Hydrogen bonding versus stacking stabilization by modified nucleobases incorporated in PNA.DNA duplexes

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Modified nucleobases are crucial for enhancing nucleic acid stability and function.
• Peptide nucleic acid (PNA).DNA duplexes offer unique properties for molecular recognition.

Purpose of the Study:

• To investigate the thermodynamic effects of incorporating 2,6-diaminopurine (D) and bicyclic thymine (bT) into PNA.DNA duplexes.
• To elucidate the contributions of hydrogen bonding and base stacking to duplex stabilization.

Main Methods:

• Thermal denaturation studies were employed to analyze the thermodynamics of PNA.DNA duplex formation.
• Dimethyl formamide was used to probe the nature of stabilizing interactions.

Main Results:

• Both D and bT nucleobases significantly stabilize PNA.DNA duplexes through enthalpic contributions.
• The stabilizing effect of bT is largely dependent on hydrophobic stacking, unlike D.
• Increased numbers of modified bases enhance stabilization, with minor compromise to single base discrimination.

Conclusions:

• Modified nucleobases D and bT offer effective strategies for stabilizing PNA.DNA duplexes.
• Understanding the interplay of hydrogen bonding and hydrophobic interactions is key to designing stable nucleic acid structures.
• Sequence context plays a critical role in the performance of modified nucleobases in sequence discrimination.