manner. The finite-displacement, elastic-plastic analysis was conducted on simply-supported square plates under compression by varying the plate thickness and the initial deflection of a sinusoidal form. In association with an increase of the plate slenderness parameter (decrease of plate thickness), the predominant buckling is shown to change from (1) plastic buckling to (2) unstable elastic-plastic buckling and to (3) elastic stable bifurcation followed by a maximum point of load. In accordance with the change of the mechanism of buckling, the power law is changed pertinently to describe the complex imperfection sensitivity of the compression plates in a synthetic manner. The extended imperfection sensitivity law is thus advanced as a simple and strong tool to describe the ultimate buckling strength of elastic-plastic plates. 相似文献
974.
975.
Dr. Akira Ueda Hideki Wasa Dr. Shinsuke Nishida Dr. Yuki Kanzaki Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Prof. Dr. Yasushi Morita 《化学:亚洲杂志》2013,8(9):2057-2063
A triangulene‐based C2‐symmetric 33 π‐conjugated stable neutral π‐radical, 2. , which possesses two dicyanomethylene groups and one oxo group, has been designed, synthesized, and isolated as an analogue of tris(dicyanomethylene) derivative 1. and trioxo derivative TOT. with C3 symmetry. Effects of molecular‐symmetry reduction and electron‐accepting substituents on this fused polycyclic neutral π‐radical system were studied in terms of their molecular structure, electronic‐spin structure, and electrochemical and optical properties with the help of theoretical calculations. Interestingly, this system ( 2. ) has a four‐stage redox ability, like TOT. , as well as low frontier energy levels and a small SOMO–LUMO gap, similar to 1. , in spite of the loss of the degenerate LUMOs in symmetry‐lowered 2. , which is associated with the attachment of the weaker electron‐accepting oxo group instead of the dicyanomethylene group in 1. . These prominent results are attributable to the structural and electronic properties in the triangulene‐based highly delocalized fused polycyclic neutral π‐radical system. 相似文献
976.
977.
Kazuya Matsuo Dr. Rui Kamada Dr. Keigo Mizusawa Dr. Hirohiko Imai Dr. Yuki Takayama Dr. Michiko Narazaki Prof. Dr. Tetsuya Matsuda Dr. Yousuke Takaoka Prof. Dr. Itaru Hamachi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12875-12883
Specific turn‐on detection of enzyme activities is of fundamental importance in drug discovery research, as well as medical diagnostics. Although magnetic resonance imaging (MRI) is one of the most powerful techniques for noninvasive visualization of enzyme activity, both in vivo and ex vivo, promising strategies for imaging specific enzymes with high contrast have been very limited to date. We report herein a novel signal‐amplifiable self‐assembling 19F NMR/MRI probe for turn‐on detection and imaging of specific enzymatic activity. In NMR spectroscopy, these designed probes are “silent” when aggregated, but exhibit a disassembly driven turn‐on signal change upon cleavage of the substrate part by the catalytic enzyme. Using these 19F probes, nanomolar levels of two different target enzymes, nitroreductase (NTR) and matrix metalloproteinase (MMP), could be detected and visualized by 19F NMR spectroscopy and MRI. Furthermore, we have succeeded in imaging the activity of endogenously secreted MMP in cultured media of tumor cells by 19F MRI, depending on the cell lines and the cellular conditions. These results clearly demonstrate that our turn‐on 19F probes may serve as a screening platform for the activity of MMPs. 相似文献
978.
Shuji Kondo Masakazu Takesue Masahiro Suzuki Hideo Kunisada Yasuo Yuki 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):2033-2040
Abstract Polymer-supported dimethylformamides were prepared by copolymerization of N-methyl-N-(p-vinylbenzyl)formamide, styrene, and divinylbenzene with AIBN. These polymers displayed catalytic activity for the reaction of alkyl bromides with alkali metal thiocyanates and potassium acetate in a solid-solid-liquid triphase system, although the corresponding monomeric formamides were inactive. The catalytic activity depended remarkably on the copolymer composition. Further, the catalytic reaction was affected by some experimental parameters such as stirring speed, particle size, degree of crosslinking, and solvent. A plausible catalytic reaction mechanism consisting of collisional contact between the solid catalysts and reagents was proposed. 相似文献
979.
Tae Seok Kwon Sadanori Kumazawa Tetsuya Yokoi Shuji Kondo Hideo Kunisada Yasuo Yuki 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1553-1567
Abstract Photopolymerization of styrene in the presence of diphenyl diselenide proceeded smoothly. The polymer yields and the number average molecular weight (Mn) of the polymers increased with reaction time. Further, a linear relationship was found for a plot of Mn for polystyrene versus polymer yield. These results indicate that this polymerization proceeds through a living radical mechanism. Photopolymerization of styrene with bis(p-tertbutylphenyl) diselenide afforded a telechelic polystyrene with terminal arylseleno groups. The resulting polymer underwent the reductive elimination of terminal seleno groups by the reaction with tri-n-butyltin hydride. Moreover, this telechelic polymer was treated with hydrogen peroxide to afford polystyrene with carbon-carbon double bonds at both chain ends. 相似文献
980.
Yasuharu Kato Tomohiro Kuroda Yichao Huang Risa Ohta Yuki Goto Hiroaki Suga 《Angewandte Chemie (International ed. in English)》2020,59(2):684-688
The Ψ[CH2NH] reduced amide bond is a peptide isostere widely used in the development of bioactive pseudopeptides. Reported here is a method of chemoenzymatic posttranslational modification for the synthesis of Ψ[CH2NH]‐containing peptides converted from ribosomally expressed peptides. The posttranslational conversion composed of an enzymatic cyclodehydration and facile two‐step chemical reduction achieves deoxygenation of a specific amide bond present in a nonprotected peptide in water. This method generates the Ψ[CH2NH] bond in peptides and is applicable to various peptide sequences, potentially enabling the preparation of a library of Ψ[CH2NH]‐containing peptides. 相似文献