Synthesis of functionalized rab GTPases by a combination of solution- or solid-phase lipopeptide synthesis with expressed protein ligation

Prenylated proteins with non-native functionalities are generally very difficult to obtain by recombinant or enzymatic means. The semisynthesis of preparative amounts of prenylated Rab guanosine triphosphatases (GTPases) from recombinant proteins and synthetic prenylated peptides depends largely on the availability of functionalised prenylated peptides corresponding to the proteins' native structure or modifications thereof. Here, we describe and compare solution-phase and solid-phase strategies for the generation of peptides corresponding to the prenylated C terminus of Rab7 GTPase. The solid-phase with utilisation of a hydrazide linker emerges as the more favourable approach. It allows a fast and practical synthesis of pure peptides and gives a high degree of flexibility in their modification. To facilitate the analysis of semisynthetic proteins, the synthesised peptides were equipped with a fluorescent group. Using the described approach, we introduced fluorophores at several different positions of the Rab7 C terminus. The position of the incorporated fluorescent groups in the peptides did not influence the protein-ligation reaction, as the generated peptides could be ligated onto thioester-tagged Rab7. However, it was found that the positioning of the fluorescent group had an influence on the functionality of the Rab7 proteins; analysis of the interaction of the semisynthetic Rab7 proteins with REP (Rab escort protein) and GDI (guanosine diphosphate dissociation inhibitor) molecules revealed that modification of the peptide side chains or of the C-terminal isoprenoid did not significantly interfere with complex formation. However, functionalisation of the C terminus was found to have an adverse effect on complex formation and stability, possibly reflecting low structural flexibility of the Rab GDI/REP molecules in the vicinity of the lipid-binding site.     

Reactivity in the solid state between CoWO4 and RE2WO6 where RE = Sm, Eu, Gd

Reactivity in the solid state between CoWO₄ and some rare-earth metal tungstates RE₂WO₆ (RE = Sm, Eu, Gd) was investigated by the XRD method. Two families of new isostructural cobalt and rare-earth metal tungstates, Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆, were synthesized. The Co₂RE₂W₃O₁₄ phases are formed by heating in air the CoWO₄ and RE₂WO₆ compounds mixed at the molar ratio 2:1, while the CoRE₄W₃O₁₆ phases are synthesized at the molar ratio of CoWO₄/RE₂WO₆ equals to 1:2. The Co₂RE₂W₃O₁₄ phases as well as the CoRE₄W₃O₁₆ compounds crystallize in the orthorhombic system. The Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compound melt above 1150 °C. A melting manner of the Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compounds was determined in an inert atmosphere. The formation of CoWO_4−x phase was observed during heating in an inert atmosphere.     

Dependence of Elution Curve and Adsorption Isotherms of Insulin on composition of Mobile Phase of Frontal Analysis in Reversed Phase Liquid Chromatography

With frontal analysis(FA),the dependence of adsorption isotherms of insulin on the composition of mobile phase in reversed phase liquid chromatography (RPLC) has been investigated,This is also a good example to employ the stoichiometric displacement theory (SDT) for ivestigating solute adsorption in physical chemistry.Six kinds of mobile phase in RPLC were employed to study the effects on the elution curves and adsorption isotherms of insulin.the key points of this paper are:(1) the stability of insulin due to delay time after preparing,the organic solvent concentration,the kind and the concentration of ion-pairing agent in mobile phase were found to affect both elution curve and adsorption isotherm very seriously.(2)To obtain a valid and comparable result,the composition of the mobile phase employed in FA must be as same as possible to that in usual RPLC of either analytical scale or preparative purpose.(3)Langmuir Equation and the SDT were employed to imitate these obtained adsorption isotherms.The expression for solute adsorption from solution of the SDT was found to have a better elucidation to the insulin adsorption from mobile phase in RPLC.     

分散固相萃取结合气相色谱-高分辨质谱快速筛查酱油中多种氯丙醇

建立了酱油中1，3-二氯-2-丙醇、2，3-二氯-1-丙醇、3-氯-1，2-丙二醇和2-氯-1，3-丙二醇的分散固相萃取-气相色谱-高分辨质谱快速筛查检测方法。样品采用乙酸乙酯提取，提取液浓缩后经N-丙基乙二胺净化，气相色谱-高分辨质谱测定，内标法定量。结果表明，该方法对于酱油中4种氯丙醇的定量限为0.5~10 μg/kg。在3个浓度水平下的加标回收率为78%~103%；相对标准偏差均不大于8.8%。该方法快速、简便、准确、灵敏，可作为酱油中4种氯丙醇的有效检测方法。     

Composting of urban solid residues (USR) by different dispositions

The thermal behavior and non-isothermal kinetics of thermal decomposition of three different kinds of composting of the USR like: stack with drilled PVC tubes (ST), revolved stack (SR) and stack with material of structure (SM), from the usine of composing of Araraquara city, Săo Paulo state, Brazil, within a period of 132 days of composting were studied. Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the cellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated from that process. Due to that behavior, the cellulosic fraction decomposition could be kinetically evaluated through non-isothermal methods of analysis. The values obtained were: average activation energy, Ea=248, 257 and 259 kJ mol^-1 and pre- exponential factor, logA=21.4, 22.5, 22.7 min^-1, to the ST, SR and SM, respectively. From Ea and logA values and DSC curves, Málek procedure could be applied, suggesting that the SB (Šesták-Berggren) kinetic model is the appropriated one to the first thermal decomposition step. This revised version was published online in July 2006 with corrections to the Cover Date.     

偏钛酸型锂离子交换剂固相合成反应动力学

偏钛酸型锂离子交换剂固相合成反应动力学钟辉＊郭灵虹（成都理工学院应用化学系成都６１００５９）（四川联合大学分析测试中心成都）关键词偏钛酸锂，离子交换剂，合成，固相反应动力学１９９７－０８－２５收稿，１９９７－１２－１０修回四川省应用基础研究基金资助项...     

Solid Phase Extraction and Simultaneous Spectrophotometric Determination of Trace Amounts of Copper and Iron Using Mixture of Ligands

 A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of iron (as its bathophenanthroline complex) and copper (as its neocuproine complex) using octadecyl silica cartridges and dual wavelength spectrophotometry is presented. The dual wavelength method (533 nm for the iron-bathophenanthroline and 454 nm for the copper-neocuproine as the analytical wavelength) is used to eliminate spectral interferences. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of neocuproine, bathophenanthroline and hydroxylamine hydrochloride, type and least amount of eluent for elution of iron and copper complexes from cartridge, break-through volume and limit of detection are evaluated. The effects of various cationic and anionic interferences on percent recovery of iron and copper are also studied. Extraction efficiencies >95% are obtained by elution of cartridges with minimal amount of organic solvent. Iron and copper were determined in the range of 3–100 ng mL⁻¹. The limits of detection are 0.98 and 1.13 ng mL⁻¹ for iron and copper, respectively. The proposed method is applied successfully to the determination of both analytes in river, tap and well water samples. Author for correspondence. E-mail: yyamini@modares.ac.ir Received September 18, 2002; accepted December 12, 2002 Published online May 5, 2003     

Structure and Electric Conductivity of (La,Sr)(Ga,Mg)O3-α Solid Electrolyte

Electric conductivity, Raman spectra, and thermal expansion of La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 solid solution (LSGM1218) based on lanthanum gallate were studied at various temperatures, and Xray phase analysis was performed at room temperature. Dilatometric measurements showed that secondorder phase transitions occur at 775±10$ and 880± 20 K. The transition around 880 K is confirmed by Raman spectra and by a change in the conductivity activation energy in this temperature range. This transition is associated with a symmetry change in the oxygen sublattice.     

用MES及XRD研究FT合成催化剂的活性结构

采用穆斯堡尔谱及Ｘ光衍射法研究了共沉淀法制备的不同Ｆｅ／Ｍｎ比催化剂在焙烧、合成气还原及ＦＴ反应后体系相结构的变化。结果表明：锰助剂的加入使催化本相由铁磁性逐渐转化为超顺磁性，相应使催化剂还原逐渐难，Ｍｎ助剂促进了ＦＴ合成反应进行。反应性能与Ｆｅ／Ｍｎ尖晶石（Ｆｅ１－ｙＭｎｙ）３Ｏ４组成含量及式中ｙ大小密切相关，与ＭｎＣｏ３及ＭｎＯ的存在也有一定关系。富铁催化剂中Ｍｎ主要起电子助剂作用，而富锰催化     

Small angle neutron scattering studies on nonaqueous dispersions of calcium carbonate Part 2. Determination of the form factor for concentric spheres

Colloidal dispersions of calcium carbonate, stabilised primarily by a surface active agent, in both toluene and dodecane have been examined by small angle neutron scattering. A model has been developed to simulate the scattering behaviour of the particles and is based on the idea of a concentric sphere with a homogeneous layer of adsorbed material surrounding a core particle. Computations based on the model show a wide variation of scattering behaviour with variation of the coherent scattering length of the dispersion medium. These predictions were confirmed by experiment. A method is described for analysis of the experimental data which leads to a determination of the thickness of the adsorbed layer, the radius of the core particle and the standard deviation of core particle radius.