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431.
432.
Dr. Yukihiro Yoshida Kazuhide Isomura Prof. Hideo Kishida Yoshihide Kumagai Prof. Motohiro Mizuno Dr. Masafumi Sakata Dr. Takashi Koretsune Dr. Yoshiaki Nakano Prof. Hideki Yamochi Dr. Mitsuhiko Maesato Prof. Gunzi Saito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):6023-6030
Coronene, which is the smallest D6h‐symmetric polycyclic aromatic hydrocarbon, attracts particular attention as a basic component of electronic materials because it is the smallest fragment of graphene. However, carrier generation by physical methods, such as photo‐ or electric field‐effect, has barely been studied, primarily because of the poor π‐conduction pathway in pristine coronene solid. In this work we have developed unprecedented π‐stacking columns of cationic coronene molecules by electrochemical hole‐doping with polyoxometallate dianions. The face‐to‐face π–π interactions as well as the partially charged state lead to electrical conductivity at room temperature of up to 3 S cm?1, which is more than 10 orders of magnitude higher than that of pristine coronene solid. Additionally, the robust π–π interactions strongly suppress the in‐plane rotation of the coronene molecules, which has allowed the first direct observation of the static Jahn–Teller distortion of cationic coronene molecules. 相似文献
433.
Isao Fujii Makoto Hashimoto Kaori Konishi Akiko Unezawa Haruka Sakuraba Kenta Suzuki Harue Tsushima Miho Iwasaki Satsuki Yoshida Akane Kudo Rina Fujita Aika Hichiwa Koharu Saito Takashi Asano Jun Ishikawa Daigo Wakana Yukihiro Goda Ayumi Watanabe Mamoru Watanabe Yui Masumoto Junichiro Kanazawa Hajime Sato Masanobu Uchiyama 《Angewandte Chemie (International ed. in English)》2020,59(22):8464-8470
Shimalactones A and B are neuritogenic polyketides possessing characteristic oxabicyclo[2.2.1]heptane and bicyclo[4.2.0]octadiene ring systems that are produced by the marine fungus Emericella variecolor GF10. We identified a candidate biosynthetic gene cluster and conducted heterologous expression analysis. Expression of ShmA polyketide synthase in Aspergillus oryzae resulted in the production of preshimalactone. Aspergillus oryzae and Saccharomyces cerevisiae transformants expressing ShmA and ShmB produced shimalactones A and B, thus suggesting that the double bicyclo‐ring formation reactions proceed non‐enzymatically from preshimalactone epoxide. DFT calculations strongly support the idea that oxabicyclo‐ring formation and 8π‐6π electrocyclization proceed spontaneously after opening of the preshimalactone epoxide ring through protonation. We confirmed the formation of preshimalactone epoxide in vitro, followed by its non‐enzymatic conversion to shimalactones in the dark. 相似文献
434.
Thanyada Sukmanee Dr. Kanet Wongravee Dr. Yasutaka Kitahama Prof. Dr. Sanong Ekgasit Dr. Tamitake Itoh Dr. Prompong Pienpinijtham Prof. Dr. Yukihiro Ozaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14672-14677
Discrimination between enantiomers is achieved by tip-enhanced Raman scattering (TERS) using a silver tip that is chemically modified by an achiral para-mercaptopyridine (pMPY) probe molecule. Differences in the relative intensities of the pMPY spectra were monitored for three pairs of enantiomers containing hydroxy (−OH) and/or amino (−NH2) groups. The N: or N+−H functionality of the pMPY-modified tip participates in hydrogen-bond interactions with a particular molecular orientation of each chiral isomer. The asymmetric arrangement of silver atoms at the apex of the tip induces an asymmetric electric field, which causes the tip to become a chiral center. Differences in the charge-transfer (CT) states of the metal-achiral probe system in conjunction with the asymmetric electric field produce different enhancements in the Raman signals of the two enantiomers. The near-field effect of the asymmetric electric field, which depends on the number of analyte functional groups capable of hydrogen-bond formation, improves the degree of discrimination. 相似文献
435.
Pongpol Thanuphol Yukihiro Asami Kazuro Shiomi Ariyaphong Wongnoppavich Patoomratana Tuchinda 《Natural product research》2018,32(14):1682-1689
The ethanolic extract from the stem bark of Goniothalamus marcanii Craib was shown in preliminary brine shrimp lethality data having good cytotoxic activity. Further bioassay guided isolation was done by means of solvent partition, chromatography and precipitation to provide four isolated compounds: a novel compound 1 with the core structure of 1-azaanthraquinone moiety referred as marcanine G; as well as compounds 2–4 with known aristolactam structures namely, piperolactam C, cepharanone B and taliscanine. These compounds were characterised by spectroscopic techniques. The assessment of cytotoxicity was established on an SRB assay using doxorubicin as a positive control. Marcanine G (1) was considered the most active compound indicating the IC50 values of 14.87 and 15.18 μM against human lung cancer cells (A549) and human breast cancer cells (MCF7), respectively. However, 2 showed mild activity with the IC50 values of 83.72 and 82.32 μM against A549 and MCF7 cells, respectively. 相似文献
436.
Shuzo Matsumoto Yuka Taniguchi Yukihiro Fukunaga Hiromichi Nakashima Keiichi Watanabe Shoji Yamashita Etsuko Nishimoto 《Journal of fluorescence》2013,23(3):407-415
The structural feature of unfolding intermediate of pokeweed anti-viral protein (PAP) was characterized using time-resolved fluorescence spectroscopic methods to elucidate protein folding/unfolding process. CD and fluorescence spectra consistently demonstrated that the unfolding of PAP completed at 4 M of guanidine hydrochloride (GuHCl). The fluorescence resonance energy transfer (FRET) and time-resolve fluorescence depolarization analysis of Trp208 and Trp237 located in the C-terminal domain of PAP suggested that peculiar unfolding intermediate populated before reaching to the unfolding state. The FRET distance of Trp237 to Tyr182 was extended to more than 28 Å with keeping the compact conformation in the unfolding intermediate state populated in the presence of 2 M GuHCl. On the other hand, Trp208 maintained the energy transfer pair with Tyr72 near the active site, although the rotational freedom was increased a little. There results suggest that the most distinguished structural feature of the unfolding intermediate of PAP is the separation of C-terminal domain from N-terminal domain. FRET and fluorescence depolarization studies also showed that C-terminal domain would be more separated to liberate the segmental motions of Trp208 and Trp237 distinctly at the unfolding state. 相似文献
437.
Dariusz Sobolewski Edyta Proniewicz Dominika Skouba Adam Prahl Yukihiro Ozaki Younkyoo Kim Leonard M. Proniewicz 《Journal of Raman spectroscopy : JRS》2013,44(2):212-218
In this paper, the surface‐enhanced Raman scattering (SERS) spectra of the potent B2 bradykinin receptor antagonists, [D‐Arg0,Hyp3,Thi5,8,L‐Pip7]BK, Aaa[D‐Arg0,Hyp3,Thi5,8,L‐Pip7]BK, [D‐Arg0,Hyp3,Thi5,D‐Phe7,L‐Pip8]BK, and Aaa[D‐Arg0,Hyp3,Thi5,D‐Phe7,L‐Pip8]BK, were measured when immobilized onto a colloidal assembly of apparently randomly adhering Ag spheres with diameters of approximately 20 – 25 nm. The observed SERS bands corresponding to different vibrational modes of the molecule, attached to or near Ag, and the variations in these bands resulting from competitive interactions of the functional groups of the peptides with the SERS‐active Ag surfaces were analyzed in this study. Briefly, it was shown that Pip, in generally in vertical orientation, and Thi, in the edge‐on position, relative to the colloidal Ag surface interacted with this surface through their lone electron pairs on the nitrogen and sulfur atoms, respectively. The imide bond of the X‐Pro peptide linkage and the guanidine group of Arg were involved in the adsorption process. In addition, it was demonstrated that the specific differences in the amino acid sequences slightly influenced the mode of adsorption. For example, Aaa in Aaa[D‐Arg0,Hyp3,Thi5,8,L‐Pip7]BK and Aaa[D‐Arg0,Hyp3,Thi5,D‐Phe7,L‐Pip8]BK and D‐Phe (vertical with respect to the colloidal Ag surface) in [D‐Arg0,Hyp3,Thi5,D‐Phe7,L‐Pip8]BK, and Aaa[D‐Arg0,Hyp3,Thi5,D‐Phe7,L‐Pip8]BK assisted in the adsorption of these peptides onto the colloidal Ag particles. To discuss these spectral alterations due to the different surface adsorption mechanisms of these peptides, the spectral changes were analyzed according to the adsorption process and Fourier‐transform‐Raman spectra. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
438.
Yukihiro Yoshimura Takahiro Takekiyo Chikara Okamoto Naohiro Hatano Hiroshi Abe 《Journal of Raman spectroscopy : JRS》2013,44(3):475-480
We have investigated temperature‐induced Raman spectral changes of deuterated water in an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF4]), between room temperature and 77 K. The comparison of the OH and OD stretching vibrational spectra at 77 K shows that the strength of the hydrogen bonds in [bmim][BF4]–water mixtures strongly depends on the type of water, i.e. H2O and D2O. In the [bmim][BF4]–D2O system, remarkably strong hydrogen bonds form at low temperatures, but they switch to nearly free hydrogen bonds on heating. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
439.
Hidetaka Yuge Takeshi Ken Miyamoto Tomofumi Kikuchi Yukihiro Iwasaki 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):m594-m596
In the first bis[ruthenium(II)–porphyrin]–dicarbene complex, μ‐[1,4‐phenylenebis(phenylmethylidene‐κC)]bis[(ethanol‐κO)(5,10,15,20‐tetra‐p‐tolylporphyrinato‐κ4N)ruthenium(II)] 1,2‐dichloroethane trisolvate, [Ru2(C20H14)(C48H36N4)2(C2H6O)2]·3C2H4Cl2, an inversion center is located at the center of the μ‐phenylene group, leading to a parallel arrangement for the pair of porphyrin ring systems. The bond lengths and angles compare favourably with literature values for ruthenium–porphyrin–monocarbene complexes; the Ru=C(carbene) bond length and the C(phenyl)—C(carbene)—C(phenylene) angle are 1.865 (3) Å and 112.3 (3)°, respectively. The RuII ion is displaced out of the C20N4 porphyrin least‐squares plane (by 0.2373 Å) toward the bridging ligand of the Ci‐symmetry dimer. The porphyrin ring systems of the dimer thus exhibit mildly domed conformations. 相似文献
440.
Ikuma Kuroda Yukihiro Shintani Masanori Motokawa Shuzo Abe Masahiro Furuno 《Analytical sciences》2004,20(9):1313-1319
A methodology of phosphopeptide-selective analysis coupled with column-switching HPLC utilizing titania as precolumn media is presented. Phosphopeptides were selectively enriched on titania packing within a protein/peptide mixture without any additional procedure, and analyzed by column-switching high-performance liquid chromatography. First, phospho-compounds were separated from complex mixtures by trapping them under acidic conditions on a titania packing, where non-phosphorylated compounds were effused out of the precolumn. Subsequently, phospho-compounds were desorbed from the titania column under a specific condition and analyzed. The behavior of phospho-compounds on a titania surface, especially adsorption/desorption, was precisely examined and optimized. A phosphoric buffer was successively employed for the elution of phosphopeptides on a titania surface by competition with the free phosphate group. From the successes of a selective concentration/analysis of phosphopeptides with column-switching HPLC with a titania precolumn, a novel phosphopeptide-selective RP-HPLC analysis has been shown to have an application possibility as a tool for phosphoproteomics. 相似文献