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911.
Yamamoto Y Koizumi T Katagiri K Furuya Y Danjo H Imamoto T Yamaguchi K 《Organic letters》2006,8(26):6103-6106
[Structure: see text] Bis(phosphine)boronium salts 3a-c were designed and prepared as key building blocks for the synthesis of highly congested diphosphinobenzenes. The preparation of sterically hindered ortho-phenylene-bridged diphosphines 1a-c was achieved by the reaction of the bis(phosphine)boronium salts 3a-c with difluorobenzenechromium complex 2 and subsequent removal of the BH2 group. The steric nature of diphosphine 1a was revealed in single-crystal X-ray analysis of its Rh complex. 相似文献
912.
[Structure: see text] PtCl4-catalyzed cyclization reactions of homopropargyl azide derivatives to pyrrole rings were investigated. Using ethanol as solvent with 2,6-di-tert-butyl-4-methylpyridine as the base was found to be the best set of conditions for effecting this ring-closing reaction. These reaction conditions can be applied to the preparation of functionalized pyrrole derivatives, with no effect on the functional groups. 相似文献
913.
Application of the Buchwald protocol to the coupling of o-bromobenzoates and 1-tetralones directly affords benzodihydronaphthopyrones with a fused tetracyclic system. Aromatization of the 7,8-dimethoxy-2,3-methylenedioxy derivative yielded arnottin I, whereas oxidation with dioxirane afforded dihydroarnottin II composed of a spiro phthalide-tetralone system. Sharpless asymmetric dihydroxylation using AD-mix yielded optically active dihydroarnottin II with good enantioselectivity. The absolute stereochemistry of the stereogenic center in the (+)-spiro product was determined to be R by X-ray crystallographic analysis of the dibromo derivative. (+)-Dihydroarnottin II was subjected to successive bromination and dehydrobromination to prepare (-)-arnottin II. The R-configuration of natural (-)-arnottin II, previously assigned by application of the exciton chirality method to the Cotton effects observed in the CD spectrum, was confirmed by asymmetric synthesis. 相似文献
914.
Fumihiro Ito Taki Ukari Momoka Takasaki Kentaro Yamaguchi 《Tetrahedron letters》2012,53(26):3378-3381
We have designed new cleavable cross-linkers for biomolecules containing the 2,6-bis(oxazolinyl)pyridine (pybox) lanthanum complex. These species can effectively donate multiple charges to afford cross-linker ions for target biomolecules. The cross-linkers are cleaved easily by adding water. Moreover, we were able to detect chain structures of target molecules, including biomolecules and carbon clusters, such as fullerene C60, by the addition of some MS ionic probes. Cold-spray ionization mass spectrometry demonstrated the applications of multiply charged ionic probes as cleavable cross-linkers and polymerization reagents. 相似文献
915.
Takahashi S Tsuji K Ueda T Okahata Y 《Journal of the American Chemical Society》2012,134(15):6793-6800
During translation, the biosynthesis of polypeptides is dynamically regulated. The translation rate along messenger RNA (mRNA), which is dependent on the codon, structure, and sequence, is not always constant. However, methods for measuring the duration required for polypeptide elongation on an mRNA of interest have not been developed. In this work, we used a quartz crystal microbalance (QCM) technique to monitor mRNA translation in an Escherichia coli cell-free translation system in real time. This method permitted us to evaluate the translation of proteins of interest fused upstream of a streptavidin-binding peptide (SBP) fusion protein. The translation of mRNA encoding the SBP fusion protein alone was observed as a mass increase on a streptavidin-modified QCM plate. Addition of the protein of interest resulted in a delay in the mass change corresponding to the traveling time of the ribosome along the coding region of the protein of interest. With this technique, the lengths of coding sequences, codon usages, influences of unique sequences, and various protein-coding sequences were evaluated. The results showed that the traveling time of the translating ribosome depends on the length of the coding region translated but is also affected by the sequence itself. Differences in the time lags for various proteins imply that mRNA coding sequences may regulate gene expression. 相似文献
916.
917.
Yoshikazu Mizuguchi Kentaro Hamada Kazuki Goto Hiroshi Takatsu Hiroaki Kadowaki Osuke Miura 《Solid State Communications》2012,152(12):1047-1051
The low-temperature crystal structure of Fe1.13Te, which exhibits an anomalous two-step magnetic transition, was clarified by the systematic x-ray diffraction measurements. It was found that two-step structural phase transition, tetragonal–orthorhombic–monoclinic, occurred correspondingly to the two-step magnetic transition. The detailed analysis of the profile at 5 K indicated the coexistence of the minor orthorhombic area inside the major, monoclinic lattice, which could explain the lower-shift (suppression) of the antiferromagnetic transition temperature in Fe1.13Te and suggest a possibility of superconductivity at the domain boundary. 相似文献
918.
Toshiaki Asai Kensuke NagataToshiaki Mori Kentaro NagamatsuMotoaki Iwaya Satoshi KamiyamaHiroshi Amano Isamu Akasaki 《Journal of Crystal Growth》2009,311(10):2850-2852
The processes as in title of relaxation of the lattice mismatch and the recovery of crystalline quality in thick AlxGa1−xN on high-temperature-grown AlN were investigated. When x=0.3, rapid lattice relaxation occurred over a few microns, then the crystalline quality gradually recovered over 10 μm. In contrast, when x=0.7, relaxation of the lattice mismatch gradually occurred over 5 μm. 相似文献
919.
920.
Kentaro Hori 《Communications in Mathematical Physics》1996,182(1):1-32
A study of the gauged Wess-Zumino-Witten models is given focusing on the effect of topologically non-trivial configurations
of gauge fields. A correlation function is expressed as an integral over a moduli space of holomorphic bundles with quasi-parabolic
structure. Two actions of the fundamental group of the gauge group is defined: One on the space of gauge invariant local fields
and the other on the moduli spaces. Applying these in the integral expression, we obtain a certain identity which relates
correlation functions for configurations of different topologies. It gives an important information on the topological sum
for the partition and correlation functions. 相似文献