Quadruplex to Watson-Crick duplex transition of the thrombin binding aptamer: a fluorescence resonance energy transfer study
Quadruplex to Watson-Crick duplex transition of the thrombin binding aptamer: a fluorescence resonance energy transfer study
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DOI：
10.1016/j.bbrc.2004.05.052
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发表时间：
2004-07-02
影响因子：
3.1
通讯作者：
Maiti, S
中科院分区：
文献类型：
--
作者：
Kumar, N;Maiti, S
研究了富含鸟嘌呤的凝血酶结合元件与K+和Na+离子结合形成四链体和与其互补链结合打开这些四链体的热力学参数。为此，取用5 ′-荧光素和3 ′-四甲基罗丹明标记的15聚体脱氧核苷酸d（G（2）T（2）G（2）TGTG（2）T（2）G（2）），并监测荧光共振能量转移作为金属离子或互补链浓度的函数。从FRET研究获得的平衡缔合常数表明，K+离子结合具有比Na+离子更高的亲和力。从温度依赖性的平衡缔合常数的研究中获得的焓变化，Δ H，表明金属离子结合后形成的四链体主要是焓驱动的。互补链的四链体的结合研究表明，开放的四链体在NaCl缓冲液中的互补链的存在下是可逆的，以及熵驱动，可以很容易地发生，而开放的同一个四链体在KCl缓冲液中遭受的可逆屏障。整体热力学参数的比较沿着与动力学研究表明，虽然四链体不能有效地竞争与双链体形成在生理pH值，他们延迟协会的两条链。(C)2004年爱思唯尔公司All rights reserved.
Thermodynamic parameters of closing up of guanine-rich thrombin binding element, upon binding to K+ and Na+ ions to form quadruplexes and opening up of these quadruplexes upon binding to its complementary strand, were investigated. For this purpose, 15 mer deoxynucleotide, d(G(2)T(2)G(2)TGTG(2)T(2)G(2)), labeled with 5'-fluorescein and 3'-tetramethylrhodamine was taken and fluorescence resonance energy transfer was monitored as a function of either metal ions or complementary strand concentrations. Equilibrium association constant obtained from FRET studies demonstrates that K+ ions bind with higher affinity than the Na+ ions. The enthalpy changes, DeltaH, obtained from temperature dependence of equilibrium association constant studies revealed that formation of quadruplex upon binding of metal ions is primarily enthalpy driven. Binding studies of complementary strand to the quadruplex suggest that opening of a quadruplex in NaCl buffer in presence of the complementary strand is enthalpic as well as entropic driven and can occur easily, whereas opening of the same quadruplex in KCl buffer suffers from enthalpic barrier. Comparison of overall thermodynamic parameters along with kinetics studies indicates that, although quadruplexes cannot efficiently compete with duplex formation at physiological pH, they delay the association of two strands. (C) 2004 Elsevier Inc. All rights reserved.