Kinetics and mechanism of the reaction of Ba(No3)2 with TiO2(anatase) in the solid-solid state and the liquid-solid state

The reaction of Ba(NO₃)₂ with TiO₂(anatase) was studied by TG and DTA. According to simultaneous TG and DTA, the reaction occurred sharply around the melting temperature of Ba(NO₃)₂, ～577°C, at low heating rates, and the reaction followed after melting of Ba(NO₃)₂ as the rate was raised. For the isothermal reactions the conversion α vs time relationship was given by the equation: kt = 1 - (1-α)^1/3. The relationship was shown by one straight line below 577°C, and by two lines with a bend above 577°C. The reaction rates at the earlier period above 577°C were about $\text{1}\text{5}$ smaller than those at the later period, which were nearly on the extrapolated log k vs 1/T line obtained below 577°C. The activation energy was 212 kJ mol^?1 for the solid-solid reaction and 231 kJ mol^?1 for the earlier period in the liquid-solid reaction.     

Stereoselective oxidation at C-4 of flavans by the endophytic fungus Diaporthe sp. isolated from a tea plant

The microbial transformation of five flavans (1-5) by endophytic fungi isolated from the tea plant Camellia sinensis was investigated. It was found that the endophytic filamentous fungus Diaporthe sp. oxidized stereoselectively at C-4 position of (+)-catechin (1) and (-)-epicatechin (2) to give the correspondent 3,4-cis-dihydroxyflavan derivatives (6, 10), respectively. (-)-Epicatechin 3-O-gallate (3) and (-)-epigallocatechin 3-O-gallate (4) were also oxidized by the fungus into 3,4-dihydroxyflavan derivatives (10, 12) via (-)-epicatechin (2) and (-)-epigallocatechin (11), respectively. Meanwhile, (-)-gallocatechin 3-O-gallate (5), (-)-catechin (ent-1) and (+)-epicatechin (ent-2), which possess a 2S-phenyl substitution, resisted the biotransformation.     

A modification of todd's triangulationJ 3

When we apply the fixed point computing method to mappings which are affine in some variables, we show that, to generate a sequence which converges to a fixed point, the mesh size need not be decreased in these coordinates. This paper modifies the triangulationJ ₃ with continuous refinement of mesh size to a triangulation such that the mesh size of in some given coordinates is constant and the mesh size in the other coordinates shrinks to zero.     

RK-805, an endothelial-cell-growth inhibitor produced by Neosartorya sp., and a docking model with methionine aminopeptidase-2

We found that a fungus Neosartorya sp. produced an angiogenesis inhibitor, RK-805. By spectroscopic analyses and semi-synthetic methods from fumagillin, the structure of RK-805 was identified as 6-oxo-6-deoxyfumagillol, which has not been reported as a natural product. RK-805 preferentially inhibited the growth of human umbilical vein endothelial cells (HUVECs) rather than that of human normal fibroblast in cell proliferation assays and blocked endothelial cell migration induced by vascular endothelial growth factor (VEGF). Moreover, RK-805 selectively inhibited methionine aminopeptidase-2 (MetAP2), but not methionine aminopeptidase-1 (MetAP1). The docked structure of RK-805 complexed with human MetAP2 indicated that not only a covalent bond between a nucleophilic imidazole nitrogen atom of His231 and the carbon of the reactive spirocyclic epoxide of RK-805, but also a hydrogen bond between NH (Asn329) and the carbonyl group of RK-805 at C-6 promote close contact in the binding pocket of the enzyme. Taken together, these results suggest that structure activity relationships of RK-805 derivatives at both C-4 and C-6, in comparison with ovalicin and TNP-470, would be useful for development of new angiogenesis inhibitors.     

Synthesis and photoluminescent properties of titanate layered oxides intercalated with lanthanide cations by electrostatic self-assembly methods

Various lanthanide cations were intercalated into the interlayer of the exfoliated H(x)Ti((2-x)/4)) square(x/4)O(4) x H(2)O (HTO) by the electrostatic self-assembly deposition (ESD) and layer-by-layer self-assembly (LBL) methods. X-ray diffraction and thermal analysis data indicated that interlayer lanthanide cations existed as an aqua ion and were coordinated with 7-10 water molecules under ambient conditions. The interlayer distances were found to be in the range 6-7 Angstrom for HTO layered oxide intercalated with a lanthanide cation. Intercalation of lanthanide cations into the interlayer by the LBL method was monitored by UV-vis spectrum and X-ray diffraction. Photoluminescence properties were also discussed in detail. Eu(3+) intercalated layered oxide exhibited intense red emission at room temperature. The presence of interlayer water molecules was found to be inevitable for the emission with high intensity. The emission intensity was significantly higher for the films conditioned at 100% RH than those at 5% RH. The icelike behavior of the confined water molecules in the interlayer around lanthanide cations was believed to be contributing highly to the emission mechanism. The mechanism was illustrated and explained by data obtained under several conditions.     

Steric effect of ortho-substituents of 1-phenyl-3-methyl-4-aroyl-5-pyrazolones on the synergic extraction of lutetium with trioctylphosphine oxide

The substituent effect of ortho-substituted 4-aroyl derivatives of 1-phenyl-3-methyl-5-pyrazolones (HA) on the adduct formation reaction between their lutetium chelates and a neutral ligand, trioctylphosphine oxide (TOPO, L), in benzene was studied using a liquid-liquid extraction system. The lutetium 4-aroyl-5-pyrazolonates react with TOPO to form LuA₃L and LuA₃L₂ types of adducts. An obvious steric hindrance of the terminal group on the adduct formation reaction was observed. Linear relationships between the acid dissociation constant of the ortho-substituted 4-aroyl-5-pyrazolone derivatives and those of the corresponding benzoic acids, between the extraction constants of lutetium and the acid dissociation constants of pyrazolones and between the adduct formation constants of TOPO and the acid dissociation constants of pyrazolones could be obtained.     

Kagomé type extra-large microporous solid based on a paddle-wheel Cu2+ dimer

A robust extra-large microporous coordination polymer with a Kagomé type structure was synthesized by carboxylate/amine multifunctional ligand with a Cu(2+) cluster and the hexagonal 1D channels ( approximately 15 A) showed type I and IV adsorption isotherms for gas molecules.     

Direct fluorometric detection of paramagnetic and heavy metal ions at sub-amol level using an aromatic polyaminocarboxylate by CZE: Combination of pre- and on-capillary complexation technique

The low sensitivity of simple CZE for detecting metal ions is a long-standing problem even when an LIF detection system is employed. We have successfully achieved an ultrasensitive CE-LIF using a simple CZE mode (typical detection limit: 10(-11)-10(-10) mol/dm(3)). Both the design of a newly synthesized ligand and the combination of a precapillary derivatizing technique with an on-capillary ternary complexing technique have enabled us to achieve this extremely low LOD and high resolution of large metal complexes. The direct fluorescent detection of the paramagnetic metal ions was achieved for the first time despite their intrinsic fluorescent quenching nature. The fluorescent ligand (L) consists of a polyaminocarboxylate chelating moiety, a strongly emissive fluorescein moiety and a spacer connecting the two portions. The migration behavior of various metal-L complexes was investigated. The resolution among the complexes was improved by the introduction of a ternary complex equilibrium of the kinetically stable mother complexes with OH(-) ion. The analytical potential of our simple system was examined, and it was proved that the system was one of the most sensitive methods without the need for any preconcentration process.     

Design and synthesis of chiral alpha,alpha-disubstituted amino acids and conformational study of their oligopeptides

alpha,alpha-Disubstituted amino acids are alpha-amino acids in which the hydrogen atom at the alpha-position of the L-alpha-amino acid is replaced with an alkyl substituent. The introduction of an alpha-alkyl substituent changes the properties of amino acids, with the conformational freedom of the side chain in the amino acids and the secondary structure of their peptides being especially restricted. The author developed a synthetic route of optically active alpha-ethylated alpha,alpha-disubstituted amino acids using chiral cyclic 1,2-diol as a chiral auxiliary. It was found that the preferred secondary structure of peptides composed of chiral alpha-ethylated alpha,alpha-disubstituted amino acids is a fully extended C5-conformation, whereas that of peptides composed of chiral alpha-methylated alpha,alpha-disubstituted amino acids is a 3(10)-helical structure. Also, a new chiral cyclic amino acid; (3S,4S)-1-amino-3,4-di(methoxy)cyclopentanecarboxylic acid {(S,S)-Ac5c(dOM)}, and a bicyclic amino acid; (1R,6R)-8-aminobicyclo[4.3.0]non-3-ene-8-carboxylic acid {(R,R)-Ab5,6= c}, in which the alpha-carbon atom is not the chiral center but chiral centers exist at the side-chain cycloalkane skeleton, were designed and synthesized. The (S,S)-Ac5c(dOM) hexa- and octapeptides preferentially formed left-handed (M) helices, in which the helical-screw direction is exclusively controlled by the side-chain chiral centers. Contrary to the left-handed helices of (S,S)-Ac(5)c(dOM) peptides, the (R,R)-Ab5,6= c hexapeptide formed both diastereomeric right-handed (P) and left-handed (M) helices, and the twelve chiral centers at the side chain showed no preference for helical-screw direction. Thus, the chiral environment at the side chain is important for the control of helical-screw direction. Furthermore, the author designed a new class of chiral cyclic alpha,alpha-disubstituted amino acids that have pendant chiral centers at the substituent of the delta-nitrogen atom. The synthetic route would provide various optically-active cyclic alpha,alpha-disubstituted amino acids bearing a pendant chiral moiety.