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Forces maintaining the DNA double helix.
European Biophysics Journal ( IF 2 ) Pub Date : 2020-05-27 , DOI: 10.1007/s00249-020-01437-w
Peter L Privalov 1 , Colyn Crane-Robinson 2
Affiliation  

Despite the common acceptance that the enthalpy of DNA duplex unfolding does not depend on temperature and is greater for the CG base pair held by three hydrogen bonds than for the AT base pair held by only two, direct calorimetric measurements have shown that the enthalpic and entropic contributions of both base pairs are temperature dependent and at all temperatures are greater for the AT than the CG pair. The temperature dependence results from hydration of the apolar surfaces of bases that become exposed upon duplex dissociation. The larger enthalpic and entropic contributions of the AT pair are caused by water fixed by this pair in the minor groove of DNA and released on duplex dissociation. Analysis of the experimental thermodynamic characteristics of unfolding/refolding DNA duplexes of various compositions shows that the enthalpy of base pairing is negligibly small, while the entropic contribution is considerable. Thus, DNA base pairing is entropy driven and is coupled to the enthalpy driven van der Waals base pair stacking. Each of these two processes is responsible for about half the Gibbs energy of duplex stabilization, but all the enthalpy, i.e., the total heat of melting, results from dissociation of the stacked base pairs. Both these processes tightly cooperate: while the pairing of conjugate bases is critical for recognition of complementary strands, stacking of the flat apolar surfaces of the base pairs reinforces the DNA duplex formed.



中文翻译:

强制维持DNA双螺旋。

尽管人们普遍认为DNA双链体的展开焓不取决于温度,并且对于由三个氢键保持的CG碱基对来说,其焓要比仅由两个氢键保持的AT碱基对的焓大,但直接量热法测量表明,焓和熵两个碱基对的贡献均取决于温度,并且在所有温度下,AT的均大于CG对。温度依赖性是由于碱基的非极性表面的水合作用而引起的,该碱基在双链解离后会暴露出来。AT对的较大的焓和熵贡献是由该对固定在DNA的小沟中并在双链解离时释放的水引起的。分析不同组成的DNA双链体展开/折叠的实验热力学特性表明,碱基配对的焓很小,可以忽略不计,而熵的贡献却很大。因此,DNA碱基配对是由熵驱动的,并且耦合到由焓驱动的范德华碱基对堆叠。这两个过程中的每个过程约占双链稳定的吉布斯能量的一半,但所有焓(即总熔化热)都是由堆叠的碱基对的解离产生的。这两个过程紧密配合:虽然共轭碱基对对于识别互补链至关重要,但碱基对的平坦非极性表面的堆叠增强了形成的DNA双链体。DNA碱基配对是由熵驱动的,并耦合到由焓驱动的范德华碱基对堆叠中。这两个过程中的每个过程约占双链稳定的吉布斯能量的一半,但所有焓(即总熔化热)是由堆叠的碱基对的解离产生的。这两个过程紧密配合:虽然共轭碱基对对于识别互补链至关重要,但碱基对的平坦非极性表面的堆叠增强了形成的DNA双链体。DNA碱基配对是由熵驱动的,并耦合到由焓驱动的范德华碱基对堆叠中。这两个过程中的每个过程约占双链稳定的吉布斯能量的一半,但所有焓(即总熔化热)是由堆叠的碱基对的解离产生的。这两个过程紧密配合:虽然共轭碱基对对于识别互补链至关重要,但碱基对的平坦非极性表面的堆叠增强了形成的DNA双链体。

更新日期:2020-05-27
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