Assay of sialyltransferase activity by reversed-phase ion-pair high-performance liquid chromatography.

Sialyltransferases (CMP-N-acetylneuraminic acid:glycoprotein sialyltransferases, EC 2.4.99.1) are involved in the transfer of a sialic acid moiety from CMP-N-acetylneuraminic acid (CMP-NeuAc) to an oligosaccharide side-chain of an acceptor, asialoglycoprotein (AGP), according to the following reaction: CMP-NeuAc + AGP----NeuAc-O-AGP + CMP. This enzyme occurs in elevated levels in the sera of patients with a wide variety of neoplastic diseases and its assay might be useful in monitoring treatment. Radioactive CMP-NeuAc has been used in assays and the radioactive sialylated product separated and counted by liquid scintillation spectrometry. This study shows that a simple, rapid, non-radiochemically based high-performance liquid chromatographic method developed for the analysis of CMP-sialic acid synthetase can be used for the quantitation of sialyltransferase activity by monitoring simultaneously the utilization of CMP-NeuAc and the release of CMP. We describe the application of this method to assay of commercially available sialyltransferase activity and to activities from synovial, ascites and gastric fluids.     

Combined Chemical and Enzymatic Synthesis of a Disialylated Tetrasaccharide Analogous to M and N Bloodgroup Determinants of Glycophorin a

Abstract

Reaction of 2,3,4,6-tetra-O-acetyl-α-D-galactopyraaosyl bromide (1) with phenyl 2-acetamido-2-deoxy-4,6-O-(4-methoxy-benzylidene)-α-D-galactopyranoside (3) mediated by mercuric salts, followed by removal of the 4-methoxybenzylidene group and O-deacylation afforded phenyl 2-acetamido-2-deoxy-3-O-p-D-galactopyranosyl-α-D-galactopyranoside (6). Compound 6 was used as a substrate for the selective introduction of two neuraminic acid residues with partially purified sialyltrans-ferase preparations. First, disaccharide 6 was treated with CMP-[¹⁴c]-NeuAc as donor substrate and CMP-NeuAc: Gal-p(l-3)-GalNac-a(2-3)sialyltransferase from human placenta to afford trisaccharide 7 (yield 85X), sialylated at C-3 of the galactose residue. Treatment of 7 with CMP-[³H]-NeuAc and a micro-somal fraction from regenerating rat liver, containing the CMP-NeuAc: NeuAc-a(2-3)-Gal-p(l-3)GalNAc-α(2-6) sialyltrans-ferase activity, gave the disialylated tetrasaccharide 8 in 10X yield.     

Systematic syntheses and inhibitory activities of bisubstrate-type inhibitors of sialyltransferases

Bisubstrate-type sialyltransferase inhibitors 1/2a-e, having CMP-NeuAc and N-acetyllactosamine (or lactose) moieties connected by an alkanedithiol linker, were synthesized systematically. A uniform synthetic strategy was adopted that consists of consecutive couplings of three components (N-acetyllactosamine or lactose, sialic acid, and CMP), followed by oxidation. Due to the sensitivity of the compounds under alkaline conditions, final deprotection required careful monitoring by (1)H NMR. The inhibitory activities of 1/2a-e toward ST6N and ST3N indicated that both the structure of the acceptor moiety and the distance between donor and acceptor moieties were important.     

Chemical-Enzymatic Synthesis of A Branched Hexasaccharide Fragment of Type Ia Group B Streptococcus Capsular Polysaccharide

ABSTRACT

A branched hexasaccharide fragment of type Ia group B streptococcal polysaccharide, α-NeuAc(2→3)-β-D-Gal(1→4)-β-D-GlcNAc(1→3)-[β-D-Glc(1→4)]-β-D-Gal(1→4)-β-D-Glc-OMe (13), has been synthesized by chemical-enzymatic procedures. Chemical synthesis of a pentasaccharide, β-D-Gal(1→4)-β-D-GlcNAc(1→3)-[β-D-Glc(1→4)]-β-D-Gal(1→4)-β-D-Glc-OMe (12), was achieved from glycosyl donor, 4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-3,6-di-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl trichloroacetimidate (9), and acceptor, methyl O-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-(1→4)-O-(2,6-di-O-benzyl-β-D-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (6), by block condensation in 41% yield. Following enzymatic sialylation of 12 at the 3-O-position of its terminal galactopyranosyl residue using recombinant α-(2→3)-sialyltransferase and CMP-NeuAc afforded 13 in 59% yield.     

荧光素衍生物在TiO_2胶体中的光物理性质研究

测定了以荧光素为光敏剂的电子给体-受体二元化合物荧光素蒽醌甲酯（FL- AQ）及模型化合物荧光素丁酯（FL4）在溶液中和在二氧化钛（TiO_2）胶体中的吸 收光谱、荧光光谱、荧光寿命等。发现荧光素蒽醌甲酯与荧光素丁酯均可通过酚羟 基较好地吸附在TiO_2胶体上。从吸收光谱可得,FL4与TiO_2形成表面络合物的表 观结合常数（K_(app)）大约为3590 mol~(-1)·L,结合率（α）为0.86;FL-AQ与 TiO_2形成表面络合物的K_(app)大约为3060 mol~(-1)·L,α为0.84。同时通过 ESR光谱讨论了光诱导电子注入机制。     

邻苯三酚红修饰碳糊电极吸附伏安法测定痕量铜

报道了采用邻苯三酚红修饰碳糊电极测定痕量铜的方法。通过在邻苯二甲酸氢钾 -氢氧化钠 (p H4.5)介质中富集 ,Cu2 +和邻苯三酚红形成络合物富集于电极表面 ,然后转换到 0 .0 50 mol· L-1的 H3PO4 中 ,经阴极还原后再进行阳极溶出伏安法测定。Cu2 +浓度在 1 .6× 1 0 -9～ 2 .8× 1 0 -7mol·L-1范围内与二次导数峰电流呈线性关系 ,检出限达 8× 1 0 -10 mol·L-1。同时 ,对电极反应机理进行了探讨。应用于合金样的测定 ,取得满意的结果。     

溶剂热法合成花朵状钴磁性粉体及表征

采用一种简单的溶剂热法成功的合成了花朵状的钴磁性粉体。通过X射线粉末衍射(XRD),扫描电子显微镜(SEM)等对样品进行物相与形貌的表征。结果表明样品为六排堆积(hcp)和面心立方结构(fcc)混合结构的钴单质,形貌为由很多个厚度约为50～150 nm的菱形花瓣构成的花朵状结构,每个花朵的尺寸约为2μm左右。采用振动样品磁强计(VSM)测试了样品的磁性能,测试表明样品在室温下表现出铁磁性,饱和磁化强度(Ms)为140 emu.g-1,剩磁(Mr)为9.4 emu.g-1,矫顽力(Hc)为280 Oe。     

聚合物共混物脆韧转变性能研究 Ⅱ准韧性聚合物共混物脆韧转变的几何模型

给出了分散相粒间基体层厚度Ｔ与分散相粒径（ｄ）、粒径分散度（σ）和分散相体积分数（）的定量关系式．发现σ对Ｔ的影响与有关，不仅Ｔ随σ的增大而增大，而且越大，这种影响越显著．用计算机图像分析仪直接测定了聚氯乙烯／丁腈橡胶、聚丙烯（ＰＰ）／三元乙丙橡胶、ＰＰ／乙烯 醋酸乙烯酯共聚物共混物的Ｔ，发现这三种共混物的Ｔ近似于对数正态分布．理论预示与实验结果很好符合．     

Reduction of colloidal manganese dioxide by manganese(II)

The reduction of colloidal MnO(2) by Mn(2+) in aqueous HClO(4) has been studied by a spectrophotometric method. The reaction product is Mn(III). The reaction is of first order in both colloidal MnO(2) and H(+), whereas it presents a fractional order (0.58+/-0.02) in Mn(2+). The reaction is retarded by addition of NaClO(4), but is not affected by addition of tert-butanol. The corresponding activation energy is 29.5+/-1.3 kJ mol(-1). The reaction is catalyzed by Na(4)P(2)O(7), and the pyrophosphate-catalyzed reaction is of first order in both colloidal MnO(2) and pyrophosphate and of fractional order (0.64+/-0.01) in Mn(2+), whereas its rate presents a complex dependence on the concentration of H(+). The pyrophosphate-catalyzed reaction is accelerated by addition of both NaClO(4) and tert-butanol. The corresponding activation energy is 49.7+/-3.0 kJ mol(-1). Mechanisms in agreement with the experimental data are proposed for both the parent and the pyrophosphate-catalyzed reactions.     

不同尺度和分散状态的钯纳米粒子红外光学性能研究

运用CO分子探针红外光谱研究不同尺度和分散状态的钯纳米粒子的红外光学性能.结果表明,粒子尺度为6.6nm分散的球型钯纳米粒子(Pdn)和粒子尺度为100～150nm分散的立方体型钯纳米粒子(Pdncube)均给出两个不同吸附方式的桥式CO红外谱峰,其吸收峰位置约在1970cm-1和1910cm-1.将Pdn引入到电极表面后,通过界面电化学诱导使之形成团聚体(Pdnag),其红外光学性能发生显著变化,表现为随着界面电化学诱导时间的增加,其1970cm-1处的谱峰方向从正常转为异常.本研究进一步证明红外谱峰方向的倒反是由于粒子间的相互作用引起的.     

Highly Sensitive Impedimetric Biosensor Based on Thermolysin Immobilized on a GCE Modified with AuNP-decorated Graphene for the Detection of Ochratoxin A

The fabrication of a thermolysin-based biosensor capable of detecting ochratoxin A (OTA) from food samples is described. The electrochemical deposition of calcium cross-linked cellulose film (CCLC) and gold nanoparticles (AuNPs) on graphene (GR) for modification of a glassy carbon electrode (GCE) is the first step. Then the thermolysin (TLN) enzyme in a polyvinyl alcohol (PVA)/polyethylenimine (PEI) matrix is immobilized. The impedimetric biosensor response is linear from 0.2 nM to 100 nM with a detection limit of 0.2 nM. The obtained stable and reproducible biosensor is then applied for the detection of OTA in spiked extracts from coffee beans.     

邻苯二甲醛-尿素柱前衍生高效液相色谱法快速检测枸杞中牛磺酸

干枸杞经粉碎、匀浆、离心后,通过阳离子交换柱脱去样品中其它氨基酸,再通过Ｚｏｒｂａｘ－Ｃ８柱进行柱前衍生分离。衍生剂：Ａ．４％ＯＰＡ甲醇溶液;Ｂ．尿素∶磷酸钠盐缓冲液（ｐＨ６．８）＝１∶３（Ｗ／Ｖ）。流动相：甲醇∶０．０１ｍｏｌ／Ｌ乙酸钠溶液（ｐＨ６．８）＝３５∶６５（Ｖ／Ｖ）。紫外检测波长３３０ｎｍ。牛磺酸浓度在０．１～１．０ｍｍｏｌ／Ｌ范围内可被定量测定。回收率可达１００．３１％±１．９８％,变异系数（ＣＶ）为１．９４％。     

非育珠背角无齿蚌软组织微量元素含量的分析

采用高频电感耦合等离子体发射光谱(ICP—AES)法测定了非育珠背角无齿蚌软组织中锰(Mn)、铁(Fe)、锌(Zn)、铬(Cr)、铝(Aj)、铜(Cu)六种微量元素及钙(Ca)、镁(Mg)的含量，分析了各种元素在不同软组织中的分布特征。结果表明：(1)在软组织中，各元素平均含量由高到低依次为：Ca，Mn，Mg，Fe，Zn，Al，Cr，Cu；(2)背角无齿蚌不同软组织中微量元素的含量不同，其中瓣鳃和外套膜中所测元素含量高于其他器官，特别是Mn，Fe的含量最高；Mn的含量甚至超过了宏量元素Mg；Al是闭壳肌中含量最丰富的微量元素。     

ADSORPTION OF SAMARIUM(Ⅲ) ON DIGLYCOLAMIDIC ACID RESIN

The sorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin(DAAR), for Sm(Ⅲ) were investigated. The optimal sorption condition of DAAR for Sm(Ⅲ) is pH=6.0 in HAc-NaAc medium. The statically saturated sorption capacity is 190mg/g resin at 298K.The Sm(Ⅲ) adsorbed on DAAR can be ehuted reaching 100% by 0.5～2.0mol/L HCl used as eluant.The resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k29s= 1.96 × 10-5 s-1. The apparent activation energy is 26k J/mol.The sorption behavior of DAAR for Sm(Ⅲ) obeys the Freundlich isotherm. The thermodynamic sorption parameters, enthalpy change △H of DAAR for Sm(Ⅲ) is 16. 9kJ/mol. The molar coordination ratio of the functional group of DAAR to Sm (Ⅲ) is 3. The sorption mechanism of DAAR for Sm(Ⅲ)was examined by using chemical method and IR spectrometry. The coordination bond was formed between oxygen atoms in the functional group of DAAR and Sm(Ⅲ).     

Studies on the polarographic behaviour of estazolam

In 0.1M NH(3)-NH(4)Cl buffer (pH 9.2) a sensitive 2-electron reduction wave of estazolam is obtained by single-sweep oscillopolarography. The peak potential is -1.08 V (vs. SCE). The peak height is proportional to the concentration of estazolam over the range 1.0 x 10(-7)-9.0 x 10( partial differential)M. The detection limit is 5.0 x 10(-8)M. The behaviour of the reduction wave has been studied and applied to the determination of estazolam. The reduction process is irreversible and the wave shows adsorptive characteristics, the behaviour obeying the Frumkin adsorption isotherm. The adsorption coefficient beta is 1.16 x 10(6) 1./mole and the interaction factor alpha is -1.06. The mechanism of the electrode reaction is discussed.     

Numerical simulation of phase separation of immiscible polymer blends on a heterogeneously functionalized substrate

The spinodal phase decomposition of an immiscible binary polymer blend system is investigated with numerical models in two-dimensional and three-dimensional (3D). The effect of the elastic energy is included. The mechanism of the evolution of the phase separation is studied and the characteristic length R(t) is shown to be proportional to t(13). In the case when the phase separation is directed by a heterogeneously functionalized substrate, the increase in the characteristic length is divided into two stages by a critical time. The R(t) approximately t(13) diagram can be fitted with a straight line in both the first and second stages. The slope of the fitting line significantly decreases after the critical time. The compatibility of the resulting pattern to the substrate pattern is also measured by a factor C(S). It is observed that there is also a critical time in the evolution of the compatibility for the cases with and without elastic energy. The critical time of C(S) is identical with the respective critical time of R(t). The lateral and vertical composition profiles functionalized substrate is observed with the 3D model. The difference mechanism of the cases with and without elastic energy is discussed.     

Studies on Adsorption Behavior and Mechanism of Copper（ Ⅱ ） onto Amino Methylene Phosphonic Acid Resin

IntroductionThe adsorption ability of the functional poly-mer used to enrich metal ions is strong and the op-eration of the functional polymer is convenient.The polymer having adsorbed metal ions can be re-covered by means of an acid or an alkaline solutionand the recovered polymeric material can bereused.The adsorption ability of the polymer withvarious functional groups is different for differentmetals.Because nucleophilic atoms such as oxy-gen,nitrogen,sulphur and phosphorous atoms cancoord…     

Chelation of vanadium(IV) by a natural and edible biopolymer poly(gamma-glutamic acid) in aqueous solution: structure and binding constant of complex

The naturally occurring edible biopolymer poly(gamma-glutamic acid) (gamma-PGA) is shown to be an efficient chelating agent of vanadium(IV). The structure of poly(gamma-glutamic acid)oxovanadium(IV) (VO-gamma-PGA) complex in solution has been analyzed by electron spin resonance and UV-visible absorption spectra. The equatorial coordination sphere of vanadium(IV) is proposed to be [2 x carboxylate (2O)-VO-(OH2)2]. The binding isotherm is determined for suspensions of gamma-PGA in vanadium(IV) oxide sulfate (VS) solutions of different concentrations, and the data have been adjusted to fit the modified Langmuir equation. The maximum amount of vanadium bound per gram of gamma-PGA is estimated to be 141 mmol . g(-1) with a binding constant of 22 L . g(-1) at pH 3.     

幼儿头发中微量元素含量与身高、体重关系研究

普查了４４９名１－６岁儿童头发中锌、铁、铜、钙、锰、铅含量,用分层聚类分析法对其身高、体重与各元素进行相关分析。幼儿身高与头发中锌含量呈相关关系,与头发中铅含量呈负相关关系。体重与头发中锌含量呈显著的正相关关系。与头发中铅含量呈负相关关系。说明锌有利于身体发育,而铅对身体发育不利。     

顺反构型[Rh(NH3)3Cl]在室温水溶液中的行为兼论铂配合物的抗癌机理及药效

In this paper the behaviour of mer-and fac-(Rh(NH3)3Cl3) in aqueous solution at room temperature is reported. The experimental results show that some obvious differences exist between the properties of mer-and fac-(Rh(NH3)3Cl3) coordination compounds in aqueous solution at room temperature. The fac-(Rh(NH3)3Cl3) is relatively stable, and the mer-(Rh(NH3)3 Cl3) is unstable. When one of its Cl^- is replaced by H2O(RH(NH3)3)(OH)2Cl2)Cl is formed. The mechanism of anti-tumour action of platinum compounds is briefly discussed.