Institute of High Technologies, Taras Shevchenko National University of Kyiv, Kyiv, 01601, Ukraine.
Department of Biology, Johns Hopkins University, Baltimore, MD, 21218, USA.
Eur Biophys J. 2019 Dec;48(8):773-779. doi: 10.1007/s00249-019-01403-1. Epub 2019 Nov 5.
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 (T). A modified approach to T prediction is required and comparison is made of current methods with an alternative protocol.
伴随大分子折叠/展开的热容变化 ΔCp 反映了它们不断变化的水合状态。DNA 双链的热变性的特征是 ΔCp 增加，但幅度远低于蛋白质。为了理解这种差异，已经确定了将 B 型 DNA 双链体展开成无规单链时溶剂可及表面积 (ΔASA) 的变化。这些结果表明，极性分量代表总 ASA 增加的约 55%，而对于相似分子量的球状蛋白质，极性分量仅占总 ASA 的约 1/3。由于暴露于极性表面会导致 ΔCp 降低，这解释了 DNA 观察到的热容增加幅度大大减小，并强调了极性相互作用在维持双链体结构中的增强作用。对 DNA 非零 ΔCp 的认识对双链体熔化温度 (T) 的计算有重要影响。需要采用改进的方法来预测 T，并对当前方法与替代方案进行比较。
