G-四联体荧光探针的研究进展

G-四联体(G-quadruplex)是一类特殊的核酸二级结构,由富含鸟嘌呤的核酸序列经折叠堆积所形成.研究发现,G-四联体在人类基因组(如端粒序列、基因启动子序列等)中广泛存在,并在调控基因的转录与表达、维持基因的稳定性以及端粒合成等重要生命过程中发挥着至关重要的作用.此外,在生物体内,G-四联体的结构、含量及分布的...     

选择性识别平行性G-四联体的方酸类近红外荧光探针的研究

G-四联体是抗肿瘤药物筛选的一个重要靶点.开发针对某些拓扑结构的G-四联体荧光探针对于研究其结构和生物学功能具有十分重要的意义.设计、合成了四个方酸类花菁荧光染料即CSTS,CSBE,CSEM和CSBM,并检测了其对不同类型DNA的选择性识别作用.结果表明,所合成的四个化合物在缓冲溶液中几乎没有荧光发射,加入正平行G-四联体之后荧光增强大约1 000倍;而加入反平行G-四链体或单双链DNA荧光仅仅增强几十倍,说明其可以特异性识别平行G-四联体.但流式实验结果显示,CSTS不能透过细胞膜,同时存在高荧光背景的缺点,因此无法应用于活体分析.而另外三个不带阴离子侧链的衍生物则容易进入细胞,进入细胞的难易顺序为CSBECSEMCSBMCSTS.高选择性、低背景荧光和易进入细胞等优点使CSBE具有作为近红外荧光探针检测生物样品中正平行G-四联体的潜力.     

用结晶紫为荧光指示剂筛选G-四链体的小分子配体

基于结晶紫(CV)与G-四链体的特异性结合以及结晶紫和端粒DNA(G-DNA)、G-四链体作用后荧光强度的差异,以天然抗肿瘤中药槲皮素为研究对象,建立了一种简单、快速、无标记筛选G-四链体配体的方法。研究了槲皮素与G-DNA的相互作用,并考察了G-DNA在K+存在下形成G-四链体后与槲皮素的作用情况。该方法已用于筛选G-四链体的小分子配体。     

基于硫代黄素T诱导G-四联体构成的生物传感器检测铅离子

硫代黄素T(ThT)荧光分子在自由状态下荧光强度很弱,通过在Tris-HCl缓冲液中加入Pb²⁺的适配体即富含G的DNA序列,可与ThT荧光分子形成G-四联体结构,使荧光信号迅速增强;向溶液中加入Pb²⁺,Pb²⁺与其适配体有很好的结合特异性,可生成更牢固的G-四联体结构,使ThT分子被释放出来,导致溶液的荧光强度降低,基于此可检测溶液中的Pb²⁺离子.实验中优化了缓冲溶液组成、ThT荧光分子浓度、Pb²⁺适配体浓度及反应时间等条件.结果表明,在10 mmol/L Tris-HCl(pH=8. 3,含2 mmol/L MgCl₂)缓冲溶液中,ThT荧光分子和Pb²⁺适配体的浓度分别为10μmol/L和200 nmol/L,反应10 min时,随着溶液中Pb2+浓度的增加,荧光强度减弱.Pb²⁺浓度在20～1000 nmol/L范围内时,荧光强度与Pb²⁺的浓度呈现良好的线性关系(R^...     

基于聚集诱导荧光性质的免标记DNA四链体检测以及凝血酶的传感研究

基于带正电荷硅杂环戊二烯衍生物的聚集诱导荧光性质,利用其与富含G的单链DNA和四链体作用后的荧光强度差别,发展了一种免标记的DNA四链体检测方法,并将该方法应用于凝血酶的荧光分析.     

含双dppz配体的钌(Ⅱ)配合物与G-四联体的相互作用研究

应用紫外-可见吸收光谱、荧光光谱、热变性、圆二色谱等方法在K+溶液中研究了富含鸟嘌呤的G-四联体(AG3(T2AG3)3)与钌髤配合物[Ru(L)(dppz)2](PF6)4(L=5,5′-二(三正丁胺基甲基)-2,2′-联吡啶离子,dppz=二吡啶并[3,2-a∶2′,3′-c]吩嗪)的相互作用。紫外和荧光滴定实验表明,配合物与G-四联体之间存在较强的亲和力,拟合得到的结合常数可达107;从热变性实验可以看出,该配合物能够有效地稳定DNA的四螺旋结构。     

聚多巴胺包埋G-四联体/血红素DNA酶制备过氧化氢生物传感器

利用多巴胺的氧化自聚实现对G-四联体/血红素DNA酶的包埋,成功构建了H2O2电化学生物传感器。DNA和血红素混合得到G-四联体/血红素复合物;DNA酶物理吸附在玻碳电极上后,将10μL 5 g/L多巴胺的磷酸盐缓冲液(pH 8.0)滴在表面,空气中的氧气氧化多巴胺形成聚多巴胺膜,实现DNA酶的固定。考察了不同DNA序列对传感器性能的影响,表明电化学与光学传感过程具有不同序列响应。此传感器对H2O2的检出限为2.2μmol/L;线性范围为0.01～1.5 mmol/L。本研究证实了利用聚多巴胺固定酶和用DNA酶代替天然酶构筑传感器的可行性。     

靶向G-四链体的小分子配体在癌症治疗中应用的研究进展

G-四链体是一类由Hoogsteen氢键维持稳定的,富含鸟嘌呤的DNA或RNA二级结构。人类基因组中存在大量潜在的形成G-四链体的序列,所形成的G-四链体结构能够调控基因组的稳定性、DNA复制和基因表达,其中包括很多与癌症相关基因。因此寻找能够诱导DNA的G富集区域形成G-四链体结构的配体,进而筛选潜在抗癌药物的先导化合物,已成为癌症治疗研究的热点之一。本文对近年来发现和设计的以G-四链体为靶点的小分子配体,按照靶向的G-四链体结构类型和配体的分子结构进行分类,综述了这类化合物在癌症治疗方面的研究进展,分析了相关靶向治疗存在的问题,并对未来的研究方向进行了展望。     

DNA G-四链体识别探针研究进展

G-四链体是一种由富含鸟嘌呤核酸序列形成的独特的二级结构,广泛分布于真核生物基因组,如端粒DNA、r DNA和一系列基因中的启动子区域。G-四链体结构对很多重要的生理过程如基因的转录、复制、重组以及保持染色体的稳定性方面具有重要作用。G-四链体的特异、高灵敏检测将为进一步了解G-四链体结构在人类细胞基因组中的分布、功能和机制奠定基础,也可能为靶向G-四链体的肿瘤治疗方法提供新的思路。因而过去几十年人们一直致力于开发设计具有高选择性和高灵敏度的G-四链体识别探针,这些探针已经广泛应用于溶液中G-四链体的识别,而且具有良好的选择性。目前也有少数探针能够直接用于检测活体G-四链体结构。本文综述了一些常见的靶向G-四链体的小分子配体,以及它们在染色体和活体细胞G-四链体检测中的应用。笔者希冀本文能为设计识别G-四链体的高性能探针,进一步实现活细胞内G-四链体的检测提供借鉴。     

基于G-四联体的纳米探针比色检测铅离子

基于纳米探针和G-四联体建立了简便快速检测铅离子的方法. 纳米探针采用金纳米粒子自组装修饰富G寡核苷酸制得, 在铅离子存在下, 纳米探针上的富G寡核苷酸形成G-四联体, 导致纳米探针凝聚变色. 在优化条件下, 比色检测铅离子的线性范围为48~480 nmol/L, 检出限为20 nmol/L; 大多数金属离子无明显干扰, 而有明显干扰的汞离子可采用与之特异结合的寡核苷酸有效消除. 将该法成功用于环境水样中铅离子的检测, 重现性(RSD<3.0%)与回收率(98.4%~101.5%)良好.     

Co(II)-salen complex encapsulated into MIL-100(Cr) for electrocatalytic reduction of oxygen

Co(II)-salen was encapsulated in MIL-100(Cr) metal organic framework by "ship in a bottle" to synthesize a new electrocatalyst, Cosalen@MIL-100(Cr). The material was characterized by XRD, FT-IR, UV-Vis and N2-adsorption. The Cosalen@MIL-100(Cr) modified glassy carbon electrode exhibits a well-defined reduction peak at the potential of –0.21 V toward the oxygen reduction reaction(ORR) by cyclic voltammetry(CV) in pH = 6.84 phosphate buffer. Almost 400 mV positive shift of potential at Cosalen@MIL-100(Cr) modified electrode for ORR compared with that at bare glassy carbon, indicates that Cosalen@MIL-100(Cr) possesses excellent electrocatalytic activity. The transferred number of electrons for ORR was determined by chronocoulometry. The result suggests that the introduction of Co(II)-salen complex into MOF increases the electrocatalytic activity via a four-electron reduction pathway. Furthermore, this electrocatalyst exhibits good stability and reproducibility.     

Syntheses and crystal structures of nickel(II), copper(II), and zinc(II) complexes with a biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand

The reactions of nickel(II), copper(II), and zinc(II) acetate salts with a potentially tetradentate biphenyl-bridged bis(pyrrole-2-yl-methyleneamine) ligand yielded three complexes with different coordination geometries. X-ray crystal structural analysis reveals that in the nickel(II) complex each nickel is five-coordinate, distorted trigonal bipyramid. In the copper(II) complex, each copper is four-coordinate, between square planar and tetrahedral. In the zinc(II) complex, each zinc is four-coordinate with a distorted tetrahedral geometry and the molar ratio of the zinc and ligand is 1 : 2.     

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.     

Synthesis,structure and properties of three one-dimensional coordination polymers {[M(II)L(NCS)2](DMF)2} n (M(II)=cadmium(II), zinc(II), manganese(II); L=1,4-bis[2-(2-pyridyl)benzimidazolato]butane)

A tetradentate N-donor ligand 1,4-bis[2-(2-pyridyl)benzimidazolato]butane (L) was prepared for construction of a coordination framework. Three one-dimensional coordination polymers {[M(II)L(NCS)₂](DMF)₂} _n (M(II) = cadmium(II), 1, zinc(II), 2, manganese(II), 3) were obtained by reaction of metal ions and L in the presence of KSCN in DMF/water. The complexes are isostructural and consist of 1D zigzag [M(II)L(NCS)₂] _n chains and DMF molecules. Within the chains, the metal atoms are each octahedrally coordinated by four N atoms of L and two N atoms of the SCN^? anions. Complexes 1 and 2 in the solid state at room temperature exhibit intense photoluminescence at 453 and 433 nm, respectively.     

Syntheses and Crystal Structures of Zinc(II) and Nickel(II) Complexes Involving Reduced Nitroxide Radicals

1 INTRODUCTION The synthesis of new molecular magnetic mate- rials that combine transition metal ions and pure organic radicals as ligating sites has attracted much more attention in the last few years[1~4]. Nitronyl ni- troxide radicals, independently or in combination with metal ions, have been one of the most studied systems in molecular magnetism for understanding the radical-radical or metal-radical interactions as well as for synthesizing organic ferromagnets and metal-radical magne…     

Acid Dissociation Behaviour and Complexation with Nickel(II), Copper(II) and Zinc(II) for Two Conformational Isomers of Dicyclohexylcyclam

Abstract

Acid dissociation constants for two conformational isomers of dicyclohexylcyclam, cis-anti-cis, (P) and cis-syn-cis, (N) have been determined at 25, 35 and 40°C, and thermodynamic data are estimated. It was found that (N) shows very different behaviour from (P). Stability constants of (P) and (N) toward Ni(II), Cu(II) and Zn(II) have been determined by pH-titration at 25°C by using a ligand exchange reaction. It is found that the (P) complex is more stable for Ni(II) and the (N) complex is more stable for Cu(II). Contributions of the cyclohexyl group to the macrocyclic effect (ME) have been also estimated by considering basicity corrections. It is found that substitution of the cyclohexyl group in cyclam increases ME only for the Ni(II) complex of (P).     

A Photoisomerizable Zinc (II) Complex Inhibits Microtubule Polymerization for Photoactive Therapy

The photoisomerization-induced cytotoxicity in photopharmacology provides a unique pathway for phototherapy because it is independent of endogenous oxygen. In this study, we developed a biosafe photoisomerizable zinc(II) complex ( Zn1 ), which releases its trans ligand ( trans -L1 ) after being irradiated with blue light. This causes the complex to undergo photoisomerization and produce the toxic cis product ( cis -L1 ) and generate singlet oxygen (¹O₂). The resulting series of events caused impressive phototoxicity in hypoxic A431 skin cancer cells, as well as in a tumor model in vivo. Interestingly, Zn1 was able to inhibit tumor microtubule polymerization, while still showing good biocompatibility and biosafety in vivo. This photoisomerizable zinc(II) complex provides a novel strategy for addressing the oxygen-dependent limitation of traditional photodynamic therapy.     

Structures and fluorescent properties of picolinato zinc(II) and cadmium(II) complexes based on tridentate and tetradentate benzimidazole ligands

Five picolinato zinc(II) and cadmium(II) complexes, [Zn(ntb)(pic)]ClO₄·CH₃OH·2H₂O (1), [Zn(bbma)(pic)]NO₃·2CH₃OH (2), [Cd(ntb)(pic)]ClO₄·0.75CH₃OH·H₂O (3), [Cd₂(bbma)₂(pic)₂](ClO₄)₂ (4), and [Cd₂(bbp)(bbp_-H)(pic)₂(C₂H₅OH)]ClO₄ (5), have been synthesized, where pic is the anion of picolinic acid, ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine, and bbp is 2,6-bis(benzimidazol-2-yl)pyridine. All the complexes were characterized by X-ray single-crystal diffraction, elemental analysis, IR, fluorescence spectroscopy, and thermal gravimetric analysis. 1–3 are mononuclear complexes in which picolinate adopts a N,O-chelating mode. 4 is a symmetrical dinuclear complex bridged by two anti-parallel picolinates in a N,O,O-coordination mode. 5 is also a dinuclear complex in which only one picolinate is a bridge. A 1-D double chain is formed by extensive H-bonds and π–π stacking in 1, while single zigzag chains are formed in 5. Complexes 2–4 all exhibit 6³-hcb 2-D frameworks. They extend to form four-connected 6⁶-dia 3-D topological nets for 2 and 4 and five-connected 4⁶·6⁴-bnn 3-D topological nets for 3. The five complexes show emission maxima in the blue region in the solid state.