金属硫蛋白加质子常数及与Cd(II)络合常数测定

用pH计和Cd离子选择电极测定了金属硫蛋白的加质子常数及其与Cd(Ⅱ)的络合常数, 用改进的简化络合模型处理实验结果, 得到了去金属硫蛋白(apo MT)中6类不同的加质子基团的数目及其加质子常数。对Cd(Ⅱ)滴定数据的计算表明, MT中两个结构域——α和β对Cd(Ⅱ)的络合常数相差约1000倍。从热力学定量描述了MT中两个结构域结合金属离子选择优先顺序。     

金属硫蛋白加质子常数及与C_d(Ⅱ)络合常数测定

用pH计和Cd离子选择电极测定了金属硫蛋白的加质子常数及其与Cd(Ⅱ)的络合常数,用改进的简化络合模型处理实验结果,得到了去金属硫蛋白(apo MT)中6类不同的加质子基团的数目及其加质子常数。对Cd(Ⅱ)滴定数据的计算表明,MT中两个结构域——α和β对Cd(Ⅱ)的络合常数相差约1000倍。从热力学定量描述了MT中两个结构域结合金属离子选择优先顺序。     

Zn_(0.15)Cd_(0.85)S量子点复合材料的合成及其对Cu~(2+)的超灵敏测定

合成了高质量的半胱氨酸修饰Zn0.15Cd0.85S量子点复合材料.利用Cu2+对量子点荧光的猝灭作用,实现了Cu2+的定量检测.所合成的Zn0.15Cd0.85S量子点对其他常见的金属离子几乎没有响应,表明该方法具有较好的选择性.在优化条件下,Zn0.15Cd0.85S量子点荧光的猝灭程度与Cu2+浓度呈良好的线性关系,线性范围为6.0nM～1.0μM,检出限为1.0nM.对0.5μM标准溶液平行测定11次,相对标准偏差为2.0%.利用标准加入法对水样中Cu2+含量进行了测定,结果令人满意.     

工程化蛋白质纳米孔实时监测镉离子与谷胱甘肽的单分子反应

本研究利用合成的全-6-季铵基-β-环糊精(Per-6-quaternary ammonium-β-cyclodextrin,p-QABCD)装备基因工程化的α-溶血素(α-Hemolysin,αHL)蛋白质纳米孔(M113R)7,构建全新的单分子纳米孔反应器,在单分子水平实现对谷胱甘肽(GSH)和镉离子(Cd2+)的络合反应的实时原位监测,并辨认络合反应的不同路径、反应中间产物和最终产物.结果表明,溶液的pH值显著影响GSH与Cd2+络合产物的络合比例.pH=7.4时,GSH与Cd2+络合反应的最终产物为Cd(GSH)2;pH=9.0时,最终产物为Cd(GSH)2和Cd2(GSH)2.其中,Cd2(GSH)2的形成遵循两种路径:(1)一个Cd2+首先结合两个GSH分子的巯基形成Cd(GSH)2,然后,第二个Cd2+结合去质子化的氨基形成Cd2(GSH)2;(2)两个Cd2+分别结合同一个GSH分子的巯基和去质子化的氨基形成Cd2(GSH)1,然后,第二个GSH分子的巯基和去质子化的氨基结合Cd2(GSH)1的Cd2+形成Cd2(GSH)2.本研究实现了在单分子水平无标记和无化学修饰研究金属离子和生物小分子的反应,对理解细胞内重金属的解毒机理和拓展纳米孔单分子技术的研究领域具有重要意义.     

基于N-(9-蒽甲基)-L-组氨酸的NOR荧光逻辑门

合成了一个新的组氨酸衍生物, N-(9-蒽甲基)-L-组氨酸(1), 并对其进行了元素分析、电喷雾电离质谱(ESI-MS)、核磁共振氢谱(1H-NMR)和碳谱(13C-NMR)等波谱表征. 考查了pH值及15种不同金属离子对其荧光强度的影响. 实验结果表明, 中性水溶液条件下, Zn2+和Cd2+能使体系荧光增强, 而Pb2+、Co2+、Hg2+、Ni2+和Cu2+等则使体系荧光有不同程度的猝灭.其中, Cu2+和Ni2+猝灭能力最强, 它们与化合物1均形成了物质的量比为1:2的配合物, 络合常数分别为2.88×10⁶和1.12×10⁶ L2·mol-2. Cu2+和Ni2+对化合物1的荧光猝灭为静态猝灭过程. 在此基础上, 以Cu2+和Ni2+作为两个输入信号, 以蒽的特征荧光发射作为输出信号, 构建了一个NOR荧光分子逻辑门.     

Effect of noncovalent complexations on coordination interactions in a tricomponent system ofβ-cyclodextrin,copper chloride and hexamethylene tetramine

This study reveals that the noncovalent complexation betweenβ-CD and Cu（HMTA）²⁺ makes a positive contribution to the coordination interaction between Cu²⁺ and HMTA in a tricomponent system.Besides,mono- and binuclear complexes:[β-CDCu]⁺ and[Cu·β-CDCu]⁺ were observed under the condition of ESI-MS.     

N-芳基香豆素甲基酮缩氨基硫脲对Cu2+的选择性比色识别

设计合成了2种新型N-芳基香豆素甲基酮缩氨基硫脲受体分子S1和S2, 利用紫外-可见(UV-Vis)吸收光谱考察了其对Fe3+, Hg2+, Ag+, Ca2+, Cu2+, Zn2+, Pb2+, Cd2+, Ni2+, Cr3+和Mg2+等阳离子的识别作用. 结果表明, 当加入Cu2+时, 溶液颜色立刻由无色变为黄色, 而加入其它阳离子则无变化, 从而实现了对Cu2+的裸眼检测, 具有专一选择性比色识别效果. 通过计算可知, 受体分子S2对Cu2+的络合常数大于S1, 且主客体间形成1: 1的配合物. 受体分子S2对Cu2+的检出限为2.0×10-7 mol/L, 稳定常数Ks=1.02×105 L/mol. 另外, 在EDTA存在时, 配合物可以释放出Cu2+, 与EDTA结合, 表现出对Cu2+的"off-on"模式.     

高电压辅助激光解吸附离子化质谱中盐效应的研究

通过与电喷雾质谱( Electrospray ionization mass spectrometry, ESI-MS)对比的方式,对高电压辅助激光解吸附离子化质谱( High-voltage-assisted laser desorption ionization mass spectrometry,HALDI-MS)中的盐效应进行了研究。在正、负离子模式下,分别以L-酪氨酸、β-环糊精、α-硫辛酸以及α-硫辛酸-β-环糊精复合体系为例,对比分析了加盐前后所得的ESI-MS和HALDI-MS谱图,发现HALDI-MS比ESI-MS具有更高的盐容忍度。本实验还发现在HALDI-MS中加入适量盐会引起α-硫辛酸与β-环糊精络合离子信号增强的特殊现象,并提出了产生这种信号增强作用的原因是溶液中盐类阳离子与α-硫辛酸-β-环糊精复合体系形成了三元复合物。     

五肽Pro-Gly-His-Glu-Tyr的合成及与铜(Ⅱ)离子的作用

通过固相多肽合成法合成了一个新的五肽Pro-Gly-His-Glu-Tyr,电喷雾质谱法测得其分子量与理论值一致。利用荧光光谱法研究了该五肽与金属离子的相互作用。结果表明,Cu2+对该肽具有很强的荧光猝灭效应,而其他金属离子的荧光猝灭较弱。该肽对Cu2+的这种特异性作用是由其独特的氨基酸序列所决定的。荧光光谱研究表明,Cu2+对五肽的猝灭机理为静态猝灭,五肽与Cu2+形成复合物的结合常数Ka为5.54×104。     

A Copper（Ⅱ）-cadmium（Ⅱ） Heterometallic Hexanuclear Complex：[Cd_4Cu_2（pdc）_4（H_2O）_（14）]（H_3pdc=3,5-Pyrazoledicarboxylic Acid）

The title complex 1,[Cd 4 Cu 2 (pdc) 4 (H 2 O) 14 ] (H 3 pdc=3,5-pyrazoledicarboxylic acid),has been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex 1 crystallizes in triclinic,space group P1 with a=0.67235(10),b=1.27935(18),c=1.28569(17) nm,α=112.633(2),β=102.971(3),γ=97.089(2)o,V=0.9673(2) nm 3,C 20 H 32 Cd 4 Cu 2 N 8 O 30,M r=1441.22,D c=2.474 g/cm 3,μ(MoKα)=3.356 mm 1,F(000)=698,S=1.003,Z=1,the final R=0.0471 and wR=0.0748 for I > 2σ(Ⅰ).In 1,two deprotonated 3,5-pyrazoledicarboxylic acids (pdc 3),one copper(Ⅱ) ion and one cadmium(Ⅱ) ion firstly form a pyrazole-bridged Cu II Cd II dinuclear unit,two of which related by an inversion center are connected by another two cadmium(Ⅱ) ions through chelating carboxylate groups to construct the copper(Ⅱ)-cadmium(Ⅱ) heterometallic hexanuclear complexes.Plenty of hydrogen bond interactions existing in the system further lead to a three-dimensional (3D) supramolecular framework.     

Determination of the metal-binding cooperativity of wild-type and mutant calbindin D9K by electrospray ionization mass spectrometry

Since the initial reports showing the ability of electrospray ionization mass spectrometry (ESI-MS) to study intact noncovalent biomolecular complexes, an increasing number of uses for this technique in studying biochemical systems is emerging. We have investigated the ability of ESI-MS to characterize the metal-binding properties of calcium (Ca2+) binding proteins by studying the incorporation of Ca2+ and cadmium (Cd2+) into wild-type and mutant calbindin D9K. ESI-MS showed that wild-type calbindin D9K binds two Ca2+ ions with similar affinities while the binding of two Cd2+ ions is sequential, as is the binding of the two Ca2+ or Cd2+ ions to the N56A mutant of calbindin. The binding of Ca2+ to the wild-type protein was clearly seen to be cooperative. These results demonstrate the potential efficacy of ESI-MS to discriminate between cooperative and independent site metal binding to metalloproteins.     

8-氨基喹啉取代苯甲酰胺衍生物对汞离子和铜离子的识别

设计合成了可识别金属离子的荧光传感分子8-氨基喹啉取代苯甲酰胺衍生物,通过核磁共振谱和质谱表征其结构;利用其光谱性质研究了该系列物质对过渡金属离子Cu2+,Hg2+,Pb2+,Zn2+,Ni2+和Cd2+的识别性质,初步探讨了其识别机理。实验表明:在乙腈中,8-氨基喹啉苯甲酰胺的吸收光谱在509nm处对Cu2+有响应,溶液由无色变成红色;而其荧光光谱对Hg2+和Cu2+有良好的选择性,荧光增强倍率分别高达368和192,与金属离子形成结合比为1:1配合物。     

Competing binding of metal ions with protein studied by microdialysis

A method has been established to study the competing binding of metal ions with protein by a combined technique of microdialysis with high performance liquid chromatography (HPLC). Ni2+, Cd2+, Zn2+, Cu2+ and human serum albumin (HSA) were chosen as model metal ions and protein. The experimental results show that Ni2+ and Cu2+ share a common primary binding site on HSA, and Zn2+ and Cd2+ share a different common primary binding site from them, but there is a common multi-metal binding site for all of those four metal ions. This method show advantages of fast sampling, easily to be operated and especially to be useful when ideal spectroscopic probes are not available for the study of interaction between protein and metal ions.     

Determination of trace metal ions by AAS in natural water samples after preconcentration of pyrocatechol violet complexes on an activated carbon column

A simple preconcentration method is described for the determination of Cu, Mn, Co, Cd, Pb, Ni and Cr in water samples by flame AAS. Trace metal ions in water were sorbed as pyrocatechol violet complexes on activated carbon column at the pH range of 4–8, then eluted with 1 M HNO₃ in acetone. The effect of major cations and anions of the natural water samples on the sorption of metal ions has been also investigated. The concentration of the metal ions detected after preconcentration was in agreement with the added amount. The present method was found to be applicable to the preconcentration of Cu, Mn, Co, Cd, Pb, Ni and Cr in natural water samples with good results such as R.S.D. from 3 to 8% (N=10) and detection limits under 70 ng l⁻¹.     

Combined ion-mobility and mass-spectrometry investigations of metallothionein complexes using a tandem mass spectrometer with a segmented second quadrupole

Rabbit metallothionein (MT) 2A complexes with Cd(II), Zn(II), Ag(I), Cu(I), Hg(II), arsenite, monomethylarsonous acid (MMA), and dimethylarsinous acid (DMA) have been examined using ion-mobility measurements and mass spectrometry in a triple-quadrupole mass spectrometer equipped with a segmented second quadrupole that doubled as an ion-mobility cell [Guo, Y.; Wang, J.; Javahery, G.; Thomson, B. A.; Siu, K. W. M. An Ion-Mobility Spectrometer with Radial Collisional Focusing. Anal. Chem.2005, 77, 266-275]. The metal ions confer conformational rigidity on the MT complexes, which counteracts Coulombic repulsion among protons added as a result of electrospray. Triply and quadruply protonated Cd(7)MT2A have smaller cross-sections than the Cd(7)MT2A structure deduced from published NMR data. For the 6+ ions, the As(6)MT2A complex has a cross-section of 790 A(2); the MMA(10)MT2A complex, 920 A(2); and the DMA(20)MT2A complex, 1220 A(2). This increase in cross-section of the As(III) species, from As(3+) to MMA to DMA, is interpreted as a consequence of decreasing multiple coordination and increasing number of methyl groups.     

纤维素纤维接枝β-环糊精的合成及其富集金属离子研究

以环氧氯丙烷作为化学修饰剂 ,在碱性介质中将 β 环糊精接枝到粘胶纤维上 ,合成了接枝 β 环糊精的功能性纤维素纤维 ,接枝 β 环糊精纤维素纤维上 β 环糊精的含量为 7 8%。研究了接枝 β 环糊精的纤维素纤维对模拟水样中无机重金属离子的富集性能 ,考察了温度、浓度、pH值对富集性能的影响 .实验结果表明 ,接枝 β 环糊精的纤维素纤维对无机重金属离子 (Cu2 + 、Pb2 + + 、Cd2 + )富集效果良好 ,其富集容量分别达到 0 2 5mmol g、0 30mmol g、0 34mmol g ,Cu2 + 、Pb2 + 、Cd2 + 与 β 环糊精富集摩尔比分别为 2 9∶1、3 9∶1、4 3∶1。     

Mass spectrometric analysis of the interactions between CP12, a chloroplast protein, and metal ions: a possible regulatory role within a PRK/GAPDH/CP12 complex

The small chloroplast protein CP12 plays the role of a protein linker in the assembly process of a PRK/GAPDH/CP12 complex that is involved in CO2 assimilation in photosynthetic organisms. The redox state of CP12 regulates its role as a protein linker. Only the oxidized protein, with two disulfide bonds, is active in complex formation. Several observations indicating that CP12 might bind a metal ion led us to screen the binding of different metal ions on oxidized or reduced CP12 using non-covalent electrospray ionization mass spectrometry (ESI-MS) experiments. The oxidized protein bound specifically Cu2+ and Ni2+ (Kd of 26+/-1 microM and 11+/-1 microM, respectively); other cations such as Fe2+ and Zn2+ did not bind, while cations such as Cd2+ formed non-specific adducts to CP12. Similar results were obtained for metal ions on screening with the reduced CP12. Interestingly, the present results suggest that Cu2+ catalyzes the re-formation of the disulfide bonds of the reduced CP12, leading to recovery of the fully oxidized CP12 that is then able to bind a Cu2+ ion. Finally the high similarity between CP12 and copper chaperones from Arabidopsis thaliana, as judged by hydrophobic cluster analysis, provides additional evidence for the relevance of metal binding for the in vivo situation. The findings that CP12 is able to bind a metal ion, and that Cu2+ catalyzes the oxidation of the thiol groups of CP12, are new characteristics of this protein that may prove to be important in the regulation of the assembly process of the PRK/GAPDH/CP12 complex.     

石英与水溶液作用的界面反应特征

矿物表面因存在有各种悬空键 ,而形成了表面活性官能团 ,称作“表面位”。对石英来说 ,表面氧离子可以与水中Ｈ+和ＯＨ- 离子反应 ,使表面产生荷电性。研究表明[1 ,2 ] ,石英对二价金属离子的吸附反应遵循Ｆｒｅｕｄｌｉｃｈ方程 ,本文在分析石英表面位及其质子化反应、表面位与重金属离子反应的基础上 ,进一步探讨石英与水溶液作用的界面反应特征及其影响因素。1　实验材料与方法石英粉末样品用王水煮洗 ,后用纯净水浸洗至无ＡｇＣｌ,过滤、1 1 0℃烘干、450℃煅烧 1 2ｈ。经ＮＯＶＡ 1 0 0 0ＶＥＲ3.7自动表面分析仪 (Ｎ2 ＢＥＴ法 )测定…     

Analysis of the metal-binding selectivity of the metallochaperone CopZ from Enterococcus hirae by electrospray ionization mass spectrometry

Metallochaperones are soluble proteins involved in metal transport and regulation in vivo. Copper metallochaperones belong to a structural family of metal binding domains displaying a ferredoxin-like fold (betaalphabetabetaalphabeta) and a consensus metal-binding motif MXCXXC. The metal-binding selectivities for this class of proteins are poorly documented so far. The present study focuses on the measurement of the selectivity of the copper metallochaperone CopZ from Enterococcus hirae for different metal ions using an experimental approach based on electrospray ionization mass spectrometry (ESI-MS). All the metal cations tested, i.e. Cu(I), Cu(II), Hg(II), Cd(II) and Co(II), form specific metal complexes with CopZ. The study of a chemically modified CopZ as well as variants of CopZ in the active site demonstrated that the complexes observed by ESI-MS, i.e. in the gas phase, corresponded to the complexes previously observed by other analytical methods in solution. Competition experiments allowed the classification of the metal ions by increasing affinities for CopZ as follows: Co < Cd < Hg < Cu. A dissociation constant in the range of 20 microM was determined for cobalt. The affinity of CopZ for the other metals tested was found to be higher, with dissociation constants smaller than micromolar.