Purification and properties of Aspartate aminotransferase (E.C. 2.6.1.1) from skeletal muscle of Cirrhina mrigala

Aspartate aminotransferase (E.C. 2.6.1.1.) from the skeletal muscle of fresh water fish Cirrhina mrigala has been purified 40 fold by ammonium sulphate fractionation, adsorption on alumina Csub(8) gel and chromatography using DEAE-cellulose column and the properties of the purified enzyme studied. The pH optimum of the enzyme is 7.8. The Km value of aspartic acid and 2-oxoglutaric acid are found to be 2.8 x 10sub(-3) M and 1.0 x 10sub(-4) M respectively. The activity of enzyme is inhibited by p-chloromercurybenzoate, hydroxylamine hydrochloride and sodium cyanide. The inhibition by pchloromercurybenzoate is reversed by reduced glutathione, B-mercaptoethanol and cysteine. Dicarboxylic acids such as maleic acid, malic acid and succinic acid inhibit the enzyme activity. The enzyme is not activated by any of the metal ions tested and heavy metal ions such as mercury and silver strongly inhibit the enzyme activity.

黄土高原陇东盆地朝那红黏土8.1～2.6 Ma的孢粉记录

IEECAS SKLLQG

2.6 s isomer of Nd-129

Nd-129 was produced by irradiation of an enriched target of Ru-96 with a Ar-36 beam and studied by using a helium-jet fast tape transport system in combination with X-gamma and gamma-gamma coincidence measurements. A 2.6s isomer of Nd-129 was observed for the first time and tentatively proposed to be the configuration of 1/2[411].

The first soluble conjugated poly(2,6-anthrylene): synthesis and properties

The first soluble conjugated poly(2,6-anthrylene) with 9,10-diphenyl-anthracene as the repeating unit is reported; photophysical studies reveal that this polymer represents a novel well-conjugated system.

Metal dependent control of cis-/trans-1,4 regioselectivity in 1,3-butadiene polymerization catalyzed by transition metal complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine

Fe(III), Cr(III), Fe(II), Co(II) and Ni(II) chloride complexes supported by 2,6-bis[1-(iminophenyl)ethyl]pyridine have been synthesized and characterized along with single crystal X-ray diffraction. These complexes, in combination with MAO, have been examined in butadiene polymerization. The catalytic activity and regioselectivity are strongly controlled by metal center and cocatalyst (MAO/Co ratio dependent in the case of Co(II) complex). The activity decreases in the order of Fe(III) > Co(II) > Cr(III) approximate to Ni (II) complexes, in consistent with the space around the metal center. Polybutadiene with different microstructure content, from high trans-1,4 units (88-95% for iron(III) and Cr(III)), medium trans-1,4 and cis-1,4 units (55% and 35%, respectively, for iron(II)) to high cis-1,4 units 79% for Co(II) and 97% for Ni(II) call be easily achieved by varying of the metal center.

Synthesis and Characterizations of Poly(9,10-bisarylethynyl-2,6-anthrylene)s and Poly(9,10-bisalkynyl-2,6-anthrylene)

A poly(9,10-bisalkynyl-2,6-anthrylene) (PI) and five poly(9,10-bisarylethynyl-2,6-anthrylene)s(P2-P6) as soluble conjugated polymers have been synthesized and characterized. All polymers exhibit two-dimensional conjugated characteristics as indicated by absorption spectra comprising multi-bands in the range of 300-600 nm. Compared with P1, polymers P2-P5, which contain phenylethynyl substituents with the longer conjugation than alkynyl groups, exhibit a similar to 60 nm red shift of absorption edge. However, further increasing the conjugation length of the arylethynyl substituents (longer than phenylethynyl) has only a no effect on the conjugation of the polymer chains, while comparing the absorption spectra of P6 with those of P2-P5.

Investigation of heptakis(2,6-di-O-methyl)-beta-cyclodextrin inclusion complexes with flavonoid glycosides by electrospray ionization mass spectrometry

The non-covalent complexes between three flavonoid glycosides (quercitrin, hyperoside and rutin) and heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). The 1:1 complexation of each flavonoid glycoside (guest) to the DM-beta-CD (host) was monitored in the negative ion mode by mixing each guest with an up to 30-fold molar excess of the host. The binding constants for all complexes were calculated by a linear equation in the order: DM-beta-CD:quercitrin > DM-beta-CD:rutin > DM-beta-CD:hyperoside. A binding model for the complexes has also been proposed based on the binding constants and tandem mass spectrometric data of these complexes.

Structure characterization and physical properties of a complex with supramolecular architectures Co-2(2,6-DPC2Co(H2O)5 center dot 2H(2)O (DPC=2,6-pyridinedicarboxylate)

Reaction of 2,6-pyridinedicarboxylic with CoCl2 . 6H(2)O in aqueous solution give rise to a three-dimensional Complex CO2(2,6-DPC)(2)Co(H2O)(5).2H(2)O (DPC = 2,6-pyridinedicarboxylate) 1. It has been characterized by elemental analyses, infrared spectra (IR) spectrum, thermogravimetric (TG) analysis, EPR spectrum, and single crystal X-ray diffraction. The complex crystallizes in the P2(1)/c space group with a = 8.3906(3) Angstrom, b = 27.4005(8) Angstrom, c = 9.6192(4) A, alpha = 90.00degrees, beta = 98.327(2)degrees, gamma = 90.00degrees, V = 2188.20(14) Angstrom(3), Z = 4. There are two types of cobalt environments: Co(1) is coordinated by four oxygen atoms from four carboxyl groups and two nitrogen 2 atoms which are all from pdc(2). Co(2) is coordinated by six oxygen atoms, five from coordinated water molecules and one from a carboxyl of pdc(2) - of which the other oxygen atom is linked to the Co(1). The extensive intermolecular hydrogen bonds are formed in the crystal by means of the five coordinated water molecules.

七-(2,6-二-O-甲基)-β-环糊精对1,1 -联萘酚对映体手性识别的电喷雾质谱研究

利用电喷雾质谱研究了β-环糊精、七-(2,6-二-O-甲基)-β-环糊精作为手性识别试剂对1,1'-联萘酚对映体的手性识别效应.实验结果表明,在气相中,β-环糊精与七-(2,6-二-O-甲基)-β-环糊精都可以与联萘酚形成非共价复合物.对形成的复合物的串联质谱研究表明,β-环糊精不能识别联萘酚对映体,而七-(2,6-二-O-甲基)-β-环糊精对联萘酚对映体有较强的手性识别效应.进一步研究表明七-(2,6-二-O-甲基)-β-环糊精与联萘酚对映体混合比例以及CID能量对于手性识别并无影响.

七-(2,6-二-O-甲基)-β-环糊精对薄荷醇对映体手性识别的电喷雾质谱研究

利用电喷雾质谱研究了七-(2,6-二-O-甲基)-β-环糊精(DM-β-CD)作为手性识别试剂对薄荷醇对映体的手性识别效应。实验结果表明,在气相条件下,DM-β-CD可以与薄荷醇形成特异性结合复合物,化学计量比为1∶1。对复合物的串联质谱研究表明,DM-β-CD对薄荷醇对映体有较强的手性识别能力,手性识别率为Rchiral=1.81。DM-β-CD与(-)-薄荷醇形成的复合物比与(+)-薄荷醇形成的复合物稳定。

X-ray crystal structure and molecular mechanics calculations of (2,6-iso-dipropyl-phenylamide) dimethyl (tetra-methylcyclopenta-dienyl) silane titanium dichloride

Crystal and molecular structure of (2.6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic. with a = 12.658 (3) Angstrom. b = 16.62 (3) Angstrom. c = 11.760 (2) Angstrom. V = 2474.2 (9) Angstrom(3). Z = 4, space group Pnma. R = 0.0399; Componud I compose of the pi-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed.

Effect and mechanism in compatibilization of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer in poly(2,6-dimethyl-1,4-phenylene oxide) poly(ethylene-ran-acrylic acid) blends

The compatibilization effect of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer, P(S-b-EOx), on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(ethylene-co-acrylic acid) (EAA) is examined in terms of phase structure and thermal, rheological and mechanical properties, and its compatibilizing mechanism is investigated by Fourier-transform infrared spectroscopy. The block copolymer, synthesized by a mechanism transformation copolymerization, is used in solution blending of PPO/EAA. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion on addition of a small amount of P(S-b-EOx). Thermal analysis indicates that the grass transition of PPO and the lower endothermic peal; of EAA components become closer on adding P(S-b-EOx), and the added diblock copolymer is mainly located at the interface between the PPO and EAA phases. The interfacial tension estimated by theological measurement is significantly reduced on addition of a small amount of P(S-b-EOx). The tensile strength and elongation at break increase with the addition of the diblock copolymer for PPO-rich blends, whereas the tensile strength increases but the elongation at break decreases for EAA-rich blends. This effect is interpreted in terms of interfacial activity and the reinforcing effect of the diblock copolymer, and it is concluded that the diblock copolymer plays a role as an effective compatibilizer for PPO/EAA blends. The specific interaction between EAA and polar parts of P(S-b-EOx) is mainly hydrogen bonding. (C) 1998 Elsevier Science Ltd. All rights reserved.