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201.
Hiroyuki Koshino Hiroyuki Osada Tatsuya Yano Jun Uzawa Kiyoshi Isono 《Tetrahedron letters》1991,32(52):7707-7710
The structures of enopeptins A and B, novel depsipeptide antibiotics with 1,3,5,7,9-decapentaene-1,10-dicarboxylic acid and 2-amino-3-hydroxycyclopent-2-enone in a side chain, were determined by chemical and spectroscopic means. 相似文献
202.
The chelating behavior of a new resin prepared by polycondensation of N-(o-hydroxybenzyl) iminodiacetic acid (o-HDA) with phenol and formaldehyde, is compared with that of the monomer, with p-HDA resin and p-HDA monomer, and with Chelex-100. The order of chelate stability for the o-HDA resin is Cu(II) > Ni(II) > Zn(II) > Co(II). An unusually high stability of the o-HDA and o-HDA resin iron(III) chelates in acidic solution is attributed to the participation of the o-hydroxyl group in the coordination process. 相似文献
203.
Rotational correlation times (τT) of the 5′-AMP molecule deduced from spin-lattice relaxation times (T1) of different protons in the molecule agree fairly well with each other in the temperature range of 3.5–74°C. The same is true with τT values deduced from 13CT1 values. These results indicate that the internal motions are slow as compared to the overall rotation of the 5′-AMP molecule. 相似文献
204.
Yoshizawa M Nagao M Umemoto K Biradha K Fujita M Sakamoto S Yamaguchi K 《Chemical communications (Cambridge, England)》2003,(15):1808-1809
Despite their structural similarity, triangular tetradentate ligands 2b and 2c experience different assembly pathways on complexation with (en)Pd(NO3)2 to give M8L4 tetrahedral (3) and open cone (4) structures, respectively, due to steric restriction by side chains at the corner or on the edge of the ligands. 相似文献
205.
Charge-transfer interactions,exciplex formations and ionic dissociations in singlet oxygen reactions
Intermolecular perturbation and configuration interaction calculations have been carried out to elucidate the attacking modes of singlet molecular oxygen (1O2) to allyl olefins and electron-rich olefins, which are classified into four groups from their molecular structures. It is found: (1) that the attacking modes are dependent on the molecular structure of substrates ; (2) that the charge-transfer (CT) interactions between 1O2 and substrates are particularly important for the formation of exciplexes through which the ene and (2+2) reactions of 1O2 proceed ; and (3) that the CT energy levels are important in governing the fraction of ionic dissociation to produce Superoxide anion and the relative ratio between the (4+2) and (2+2) reactions of 1O2 with dienes, heterocycles and related species. 相似文献
206.
Etsu Yamada Sinichi Funoki Yuko Abe Shigekazu Umemura Daisuke Yamaguchi Yasuro Fuse 《Analytical sciences》2005,21(2):89-94
Ambient particulate matter and gas in Kyoto were investigated by gravimetric analysis, X-ray fluorescence spectrometry, and ion chromatography in order to clarify their behavior and origin. The size distribution and characteristics of the chemical components in ambient particulates collected on PTFE membrane filters using an Andersen air sampler were examined from August 2001 to April 2004. A four-stage filter pack method was used to sample the atmosphere for the determination of gas (SO2, HNO3, HCl, NH3) and particulate matter (SO42, NO3, Cl-, Na+, K+, Ca2+, Mg2+, NH4+) concentrations from October 2002 to April 2004. The concentration of SPM mass was in the range of 6.7 - 80.2 microg/m3. The size distributions of SPM mass were bimodal, peaking at around 0.65 - 1.1 and 3.3 - 4.7 microm, and 40 - 85% of SPM mass was fine particles (< 2.1 microm). Na, Mg, Al, Si, Ca, Cl, and Fe were mainly present in coarse particles (2.1 to 11.0 microm), while S was present in fine particles. The concentrations of Al, Si, Ca, Mg, and Fe in fine particles increased from March to April in 2002, and those in coarse particulates increased in November 2002 and from March to April in 2004. This may be the effect of the continental yellow sand "Kosa." The differences in the size distributions of Al, Si, Ca, Mg, and Fe in particles may depend on differences in their place of occurrence and course of transport from China to Japan. The concentration of HCl gas was higher than that of particulate chloride ion in summer. Nitric acid gas existed at higher concentrations in summer, but fine particulate nitrate ion was observed in winter. The gaseous-to-fine aerosol nitrate fraction became higher at warmer temperatures. Coarse sulfate was below 10%, and SO2 gas and fine particulate sulfate were above 90%. 相似文献
207.
Amino acid amide racemizing activity was discovered in alpha-amino-epsilon-caprolactam (ACL) racemase (EC 5. 1. 1. 15) from Achromobacter obae. The enzymatic synthesis of d-alanine from l-alanine amide has been demonstrated by use of d-aminopeptidase (DAP; EC 3. 4. 11. 19) from Ochrobactrum anthropi C1-38 and ACL racemase. The conversion of 45 mM l-alanine amide was carried out at 30 degrees C for 7 h; l-alanine amide was completely converted to d-alanine, and no l-alanine was detected. The result of successive enzymatic reaction shows that the combination of ACL racemase and DAP can be applied for dynamic kinetic resolution of dl-amino acid amides to yield d-amino acids. 相似文献
208.
Makoto Wakeshima Nobuyuki Taira Aya Tobo Yasuo Yamaguchi 《Journal of solid state chemistry》2003,174(1):159-164
Magnetic and electrical properties are investigated for quaternary neodymium sulfides BaNd2TS5 (T=Co, Zn) through the specific heat, neutron diffraction, and electrical conductivity measurements. Their electrical conductivities show semiconductive behavior, which follows the Arrhenius temperature dependence with the activation energy of Ea=1.46 eV for BaNd2ZnS5 and Ea=1.19 eV for BaNd2CoS5. The specific heat of BaNd2ZnS5 has a λ-type anomaly at 2.8 K due to the antiferromagnetic ordering of the Nd3+ moments and a Schottky-type anomaly at around 60 K, which results from the crystal field splitting of the 4I9/2 ground state of the Nd3+ ion. The specific heat of BaNd2CoS5 shows two λ-type anomalies at 5.7 K due to the antiferromagnetic ordering of Nd3+ and at 58 K due to the antiferromagnetic ordering of Co2+. The latter overlaps with the Schottky-type anomaly due to the crystal field splitting of the Nd3+ ion. Neutron diffraction measurements for BaNd2CoS5 show that a magnetic arrangement of the Co2+ moments has a collinear antiferromagnetic structure, while that of the Nd3+ moments has a noncollinear one. 相似文献
209.
Star-shaped poly(1,2-phenylenevinylene)s 4-substituted with multiple pendant phenoxyls (2 and 3) were synthesized by polymerizing 2-bromo-4-(acetoxyphenyl)styrene in the presence of 1,3,5-triiodobenzene or 1,3,5-tris(3',5'-diiodophenyl)benzene as the core via a simple one-pot Heck reaction and subsequent hydrolysis, phenolate formation, and heterogeneous oxidation. ESR spectra indicated a delocalized spin distribution into the core parts of the star-shaped molecules. The polyradicals, 2 and 3, were in a high-spin state at low temperature, and the ferromagnetic behavior was enhanced for the polyradical with a higher molecular weight. Although an average S of 3 remained at 3/2 to 4/2, the polyradical 2 even with a spin concentration of 0.8 spin/unit revealed an average S of 7/2 to 8/2. The 1,3,5-benzene core acted as an effective magnetic coupler to align the spins of the pendant phenoxyls through the star-shaped pi-conjugated backbone. 相似文献
210.
Self-association system of(R)-1,3-butanediol in dilute carbon tetrachloride(CCl4)solution is studied as a model of molecular association mixture.Analysis methods including FSMWEFA(fixed-size moving window evolving factor analysis)combined with PCA(principal component analysis),SIMPLISMA (simple-to-use interactive self-modeling mixture analysis),and ITTFA(iterative target transformation factor analysis)are adopted to resolve infrared spectra of(R)-1,3-butanediol solution.Association number and equilibrium constant are computed.(R)-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system.Theoretical investigation of trimer structures is carried out with DFT(density functional theory),and structural factors are analyzed. 相似文献