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Thermodynamic contributions of the reactions of DNA intramolecular structures with their complementary strands

机译:DNA分子内结构与其互补链反应的热力学贡献

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One focus of our research is to further our understanding of the physico-chemical properties of unusual DNA structures and their interaction with complementary oligonucleotides. We have investigated three types of reactions involving the interaction of intramolecular DNA complexes with their complementary single strands of varied length. Specifically, we have used a combination of isothermal titration (ITC) and differential scanning (DSC) calorimetry and spectroscopy techniques to determine standard thermodynamic profiles for the reaction of an i-motif, G-quadruplex, and triplex with their complementary strands. The enthalpies for each reaction are measured directly in ITC titrations and compared with those obtained indirectly from Hess cycles using DSC unfolding data. All reactions investigated yielded favorable free energy contributions, indicating that each single strand is able to invade and disrupt the corresponding intramolecular DNA complex. These favorable free energy terms are enthalpy driven, which result from a compensation of exothermic contributions, due to the formation of additional base-pair stacks (or base-triplet stacks) in the duplex product (or triplex product), immobilization of electrostricted water by the base-pair and base-triplet stacks, and the removal of structural water from the reactant single strands; and endothermic contributions from the disruption of base-base stacking interactions of the reactant single strands. This investigation of nucleic acid reactions has provided new methodology, based on physico-chemical principles, to determine the molecular forces involved in the interactions between DNA nucleic acid structures. This methodology may be used in targeting reactions for the control of gene expression.
机译:我们研究的重点之一是进一步了解异常DNA结构的理化性质及其与互补寡核苷酸的相互作用。我们已经研究了三种类型的反应,涉及分子内DNA复合物与其长度可变的互补单链之间的相互作用。具体而言,我们结合了等温滴定(ITC)和差示扫描(DSC)量热法和光谱技术,确定了i-基序,G-四链体和三链体与其互补链反应的标准热力学曲线。直接在ITC滴定中测量每个反应的焓,并与使用DSC展开数据从赫斯循环间接获得的焓进行比较。研究的所有反应均产生有利的自由能贡献,表明每条单链都能够侵入并破坏相应的分子内DNA复合物。这些有利的自由能项是焓驱动的,这归因于放热作用的补偿,这是由于在双联产物(或三联产物)中形成了额外的碱基对叠层(或三胞胎叠层),电致伸缩水的固定化所致。碱基对和碱基三联体堆叠,以及从反应物单链中去除结构水;以及由于反应物单链的碱基-碱基堆积相互作用的破坏而产生的吸热作用。这项对核酸反应的研究提供了一种基于理化原理的新方法,可以确定参与DNA核酸结构之间相互作用的分子力。该方法可用于靶向反应以控制基因表达。

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