Enzymatic Construction of Artificial Base Pairs: The Effect of Metal Shielding

Th formation of metal base pairs is a versatile method for the introduction of metal cations into nucleic acids that has been used in numerous applications including the construction of metal nanowires, development of energy, charge-transfer devices and expansion of the genetic alphabet. As an alternative, enzymatic construction of metal base pairs is an alluring strategy that grants access to longer sequences and offers the possibility of using such unnatural base pairs (UBPs) in SELEX experiments for the identification of functional nucleic acids. This method remains rather underexplored, and a better understanding of the key parameters in the design of efficient nucleotides is required. We have investigated the effect of methylation of the imidazole nucleoside ( dIm ^{n Me} TP ) on the efficiency of the enzymatic construction of metal base pairs. The presence of methyl substituents on dImTP facilitates the polymerase-driven formation of dIm^4Me −Ag^I− dIm and dIm^2MeTP −Cr^III− dIm base pairs. Steric factors rather than the basicity of the imidazole nucleobase appear to govern the enzymatic formation of such metal base pairs. We also demonstrate the compatibility of other metal cations rarely considered in the construction of artificial metal bases by enzymatic DNA synthesis under both primer extension reaction and PCR conditions. These findings open up new directions for the design of nucleotide analogues for the development of metal base pairs.     

Silver(I)-Ion-Mediated Cytosine-Containing Base Pairs: Metal Ion Specificity for Duplex Stabilization and Susceptibility toward DNA Polymerases

Spectroscopic characterization of Ag^I-ion-mediated C-Ag^I-A and C-Ag^I-T base pairs found in primer extension reactions catalyzed by DNA polymerases was conducted. UV melting experiments revealed that C-A and C-T mismatched base pairs in oligodeoxynucleotide duplexes are specifically stabilized by Ag^I ions in 1:1 stoichiometry in the same manner as a C-C mismatched base pair. Although the stability of the mismatched base pairs in the absence of Ag^I ions is in the order C-A≈C-T>C-C, the stabilizing effect of Ag^I ions follows the order C-C>C-A≈C-T. However, the comparative susceptibility of dNTPs to Ag^I-mediated enzymatic incorporation into the site opposite templating C is dATP>dTTP≫dCTP, as reported. The net charge, as well as the size and/or shape complementarity of the metal-mediated base pairs, or the stabilities of mismatched base pairs in the absence of metal ions, would be more important than the stability of the metallo-base pairs in the replicating reaction catalyzed by DNA polymerases.     

金属配合物和DNA相互作用研究进展

介绍了几种目前研究较多的金属配合物的合成方法及表征手段，并以钌的配合物为例描述了其与DNA的相互作用，概述了此类新型材料在生物、医学等领域的开发及应用。     

Structure and Replication of yDNA: A Novel Genetic Set Widened by Benzo‐Homologation

In a functioning genetic system, the information‐encoding molecule must form a regular self‐complementary complex (for example, the base‐paired double helix of DNA) and it must be able to encode information and pass it on to new generations. Here we study a benzo‐widened DNA‐like molecule (yDNA) as a candidate for an alternative genetic set, and we explicitly test these two structural and functional requirements. The solution structure of a 10 bp yDNA duplex is measured by using 2D‐NMR methods for a simple sequence composed of T–yA/yA–T pairs. The data confirm an antiparallel, right‐handed, hydrogen‐bonded helix resembling B‐DNA but with a wider diameter and enlarged base‐pair size. In addition to this, the abilities of two different polymerase enzymes (Klenow fragment of DNA pol I (Kf) and the repair enzyme Dpo4) to synthesize and extend the yDNA pairs T–yA, A–yT, and G–yC are measured by steady‐state kinetics studies. Not surprisingly, insertion of complementary bases opposite yDNA bases is inefficient due to the larger base‐pair size. We find that correct pairing occurs in several cases by both enzymes, but that common and relatively efficient mispairing involving T–yT and T–yC pairs interferes with fully correct formation and extension of pairs by these polymerases. Interestingly, the data show that extension of the large pairs is considerably more efficient with the flexible repair enzyme (Dpo4) than with the more rigid Kf enzyme. The results shed light on the properties of yDNA as a candidate for an alternative genetic information‐encoding molecule and as a tool for application in basic science and biomedicine.     

Incorporation of 2'-deoxy-2'-isonucleoside 5'-triphosphates (iNTPs) into DNA by A- and B-family DNA polymerases with different recognition mechanisms

Recently, α-L-threofuranosyl nucleoside 3'-triphosphates (tNTPs) have been reported to be incorporated into DNA by DNA polymerases. Isonucleosides especially the 2'-deoxy-2'-isonucleosides, would be considered regioisomers of α-L-threofuranosyl nucleosides. Therefore, we investigated the synthesis of 2'-deoxy-2'-isonucleoside 5'-triphosphates (iNTPs) having the four natural nucleobases and their incorporation into primer-template duplexes consisting of oligonucleotides containing natural 2'-deoxyribonucleosides and 2'-deoxy-2'-isonucleosides by using primer-extension reactions. We found that Klenow fragment (exo-; an A-family DNA polymerase) has strict recognition of the shape of nucleoside 5'-triphosphates and Therminator (a B-family DNA polymerase) has strict recognition of the shape of primer-template complexes, especially two base pairs upstream of the primer 3' terminus.     

过渡金属组氨酸水杨醛Schiff碱配合物的合成及生物活性

合成了四种组氨酸水杨醛$chiff碱过渡金属配合物[Cu(His-Sal)、Ni(His-sal)、Co(His-Sal)、Mn(His-Sal),His=组氨酸,Sal=水杨醛],其结构经UV、IR,元素分析,摩尔电导分析表征.荧光光谱表明四种配合物都能强烈猝灭BSA的内源荧光.生物活性实验表明配合物对金黄色葡萄球菌...     

牛磺酸席夫碱配合物研究现状

简述牛磺酸的概念,总结分析国内外关于牛磺酸席夫碱金属配合物的研究现状。     

水杨醛缩胺类双席夫碱过渡金属配合物的合成与表征

以水杨醛与乙二胺为原料,通过席夫碱反应合成一类水杨醛缩胺类双席夫碱,并进一步与铜、锌、镍3种金属离子络合得到3种过渡金属配合物;采用元素分析、红外光谱和紫外光谱对席夫碱及其金属配合物的结构进行表征.结果表明,合成的水杨醛缩乙二胺配体分子结构与理论结构相符,且分别与铜、锌、镍离子络合形成了稳定的过渡金属配合物.     

间硝基苯胺水杨醛Schiff碱过渡金属配合物的合成及性质

合成了4种间硝基苯胺水杨醛Schiff碱过渡金属配合物,其结构经UV-Vis、IR、元素分析、摩尔电导率测定等表征。荧光光谱表明,4种配合物都能强烈猝灭牛血清白蛋白（BSA）的内源荧光。生物活性实验表明,配合物对金黄色葡萄球菌（S.aureus）、大肠杆菌（E.coli）、枯草芽孢杆菌（B.subtilis）、绿脓杆菌（P.aeruginosa）均有不同程度的抑菌作用,其中对绿脓杆菌的抑菌活性较强。4种配合物的抑菌活性均大于配体的抑菌活性。     

橙皮素及其席夫碱金属配合物的合成及性质研究

利用缩合反应,在无水乙醇中合成橙皮素金属配合物;橙皮素在无水乙醇(或异丙醇)中与苯胺生成席夫碱,用此席夫碱合成新的橙皮素席夫碱金属配合物,并对其结构进行了表征.     

西佛碱型大环多胺铜配合物的合成与表征

三乙烯四胺与乙二醛反应得到西佛碱型大环多胺化合物C16H32 N8(L)。配体L经元素分析、红外、紫外 -可见、质谱等确证。在此基础上进一步合成了其与过渡金属离子Cu2 的配合物 ,对该配合物进行了元素分析、红外、紫外 -可见、摩尔电导等表征     

西佛碱型大环多胺镉配合物的合成与表征

三乙烯四胺与乙二醛反应得到西佛碱型大环多胺化合物C16H32 N8(L)。配体L经元素分析、红外、紫外 -可见、质谱等确证。在此基础上进一步合成了其与过渡金属离子Cd2 的双核配合物 ,对该配合物进行了元素分析、红外、紫外 -可见、摩尔电导等表征     

重金属离子捕集剂水杨醛双Schiff碱的合成及应用

以2,6-吡啶二甲酸、乙二胺及水杨醛等为原料合成了一种重金属离子捕集剂水杨醛双Schiff碱N,N'-双(2-水杨醛亚胺基乙基)-2,6-吡啶二甲酰胺(Ⅱ),并以其为配体与一些重金属离子(如Cu2+、Pb2+、Hg2+、Cr3+等)进行螯合反应.结果表明,配体化合物Ⅱ能与重金属离子生成稳定性较高且不溶于水的螯合物,可以...     

Polymerase Synthesis of DNAs Bearing Vinyl Groups in the Major Groove and their Cleavage by Restriction Endonucleases

DNA molecules containing 5‐vinyluracil, 5‐vinylcytosine, or 7‐deaza‐7‐vinyladenine were prepared by polymerase incorporation of the corresponding vinyl‐modified 2′‐deoxyribonucleoside triphosphates, and the influence of the vinyl group in the major groove of DNA on the cleavage by diverse type II restriction endonucleases (REs) was studied. The presence of 5‐vinyluracil was tolerated by most of the REs, whereas only some REs were able to cleave sequences containing 7‐deaza‐7‐vinyladenine. The enzyme ScaI was found to cleave DNA containing 5‐vinylcytosine efficiently but not DNA containing the related 5‐ethynylcytosine. All other REs failed to cleave sequences containing any cytosine modifications.     

Guanine-rich DNA nanocircles for the synthesis and characterization of long cytosine-rich telomeric DNAs

Short synthetic oligonucleotides derived from the human telomeric repeat have been studied recently for their ability to fold into four-stranded structures that are thought to be important to their biological function. Because telomeric DNAs are several kilobases in length, however, their folding might well be affected by cooperative or high-order interactions in these long sequences. Here, we present a new molecular system that allows for easy synthesis of very long stretches of the cytosine-rich strand of human telomeric DNA. Small circular DNAs composed of the G-rich sequence of human telomeres were prepared and used as templates in a rolling-circle replication mechanism. To facilitate the synthesis of the repetitive G-rich circles, an orthogonal base-protection strategy that made use of dimethylformamidine-protected guanine nucleobases was developed. Nanometer-scale circles ranging in size from 42 to 54 nucleotides were prepared. Subsequently, we tested the action of various DNA polymerases on these circular templates, and identified DNA Pol I (Klenow fragment) and T7 DNA polymerase as enzymes that are able to generate very long, C-rich telomeric DNA strands. Purification and initial structural examination of these C-rich polymeric products revealed evidence of a folded structure in the polymer.     

Photofunctions in Hybrid Systems of Schiff Base Metal Complexes and Metal or Semiconductor (Nano)Materials

Composite materials very often provide new catalytic, optical or other physicochemical properties not observed for each component separately. Photofunctions in hybrid systems are an interesting topic of great importance for industry. This review presents the recent advances, trends and possible applications of photofunctions of hybrid systems composed of Schiff base metal complexes and metal or semiconductor (nano)materials. We focus on photocatalysis, sensitization in solar cells (DSSC—dye sensitized solar cell), ligand-induced chirality and applications in environmental protection for Cr(VI) to Cr(III) reduction, in cosmetology as sunscreens, in real-time visualization of cellular processes, in bio-labeling, and in light activated prodrug applications.     

金属配合物与DNA相互作用的研究进展

DNA是生物体中一类重要的生物大分子,对生命遗传密码的翻译、转录、复制起着非常重要的作用,一方面,DNA靶向化合物成为很重要的核酸探针选择对象;另一方面,临床上使用的许多抗癌药物都以DNA为作用靶点.以金属配合物与DNA的作用机理为主要内容,阐述了紫外光谱法、荧光光谱法、电化学法等多种仪器分析方法在研究金属配合物与DNA相互作用中的应用,并对今后的发展趋势进行了展望.