Mass spectrometry assisted assignments of binding and cleavage sites of Zn(Ⅱ)complex towards oxidized insulin B chain

The electrospray ionization mass spectrometry investigation showed that the binding sites of [ZnL]2+, where L is 2-[bis(2-aminoethyl)aminolethanol, with oxidized insulin B chain are Phe1, His5 and Arg22, which lead to the selective cleavages of the peptide bonds at Phe1-Val2, His5-Leu6, Glu21-Arg22, and Arg22-Gly23 of oxidized insulin B chain.     

关于一类拟线性退化抛物方程

对拟线性退化抛物方程θ_(xx)u uθ_yu-θ_tu=f(·,u)进行了研究,得到了在[O,T]×Ω上的初边值问题解的存在唯—性,这里要求T充分小．     

METAL CLUSTERS SYNTHESIZED BY SOLID STATE REACTION——PREPARATION AND CRYSTAL STRUCTURE OF TWO MIXED METAL CLUSTERS,Ni_2Nb_2Te_4(Ⅰ) AND Ni_2Ta-2Te_4(Ⅱ)

The two title compounds obtained by solid state reaction at high temperature were char-acierized as isomorphism by single--crystal X--ray diffraction. The space group of both crys-tals is C_(2v)~4-Pma2, with lattice constants a = 7.955(1), b=6.258 (1), c=7 .203(2)A forI, and a =7.914 (1), b=6.237 (1), c=7.236 (1) ? for Ⅱ, Z=2. The structures were de-termined by normal method and refined to the final R = 0.074 and 0.083, respectively. Theresults show that the structure may be regarded as building by cluster unit with formulaNi_2M_2Te_4 (M =Nb or Ta) in which two Ni atoms and two M atoms form a rhombus, whilethe Te atoms are distorted tetrahedrally coordinated with both kinds of metal atoms. In thecluster unit there exist interactions between Ni atoms as well as between Ni and M atoms.In addition, all the cluster units are linked together not only by bridging Te atoms, but alsoby weaker metal-metal interactions, so as to form two--dimensional network. Therefore, thestructure may be represented by the for     

火焰原子吸收光谱法测定含卤素金属原子簇化合物中银

本文介绍了火焰原子吸收光谱法测定含卤素金属原子簇化合物中银。研究了样品制备方法及常见共存元素干扰。平均回收率100%(99-101%),相对标准偏差<1%。用本法测定含卤素金属原子簇化合物中银,获得满意的结果。     

溶剂热法合成新型锑硒化合物[M~1(C_4H_(13)N_3)_2]_n[M~2Sb_2Se_5]_n(M~1=Mn、Co,M~2=Zn、Cd)及结构

以二乙烯三胺为模板剂,通过溶剂热法制备了一种新型有机无机杂化锑硒化合物:[M1(C4H13N3)2]n[M2Sb2Se5]n(M1=Mn、Co,M2=Zn、Cd).相比传统的有机无机杂化锑硒化合物,过渡金属Zn和Cd参与了这种化合物主框架的构建,使化合物的主框架由传统的SbSex单元转变为Zn(Cd)SbSe5的配位单元.据我们所知,这是第一次合成出Zn和Cd参与SbSex骨架配位的有机无机杂化锑硒化合物.同时,由于结构中CdSe4和ZnSe4单元的存在,使得该化合物表现出荧光性质.这种化合物的出现,使得我们有可能通过相同的途径合成出一系列具有该类型结构特征,在发光领域有潜在应用前景的新型锑硒化合物.     

(8R,8aS)-及(8R,8aR)-8-羟基-5-吲哚里西啶酮的不对称合成:两个有用的羟基吲哚里西啶合成砌块

以3-苄氧基哌啶-2,6-二酮衍生物20为起始原料,分别合成了两类新的合成砌块(8R,8aS)-及(8R,8aR)-8-羟基-5-吲哚里西啶酮19a/19b和15a/15b.19a/19b的合成是基于反式非对映立体选择性还原烷基化反应(dr=93:7),接着经4步转化而成;而化合物15a/15b的制备则以双烯29的RCM反应为关键步骤,再经顺式立体选择性催化氢化(dr=91:9)反应完成.此外,还原化合物15a得到了(8R,8aR)-8-羟基-5-吲哚里西啶18.     

(Coixan polysaccharide)-graft-polyethylenimine folate for tumor-targeted gene delivery

CP-PEI-FA was prepared as an effective vector for in vitro and in vivo tumor-targeted gene delivery. The structures of the polymers were characterized, and their DNA condensation capability, particle sizes, zeta potentials, cytotoxicity and in vitro/in vivo transfection were examined. The cytotoxicity of CP-PEI-FA was significantly lower than that of PEI 25 kDa and close to that of PEI 1200. The in vitro transfection of CP-PEI-FA was tested in C6 and HeLa cells (FR-positive cells) and A549 cells (FR-negative cells). CP-PEI-FA showed a high targeting specificity and good gene transfection efficiency in FR-positive cells. These results indicate that CP-PEI-FA is a safe and effective polyplex-forming agent for both in vitro and in vivo transfection of plasmid DNA.     

Metal–organic frameworks of zeolitic imidazolate framework-7 and zeolitic imidazolate framework-60 for fast mercury and methylmercury speciation analysis

A fluorescence sensing platform based on metal–organic frameworks (MOFs) nanoparticles (NPs) of both zeolitic imidazolate framework-7 (ZIF-7) and zeolitic imidazolate framework-60 (ZIF-60) was developed for speciation analysis of inorganic Hg [Hg(II)] and methylmercury (MeHg⁺). Microwave-ultrasound assisted synthesis was employed for the preparation of ZIF-7 and ZIF-60 NPs, with short reaction time, easy procedure, and small particle size obtained. Based on strict cavity confinement of the ZIF-7 and ZIF-60 structures, the proposed method exhibited excellent selectivity for both Hg(II) and MeHg⁺, even in the presence of the other Hg species or various cations or anions with the concentration of 50 times high. Effect of pH and ionic strength on sensing behaviour of the ZIF MOF was studied as well. The calculated detection limit is 3 ng mL⁻¹ and 6 ng mL⁻¹ for Hg(II) and MeHg⁺, respectively. Furthermore, the application of the developed method to the analysis of local drinking water was demonstrated to be feasible, and the obtained recovery was 102% and 96.2% for Hg(II) and MeHg⁺, respectively.     

Highly thermal stable transparent conducting SnO2:Sb epitaxial films prepared on α-Al2O3 (0 0 0 1) by MOCVD

Antimony-doped tin oxide (SnO₂:Sb) single crystalline films have been prepared on α-Al₂O₃ (0 0 0 1) substrates by metal organic chemical vapor deposition (MOCVD). The antimony doping was varied from 2% to 7% (atomic ratio). Post-deposition annealing of the SnO₂:Sb films was carried out at 700-1100 °C for 30 min in atmosphere ambient. The effect of annealing on the structural, electrical and optical properties of the films was investigated in detail. All the SnO₂:Sb films had good thermal stability under 900 °C, and the 5% Sb-doped SnO₂ film exhibited the best opto-electrical properties. Annealed above 900 °C, the 7% Sb-doped SnO₂ film still kept high thermal stability and showed good electrical and optical properties even at 1100 °C.     

Subunit Characteristics of Pig Pancreas Ferritin Revealed by MALDI-TOF MS and RP-HPLC

Pig pancreas ferritin（PPF） was purified by ultra-centrifugation, ion-exchange chromatography, and native gradient polyacrylamide gel electrophoresis（PAGENG）. Sodium dodecyl sulfate（SDS）-PAGE indicates that PPF consists of two subunit types, namely, H（21000） and L（19000） subunits, and its core shows an average element composition of 1698 Fe3＋ and 179 phosphate molecules within the hollow shell, giving a 9.5：1 ratio of Fe3＋ to phosphate. An off line approach combining reversed-phase high-performance liquid chromatography（RP-HPLC） with matrix-assisted laser desorption ionization time of flight mass spectrometry（MALDI-TOF MS） made the decomposition of PPF shell into H and L subunits for the analysis of mass spectrometry（MS）, giving molecular weights of both H（21014.4） and L（18319.9） subunits. Both subunit types were further identified by an approach combining peptide mass fingerprint（PMF） with database search. A ratio of 1H to 2L subunits in PPF was determined by SDS-PAGE, RP-HPLC, and MALDI-TOF MS, respectively. It is well known that the non-covalent interaction of L-L or H-L subunits is stronger than that of H-H subunits in PPF, which may be further used to explain the unclear physiological function between H and L subunits in PPF.