Studies on the coordination of Pr(III) with adrenaline by potentiometry and absorption spectroscopy

The stability constant for complex of Pr(III) with adrenaline has been determined by potentiometric titration under biological conditions (37 degrees C and 0.15 mol/L NaCl). The absorption spectra of the Pr(III)-adrenaline system exhibit characteristic bands of Pr(III) at lower pH values. However, the charge transfer band which is due to the coordination of Pr(III) with adrenaline has been observed at higher pH values.

In-situ circular dichroism spectroelectrochemical study on the redox process of norepinephrine

The redox process of norepinephrine in pH = 7.0 phosphate buffer solution at glassy carbon electrode was studied by circular dichroism spectroelectrochemistry with a long optical path thin layer cell. The spectroelectrochemical data were analyzed with the double logarithm method. According to the double logarithsmic plot results, the mechanism of electrochemical oxidation of norepinephrine is an irreversible process with a subsequent chemical reaction (EC) to form a norepinephrinechrome. Both of norepinephrinequinone and norepinephrinechrome are followed E mechanisms. Some kinetic parameters about the electrochemical process, i.e. the electron transfer coefficient and number of electron transfered, alpha n = 0.38, the formal potential, E-1(0)' = 0.20 V, the standard heterogenous electron transfer rate constant, k(1)(0) = 1.2 x 10(-4) cm s(-1) for the oxidation of norepinephrine, alpha n = 0.37, E-2(0)' = 0.25 V and k(2)(0) = 4.4 x 10(-5) cm . s(-1) for the reduction of norepinephrinequnone and alpha n = 0.33, E-3(0)' = -0.25V and k(3)(0) = 1.1 x 10(-4) cm . s(-1) for the reduction of norpinephrinechrome, were also estimated.

Binuclear lanthanide complexes as catalysts for the hydrolysis of double-stranded DNA

The efficient cleavage of plasmid DNA ( pCAT) by binuclear lanthanide complexes was investigated. At 37 degrees C and neutral pH, both Ho23+L and Er23+L promoted 100% conversion of supercoiled plasmid to the nicked circular form and linear form in 1 h. The corresponding saturation kinetics curve of cleavage of pCAT plasmid by binuclear lanthanide complexes showed the expected increase with catalyst concentration. (C) 1999 Elsevier Science S.A. All rights reserved.

Cleavage of nucleotides by Ce4+ and the lanthanide metal complexes

The cleavage of adenosine-5'-monophosphate (5'-AMP) and guanosine-5'-monophosphate (S-GMP) by Ce4+ and lanthanide complex of 2-carboxyethylgermanium sesquioxide (Ge-132) in acidic and near neutral conditions was investigated by NMR, HPLC and measuring the liberated inorganic phosphate at 37 degrees C and 50 degrees C, The results showed that 5'-GMP and 5'-AMP was converted to guanine (G), 5'-monophosphate (depurination of 5'-GMP), ribose (depurination and dephosphorylation of 5'-GMP), phosphate and adenine (A), 5'-monophosphate (depurination of 5'-AMP), ribose (depurination and dephosphorylation of 5'-AMP), phosphate respectively by Ce4+. In presence of lanthanide complexes, 5'-GMP and 5'-AMP were converted to guanosine (Guo) and phosphate and adenosine (Ado) and phosphate respectively. The mechanism of cleaving 5'-GMP and 5'-AMP is hydrolytic scission.

Analysis of mussel standard reference material by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry

A method for the analysis of mussel standard reference material by inductively coupled plasma atomic emission spectrometry( ICP-AES) and inductively coupled plasma mass spectrometry(ICP-MS) was developed. K, Na, Ca, Mg, P, Al, Fe, Zn, Mn and Sr were determined by ICP-AES and As, B, Cd, Co, Cr, Cu, Ga, Ge, Mn, Mo, Ni, Pb, Se, Sr, U and V by ICP-MS, The interference coefficients at the Mn-55, Se-78, Cu-63, Co-59, Ni-58, Ni-60, As-75, Se-77, V-51, Cr-53 and Cr-52 originating from polyatomic ion of the matrix elements (KO)-K-39-O-16, K-39(2), (ArNa)-Ar-40-Na-23, (CaO)-Ca-43-O-16, (CaO)-Ca-42-O-16, (CaO)-Ca-44-O-16, (PO2)-P-31-O-16, (ArCl)-Ar-40-Cl-35, (ArCl)-Ar-40-Cl-37, (ClO)-Cl-35-O-16, (ClO)-Cl-37-O-16 and (ArC)-Ar-40-C-12 were determined under the selected operation parameters. The major matrix elements, such as K, Na and Ca, result in the suppression of analytes signals. The apparent concentration at the significant biological element which was produced by the different digestion methods, (.) HNO3 + H2O2 (3 + 2), HNO3 + HClO4 (3 + 0.5) and HNO3 + H2SO4 (3 + 0.5),was determined. The sample digested by HNO3 + H2O2 did not give rise to interfere on the analyte, and the backgrounds of Se-77, Ga-69, Zn-67, As-75, V-51, Cr-53 and Cr-52 were increased by HNO3 + HClO4 digestion method, that affected the determination of these elements, especially the monoisotope As and V. Sample digested by HNO3 + H2SO4 increased the backgrounds at Cu-65, Zn-64 and Zn-67. Detection limits of ICP-AES are 0.001 similar to 0.75 mg/L and those of ICP-MS are 0.005 similar to 1.01 mu g/L. The relative standard derivations of ICP-AES and ICP-MS are 2.7% similar to 12.8%, 3.4% similar to 24.8%, respectively.

Purification and characterization of L-amino acid oxidase from Agkistrodon blomhoffii ussurensis snake venom of Changbai Mountains

The L-a. a, oxidase of Agkistrodon blomhof fii ussurensis of Changbai Mountains in northeast of China has been separated by using ion-exchange and gel filtration techniques, This enzyme is composed of two subunits, the molecular weight of one subunit is about 36 000, the another is about 57 000, determined by sodium dodecyl sulfate-polyacryamide gel electrophoresis and matrix assisted laser desorption ion/time of flight mass spectrometry, The activity of L-a, a. oxidase determined using L-Leu as substrate. The optimal pH of the enzyme is 4. 5 similar to 5. 5 and 8 similar to 9. The UV-Visible absorption spectrum of L-a, a. oxidase shows the characteristics of flavor-proteins.

Synthesis and properties of thermotropic copoly(ester imide)s

A dicarboxylic acid, N,N'-hexane-1,6-diylbis(trimellitimide), was prepared by the reaction of trimellitic anhydride with 1,6-hexane diamine. From the diacid, a series of copoly(ester imide)s had been synthesized by thermal condensation with p-hydroxybenzoic acid and diphenols with different structures. Properties of the resulting copoly(ester imide)s were characterized by polarized light microscopy, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Most of the copoly(ester imide)s formed a nematic phase over a wide temperature range above their melt. The effects of the copoly(ester imide)s composition and the structures of diphenols on the temperature related to liquid crystalline transition were investigated.

Study of photochemical fluorescence enhancement of the terbium-lomefloxacin complex

Lomefloxacin (LMFX) and terbium ion can form a complex and the sensitized fluorescence of the terbium ion can be observed. It was found that the sensitized fluorescence intensity can be notably enhanced when the terbium complex is exposed to 365 nm ultraviolet light. By the fluorescence spectra, phosphorescence spectra, fluorescence quantum yield and fluorescence lifetime of the system, it was proved that irradiation of the complex made it undergo a photochemical reaction and a new terbium complex which is more favorable to intramolecular energy transfer was formed. This is why the sensitized fluorescence enhancement can be observed. (C) 1999 Elsevier Science S.A. All rights reserved.

白眉蝮蛇蛇毒L-氨基酸氧化酶的纯化与表征

用离子交换和凝胶过滤层析技术从长白山白眉蝮蛇蛇毒(A gkistrodon blom hoffii ussurensis)中分离得到了L氨基酸氧化酶(L-amino acid oxidase)，经SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)和基体辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)鉴定，发现L-氨基酸氧化酶由两个不相等的亚基组成，一个亚基的分子量约为36000，另一个亚基分子量约为57000．以L-亮氨酸作为底物进行L-氨基酸氧化酶活力测定时发现，其反应的适宜PH值为45.5和89，紫外吸收光谱明显表现出核黄素蛋白的特征

去甲肾上腺素电极过程的圆二色谱电化学研究

现场圆二色薄层光谱电化学研究去甲肾上腺素的电化学氧化还原过程 .研究表明去甲肾上腺素 ( pH =7.0磷酸缓冲溶液中 )在玻碳电极上经历了不可逆的电化学氧化 ,且遵从后行化学反应 (EC)机理 ,去甲肾上腺素醌和去甲肾上腺素红的再还原遵从简单电子转移 (E)机理 .由双对数法获得去甲肾上腺素电化学氧化的式电位为E10’=0 .2 0V ,电子转移系数和电子转移数之积为αn =0 .38,标准复相电极反应常数k10 =1 .2× 1 0 -4 cm·s-1.去甲肾上腺素醌和去甲肾上腺素红的电化学还原反应参数分别为E2 0’=0 .2 5V ,αn =0 .37,k2 0 =4.4× 1 0 -5 cm·s-1和E3 0’=- 0 .2 5V ,αn =0 .33,k3 0 =1 .1× 1 0 -4 cm·s-1.

电感耦合等离子体光谱和质谱法分析贻贝标准物质

采用电感耦合等离子体光谱和质谱法分析了贻贝标准物质,光谱法测定K、Na、ca、Mg、P、Al、Fe、Zn、Nn和Sr,质谱法测定As、B、Cd、Co、Cr、Cu、Ca、Ce、Mn、Mo、Ni、Pb、Se、Sr、U和V。在优化的工作条件下,测定了来自基体元素K、Na、Ca、P、Cl和C的多原子离子~(39)K~(16)O、~(39)K_2、~(40)Ar~(23)Na、~(43)Ca~(16)O、~(42)Ca~(16)O、~(44)Ca~(16)O、~(31)P~(16)O_2、~(40)Ar~(37)Cl、~(35)Cl~(16)O、~(37)Cl~(16)O和~(40)Ar~(12)C对~(55)Mn、~(78)Se、~(63)Cu、~(59)Co、~(58)Ni、~(60)Ni、~(75)As、~(77)Se、~(51)V、~(53)Cr和~(52)Cr的干扰系数以及HNO_3+H_2O_2(3+2)、HNO_3+HClO_4(3+0.5)和HNO_3+H_2SO_4(3+0.5)等3种样品消解方法在一些生物重要元素的同位素处产生的表观浓度。光谱法的检出限0.001～0.75mg/L;质谱法的检出限0....

Dynamic light-scattering characterization of the molecular weight distribution of a broadly distributed phenolphthalein poly(aryl ether ketone)

Using a recently developed laser light-scattering (LLS) procedure, we accomplished the characterization of a broadly distributed unfractionated phenolphthalein poly(aryl ether ketone) (PEK-C) in CHCl3 at 25 degrees C. The laplace inversion of precisely measured intensity-intensity time correlation function from dynamic LLS leads us first to an estimate of the characteristic line-width distribution G(Gamma) and then to the translational diffusion coefficient distribution G(D). By using a previously established calibration of D (cm(2)/s) = 2.37 X 10(-4)M(-0.57), were able to convert G(D) into a differential weight distribution f(w)(M). The weight-average molecular weight M(w) calculated from f(w)(M) agrees well with that directly measured in static LLS. Our results indicate that both the calibration and LLS procedure used in this study are ready to be applied as a routine method for the characterization of the molecular weight distribution of PEK-C. (C) 1996 John Wiley & Sons, Inc.

气相离子C_(18)H_(37)NH_3~+在低碰撞能下的远电荷碎裂反应

本文研究了电子轰击、化学电离条件下四碘合钴酸十八胺、四氯合钴酸十八胺加热分解产生的C_(18)H_(37)NH_3~+(m/z270)离子碰撞诱导解离谱,在低碰撞能量范围(0～10eV)、多次碰撞条件下观察到了远电荷碎裂反应,给出了反应所需内能的估计值,该离子比直接由正十八胺质子化得到的离子具有较高的内能。

α-K_3H_4[SiW_9Al_3(H_2O)_3O_(37)]·7H_2O的晶体结构

三取代杂多化合物的母体XM_9是由Keggin结构阴离子XM_(12)衍生而来.它有2种异构体:从XM_(12)中移出1个M_3O_(13)基团得B型异构体;从XM_(12)中的3个M_3O_(13)中各移出1个MO_6后得到A型异构体.Hervé等人曾指出α-和β-SiW_9均为B型结构,但Robert等在测定β-Na_9H(SiW_9O_(34))·23H_2O的晶体结构时发现,β-SiW_9为A型结构,α-SiW_9结构类型尚未定论,由于2种构型阴离子的配位能力及聚合能力不同,确定其结构类型及其变化情况是十分必要的,本文由α-SiW_9合成了α-K_3H_4[SiW_9A1_3(H_2O)_3O_(37)],用X射线衍射法测定了其晶体结构。