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361.
Two polar photoproducts of allethrin, allethrolone and allethronyl glyoxylate, were isolated and identified. The formation mechanisms of these were also discussed. 相似文献
362.
We study the transition from the vibrational, SU(5), to the rotational, SU(3), limit of the interacting boson model. We show how this model can be used to calculate energies, electromagnetic transitions, multipole moments, nuclear radii, and two-nucleon transfer intensities in transitional nuclei. 相似文献
363.
We describe an improved method for purification of sedimentary vanadyl and nickel porphyrins (i.e., naturally occurring metalloalkylporphyrins). For the purpose of compound-specific isotopic analyses, various sedimentary porphyrins were purified from the complex natural mixtures by the dual-step high-performance liquid chromatography (HPLC) method. The high-sample-capacity reversed-phase HPLCs by adding N,N-dimethylformamide to the mobile phase allow an efficient collection of fractions containing the target compounds even using analytical-scale columns. Furthermore, this method achieved improved chromatographic resolutions but significantly reduced the overall retention time down to 60% compared with the previous work. The target compounds were then isolated with the normal-phase HPLC with the baseline-resolution, which is necessary to avoid chromatographic isotopic fractionation. One of the advantages of this method is that it requires neither derivatization nor demetallation. The purity of these isolated compounds was demonstrated by various HPLC online detection methods utilizing a photodiode-array detector, a mass selective detector. The overall recoveries of Ni porphyrin, VO porphyrin, and porphyrin-free base, respectively, were estimated to be approximately 50-60%, 65%, and 85%. 相似文献
364.
Kanazawa N Onose Y Arima T Okuyama D Ohoyama K Wakimoto S Kakurai K Ishiwata S Tokura Y 《Physical review letters》2011,106(15):156603
We have observed an unconventional, likely topological, Hall effect over a wide temperature region in the magnetization process of a chiral-lattice helimagnet MnGe. The magnitude of the topological Hall resistivity is nearly temperature-independent below 70 K, which reflects the real-space fictitious magnetic field proportional to a geometric quantity (scalar spin chirality) of the underlying spin texture. From the neutron diffraction study, it is anticipated that a relatively short-period (3-6 nm) noncoplanar spin structure is stabilized from the proper screw state in a magnetic field to produce the largest topological Hall response among the B20-type (FeSi-type) chiral magnets. 相似文献
365.
The expeditious and efficient [3+2] coupling approach of quinone monoacetals 1 with alkene nucleophiles 2 by the action of an activated Br?nsted acid in the presence of a hydrogen bond donor perfluorinated alcohol has been achieved. With the optimized combined acid, the reaction could proceed under mild conditions by only mixing the two reactants to afford the cycloadducts 3 in a short time (within 10 min) with good to quantitative yields. 相似文献
366.
Aromatic carboxamides and 2-phenylpyridine derivatives can be ortho-alkylated with Grignard reagents in the presence of a cobalt catalyst and DMPU as a ligand. The reaction proceeds smoothly at room temperature, using air as the sole oxidant. The dialkylated product is selectively obtained when N-methylcarboxamide is employed as a substrate, whereas N-phenyl- or N-isopropylcarboxamide preferentially gives the monoalkylated product. 相似文献
367.
Structures of the [C(6)H(6)-(CH(3)OH)(2)](+) cluster cation are investigated with infrared (IR) spectroscopy. While the noncovalent type structure has been confirmed for the n = 1 cluster of [C(6)H(6)-(CH(3)OH)(n)](+), only contradictory interpretations have been given for the spectra of n = 2, in which significant changes have been observed with the Ar tagging. In the present study, we revisit IR spectroscopy of the n = 2 cluster from the viewpoint of the σ-complex structure, which includes a covalent bond formation between the benzene and methanol moieties. The observed spectral range is extended to the lower-frequency region, and the spectrum is measured with and without Ar and N(2) tagging. A strongly hydrogen-bonded OH stretch band, which is characteristic to the σ-complex structure, is newly found with the tagging. The remarkable spectral changes with the tagging are interpreted by the competition between the σ-complex and noncovalent complex structures in the [C(6)H(6)-(CH(3)OH)(2)](+) system. This result shows that the microsolvation only with one methanol molecule can induce the σ-complex structure formation. 相似文献
368.
Extracellular Production and Characterization of <Emphasis Type="BoldItalic">Streptomyces</Emphasis> X-prolyl Dipeptidyl Aminopeptidase 总被引:1,自引:0,他引:1
Hatanaka T Yamasato A Arima J Usuki H Yamamoto Y Kumagai Y 《Applied biochemistry and biotechnology》2011,164(4):475-486
X-prolyl dipeptidyl aminopeptidases (X-PDAPs) are useful in various food industries. In this study, we performed sequence-based
screening to obtain a stable X-PDAP enzyme from thermophilic Streptomyces strains. We found three genes that encoded X-PDAP from Streptomyces thermoluteus subsp. fuscus NBRC 14270 (14270 X-PDAP), Streptomyces thermocyaneoviolaceus NBRC 14271 (14271 X-PDAP), and Streptomyces thermocoerulescens NBRC 14273, which were subsequently cloned and sequenced. The deduced amino acid sequences of these genes showed high similarity,
with ~80% identity with each other. The isolated X-PDAPs and an X-PDAP from Streptomyces coelicolor were expressed in Streptomyces lividans using a hyperexpression vector: pTONA5a. Among these genes, only 14270 and 14271 X-PDAPs caused overexpression and extracellular production without artificial signal
peptides. We also characterized the biochemical properties of purified 14271 X-PDAP. In addition, we found that, in peptide
synthesis via an aminolysis reaction, this enzyme recognized d-amino acid derivatives as acyl acceptors, similar to l-amino acid derivatives. 相似文献
369.
A cobalt-Xantphos-catalyzed, LiCl-mediated system has been developed for the direct and expedient preparation of arylzinc reagents in THF from the corresponding aryl iodides, bromides, and chlorides. Owing to the use of THF as a versatile solvent, the thus-formed arylzinc reagents displayed a high degree of compatibility with a variety of conventional as well as newly emerging metal-catalyzed cross-coupling reactions. 相似文献
370.
Versatile and gigantic magnetoelectric (ME) phenomena have been found for a single crystal of DyFeO3. Below the antiferromagnetic ordering temperature of Dy moments, a linear-ME tensor component as large as alphazz approximately 2.4 x 10(-2) esu is observed. It is also revealed that application of magnetic field along the c axis induces a multiferroic (weakly ferromagnetic and ferroelectric) phase with magnetization [> or =0.5 microB/formula unit (f.u.)] and electric polarization (> or =0.2 microC/cm2) both along the c axis. Exchange striction working between adjacent Fe3+ and Dy3+ layers with the respective layered antiferromagnetic components is proposed as the origin of the ferroelectric polarization in the multiferroic phase. 相似文献