The heat capacity change, ΔCp, accompanying the folding/unfolding of macromolecules reflects their changing state of hydration. Thermal denaturation of the DNA duplex is characterized by an increase in ΔCp but of much lower magnitude than observed for proteins. To understand this difference, the changes in solvent accessible surface area (ΔASA) have been determined for unfolding the B-form DNA duplex into disordered single strands. These showed that the polar component represents ~ 55% of the total increase in ASA, in contrast to globular proteins of similar molecular weight for which the polar component is only about 1/3rd of the total. As the exposure of polar surface results in a decrease of ΔCp, this explains the much reduced heat capacity increase observed for DNA and emphasizes the enhanced role of polar interactions in maintaining duplex structure. Appreciation of a non-zero ΔCp for DNA has important consequences for the calculation of duplex melting temperatures (Tm). A modified approach to Tm prediction is required and comparison is made of current methods with an alternative protocol.

中文翻译：

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DNA的热力学：热容量在双链体展开时发生变化。

伴随着大分子的折叠/展开的热容变化ΔCp反映了其水合状态的变化。DNA双链体的热变性的特征在于ΔCp的增加，但幅度比蛋白质观察到的低得多。为了理解这种差异，已经确定了溶剂可及表面积（ΔASA）的变化，以将B型DNA双链体展开为无序的单链。这些表明极性成分代表了ASA总增加量的〜55％，与分子量相似的球形蛋白质相反，极性成分仅占总数的1/3。由于极性表面的暴露导致ΔCp的降低，这解释了对于DNA观察到的热容增加大大降低，并强调了极性相互作用在维持双链体结构中的增强作用。DNA的非零ΔCp升值对双链解链温度（Tm）的计算具有重要意义。需要一种改进的Tm预测方法，并将当前方法与替代协议进行比较。