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991.
Construction of a Triangle‐Shaped Trimer and a Tetrahedron Using an α‐Helix‐Inserted Circular Permutant of Cytochrome c555
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Akiya Oda Dr. Satoshi Nagao Dr. Masaru Yamanaka Ikki Ueda Dr. Hiroki Watanabe Prof. Dr. Takayuki Uchihashi Dr. Naoki Shibata Prof. Dr. Yoshiki Higuchi Prof. Dr. Shun Hirota 《化学:亚洲杂志》2018,13(8):964-967
Highly‐ordered protein structures have gained interest for future uses for biomaterials. Herein, we constructed a building block protein (BBP) by the circular permutation of the hyperthermostable Aquifex aeolicus cytochrome (cyt) c555, and assembled BBP into a triangle‐shaped trimer and a tetrahedron. The angle of the intermolecular interactions of BBP was controlled by cleaving the domain‐swapping hinge loop of cyt c555 and connecting the original N‐ and C‐terminal α‐helices with an α‐helical linker. We obtained BBP oligomers up to ≈40 mers, with a relatively large amount of trimers. According to the X‐ray crystallographic analysis of the BBP trimer, the N‐terminal region of one BBP molecule interacted intermolecularly with the C‐terminal region of another BBP molecule, resulting in a triangle‐shaped structure with an edge length of 68 Å. Additionally, four trimers assembled into a unique tetrahedron in the crystal. These results demonstrate that the circular permutation connecting the original N‐ and C‐terminal α‐helices with an α‐helical linker may be useful for constructing organized protein structures. 相似文献
992.
Akane Yamakawa Akinori Takeuchi Yasuyuki Shibata Sylvain Berail Olivier François Xavier Donard 《Accreditation and quality assurance》2016,21(3):197-202
Hg isotopic ratios of NIES CRM No. 13 Human Hair were analyzed using cold vapor generation coupled to multi-collector inductively coupled plasma mass spectrometer to meet the growing demand for better understanding of Hg exposure routes by using Hg isotopic compositions in human hair samples. To validate and assure the accuracy of our analytical method, (1) the reproducibility of the Hg isotopic measurement was monitored and (2) the Hg isotopic compositions of four secondary reference materials—IAEA-085, IAEA-086, and CRPG-RL24H—were measured. Our results for NIES CRM No. 13 show the mass-dependent fractionation values of δ 199Hg = (2.13 ± 0.07) ‰, δ 200Hg = (0.98 ± 0.08) ‰, δ 201Hg = (2.77 ± 0.10) ‰, δ 202Hg = (1.89 ± 0.10) ‰, and δ 204Hg = (2.76 ± 0.16) ‰ (2SD, n = 11) and the mass-independent fractionation values of Δ 199Hg = (1.65 ± 0.06) ‰, Δ 200Hg = (0.04 ± 0.04) ‰, Δ 201Hg = (1.36 ± 0.07) ‰, and Δ 204Hg = (?0.04 ± 0.11) ‰ (2SD, n = 11). Interlaboratory comparison of the CRM performed at the University of Pau showed good agreement with the values obtained at NIES. 相似文献
993.
Rhodium(III)‐Catalyzed Tandem [2+2+2] Annulation–Lactamization of Anilides with Two Alkynoates via Cleavage of Two Adjacent C−H or C−H/C−O bonds
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Miho Fukui Dr. Yu Shibata Yuki Hoshino Haruki Sugiyama Kota Teraoka Prof. Dr. Hidehiro Uekusa Prof. Dr. Keiichi Noguchi Prof. Dr. Ken Tanaka 《化学:亚洲杂志》2016,11(16):2260-2264
An electron‐deficient CpE rhodium(III) complex bearing a cyclopentadienyl ligand with two ethyl ester substituents catalyzes the tandem [2+2+2] annulation–lactamization of acetanilides with two alkynoates via cleavage of adjacent two C?H bonds to give densely substituted benzo[cd]indolones. The reactions of meta‐methoxy‐substituted acetanilides with two alkynoates also provided benzo[cd]indolones via cleavage of adjacent C?H/C?O bonds. Furthermore, 3,5‐dimethoxyacetanilides reacted with two alkynoates to give dearomatized spiro compounds. 相似文献
994.
Catalytic and Enantioselective Synthesis of Chiral Multisubstituted Tribenzothiepins by Intermolecular Cycloadditions
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Yu‐ki Tahara Riku Matsubara Akihito Mitake Tatsuki Sato Dr. Kyalo Stephen Kanyiva Prof. Dr. Takanori Shibata 《Angewandte Chemie (International ed. in English)》2016,55(14):4552-4556
The first catalytic and highly enantioselective synthesis of tribenzothiepin derivatives was achieved. Two types of intermolecular cycloadditions using either diphenyl‐sulfide‐tethered diynes or 2‐phenyl sulfanylbenzene‐tethered diynes with a monoalkyne successfully gave chiral multisubstituted tribenzothiepins in good to excellent ee values under mild conditions. The inversion energy of this saddle‐shaped molecule was calculated by measurement of the racemization rate of chiral tribenzothiepins using the Eyring kinetic equation under heating conditions. The present protocol could also be used to prepare a chiral tribenzoselenepin. 相似文献
995.
Kazuki Sakashita Dr. Yu Shibata Prof. Dr. Ken Tanaka 《Angewandte Chemie (International ed. in English)》2016,55(23):6753-6757
It has been established that a cationic rhodium(I)/binap complex catalyzes the cross‐cyclotrimerization of two molecules of a monosubstituted allene with one molecule of a functionalized alkyne to give 3,6‐dialkylidenecyclohex‐1‐enes. In contrast, the reactions involving di‐ or trisubstituted allenes and/or unfunctionalized alkynes afforded cross‐dimerization products, substituted dendralenes, through β‐hydrogen elimination from the corresponding rhodacycles. 相似文献
996.
Nakahara H Lee S Sugihara G Chang CH Shibata O 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3370-3379
Interfacial behavior was studied on the pulmonary lipid mixture containing a newly designed amphiphilic alpha-helical peptide (Hel 13-5) that consists of 13 hydrophobic and 5 hydrophilic amino acid residues. Moreover, the data obtained were compared with those of commercially available Surfacten (Surfactant TA) which has been clinically used for neonatal respiratory distress syndrome (NRDS) in Japan. Surface pressure (pi)-A and surface potential (DeltaV)-area (A) isotherms were measured for our synthetic preparations and Surfacten. Herein, a mixture of dipalmitoylphosphatidylcholine (DPPC)/egg-phosphatidylglycerol (PG)/palmitic acid (PA) (68:22:9 by weight) was used as the constituent of basic preparations. Monolayers were spread on 0.02 M Tris buffer (pH 7.4) with 0.13 M NaCl at the air/liquid interface, and the surface behavior was investigated by employing the Wilhelmy method, an ionizing electrode method, and fluorescence microscopy (FM). Cyclic compression and expansion isotherms of the prepared materials (or products) (DPPC/PG/PA/Hel 13-5) were examined to confirm the spreading and respreading ability. For the prepared products, a plateau region exists on pi-A and DeltaV-A isotherms at approximately 42 mN m(-1), indicating that Hel 13-5 is squeezed out of surface monolayers together with fluid components (PG) upon lateral compression. That is, the squeeze-out phenomenon induces a 2D-3D phase transformation. In particular, the inclination of the pi-A isotherms at X(Hel 13-5) = 0.1 in the plateau region was almost zero irrespective of the molecular area. As proposed in the earlier report (Nakahara, H.; Lee, S.; Sugihara, G.; Shibata, O. Langmuir 2006, 22, 5792-5803), an observed refluorescence phenomenon was discussed for FM measurements. This phenomenon provides evidence of the squeeze-out motion with fluid molecules. Furthermore, the cyclic pi-A and DeltaV-A isotherms show larger hysteresis areas and better respreading abilities in comparison with the previous ternary systems (DPPC/PG/Hel 13-5 and DPPC/PA/Hel 13-5) that are very important properties in pulmonary functions. FM photographs and the temperature dependence of pi-A and DeltaV-A isotherms suggest that the phase behavior of the present preparation product is very similar to that of Surfacten in terms of the domain size and in parameters such as collapse pressures, maximum DeltaV values, and so on. These results demonstrate that PG and PA even in the present preparations work well for compression-expansion cycling as is the case in the previous ternary systems, and the present preparations show comparable properties to Surfacten in vitro. 相似文献
997.
Tetsutaro Shibata 《Journal d'Analyse Mathématique》2007,102(1):347-358
We study the nonlinear Sturm-Liouville problem
where λ > 0 is an eigenvalue parameter and f(u) is a rapidly increasing function. For better understanding of the global behavior of the bifurcation branch in R+ × L
2(I), we establish precise asymptotic formulas up to the third term for the eigenvalue λ(α) associated with the eigenfunction
u
α with ‖u
α‖2 = α, as α → ∞. We show that there exists a new type of asymptotic formula for λ (α) as α → ∞. 相似文献
998.
Matsumoto Y Nakahara H Moroi Y Shibata O 《Langmuir : the ACS journal of surfaces and colloids》2007,23(19):9629-9640
The novel perfluorinated double long-chain salts with divalent counterions of separate electric charge, 1,1-(1,omega-alkanediyl)-bispyridinium perfluorotetradecane- carboxylate [CnBP(FC14)2 : n = 2, 6, 10, 14], were newly synthesized and their interfacial behavior was investigated by Langmuir monolayer methods. Surface properties [surface pressure (pi)-, surface potential (DeltaV)-, dipole moment (micro perpendicular)-area (A) isotherms] and morphological images of CnBP(FC14)2 monolayers on a subphase of water and on various NaCl concentrations were measured by employing the Wilhelmy method, the ionizing electrode method, fluorescence microscopy (FM), and Brewster angle microscopy (BAM). CnBP(FC14)2 formed a stable monolayer on water at 298.2 K, where these pi-A isotherms shifted to a larger molecular area with increasing charge separation and had no transition point from a disordered phase to an ordered one. On the contrary, the pi-A isotherms on NaCl solutions moved to the smaller areas, showed the transition and higher collapse pressures compared to the pi-A isotherms on water. These results suggested that a sodium chloride subphase induced the condensation of CnBP(FC14)2 molecules upon compression. In addition, it is quite noticeable that a dissociation of CnBP counterion from CnBP(FC14)2 occurs on NaCl solutions, depending on the extent of charge separation. This phenomenon was supported by the changes of the limiting area, transition pressure, collapse pressure, repeated compression-expansion cycle curve, and DeltaV behavior of perfluorotetradecanoic acid (FC14). Furthermore, temperature dependence of these monolayers was investigated, and an apparent molar quantity change on the phase transition was evaluated on 0.15 M NaCl. The morphological behavior of CnBP(FC14)2 and FC14 monolayers was also confirmed by FM and BAM images. 相似文献
999.
Novel fluorine-containing 1,10-phenanthrolines having dialkyl-, alkyl, and arylaminomethyl substituents at the 3-position were easily synthesized in moderate yields by the pyridine-ring formation reaction of N-propargyl-5,7-bis(trifluoroacetyl)-8-quinolylamine with various amines. Unexpectedly, the reactive intermediates 1,4-dihydro-1,10-phenanthrolin-4-ols were isolated for the first time in the reactions with dialkylamines. 相似文献
1000.
Shibata T Tahara YK Tamura K Endo K 《Journal of the American Chemical Society》2008,130(11):3451-3457
The intramolecular cycloaddition of 1,n-diene-ynes (n = 4-6), where alkyne and alkene moieties are connected by a 1,1-disubstituted alkene, was examined using a chiral rhodium catalyst, and various types of cycloadducts with quaternary carbon stereocenter(s) were obtained in high to excellent enantiomeric excess. In the case of 1,4-diene-ynes, tricyclic, bicyclic, and spirocyclic compounds were obtained depending upon the substituents at the 2-position of the 1,4-diene moiety and those at their alkyne termini. On the other hand, 1,5- and 1,6-diene-ynes gave tricyclic and bicyclic compounds, which included medium-sized ring systems. The mechanistic considerations for different reaction pathways and the synthetic transformation of tricyclic products into functionalized spirocyclic compounds are also described. The reaction of enediynes, where two alkyne moieties are connected by a 1,1-disubstituted alkene, was also examined, and sterically strained tricyclic compounds with two carbon stereocenters were obtained. 相似文献