异代酯基枝状分子表面组装及结构转化机理的STM研究

利用扫描隧道显微技术(STM)研究了3种异代酯基Janus枝状分子(G₁G₂COOCH₃, G₀G₃COOCH₃, G₁G₃COOCH₃)在高定向裂解石墨(HOPG)表面的组装结构. 室温下, G₁G₂COOCH₃, G₀G₃COOCH₃和G₁G₃COOCH₃分别在表面形成有序、局部有序及无序结构. 将样品加热至60~80 ℃后, 表面无序结构可以转化为有序的二聚体密堆积结构. 实验结果表明, 随着枝状分子代数的增加, 分子之间及分子与基底之间作用力增强, 室温下分子组装行为更依赖于分子吸附动力学过程, 组装结构趋于无序化, 而加热可以增强枝状分子在表面的活动性, 调整分子的位置关系, 使表面无序结构转化为热力学稳定的有序二聚体密堆积组装结构.     

用二维核磁共振研究[Co(phen)2(HNAIP)]Cl3配合物与错配及正常寡聚核苷酸的作用

为了开发能识别正常与错配核酸的探针, 首次合成了[Co(phen)₂(HNAIP)]Cl₃金属配合物, 并利用二维核磁研究了此配合物与错配d(CCGAATGAGG)₂及正常d(CCTAATTAGG)₂寡聚核苷酸的相互作用, 首次发现, [Co(phen)₂(HNAIP)]Cl₃是从“大沟”插入到错配碱基对G₃A₄和G₇A₈之间, 能够很好地识别G:A错配; 而[Co(phen)₂(HNAIP)]Cl₃与正常的寡聚核苷酸的作用, 则是从小沟插入, 即[Co(phen)₂(HNAIP)]Cl₃与错配和正常寡聚核苷酸在不同位置及不同沟槽存在明显的插入式结合、并且有明显的差异, 这就有可能被用来作为识别正常与错配寡聚核苷酸的探针.     

过氧氨三乙酸钛配合物分子前体热分解制备纯钛基复氧化物

在pH=2.5～4.0的条件下,以四氯化钛、过氧化氢和氨三乙酸为原料反应得到四种过氧酸钛配合物(NH₄)₄[Ti₂O～(O₂)2(ta)₂]·4H₂O (1), K₄[Ti₂O(O₂)₂(ta)₂]·6H₂O (2), Sr₂[Ti₂O(O₂)₂(ta)₂]·10H₂O (3)和Ba₂[Ti₂O(O₂)₂(ta)₂]·10H₂O (4) (H3ta=C₆H₆O₆N).配合物的EA, UV-vis, IR和X射线单晶分析表明它们含有相同的双核过氧氨三乙酸钛的阴离子结构,钛原子与过氧基团、四齿氨三乙酸和桥氧七配位.3和4中的阳离子锶和钡分别与周围的水分子和羧基氧形成九配位和十配位.配合物1, 3和4在空气中600℃分解,XRD分析表明分别得到金红石型TiO₂, SrTiO₃和四方BaTiO₃纯相.     

NiO@SnO2@Zn2TiO4@TiO2同轴四层纳米电缆的制备、表征及形成机理研究

采用静电纺丝技术, 通过改进实验装置, 在最佳的纺丝条件下制备了[Ni(CH₃COO)₂＋PVP]@[SnCl₄＋PVP]@[Zn(CH₃COO)₂＋PVP]@[Ti(OC₄H₉)₄＋CH₃COOH＋PVP]前驱体复合电缆, 将其进行热处理, 制备出NiO@ SnO₂@Zn₂TiO₄@TiO₂同轴四层纳米电缆. 采用热重-差热(TG-DTA)、X射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析技术对样品进行了表征. 结果表明, 所得产物为同轴四层纳米电缆, 芯层为NiO, 直径为35～55 nm|第二层为SnO₂, 厚度为30～50 nm|第三层为Zn₂TiO₄, 厚度为25～40 nm|壳层为TiO₂, 厚度为40～90 nm. 对同轴四层纳米电缆的形成机理进行了探讨.     

氰基桥联铁钴链状配合物的结构与磁性

利用三氰基构筑单元(Bu₄N)[Fe(PzTp)(CN)₃](PzTp=tetrakis(pyrazolyl)borate)和(E)-1-苯乙烯基-1H-咪唑(Bzi),合成了2例氰基桥联的铁钴链状配位聚合物。单晶X射线衍射表明,配合物[Fe(PzTp)(CN)₃]₂[Co(Bzi)₄]₂(ClO₄)₂·H₂O (1)为方波形单链结构,而配合物[Fe(PzTp)(CN)₃]₂[Co(Bzi)₂]·CH₃OH (2)则形成含有甲醇溶剂分子的双“之”字形双链结构。磁学研究显示,配合物1在360 K左右显示出热诱导的自旋转变,而配合物2在大约200 K显示出溶剂诱导的两步自旋转变。变温红外光谱证实了热诱导的金属间电荷转移行为。此外,光磁实验显示,当用808和532 nm的光交替照射时,1显示出可逆的光诱导电荷转...     

两个多钒盖帽的Keggin型多铌钒酸盐衍生物的水热合成与表征

通过水热方法合成了2个由多铌酸盐和过渡金属配合物形成的有机-无机杂化配合物[Cu(TETA)]₄[VNb₁₂(VO)₄O₄₀][OH]·10H₂O(1)和[Cu(TETA)]₄[VNb₁₂(VO)₆O₄₀][OH]₅·5H₂O(2)(TETA=三亚乙基四胺). 化合物1和2的多阴离子分别是由4个{VO₅}帽和6个{VO₅}帽加盖在Keggin型多铌酸盐的方形缺口上形成的, 它们通过多酸阴离子中Nb-O_t (O_t =端氧)与[Cu(TETA)]²⁺配合物的金属中心配位构筑形成三维结构. 价键计算结果表明, Keggin中心的钒为+5价, 帽位的钒为+4价, X射线光电子能谱分析(XPS)结果也证实了这一结论. 通过单晶X射线衍射分析、红外光谱(IR)、粉末X射线衍射(PXRD)、热重(TG)分析和元素分析对这2个化合物的结构和性质进行了表征.     

簇合物裂解法合成二硫纶化合物

以[Me₄N]₂[M₄(SPh)₁₀]和[Me₄N]₄[S₄M₁₀(SPh)₁₆](M=Cd,Zn)为前驱体,采用簇合物裂解法合成了配合物(Bu₄N)₂[Cd(mnt)₂]、(Bu₄N)₂[M(dmit)₂](M=Cd,Zn)以及双核配合物(Me₄N)₂[Zn₂(Sph)₂·(S₂TTF(SCH₂)₂)₂].运用PM3计算方法得到了各种二硫纶盐配体中硫负离子的静电荷大小关系:mnt^2->SPh^->dmit^2->[(MeS)₂TTFS₂]^2-≈[(CH₂S)₂TTFS₂]^2-.在理论计算及实验结果的基础上,探讨了配体上硫负离子的静电荷大小与反应产物间的关系.     

取代基对咪唑[4,5-f]-1,10-邻菲罗啉Ru(Ⅱ)配合物的温敏性能影响

合成了3种具有不同取代基的咪唑[4, 5-f]-1,10-邻菲罗啉配体L¹~L³及其Ru(Ⅱ)配合物[Ru(L¹)₃]、[Ru(L²)₃]和[Ru(L³)₃],并进行了表征。这些Ru(Ⅱ)配合物在溶液中具有π→π^*跃迁吸收峰和金属到配体的电荷转移跃迁(MLCT)吸收峰,其发光峰位约为590 nm左右。将Ru(Ⅱ)配合物掺杂到聚甲基丙烯酸甲酯(PMMA)中得到相应的温敏漆。Ru(Ⅱ)配合物在PMMA膜中的吸收峰精细结构消失,且在长波方向663 nm附近有新的发射峰,表明Ru(Ⅱ)配合物在PMMA膜中有聚集。温度升高后,Ru(Ⅱ)配合物在PMMA膜中的发射峰强度逐渐减弱。分别计算了在30~60 ℃和60~90 ℃区间内非辐射活化能E_nr和温度灵敏度S_T。结果表明,具有苯基取代的咪唑[4, 5-f]-1,10-邻菲罗啉配体的[Ru(L¹)₃]配合物,比咪唑[4, 5-f]-1,10-邻菲罗啉Ru(Ⅱ)配合物[Ru(L²)₃]及烷基取代基的咪唑[4, 5-f]-1,10-邻菲罗啉Ru(Ⅱ)配合物[Ru(L³)₃]具有更高的温度灵敏度。     

过渡金属-联咪唑-Dawson型钨磷酸盐杂化化合物的酶固定化性能

利用水热法和直接沉淀法, 设计合成了5例由过渡金属(TM)-联咪唑配阳离子与Dawson型钨磷酸阴离子构成的多金属氧酸盐(POM)基有机-无机杂化化合物[Ni(H₂biim)₃]₄[Ni(H₂biim)₂(P₂W₁₈O₆₂)₂]·2H₂O(1), [Co^III(H₂biim)₃]₂[P₂W₁₈O₆₂]·8H₂O(2), [Cu(H₂biim)₂]₃[P₂W₁₈O₆₂]·4H₂O(3), [Co^II(H₂biim)₃]₂H₂[P₂W₁₈O₆₂]·9H₂O(4)和 [Ni(H₂biim)₃]₃[P₂W₁₈O₆₂]·2H₂O(5); 并利用X射线单晶衍射分析(SC-XRD)、 红外光谱(IR)和热重-差热分析 (TG-DTA)等对其进行了表征. 化合物1~5作为载体用于固定辣根过氧化物酶(HRP)时, 显示出了较高的酶固定化能力. 另外, 利用圆二色光谱(CD)和激光扫描共聚焦显微镜(LSCM)等方法评价了固定化酶HRP/1~HRP/5的重复使用性、 储存稳定性和检测过氧化氢(H₂O₂)的性能. 由于该类POMs与HRP间存在强的相互作用, 利用简单的物理吸附法即可实现POMs对HRP的固载. POMs对酶的固定不但提高了HRP对使用及储存环境的耐受性, 同时也拓展了POMs在酶固定化领域的应用.     

Self-assembly of three Ag-polyoxovanadates frameworks for their efficient construction of C–N bond and detoxification of simulant sulfur mustard

Three imidazole-modified Ag-polyoxovanadates frameworks（APFs） with a controllable molar ratio of Ag+to polyoxovanadates（POVs） [Ag（IM）₂]₂V₄O₁₂·2Ag（IM）₂（APF-1）, [Ag₂（1-e IM）₄]₂[Ag（1-e IM）₂]3·2Ag（1-e IM）₂·3（1-He IM）[V₁₀O₂₈]₂（APF-2） and [Ag（1-pIM）₂]₃[HV₁₀O₂₈]·2Ag（1-pIM）₂·2H₂O（APF-3）(IM = imidaz...     

The natural product prodigiosin binds G-quadruplex DNA

Prodigiosin, a metabolite isolated from Serratia bacteria, is a potent anti-cancer agent. The goal of this research was to determine if prodigiosin could bind to G-quadruplex DNA. We found by using UV–vis spectroscopy that the G-quadruplex K⁺√d[TG₄T]₄, but not the single-stranded Li⁺√d[TG₄T], increased the water solubility of prodigiosin. In addition, we found that prodigiosin's fluorescence was strongly enhanced in the presence of K⁺√d[TG₄T]₄, further evidence for quadruplex-ligand binding. Using ¹H and ³¹P NMR experiments, we confirmed that prodigiosin binds at the 3′-end of K⁺√d[TG₄T]₄. Saturation transfer difference NMR experiments, done by irradiating the G5 H8 signal in K⁺√d[TG₄T]₄, indicated specific interactions between the G-quadruplex and prodigiosin's A and B rings. This study raises the possibility that G-quadruplex DNA may well be a target for the anti-cancer agent prodigiosin.     

Charge and substituent effects on the stability of porphyrin/G‐quadruplex adducts

The adduct ions of two tetramolecular G‐quadruplexes formed from the d(TGGGGT) and d(TTGGGGGT) single strands with a group of cationic porphyrins, with different charges and substituents, and one neutral porphyrin, were investigated by ESI‐MS and ESI‐MS/MS in the negative ion mode. Formation of [Q + nNH₄⁺+P^p+‐(z + n + p)H⁺]^z‐ adduct ions (where Q = quadruplex, n = number of quartets minus 1, P = porphyrin and p⁺ =0,1,2,3,4) indicates that the porphyrins are bound outside the quadruplexes providing an additional stabilization to those structures. The fragmentation pathways of the [Q + nNH₄⁺+P^p+‐(z + n + p)H⁺]^z‐ adduct ions depend on the number of positive charges (p⁺) of the porphyrins and on the overall complex charge (z^‐), but do not show a significant dependence on the type of the substituent groups in the porphyrins. Formation of the ‘unfilled’ ions [Q + P^p+‐(z + p)H⁺]^z‐ predominates for porphyrins with a higher number of positive charges. Strand separation with the formation of [T + P^p+‐(z‐2 + p)H⁺]^(z‐2)‐ and (SS‐2H⁺)^2‐ ions, where T = [d(TG₄T)]₃ and [d(T₂G₅T)]₃ and SS = d(TG₄T) and d(T₂G₅T) is only observed for the complexes with a higher overall negative charge. Porphyrin loss with the formation of [Q + nNH₄⁺‐(z + n)H⁺]^z‐ ions occurs predominantly for the neutral and monocharged porphyrins. The predominant formation of the ‘unfilled’ ions, [Q + P^p+‐(z + n)H⁺]^z‐, for porphyrins with a higher number of charges shows that these porphyrins can prevent strand separation and preserve, at least partially, the quadruplex structure. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and characterization of a bunchy oligonucleotide forming a monomolecular parallel quadruplex structure in solution

A cluster of four d(TG₄T) hexanucleotides with the 3′-ends linked together by a bunchy spacer has been synthesized and shown to form a monomolecular parallel quadruplex 5 in solution characterized by four G-quartets. ¹H NMR spectroscopy and CD thermal denaturation experiments indicate the monomolecular quadruplex (5) to be more stable than the tetramolecular counterpart [d(TG₄T)]₄.     

Parallel G-quadruplex Structures Increase Cellular Uptake and Cytotoxicity of 5-Fluoro-2′-deoxyuridine Oligomers in 5-Fluorouracil Resistant Cells

Fluoropyrimidines, such as 5-fluorouracil (5-FU) and related prodrugs have been considered first-line chemotherapy agents for the treatment of colorectal cancer. However, poor specificity and tumor cell resistance remain major limiting bottlenecks. G-quadruplexes, have been suggested as preferred nanostructures for enhancing cellular uptake mediated by G-quadruplex binding proteins which are abundant at the membranes of some tumor cells. In the current study, we propose a new strategy to deliver 5-fluoro-2′-deoxyuridine (5-FdU) monophosphate, the main active drug from 5-FU derivatives that may circumvent the cellular mechanisms of FU-resistant cancer cells. Two G-quadruplexes delivery systems containing four and six G-tetrads ((TG₄T) and (TG₆T)) linked to a FdU oligonucleotide were synthesized. Biophysical studies show that the G-quadruplex parallel structures are not affected by the incorporation of the 5 units of FdU at the 5’-end. Internalization studies confirmed the ability of such G-quadruplex nanostructures to facilitate the transport of the FdU pentamer and increase its cytotoxic effect relative to conventional FU drug in FU-resistant colorectal cancer cells. These results suggest that FdU oligomers linked to G-quadruplex parallel sequences may be a promising strategy to deliver fluoropyrimidines to cancer cells.     

Binding of malachite green promotes stability and shows preference for a human telomere DNA G-quadruplex

A single-stranded human telomere DNA sequence can fold into an intramolecular G-quadruplex structure, which has been shown to inhibit telomerase activity. Small molecules that selectively target and stabilise the G-quadruplex structure have been proposed as potential anticancer drugs. In this study, we analysed the properties of binding of malachite green, a cationic triphenylmethane dye, to the G-quadruplex of d[(T₂AG₃)₄] by UV spectroscopy of thermal melting analysis, a competitive equilibrium dialysis assay, and absorption and circular dichroism spectroscopies. When binding to malachite green, the quadruplex structure that formed in the presence of K⁺ ions was stabilised with an increase in melting temperatures by 6 °C. Malachite green showed selective binding to the G-quadruplex in the presence of duplex and single-stranded DNAs, owing to which it presents higher potential for anticancer therapy, compared to other triphenylmethane dyes. The induced signals of circular dichroism indicate that the binding mode of malachite green involves intercalation between adjacent guanine tetrads of the G-quadruplex.     

Neutral and Negatively Charged Phosphate Modifications Altering Thermal Stability,Kinetics of Formation and Monovalent Ion Dependence of DNA G‐Quadruplexes

The effect of phosphate group modifications on formation and properties of G‐quadruplexes (G4s) has not been investigated in detail. Here, we evaluated the structural, thermodynamic and kinetic properties of the parallel G‐quadruplexes formed by oligodeoxynucleotides d(G₄T), d(TG₄T) and d(TG₅T), in which all phosphates were replaced with N‐methanesulfonyl (mesyl) phosphoramidate or phosphoryl guanidine groups resulting in either negatively charged or neutral DNA sequences, respectively. We established that all modified sequences were able to form G‐quadruplexes of parallel topology; however, the presence of modifications led to a decrease in thermal stability relative to unmodified G4s. In contrast to negatively charged G4s, assembly of neutral G4 DNA species was faster in the presence of sodium ions than potassium ions, and was independent of the salt concentration used. Formation of mixed G4s composed of both native and neutral G‐rich strands has been detected using native gel electrophoresis, size‐exclusion chromatography and ESI‐MS. In summary, our results indicate that the phosphate modifications studied are compatible with G‐quadruplex formation, which could be used for the design of biologically active compounds.     

Peroxidase activity-structure relationship of the intermolecular four-stranded G-quadruplex-hemin complexes and their application in Hg ion detection

The peroxidase activities of the complexes of hemin and intermolecular four-stranded G-quadruplexes formed by short-stranded X_nG_mX_p sequences (X = A, T or C), especially T_nG_mT_p sequences, were compared. The results, combining with those of circular dichroism (CD) spectra and acid-base transition study for DNA-hemin complexes, provide some important information about DNAzymes based on G-quadruplex-hemin complexes, such as the formation of a G-quadruplex structure is an important factor for determining whether a DNA sequence can enhance the catalytic activity of hemin; both intramolecular parallel G-quadruplexes and intermolecular four-stranded parallel G-quadruplexes can enhance the catalytic activity of hemin; the addition of T nucleotides to the 5′-end of a G-tract confers corresponding G-quadruplex greatly enhanced catalytic activity, whereas the addition of T nucleotides to the 3′-end of the G-tract has little effect; the high catalytic activity of hemin in the presence of some short-stranded G-rich sequences may be a result of the reduction of the acidity of the bound hemin cofactor. These studies provide more information for the DNA-hemin peroxidase model system, may help to elucidate the structure-function relationship of peroxidase enzymes and to develop novel, highly efficient peroxidase-liking DNAzymes. As a sequence of such an investigation, a new Hg²⁺ detection method was developed.     

One Terminal Guanosine Flip of Intramolecular Parallel G-Quadruplex: Catalytic Enhancement of G-Quadruplex/Hemin DNAzymes

Numerous studies have shown compelling evidence that incorporation of an inversion of polarity site (IPS) in G-rich sequences can affect the topological and structural characteristics of G-quadruplexes (G4s). Herein, the influence of IPS on the formation of a previously studied intramolecular parallel G4 of d(G₃TG₃TG₃TG₃) (TTT) and its stacked higher-order structures is explored. Insertion of 3′–3′ or 5′–5′ IPS did not change the parallel folding pattern of TTT. However, both the species and position of the IPS in TTT have a significant impact on the G4 stability and end-stacking through the alteration of G4–G4 interfaces properties. The data demonstrate that one base flip in each terminal G-tetrad can stabilize parallel G4s and facilitate intermolecular packing of monomeric G4s. Such modifications can also enhance the fluorescence and enzymatic performances by promoting interactions between parallel G4s with N-methyl mesoporphyrin IX (NMM) and hemin, respectively.     

Inducement and stabilization of G-quadruplex DNA by a thiophene-containing dinuclear ruthenium(II) complex

G-quadruplex structures are attractive targets for the development of anticancer drugs, as their formation in human telomere could impair telomerase activity, thus inducing apoptosis in cancer cells. In this work, a thiophene-containing dinuclear ruthenium(II) complex, [Ru₂(bpy)₄(H₂bipt)]⁴⁺ {bpy = 2,2′-bipyridine, H₂bipt = 2,5-bis[1,10]phenanthrolin[4,5-f]-(imidazol-2-yl)thiophene}, was prepared and the interaction between the complex and human telomeric DNA oligomers 5′-G₃(T₂AG₃)₃-3′ (HTG21) has been investigated by UV-Vis, fluorescence and circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assay, polymerase chain reaction (PCR) stop assay, fluorescent intercalator displacement (FID) titrations, Job plot and color reaction studies. The results indicate that the complex can well induce and stabilize the formation of antiparallel G-quadruplex of telomeric DNA in the presence or absence of metal cations, and the ΔT_m value of the G-quadruplex DNA treated with the complex was obtained to be 12.8 °C even at levels of 50-fold molar of duplex DNA (calf-thymus DNA), suggesting that the complex exhibits higher G-quadruplex DNA selectivity over duplex DNA. The complex shows high interaction ability with G-quadruplex DNA at (1.17 ± 0.12) × 10⁷ M^?1 binding affinity using a 2:1 [complex]/[quadruplex] binding mode ratio. A novel visual method has been developed here for making a distinction between G-quadruplex DNA and duplex DNA by our ruthenium complex binding hemin to form the hemin-G-quadruplex DNAzyme.     

联吡啶[3,2-a：2’,3-c]-7-氮杂-吩嗪铜(I)配合物的合成、表征及其与DNA的相互作用

合成了邻菲罗啉衍生物联吡啶[3,2-a:2',3'-c]-7-氮杂-吩嗪(dpapz)及其铜(I)配合物[Cu(dpapz)₂]PF₆, 利用核磁共振氢谱(¹H NMR), 傅里叶变换红外(FTIR)光谱, 高分辨质谱(HR ESI-MS)等对合成的化合物进行了表征.采用紫外-可见吸收光谱,荧光光谱, DNA熔解温度实验和循环伏安方法研究了dpapz和[Cu(dpapz)₂]PF₆与小牛胸腺DNA(CT DNA)的相互作用. 配体dpapz与小牛胸腺DNA(CT DNA)作用时未观察到吸收峰红移并且减色效应较小(<30%), 且DNA熔解温度也上升较小(ΔT_m=7.8 ℃), 说明dpapz以沟槽结合的方式与CT DNA相互作用. 而[Cu(dpapz)₂]PF₆与CT DNA作用时, 可观测到较小的吸收峰红移(2-3 nm)和较大的减色效应(>50%), 同时DNA熔解温度上升较大(ΔT_m=11.1 ℃), 表明[Cu(dpapz)₂]PF₆以静电相互作用和部分扦插的方式与DNA结合. 溴乙锭(EB)荧光竞争实验和循环伏安实验进一步证实了这一结论. 配体dpapz和[Cu(dpapz)₂]PF₆与DNA的结合常数分别为2.88×10⁵和5.32×10⁵ mol·L^-1. 光照条件下, [Cu(dpapz)₂]PF₆产生单重态氧的能力与dpapz相当, 但产生超氧负离子自由基的能力要弱于dpapz. 活性氧猝灭实验表明, 超氧负离子自由基、单重态氧和羟基自由基均参与了dpapz和[Cu(dpapz)₂]PF₆对DNA的光损伤作用. [Cu(dpapz)₂]PF₆对DNA的亲和性要高于对dpapz的, 使得[Cu(dpapz)₂]PF₆对质粒DNA的光损伤效率明显强于dpapz.