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101.
Abstract Thermoluminescence (TL) and ESR phenomena induced by X-ray irradiation of the mixed samples of K2SO4 and alkaline earth metal sulfate (MgSO4 or BaSO4) were investigated in terms of the reactivities and the crystallogrpahic properties. A high intensive TL resulted from the diffusion of a small amount of Mg2+ into K2SO4 crystals. The amount formed of K2Mg2(SO4)3, langbeinite, compound had a maximum at the stoichiometric composition. From the ESR measurements, SO? 3 radicals were found to be easily formed in the langebeinite by excitation. Both the TL and the ESR phenomena were hardly observed in the K2SO4–BaSO4 system due to little diffusion of Ba2+ with much larger radius than Mg2+. The results were mainly discussed on the basis of the radii of the component cations in these systems. In addition, the fundamental data as to the application to the ESR dosimetry were obtained. 相似文献
102.
Kinoshita M Murakami E Oda Y Funakubo T Kawakami D Kakehi K Kawasaki N Morimoto K Hayakawa T 《Journal of chromatography. A》2000,890(2):261-271
Frontal affinity chromatography is a method for quantitative analysis of biomolecular interactions. We reinforced it by incorporating various merits of a contemporary liquid chromatography system. As a model study, the interaction between an immobilized Caenorhabditis elegans galectin (LEC-6) and fluorescently labeled oligosaccharides (pyridylaminated sugars) was analyzed. LEC-6 was coupled to N-hydroxysuccinimide-activated Sepharose 4 Fast Flow (100 μm diameter), and packed into a miniature column (e.g., 10×4.0 mm, 0.126 ml). Twelve pyridylaminated oligosaccharides were applied to the column through a 2-ml sample loop, and their elution patterns were monitored by fluorescence. The volume of the elution front (V) determined graphically for each sample was compared with that obtained in the presence of an excess amount of hapten saccharide, lactose (V0); and the dissociation constant, Kd, was calculated according to the literature [K. Kasai, Y. Oda, M. Nishikawa, S. Ishii, J. Chromatogr. 376 (1986) 33]. This system also proved to be useful for an inverse confirmation; that is, application of galectins to an immobilized glycan column (in the present case, asialofetuin was immobilized on Sepharose 4 Fast Flow), and the elution profiles were monitored by fluorescence based on tryptophan. The relative affinity of various galectins for asialofetuin could be easily compared in terms of the extent of retardation. The newly constructed system proved to be extremely versatile. It enabled rapid (analysis time 12 min/cycle) and sensitive (20 nM for pyridylaminated derivatives, and 1 μg/ml for protein) analyses of lectin–carbohydrate interactions. It should become a powerful tool for elucidation of biomolecular interactions, in particular for functional analysis of a large number of proteins that should be the essential issues of post-genome projects. 相似文献
103.
Shusuke Yamanaka Keita Kanda Toru Saito Yasutaka Kitagawa Takashi Kawakami Masahiro Ehara Mitsutaka Okumura Haruki Nakamura Kizashi Yamaguchi 《Chemical physics letters》2012
We assessed the applicability and basis set dependency of the B3LYP functional to investigate magnetic interactions of Mn complexes. For the purpose, we constructed a test set consisting of 16 Mn complexes with various oxidation states and structural motifs.The B3LYP results correctly reproduced magnetism and magneto–redox correlation of the standard μ-oxo motifs with superexchange paths, while it does not work for weak magnetic complexes. We also showed that a modest basis set yields results similar to those of triple-zeta plus diffuse-and-polarization functions. This basis set is expected to be a standard basis set for investigating magnetism of manganese complexes. 相似文献
104.
Chiral‐Substrate‐Assisted Stereoselective Epoxidation Catalyzed by H2O2‐Dependent Cytochrome P450SPα
Dr. Takashi Fujishiro Dr. Osami Shoji Dr. Norifumi Kawakami Takahiro Watanabe Dr. Hiroshi Sugimoto Dr. Yoshitsugu Shiro Prof. Dr. Yoshihito Watanabe 《化学:亚洲杂志》2012,7(10):2286-2293
The stereoselective epoxidation of styrene was catalyzed by H2O2‐dependent cytochrome P450SPα in the presence of carboxylic acids as decoy molecules. The stereoselectivity of styrene oxide could be altered by the nature of the decoy molecules. In particular, the chirality at the α‐positions of the decoy molecules induced a clear difference in the chirality of the product: (R)‐ibuprofen enhanced the formation of (S)‐styrene oxide, whereas (S)‐ibuprofen preferentially afforded (R)‐styrene oxide. The crystal structure of an (R)‐ibuprofen‐bound cytochrome P450SPα (resolution 1.9 Å) revealed that the carboxylate group of (R)‐ibuprofen served as an acid–base catalyst to initiate the epoxidation. A docking simulation of the binding of styrene in the active site of the (R)‐ibuprofen‐bound form suggested that the orientation of the vinyl group of styrene in the active site agreed with the formation of (S)‐styrene oxide. 相似文献
105.
N-(omega-Bromoalkyl)-amino acid derivatives, readily prepared from natural alpha-amino acids, gave cyclic amino acids with a quaternary stereocenter by treatment with potassium hexamethyldisilazaide in DMF. The chirality of parent amino acids was almost completely preserved during an enolate-formation and cyclization process, giving aza-cyclic amino acids in up to 98% ee in retention of configuration. This method is applicable to the asymmetric synthesis of azetidine, pyrrolidine, piperidine, and azepane derivatives. The asymmetric cyclization seems to proceed via an axially chiral enolate intermediate and not through a concerted SEi process. 相似文献
106.
Oderaotoshi Y Cheng W Fujitomi S Kasano Y Minakata S Komatsu M 《Organic letters》2003,5(26):5043-5046
High diastereo- and enantioselectivities were obtained for the asymmetric 1,3-dipolar cycloaddition of azomethine ylides generated from N-alkylideneglycine esters with dipolarophiles using chiral phosphine-copper complexes as catalysts. Whereas the cycloaddition of azomethine ylides catalyzed by metal salts generally afforded endo-adducts as the predominant product, the present method is the first example of an exo-selective cycloaddition. [reaction: see text] 相似文献
107.
Okada Y Yokozawa M Akiba M Oishi K O-kawa K Akeboshi T Kawamura Y Inokuma S Nakamura Y Nishimura J 《Organic & biomolecular chemistry》2003,1(14):2506-2511
A variety of aromatic compounds with both activating and deactivating substituents were brominated with sodium monobromoisocyanurate (SMBI) 1, diethyl ether, diethyl ether-methanesulfonic acid, trifluoroacetic acid, or sulfuric acid were employed as solvents. Thus nitrobenzene was conveniently brominated in sulfuric acid, benzene was readily monobrominated in diethyl ether-methanesulfonic acid, and phenol was selectively brominated at the ortho position under mild conditions in refluxing diethyl ether. With substituents that are easily protonated, trifluoroacetic acid may be employed as solvent in the reaction with 1, in contrast NBS was ineffective in trifluoroacetic acid. This renders 1 a superior reagent relative to NBS. In addition to aromatics, alkenes, ketones and esters were also brominated with 1. Diethyl malonate was brominated with 1 and then subjected to a Bingel reaction with NaH to afford the desired methanofullerene in reasonable yield. 相似文献
108.
Tsuchimoto T Kamiyama S Negoro R Shirakawa E Kawakami Y 《Chemical communications (Cambridge, England)》2003,(7):852-853
A palladium-indium triflate catalyst was found to be much more active for the dimerization of vinylarenes compared with generally used cationic palladium(II) catalysts. 相似文献
109.
Hiroshi Jinnai Hirokazu Hasegawa Yukihiro Nishikawa G. J. Agur Sevink Michael B. Braunfeld David A. Agard Richard J. Spontak 《Macromolecular rapid communications》2006,27(17):1424-1429
Summary: Coexisting bicontinuous morphologies, one ordered and one disordered, are investigated in a macrophase‐separated poly(styrene‐block‐isoprene) diblock copolymer/homopolystyrene (SI/hS) blend. Two‐phase behavior is attributed to the relatively high hS/S mass ratio (0.92). According to its crystallographic signature and channel coordination as discerned from three‐dimensional (3D) images generated by transmission electron microtomography (TEMT), the ordered morphology is classified as gyroid. The 3D local and global topological characteristics of both bicontinuous morphologies as measured directly from TEMT images are reported. The disordered morphology is further compared with molecular‐field simulations to ascertain the spatial distribution of the constituent species within the blend, thereby demonstrating the utility of high‐resolution 3D imaging coupled with molecular‐level simulations.
110.
Fumitoshi Kaneko Yukihiro Uda Atsushi Kajiwara Nobutaka Tanigaki 《Macromolecular rapid communications》2006,27(19):1643-1647
Summary: The formation of a molecular‐complex crystalline phase of syndiotactic polystyrene (sPS) that contains a stable nitroxide radical compound, 2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl (TEMPO), is confirmed by IR and electron spin resonance (ESR) spectroscopy, X‐ray diffractometry, and thermogravimetric analysis. Through a guest exchange procedure assisted by a plasticizing agent, the original guest (chloroform) contained in the starting clathrate phase is completely replaced by TEMPO. Although the conformational regularity of the sPS helices in the resultant crystalline phase that contains TEMPO is similar to that in the starting clathrate phase, the host lattice expands in the 010 direction. The guest TEMPO molecules exhibit a significantly broadened ESR signal because of their highly concentrated state in the complex crystalline phase.