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Published on: August 23, 2022
Determining DNA supercoiling enthalpy by isothermal titration calorimetry
Xiaozhou Xu1, Xiaoduo Zhi, Fenfei Leng
1Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA.
Biochimie
|September 4, 2012
Summary
DNA supercoiling is crucial for DNA replication and transcription. Researchers quantified its enthalpy, finding it
Area of Science:
- Biochemistry and Molecular Biology
- DNA dynamics and thermodynamics
Background:
- DNA supercoiling is essential for DNA replication, recombination, and transcription.
- Understanding the energetics of DNA supercoiling is key to elucidating its biological roles.
Purpose of the Study:
- To determine the DNA supercoiling enthalpy of plasmid pXXZ6.
- To partition DNA supercoiling free energy into enthalpic and entropic components.
Main Methods:
- Utilized DNA intercalators (ethidium bromide, daunorubicin) with differential binding enthalpies to various DNA forms.
- Quantified DNA supercoiling enthalpy using a 4.5 kb plasmid (pXXZ6).
Main Results:
- Determined the DNA supercoiling enthalpy of plasmid pXXZ6 to be approximately 11.5 kcal/mol per linking number change.
- Showed that unfavorable DNA supercoiling free energy arises from positive supercoiling enthalpy.
- Identified a large, favorable entropy term (TΔS) that compensates for the positive enthalpy.
Conclusions:
- The study provides a quantitative measure of DNA supercoiling enthalpy.
- Unfavorable enthalpy is a major contributor to the free energy cost of DNA supercoiling.
- Favorable entropy plays a critical role in stabilizing supercoiled DNA structures.
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