Heat capacity changes associated with guanine quadruplex formation: An isothermal titration calorimetry study
Heat capacity changes associated with guanine quadruplex formation: An isothermal titration calorimetry study
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DOI：
10.1002/bip.20918
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发表时间：
2008-04-01
期刊：
影响因子：
2.9
通讯作者：
Shafer, Richard H.
中科院分区：
文献类型：
--
作者：
Majhi, Pinaki R.;Qi, Jianying;Shafer, Richard H.
这项研究解决了在过量一价盐存在的情况下几种单分子四链体的形成焓的温度依赖性。我们检查了一系列具有生物学意义的富含鸟嘌呤的 DNA 序列：凝血酶结合适体 (TBA) (d(G(2)T(2)G(2)TGTG(2)T(2)G(2))、PS2.M、催化活性适体 (d(GTG(3)TAG(3)CG(3)T(2)G(2))) 和人端粒重复序列 (HT) (d(AG(3)(TZAG(3))(3)))。我们确认了四链体结构的存在，并确定了四链体构象稳定的温度范围。然后，我们将 DNA 添加到含有过量 NaCl 或 KCl 的溶液中。在这种方法中，仅进行了几次添加，并且仅测量了四链体形成的热函，以确定伴随的热函变化的温度依赖性。为了控制 DNA 折叠过程中非特异性盐相互作用的影响，我们通过用类似但非折叠序列替换四链体形成序列来重复实验，以获得仅涉及四链体折叠过程的最终焓值，四链体形成是放热的，但随着温度的升高而增加。威利期刊公司
This study addresses the temperature dependence of the enthalpy of formation for several unimolecular quadruplexes in the presence of excess monovalent salt. We examined a series of biologically significant guanine-rich DNA sequences: thrombin binding aptamer (TBA) (d(G(2)T(2)G(2)TGTG(2)T(2)G(2)), PS2.M, a catalytically active aptamer (d(GTG(3)TAG(3)CG(3)T(2)G(2))), and the human telomere repeat (HT) (d(AG(3)(TZAG(3))(3))). Using CD spectra and UV melting, we confirmed the presence of quadruplex structures and established the temperature range in which quadruplex conformation is stable. We then performed ITC experiments, adding DNA to a solution containing excess NaCl or KCl. In this approach, only several additions are made, and only the enthalpy of quadruplex formation is measured. This measurement was repeated at different temperatures to determine the temperature dependence of the enthalpy change accompanying quadruplex formation. To control for the effect of nonspecific salt interactions during DNA folding, we repeated the experiment by replacing the quadruplex-forming sequences with a similar but nonfolding sequence. Dilution enthalpies were also subtracted to obtain the final enthalpy value involving only the quadruplex folding process. For all sequences studied, quadruplex formation was exothermic but with an increasing magnitude with increasing temperature. These results are discussed in terms of the change in heat capacity associated with quadruplex formation. (c) 2008 Wiley Periodicals, Inc.