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首页> 外文期刊>Spectrochimica acta, Part A. Molecular and biomolecular spectroscopy >Fluorescence anisotropy and FRET studies of G-quadruplex formation in presence of different cations
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Fluorescence anisotropy and FRET studies of G-quadruplex formation in presence of different cations

机译：存在不同阳离子时G-四链体形成的荧光各向异性和FRET研究

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Results of the steady-state fluorescence, anisotropy and FRET measurements of G-quadruplex formation in the presence of selected cations (Li+, Na+, K+, NEt4+ and Mg2+) are reported. Three different fluorescent oligonucleotides with human telomeric sequence labeled with fluorescein (FAM) and tetramethylrhodamine (TAMRA) were investigated: a dual-labeled 21-mer denoted as PSO (Potassium Sensing Oligonucleotide) and two 5'- and 3'- single-labeled probes, FAM-21 and 2 1-TAMRA, respectively. The fluorescence signal of FAM-21 increased significantly for all systems and the fluorescence enhancement was comparable in magnitude for monovalent cations but it was more pronounced for Mg2+ cation. This phenomenon was attributed to the protolytic equilibria of FAM affected by the variation in ionic strength. On the other hand, fluorescence of TAMRA was enhanced selectively by Na(I) cation that was explained by the dequenching of TAMRA emission originated from the peculiarity of the basket-type structure of Na(I)-quadruplex. Anisotropy of FAM-21 (but not 21-TAMRA) appeared to be sensitive to the G-quadruplex formation, showing significant increase with an increase in cation concentration and indicating some restrictions in rotational depolarization of FAM. FRET experiments revealed that all tested cations caused quenching of FAM fluorescence in PSO, but only Na+ and K+ ions produced sensitized emission of TAMRA acceptor. Higher FRET efficiency observed in the presence of sodium ion was attributed to the specific spectral factor and steric interactions in the basket-type Na(I)-quadruplex. (c) 2005 Elsevier B.V. All rights reserved.
机译：报告了在选定阳离子（Li +，Na +，K +，NEt4 +和Mg2 +）存在下G-四链体形成的稳态荧光，各向异性和FRET测量结果。研究了三种不同的具有人类端粒序列的荧光寡核苷酸，它们分别用荧光素（FAM）和四甲基罗丹明（TAMRA）标记：一个双标记的21-mer，称为PSO（钾传感寡核苷酸）和两个5'-和3'-单标记的探针，FAM-21和2 1-TAMRA。 FAM-21的荧光信号在所有系统中均显着增加，并且荧光增强的幅度与单价阳离子相当，但对于Mg2 +阳离子则更为明显。这种现象归因于FAM的蛋白水解平衡，受离子强度变化的影响。另一方面，通过Na（I）阳离子选择性地增强了TAMRA的荧光，这是由于Na（I）-四链体的篮型结构的特殊性导致的TAMRA发射的猝灭所解释的。 FAM-21（而不是21-TAMRA）的各向异性似乎对G-四链体形成敏感，随着阳离子浓度的增加而显着增加，并且表明FAM的旋转去极化有一些限制。 FRET实验表明，所有测试的阳离子均会导致PSO中FAM荧光的猝灭，但只有Na +和K +离子会产生TAMRA受体的敏化发射。在钠离子存在下观察到的更高的FRET效率归因于篮型Na（I）-四链体中的特定光谱因子和空间相互作用。 （c）2005 Elsevier B.V.保留所有权利。

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