Energetic basis of hydrogen bond formation in aqueous solution

Area of Science:

• Biophysics
• Biochemistry
• Molecular Biology

Background:

• Thermodynamic forces of hydrogen bond formation in macromolecules are complex and debated.
• Energetic parameters of Adenine-Thymine (AT) and Guanine-Cytosine (GC) base pairs in DNA duplexes offer insights into these forces.

Purpose of the Study:

• To investigate the thermodynamic driving forces behind hydrogen bond formation in macromolecules.
• To explore the role of entropy and enthalpy in the formation of DNA base pairs and ionic bonds.

Main Methods:

• Comparative analysis of energetic parameters of AT and GC base pairs in DNA duplexes.
• Examination of thermodynamic principles governing 'naked' hydrogen bond formation.
• Analogy drawn with the formation of ionic bonds, such as between DNA-binding proteins and DNA phosphates.

Main Results:

• Formation of 'naked' hydrogen bonds is a non-enthalpic process, primarily driven by an increase in entropy.
• This entropy increase results from the release of tightly bound water molecules from polar groups.
• A thermodynamic parallel exists between hydrogen bond formation in DNA base pairs and ionic bond formation.

Conclusions:

• The non-enthalpic, entropy-driven nature of hydrogen bond formation is not unique to DNA base pairing.
• This principle extends to other polar non-covalent interactions, such as ionic bonds in protein-DNA interactions.
• Water release plays a crucial role in the thermodynamics of polar non-covalent bond formation in biological systems.