猴金属硫蛋白突变体(N4C, T27C, N4C/T27C)的构建、表达与结构性质研究

在哺乳动物金属硫蛋白的61或62个氨基酸残基中,有20个十分保守的Acysteines,它们通常结合7个二介后过渡金属离了如ZN2+和Cd2+[1,2]等,并形成两个结构域[3],在N-端B-donain[M(I)3-Cys9]的中,3个二价后过渡金属离子均以两上端基巯基和两个桥基巯的相同方式与肽链上的半胱氨酸配位,而在C-端的a-domain[M(I)-Cys11]配位方式分为两类;两上二价后过渡金属离子分别与3个桥基巯基和1个端基配位,另两个二价后过渡金属的配位方式与中的相似,金属硫蛋白在一级序列上最显著的特征是存在多个片段,其中X是非半胱氨酸氨基酸残基[1,7].     

杂多化合物催化性能的研究——第四周期过渡金属钼磷三元杂多化合物的合成及表征

本文用改进的方法成功地合成了以第四周期二价过渡金属离子取代12-钼磷杂多酸中的一个钼,并保持Keggin结构的五个新化合物:Na_5[PZ(H_2O)Mo_(11)O_(39)·5H_2O,其中Z分别为Mn、Co、Ni、Cu、Zn,并利用红外光谱及热分析等手段对合成产物的结构及热稳定性作了系统的研究,结果表明,合成产物与12-钼磷杂多化合物具有类似的结构,但合成产物的热稳定性明显低于12-钼磷杂多化合物。     

二价金属离子激活铜超氧化物歧化酶断裂DNA的活性

以铜超氧化物歧化酶(CunSOD, n＝1—4)作为野生型CuZnSOD突变体的一种模型, 研究了其在二价金属离子(Mg2+, Mn2+)存在下由非氧化途径断裂DNA的活性, 并与CuZnSOD和脱辅基SOD(apoSOD)进行了比较. 结果表明, 在Mg2+或Mn2+存在下, CunSOD断裂DNA的活性高于CuZnSOD和apoSOD, 并且DNA的断裂活性受二价金属离子浓度、pH及酶浓度等因素影响. 相对活性及动力学参数的测定结果表明, CunSOD断裂DNA的相对能力按Cu1SOD2SOD≈Cu4SOD3SOD的顺序变化.     

手性三菲咯啉合镍与DNA的立体选择性研究

有关 DNA与金属配合物反应机理和作用模式的探讨是生物无机化学研究的重要内容之一 .目前的研究 [1～ 4] 表明 ,有大共轭配体配位的八面体金属配合物以静电作用或插入方式与DNA结合 .外消旋 [Ni( phen) 3]2 +及其旋光异构体与 DNA作用机理的研究曾有报道 [4] .但用电化学方法研究其旋光异构体与 DNA作用则未见详细报道 .本文用电化学方法和 CD谱研究了 Δ- ,∧ - [Ni( phen) 3]2 +配合物与 DNA的作用 .两种方法所得结果均表明 Δ- ,∧ - [Ni( phen) 3]2 +与 DNA作用时 ,Δ构型配合物的插入作用比∧构型配合物的强 .该法与平衡透析…     

Mn^3＋引发淀粉与丙烯腈接枝共聚物的研究

用过渡金属离子或其配合物引发淀粉的接枝共聚是一个饶有兴趣的课题。Ce~(4 )离子引发淀粉与烯类单体的接枝共聚已有广泛报道。Mehrotra等用稳定的[Mn(H_2P_2O_7)_3]~(3-)引发淀粉与烯类单体的接枝共聚取得了满意的结果。本文报道用电镜,x-射线衍射和热重分析等方法对这一接枝共聚物的形态、结构和热稳定性的研究结果。     

杯芳烃酰胺类衍生物对金属离子的萃取性能

以吗啉和六氢吡啶修饰的四种对叔丁基杯[n]芳烃酰胺类衍生物(n=6,8)为萃取试剂,研究了它们对Na+,K+及部分过渡金属等十种金属离子的萃取作用.结果表明此类杯芳烃酰胺类衍生物对过渡金属离子有良好的选择性识别作用.其中,吗啉取代基修饰的杯[8]芳烃萃取效果最好.     

d(GGTATACC)2与乙二胺四乙酸在溶液中的相互作用

空气的尘埃中含有一种核苷酸降解酶,这种酶很容易被溶液中痕量的Mg2+等金属离子激活,从而使溶液中的DNA或RNA解链或失活.因而用NMR方法研究核酸的溶液结构时,需要在磷酸缓冲溶液中加入乙二胺四乙酸(EDTA)或其钠盐,保持其浓度大于0.1mmol/L[1～3],利用EDTA与包括Mg2+在内的众多金属离子的强络合作用,解除Mg2+等金属离子对核苷酸降解酶的激活功能,达到保护核酸活性的目的.     

磷酸二甲酯阴离子(DMP~-)与一价、二价金属离子 相互作用的理论研究

在B3LYP、HF和MP2水平上运用全电子从头算(AE)和相对论有效实势(RECP)及6-311+G**和LanL2DZ基组计算Ⅰa、Ⅰb、Ⅱa和Ⅱb族金属离子与磷酸二甲酯阴离子(DMP-)的相互作用。 RECP用于除Li+、Be2+外所有的金属离子。 对Na+、K+、Cu+、Mg2+、Ca2+、Zn2+用AE和RECP 2种方法处理。 结果表明:RECP能可靠地用于重金属离子络合物; 二价金属离子络合物(DMP-—M2+)比一价金属离子络合物 (DMP-—M+)稳定;二价金属离子(M2+)可能比一价金属离子(M+)更易使多核苷酸折叠。     

多硫二硫醇烯配合物[Ni(C5S9)2]电磁学性能的研究

多硫 1 ,2 二硫醇烯能与过渡金属离子形成具有特殊平面共轭结构的稳定配合物 ,是构成有机导体或超导体的基本“砖块”[1,2 ] 。配合物的晶体结构研究表明 ,分子之间通过Ｓ…Ｓ原子ｐ轨道的重叠而存在的超分子相互作用是配合物具有高导电性的一个重要特征[3 ] 。增加分子间超分子相互作用的一个有效方法是增加配体上硫原子的个数。我们以Ｃ6Ｓ10 (图 1 )为中间体得到Ｃ5Ｓ2 -9(图2 ) ,与Ｎｉ2 + 离子配位后在四种不同阳离子作用下生成 (Ｃａｔ)2 [Ｎｉ(Ｃ5Ｓ9)2 ]型二价阴离子配合物。当这些配合物用Ｉ2 氧化时都生成了中性配位化合物 [Ｎｉ…     

钌(Ⅱ)多吡啶配合物与DNA相互作用的光切割与荧光性质研究

利用琼脂糖凝胶电泳法研究了钌(Ⅱ)多吡啶配位物[Ru(bpy)2(ODCIP)]2+(bpy:2,2'-联吡啶,ODCIP:含多个配位中心的多吡啶配体,3,4-二氯基-咪唑并[4,5-f][1,10]邻菲咯啉)对pBR322质粒DNA的光切割作用及其可能机理,并运用紫外可见吸收光谱、荧光光谱和琼脂糖凝胶电泳法研究了[Ru(bpy)2(ODCIP)]2+与Zn2+配位后与DNA的光谱性质和光切割作用.结果表明[Ru(bpy)2(ODCIP)]2+对DNA有较好的光切割作用,其机理可能是产生了超氧阴离子自由基和单线态氧.[Ru(bpy)2(ODCIP)]2+与Zn2+配位可能形成的双核配位物[Ru(bpy)2(ODCIP)Zn]4+与DNA也能进行插入结合,对DNA的光切割效果并没有明显增强。     

Effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water coordination on the structure of glycine and zwitterionic glycine

Interactions between metal ions and amino acids are common both in solution and in the gas phase. Here, the effect of metal ions and water on the structure of glycine is examined. The effect of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) and water on structures of Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (m = 0, 2, 5) complexes have been determined theoretically by employing the hybrid B3LYP exchange-correlation functional and using extended basis sets. Selected calculations were carried out also by means of CBS-QB3 model chemistry. The interaction enthalpies, entropies, and Gibbs energies of eight complexes Gly.Mn+ (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) were determined at the B3LYP density functional level of theory. The computed Gibbs energies DeltaG degrees are negative and span a rather broad energy interval (from -90 to -1100 kJ mol(-1)), meaning that the ions studied form strong complexes. The largest interaction Gibbs energy (-1076 kJ mol(-1)) was computed for the NiGly2+ complex. Calculations of the molecular structure and relative stability of the Gly.Mn+(H2O)m and GlyZwitt.Mn+(H2O)m (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+; m = 0, 2, and 5) systems indicate that in the complexes with monovalent metal cations the most stable species are the NO coordinated metal cations in non-zwitterionic glycine. Divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ prefer coordination via the OO bifurcated bonds of the zwitterionic glycine. Stepwise addition of two and five water molecules leads to considerable changes in the relative stability of the hydrated species. Addition of two water molecules at the metal ion in both Gly.Mn+ and GlyZwitt.Mn+ complexes reduces the relative stability of metallic complexes of glycine. For Mn+ = Li+ or Na+, the addition of five water molecules does not change the relative order of stability. In the Gly.K+ complex, the solvation shell of water molecules around K+ ion has, because of the larger size of the potassium cation, a different structure with a reduced number of hydrogen-bonded contacts. This results in a net preference (by 10.3 kJ mol(-1)) of the GlyZwitt.K+H2O5 system. Addition of five water molecules to the glycine complexes containing divalent cations Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+ results in a net preference for non-zwitterionic glycine species. The computed relative Gibbs energies are quite high (-10 to -38 kJ mol(-1)), and the NO coordination is preferred in the Gly.Mn+(H2O)5 (Mn+ = Mg2+, Ca2+, Ni2+, Cu2+, and Zn2+) complexes over the OO coordination.     

Speciation of cyclo(Pro-Gly)<Subscript>3</Subscript> and its divalent metal-ion complexes by electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to study the binding of selected group II and divalent transition-metal ions by cyclo(Pro-Gly)3 (CPG3), a model ion carrier peptide. Metal salts (CatXn) were combined with the peptide (M) at a molar ratio of 1:10 M/Cat in aqueous solvents containing 50% vol/vol acetonitrile or methanol and 1 or 10 mM ammonium acetate (NH4Ac). Species detected include [M+H]+, [M+Cat-H]+, [M2+Cat]2+, [M+Cat+Ac]+, and [M+Cat+X]+. The relative stabilities of complexes formed with different cations (Mg2+, Ca2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) were determined from the abundance of 1:1 and 2:1 M/Cat species relative to that of the unbound peptide. The largest metal ions (Ca2+, Sr2+, and Mn2+) formed the most stable complexes. Reducing the buffer concentration increased the overall extent of metal binding. Results show that the binding specificity of CPG3 depends upon the size of the metal ion and its propensity for electrostatic interaction with oxygen atoms. Product ion tandem mass spectrometry of [M+H]+ and [M+Cu-H]+ confirmed the cyclic structure of the peptide, although the initial site(s) of metal attachment could not be determined.     

Construction and control of plasmid DNA network

The influences of different cations on plasmid DNA network structures on a mica substrate were investigated by atomic force microscopy (AFM). Interactions between the DNA strands and mica substrate, and between the DNA strands themselves were more strongly influenced by the complex cations (Fe(phen)3(2+), Ni(phen)3(2+), and Co(phen)3(3+)) than by the simple cations (Mg2+, Mn2+, Ni2+, Ca2+, Co3+). The mesh height of the plasmid DNA network was higher when the complex cations were added to DNA samples. The mesh size decreased with increasing DNA concentration and increased with decreasing DNA concentration in the same cation solution sample. Hence, plasmid DNA network height can be controlled by selecting different cations, and the mesh size can be controlled by adjusting plasmid DNA concentration.     

Ionization and collision-induced fragmentation of N-linked and related carbohydrates using divalent cations

Maltoheptaose and several N-linked glycans were ionized by electrospray as adducts with the divalent cations Mg2+, Ca2+, Mn2+, Co2+ and Cu2+. [M + metal]2+ ions were the major species in all cases with calcium giving the highest sensitivity. In addition, copper gave [M + Cu]+ ions. Other cations gave singly charged ions only by elimination of a protonated monosaccharide. Fragmentation of the [M + metal]2+ ions produced both singly and doubly charged ions with the relative abundance of doubly charged ions decreasing in the order Ca > Mg > Mn > Co > Cu. Singly charged ions were formed by elimination of a protonated monosaccharide residue followed, either by successive monosaccharide residue losses, or by a 2,4A cross-ring cleavage of the reducing-terminal monosaccharide. Formation of doubly charged fragments from [M + metal]2+ ions involved successive monosaccharide-residue losses either with or without O,2A or 2,4A cross-ring cleavages of the reducing-terminal monosaccharide. Abundant diagnostic doubly charged ions formed by loss of the 3-antenna from the O,2A cross-ring product were specific to [M + Ca]2+ ions. Fragmentation of [M + Cu]+ ions was similar to that of the corresponding [M + H]+ ions in that most cross-ring fragments were absent.     

二价金属离子对平阳霉素与DNA作用的影响

二价金属离子对平阳霉素与ＤＮＡ作用的影响王自春，黄登宇，袁静明（山西大学分子科学研究所，太原，０３０００６）关键词二价金属离子，平阳霉素，ＤＮＡ平阳霉素（简称ＢＬＭ－Ａ５）是抗肿瘤抗生素博莱霉素的成分之一，其化学结构、理化性质和药理作用虽基本相同［１...     

Kinetic and mechanistic analysis of nonenzymatic, template-directed oligoribonucleotide ligation

The role of divalent cations in the mechanism of pyrophosphate-activated, template-directed oligoribonucleotide ligation has been investigated. The dependence of the reaction rate on Mg2+ concentration suggests a kinetic scheme in which a Mg2+ ion must bind before ligation can proceed. Mn2+, Ca2+, Sr2+, and Ba2+ can also catalyze the reaction. Although Pb2+ and Zn2+ do not catalyze the reaction in the absence of other divalent ions, they significantly modulate the reaction rate when added in the presence of Mg2+, with Pb2+ stimulating the reaction (up to 65-fold) and Zn2+ inhibiting the reaction. The logarithm of the ligation rate increases linearly, with slope of 0.95, as a function of pH, indicating that the reaction involves a single critical deprotonation step. The ligation rates observed with the different divalent metal ion catalysts (Mn2+ > Mg2+ > Ca2+ > Sr2+ = Ba2+) vary inversely with the pKa values of their bound water molecules. The pH profile and these relative ligation rates suggest a mechanism in which a metal-bound hydroxide ion located near the ligation junction promotes catalysis, most likely by deprotonation of the hydroxl nucleophile. The effects of changing either the leaving group or the attacking hydroxyl, together with the large delta S(++) value for oligonucleotide ligation (about -20 eu), are consistent with an associative transition state.     

Simultaneous separation of nine metal ions and ammonium with nonaqueous capillary electrophoresis

A simple and fast method for simultaneous separation of nine metal cations Ni2+, Cu2+, Co2+, Zn2+ Cd2+, K+, Na+, Mg2+ and Ca2+, and NH4+ in methanol is reported. The optimization for separation these 10 cations was achieved by using 0.5% acetic acid and 10 mM imidazole as electrolyte. The effects of water and ionic strength in the sample are discussed. The sensitive detection of transition metal ions was accomplished at 191 nm. The optimized method demonstrated high efficiency and good reproducibility, and was applied successfully to the qualitative and quantitative determination of transition metal ions in water samples, chemical reagents, oral zinc gluconate solution and human plasma.     

Tandem mass spectra of divalent metal ion adducts of glycosyl sulfides, sulfoxides and sulfones; distinction among stereoisomers

The tandem mass spectra of the divalent metal ion (Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Ni2+, Co2+ and Zn2+) adducts of acetylated 1,2-trans-glycosyl sulfides, sulfoxides and sulfones were examined using low energy collision-induced dissociation on a Quattro II quadrupole tandem mass spectrometer. Abundant doubly charged ions, such as [3M + Met]2+ and [2M + Met]2+, were observed with alkaline earth metal chlorides. The other ions observed were [M + MetCl]+, [M + MetOAc]+, [M + MetO2SPh]+ and [2M + MetCl]+. The deprotonated metal adducts [M + Met-H]+ were seen only in the sulfones. The divalent metal ion adducts showed characteristic fragmentation pathways for the glycosyl sulfides, sulfoxides and sulfones, depending on the site of metal attachment. The doubly charged metal ion adducts dissociate to two singly charged ions, [M + MetOAc]+ and [M - OAc]+, in the sulfides and sulfoxides. In the sulfones, the adducts dissociate to [M + MetO2SPh]+ and [M - O2SPh]+. In contrast to the alkaline earth metals, which attach to the acetoxy functions, the transition metals attach to the sulfide and sulfoxide functions. The metal chloride adducts display characteristic fragmentation for the sulfides, sulfoxides and sulfones. The glucosyl, mannosyl and galactosyl sulfides, sulfoxides and sulfones could be differentiated on the basis of the stereochemically controlled MS/MS fragmentations of the metal chloride adducts.     

DNA condensation and its thermal stability influenced by phospholipid bilayer and divalent cations

We studied the effect of divalent alkaline earth metal cations Ca2?, Mg2? and transition metals Co2?, Ni2?, Cu2? and Zn2? on DNA condensation and its protection against thermal denaturation in presence of dioleoylphosphatidylcholine liposomes (DOPC). Experimental results have shown that Ca2? and Mg2? as well as Zn2? mediate DNA condensation. Cu2? causes DNA double helix destabilization, and does not mediate binding between DNA and DOPC liposomes. Co2? and Ni2? can interact with DNA on both ways mentioned above. Static light scattering was use to follow the size of aggregates in DNA condensation process. Phospholipid bilayer and divalent cations protect condensed DNA against thermal destabilization. The highest stabilization effect was found in aggregates with Ca2? and Zn2?, whereas in presence of either Co2? or Ni2? some volume fraction of DNA is denatured.     

NMR, UV-vis and CD study on the interaction of pradimicin BMY-28864 with divalent cations of alkaline earth metal

In order to clarify the mechanism of the calcium-activated anti-fungal action of pradimicin derivatives, we investigated the compatibility of four divalent metal cations, Ca2+, Mg2+, Sr2+ and Ba2+, when combined with pradimicin BMY-28864 in an aqueous solution. The 1H NMR studies suggest that all the tested cations can induce a chemical exchange between two types of aggregation of BMY-28864 in an aqueous solution. The exchange rate, however, varies according to the cation species. In descending order they are: Ba2+ > Sr2+ > Ca2+ > Mg2+. The differences in the binding ability of BMY-28864 to the cations and the solubility of the chloride salts are explained by the electronegativity of these cations. The UV-Vis and CD spectra of these solutions show isosbestic points that correspond to an exchange process in the cations' binding to BMY-28864. The results provide experimental support for the hypothesis that there is a common mechanism underlying their cations interactions with the antibiotic. The CD study also provided evidence about the stoichiometric relation of the divalent metal ions to the antibiotic, 1:2, which was obtained by NMR analyses.