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Fluorescence studies on the interaction of ethidium bromide with duplex, triplex and quadruplex DNA structures

Science China Chemistry 1999年第1期42卷 62-69页

作者：孙雪光曹恩华何裕建秦静芬 Chinese Academy of Sciences Institute of Biophysics Beijing China

Under different conditions, oligonucleotides can form several alternative DNA structures such as duplex, triplex and quadruplex. All these structures can interact with ethidium bromide (EB) and make its fluorescence intensity change. The fluorescence spectra and other related parameters provided by static fluorescence techniques showed that the interaction mechanisms between EB and these structures were not always the same. Among them, B type duplex and triplex DNA adopt an intercalative mode when binding to the EB, which has a relatively high efficiency of energy transfer and the fluorescence of EB cannot be quenched easily. While for the parallel duplex DNA, the interaction mode is an outside binding in which energy transfer can hardly happen and its fluorescence intensity as well as Stern-Volmer constant is almost the same to the free EB. For the quadruplex, the binding mechanism to EB is more complex. Results from the energy transfer and quenching studies indicate that the two interaction modes noted above probably coexist at the same time.

关键词： duplex triplex quadruplex ethidium bromide interaction

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Cytotoxicities, Telomerase and Topoisomerases I Inhibitory Activities and Interactions of Terpyridine Derivatives with DNAs

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Chemical Research in Chinese Universities 2015年第6期31卷 970-975页

作者： WEI Chunying GAO Ning Key Laboratory of Chemical Biology and Molecular Engineering Ministry of Education Institute of Molecular Science Shanxi University Taiyuan 030006 P. R. China

A novel compound 4-methyl-7-{[4-（2,2＇：6＇,2＂-terpyridin-4＇-yl）benzyl]amino}-2H-chromen-2-one（1） was synthesized, and its DNA-binding properties, cytotoxicity, and telomerase and Topo I inhibitory activities were evaluated. For comparison, the anti-proliferative and Topo I inhibitory activities of another two analogues 2 and 3 were also investigated. Compound 1 is able to stabilize the structures of human telomere（h-tert） and promoter（c-myc and c-kit2） G-quadruplexes and h-tert i-motif. The association constants（Kb） are about 106 L/mol for h-tert G-quadruplex and/-motif, while the values are about l0s L/mol for both promoter G-qaudruplexes and calf thymus DNA（ct-DNA）. The binding of compound 1 induces the change of h-tert G-quadruplex from hybrid to antiparallel structure and exhibits 88.7% inhibition of telomerase activity at 8 μmol/L. Both compounds 1 and 3 inhibit signifi- cantly Topo I-mediated relaxation of pBR322 DNA. Compounds 1 and 2 show a high inhibitory efficacy on HepG2 and MCF-7 cancer cell lines with IC50 values of about 10^-6 mol/L. The three compounds also induce a delay of cell cycle progression. The coumarin group is vital for improving the biological activity ofterpyridine derivatives.

关键词： Terpyridine Coumarin quadruplex Telomerase Topoisomerase I

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Circular dichroism spectra of different structures formed by the oligonucleotides

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Chinese Science Bulletin 1998年第17期43卷 1456-1460页

作者： Xueguang Sun Enhua Cao Chunli Bai Yujian He Jingfen Qin Chinese Acad Sci Inst Biophys Beijing 100101 Peoples R China Chinese Acad Sci Inst Chem Beijing 100080 Peoples R China

Under different conditions, oligonucleotides can form several different DNA structures such as duplex, triplex and quadruplex. All these structures exhibit an obvious difference in their CD spectra. The common characteristic is that they show a negative band at 240 nm, while in the range of 260-300 nm, the spectra are different from each other. Many factors such as chain direction, sugar puckering mode, orientation of the glycosyl bond, base stacking and sequence can affect their conformation and then show diversity and complexity in their spectra. By studying and comparing these spectra, more information about their conformations can be obtained to help predict some new structures. Furthermore, the spectra can also provide a base to study their potential biological functions.

关键词： duplex triplex quadruplex CD spectrum.

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Circular dichroism spectroscopic studies on structures formed by telomeric DNA sequences in vitro

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Chinese Science Bulletin 2000年第21期45卷 1959-1963页

作者： ZHANG Xiaoyan CAO Enhua SUN Xueguang BAI Chunli Institute of Biophysics Chinese Academy of SciencesBeijing 100101China Institute of Chemistry Chinese Academy of SciencesBeijing 100101China

Telomere plays an important role in cellular processes, such as cell aging, death and carcinogenisis. Having special sequences, it can form quadrupiex structure in vitro. Circular dichroism (CD) spectroscopic studies show that TTAGGG, (TTAGGG)2 and (TTAGGG)4 can all form quadrupiex in vitro and exist mainly as parallel quadrupiex without metal ions. Both K+ and Na+ can stabilize the tetrameric structure and facilitate the forming of anti-parallel conformation. Furthermore, the conformations of quadrupiex can also be affected by sequence length, the nature and concentration of metal ions.

关键词： human telomere quadruplex conformation CD spectrum K+ Na+ cation concentration.

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