Luminescence study of G-quadruplex formation in the presence of Tb3+ ion
Luminescence study of G-quadruplex formation in the presence of Tb3+ ion
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DOI：
10.1016/j.jinorgbio.2006.12.013
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发表时间：
2007-04-01
影响因子：
3.9
通讯作者：
Juskowiak, Bernard
中科院分区：
文献类型：
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作者：
Galezowska, Elzbieta;Gluszynska, Agata;Juskowiak, Bernard
用荧光光谱和圆二色性研究了Tb ~（3+）与人端粒重复序列d（G（3）T（2）AG（3）TAG（3）T（2）AG（3））（htel ~（21））的相互作用。由于来自鸟嘌呤的能量转移而导致的Tb 3+发光增强，表明Tb 3+离子被包裹在四链体核心的中央腔中。镧系离子（Eu 3+和Tb 3+）介导四链体结构形成的能力已通过使用荧光素和罗丹明FRET配偶体标记的寡核苷酸探针FAM-htel 21-塔姆拉的荧光能量转移测量进一步证明。圆二色性光谱显示Tb ~（3+）/htel ~（21）四链体具有与钠四链体类似的反平行链取向。Tb 3+结合平衡已被调查的情况下，存在和存在的竞争金属阳离子。在低Tb 3+浓度（8 μ M）下，Tb 3 +/htel 21四链体稳定性非常高（5 × 10（6）M-1），并且观察到每个四链体分子具有5-7个Tb 3+离子的化学计量。荧光和CD滴定实验表明，四链体的空腔中可容纳两个Tb ~（3+）离子，其余Tb ~（3+）离子可能与四链体的TTA环结合。更高浓度的Tb 3+（高于10 μ M）导致Tb 3+离子的过度结合，其最终使四链体不稳定，四链体经历转化成不同组织的组装体。这种组装体（可能具有多个正电荷）表现出动力学稳定性，这表现为竞争阳离子（Li+、Na+、K+）置换Tb 3+离子的非常缓慢的动力学。(c)2007年爱思唯尔公司All rights reserved.
The interactions of Tb3+ with the quadruplex-forming oligonucleotide bearing human telomeric repeat sequence d(G(3)T(2)AG(3)TAG(3)T(2)AG(3)), (htel21), have been studied using luminescence spectroscopy and circular dichroism (CD). Enhanced luminescence of Tb3+, resulting from energy transfer from guanines, indicated encapsulation of Tb3+ ion in the central cavity of quadruplex core. The ability of lanthanide ions (Eu3+ and Tb3+) to mediate formation of quadruplex structure has been further evidenced by the fluorescence energy transfer measurements with the use of oligonucleotide probe labeled with fluorescein and rhodamine FRET partners, FAM-htel21-TAMRA. The CD spectra revealed that Tb3+/htel21 quadruplex possesses antiparallel strand orientation, similarly as sodium quadruplex. Tb3+ binding equilibria have been investigated in the absence and the presence of competing metal cations. At low Tb3+ concentration (8 mu M) Tb3+/htel21 quadruplex stability is very high (5 x 10(6) M-1) and stoichiometry of 5-7 Tb3+ ions per one quadruplex molecule is observed. Luminescence and CD titration experiments suggested that the cavity of quadruplex accommodates two Tb3+ ions and the remaining Tb3+ ions bind probably to TTA loops of quadruplex. Higher concentration of Tb3+ (above 10 mu M) results in the excessive binding of Tb3+ ions that finally destabilizes quadruplex, which undergoes transformation into differently organized assemblies. Such assemblies (probably possessing multiple positive charge) exhibit kinetic stability, which is manifested by a very slow kinetics of displacement of Tb3+ ion by competing cations (Li+, Na+, K+). (c) 2007 Elsevier Inc. All rights reserved.