Hardin C C, Perry A G, White K
Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695-7622, USA.
Biopolymers. 2000;56(3):147-94. doi: 10.1002/1097-0282(2000/2001)56:3<147::AID-BIP10011>3.0.CO;2-N.
The dissociation and assembly of quadruplex DNA structures (and a few quadruplex RNAs) have been characterized at several levels of rigor, ranging from gross descriptions of factors that govern each process, to semiquantitative comparisons of the relative abilities of these factors to induce stabilization or destabilization, to quantitative studies of binding energies (thermodynamics), transformational rates (kinetics), and analysis of their transition-state energies and mechanisms. This survey classifies these factors, describes the trends and focuses on their interdependencies. Quadruplex assembly is induced most efficiently by added K(+) and elevating the strand concentration; however, Na(+), NH(4)(+), Sr(2+), and Pb(2+) are also very effective stabilizers. Quadruplex dissociation is typically accomplished by thermal denaturation, "melting"; however, when the quadruplex and monovalent cation concentrations are low enough, or the temperature is sufficiently high, several divalent cations, e.g., Ca(2+), Co(2+), Mn(2+), Zn(2+), Ni(2+) and Mg(2+) can induce dissociation. Stabilization also depends on the type of structure adopted by the strand (or strands) in question. Variants include intramolecular, two- and four-stranded quadruplexes. Other important variables include strand sequence, the size of intervening loops and pH, especially when cytosines are present, base methylation, and the replacement of backbone phosphates with phosphorothioates. Competitive equilibria can also modulate the formation of quadruplex DNAs. For example, reactions leading to Watson-Crick (WC) duplex and hairpin DNAs, triplex DNAs, and even other types of quadruplexes can compete with quadruplex association reactions for strands. Others include nonprotein catalysts, small molecules such as aromatic dyes, metalloporphyrins, and carbohydrates (osmolytes). Other nucleic acid strands have been found to drive quadruplex formation. To help reinforce the implications of each piece of information, each functional conclusion drawn from each cited piece of thermodynamic or kinetic data has been summarized briefly in a standardized table entry.
四链体DNA结构（以及少数四链体RNA）的解离和组装已在多个严谨程度层面上得到了表征，从对控制每个过程的因素的总体描述，到对这些因素诱导稳定或不稳定的相对能力的半定量比较，再到对结合能（热力学）、转化速率（动力学）以及它们的过渡态能量和机制的定量研究。本综述对这些因素进行了分类，描述了其趋势，并着重关注了它们之间的相互依赖性。添加K(+)并提高链浓度能最有效地诱导四链体组装；然而，Na(+)、NH(4)(+)、Sr(2+)和Pb(2+)也是非常有效的稳定剂。四链体解离通常通过热变性，即“解链”来实现；然而，当四链体和单价阳离子浓度足够低，或温度足够高时，几种二价阳离子，如Ca(2+)、Co(2+)、Mn(2+)、Zn(2+)、Ni(2+)和Mg(2+)可以诱导解离。稳定性还取决于所讨论的链（或多条链）所采用的结构类型。变体包括分子内、双链和四链四链体。其他重要变量包括链序列、间隔环的大小和pH值，尤其是当存在胞嘧啶时、碱基甲基化，以及用硫代磷酸酯取代主链磷酸酯。竞争平衡也可以调节四链体DNA的形成。例如，导致沃森-克里克（WC）双链和发夹DNA、三链DNA，甚至其他类型四链体的反应可以与四链体结合反应竞争链。其他因素包括非蛋白质催化剂、小分子，如芳香族染料、金属卟啉和碳水化合物（渗透剂）。已发现其他核酸链可驱动四链体形成。为了强化每条信息的影响，从每条引用的热力学或动力学数据得出的每个功能结论都已在标准化的表格条目中简要总结。
