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51.
Sensitive, reactive, and hydrophilic fluorogenic reagents for thiols with the benzofurazan skeleton, 4-(N-acetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (AcABD-F) and 4-(N-trichloroacetylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (TCAcABD-F) have been developed. These reagents reacted with thiols within 10 min at 60 degrees C. AcABD-F and TCAcABD-F themselves do not fluoresce but are strongly fluorescent after the reaction with thiol compounds. The generated derivatives were highly water-soluble, since they dissociated a proton and ionized in the neutral pH region. The derivatives with four biologically important thiol compounds were separated on a reversed-phase HPLC column and detected fluorometrically at 504 nm with excitation at 388 nm. The detection limit attained for homocysteine with AcABD-F was 25 fmol on column (11 nM) (signal-to-noise ratio = 3), and that for glutathione with TCAcABD-F was 45 fmol on column (20 nM). 相似文献
52.
Becker-Szendy R Bratton CB Cady R Casper D Dye ST Gajewski W Goldhaber M Haines TJ Halverson PG Jones TW Kielczewska D Kropp WR Learned JG LoSecco JM Matsuno S McGrew C Mudan MS Price L Reines F Schultz J Sobel HW Stone JL Sulak LR Svoboda R Wittel F 《Physical review D: Particles and fields》1991,43(4):1413-1415
53.
Koga T Taguchi K Kobuke Y Kinoshita T Higuchi M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(5):1146-1156
The self-assembly of peptides and proteins into beta-sheet-rich high-order structures has attracted much attention as a result of the characteristic nanostructure of these assemblies and because of their association with neurodegenerative diseases. Here we report the structural and conformational properties of a peptide-conjugated graft copolymer, poly(gamma-methyl-L-glutamate) grafted polyallylamine (1) in a water-2,2,2-trifluoroethanol solution as a simple model for amyloid formation. Atomic force microscopy revealed that the globular peptide 1 self-assembles into nonbranching fibrils that are about 4 nm in height under certain conditions. These fibrils are rich in beta-sheets and, similar to authentic amyloid fibrils, bind the amyloidophilic dye Congo red. The secondary and quaternary structures of the peptide 1 can be controlled by manipulating the pH, solution composition, and salt concentration; this indicates that the three-dimensional packing arrangement of peptide chains is the key factor for such fibril formation. Furthermore, the addition of carboxylic acid-terminated poly(ethylene glycol), which interacts with both of amino groups of 1 and hydrophobic PMLG chains, was found to obviously inhibit the alpha-to-beta structural transition for non-assembled peptide 1 and to partially cause a beta-to-alpha structural transition against the 1-assembly in the beta-sheet form. These findings demonstrate that the amyloid fibril formation is not restricted to specific protein sequences but rather is a generic property of peptides. The ability to control the assembled structure of the peptide should provide useful information not only for understanding the amyloid fibril formation, but also for developing novel peptide-based material with well-defined nanostructures. 相似文献
54.
Kazuhiro Endo Hideo Ihara Kazuhiro Watanabe Shun-Ichi Gonda 《Journal of solid state chemistry》1981,39(2):215-218
Transition-metal trisulfides, TiS3, NbS3, and TaS3, with a quasi-one-dimensional structure are investigated by X-ray photoelectron spectroscopic (XPS) measurements to obtain information on the valence band structures. The band structures at the Fermi level of these compounds correspond well to their transport properties. A shoulder is observed at the top of the valence band in NbS3 and TaS3, suggesting that this band is made up of the metal dz2 electrons. The dz2 band is occupied in NbS3 and TaS2 and empty in TiS3. The characteristic features at the top of the valence band in NbS3 imply the occurrence of dz2 band separation, which leads to a semiconducting nature. 相似文献
55.
Ken-Ichi Okamoto Kazuhiro Tanaka Michiaki Muraoka Hidetoshi Kita Yutaka Maruyama 《Journal of Polymer Science.Polymer Physics》1992,30(11):1215-1221
Gas permeability and permselectivity are investigated for polybenzoxazoles from bis(3-amino-4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (BAHHP) and aromatic diacid chlorides. Effects of thermal cyclization on the permeation properties are also investigated. The polybenzoxazole from BAHHP and 4,4′-(1,1,1,3,3,3-hexafluoroisopropylidene)dibenzoyl chloride (HFDB) displays high performance for CO2/CH4 separation ( $ {\rm P}_{{\rm CO}_2 } $ = 6.1 × 10?9 cm3 (STP) cm?1 s?1 cm-Hg?1, and $ {{{\rm P}_{{\rm CO}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm CO}_2 } } {{\rm P}_{{\rm CH}_4 } }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CH}_4 } }} $ = 38 at 35°C). The polybenzoxazole from BAHHP and 2,6-naphthalene dicarbonyl chloride displays high performance for H2/CO or H2/CH4 separation ( $ {\rm P}_{{\rm H}_2 } $ = 2.4 × 10?9 cm3 (STP) cm?1 s?1 cm-Hg?1, $ {{{\rm P}_{{\rm H}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm H}_2 } } {{\rm P}_{{\rm CO}} }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CO}} }} $ = 71, and $ {{{\rm P}_{{\rm H}_2 } } \mathord{\left/ {\vphantom {{{\rm P}_{{\rm H}_2 } } {{\rm P}_{{\rm CH}_{\rm 4} } }}} \right. \kern-\nulldelimiterspace} {{\rm P}_{{\rm CH}_{\rm 4} } }} $ = 250). Permeation properties for the polybenzoxazole from BAHHP and HFDB are close to those for a polyimide of similar chemical structure. The permeation properties are discussed in connection with packing density and local segmental mobility. © 1992 John Wiley & Sons, Inc. 相似文献
56.
Kazunori Masuko Chiharu Kumano Ryo Sugawara Kazuhiro Nakabayashi Hideharu Mori 《Journal of polymer science. Part A, Polymer chemistry》2021,59(15):1664-1677
A series of amino-acid-based amphiphilic diblock copolymer nano-objects having different morphologies were developed by reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N-acryloyl amino acid) macro-chain transfer agents (CTAs), including three carboxylic-acid-containing ones, poly(N-acryloyl-l -proline) (PAProOH), poly(N-acryloyl-4-trans-hydroxy-l -proline) (PAHypOH), and poly(N-acryloyl-l -threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate-terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen-bonding and ionic interactions of the macro-CTAs on the assembled structures of the nano-objects were evaluated using six different macro-CTAs. Transforming the products from methanol to water via dialysis produced amino-acid-based block copolymer nano-objects, exhibiting pH-responsive morphological change, in aqueous solution. 相似文献
57.
Kazuhiro Kuwae 《Potential Analysis》2012,37(4):387-413
We give a stochastic proof of an extension of E. Calabi??s strong maximum principle under some geometric conditions in the framework of strong Feller diffusion processes associated to local regular semi-Dirichlet forms with lower bounds. As a corollary, our notion of subharmonicity implies a notion of viscosity subsolution in a stochastic sense. We can apply our result to singular geometric object like Alexandrov space, limit space under spectral distance of Riemannian manifolds with uniform lower Ricci curvature bound and so on. 相似文献
58.
Kazuhiro Nakabayashi Shigeki Sobu Yuji Kosuge Hideharu Mori 《Journal of polymer science. Part A, Polymer chemistry》2018,56(19):2175-2182
This work demonstrates the UV nanoimprinting lithography (UV-NIL) of high refractive index and highly transparent polythioethers based on thiol-ene click chemistry. Herein, 9,9-bis(3-mercaptopropylphenylether)fluorene (BMPF) is designed as a new thiol monomer with a high refractive index, high transparency, and good processability for UV-NIL. Colorless polythioethers are synthesized from BMPF and ene monomers under mild thiol-ene click reaction conditions. Excellent transmittance (96%) of 400 nm light is observed in all the polymer films and high refractive index values of 1.5972–1.6382 are attained. UV-NIL using thiol-ene photopolymerization affords polymer nanoimprinting patterns with various features on the order of 100–500 nm without any fractures. To the best of our knowledge, this is the first report on UV-NIL of high refractive index and highly transparent polymers. Through proper monomer and polymer design, novel polythioethers with suitable glass transition temperature (T g) values are developed with high refractive index, high transparency, and good UV-NIL processability. Furthermore, UV-NIL based on thiol-ene click chemistry is accomplished at the nanoscale. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2175–2182 相似文献
59.
Kazuhiro Marumo Manabu Itoh Sungmin Kang Koichi Sakajiri Junji Watanabe 《Liquid crystals》2013,40(2):234-238
Galactose derivatives were explored as chiral dopants, effective for inducing chiral nematic liquid crystal (LC) phases. Galactose bearing O-isopropylidene substituents at the C3 and C4 and butoxybiphenyl substituents at the C2 and C6 positions exhibits a high helical twisting power (HTP) value of ?74.4 μm?1. Such a high HTP value for the galactose derivative is attributed to (1) linkage of the C3 and C4 carbons with the O-isopropylidene substituent, which places the C2 and C6 substitutes in a skew arrangement at a large angle and (2) enhancement of the affinity with the host nematic LCs by incorporating aromatic substituents at the C2 and C6 positions that are similar to those in the host. 相似文献
60.
Selective Exo‐Enzymatic Labeling of N‐Glycans on the Surface of Living Cells by Recombinant ST6Gal I