Thermodynamics of single strand DNA base stacking

Area of Science:

• Biophysics
• Molecular Biology
• Thermodynamics

Background:

• Single-stranded DNA (ssDNA) can form stacked conformations.
• Understanding the thermodynamics of these transitions is crucial for predicting DNA behavior.

Purpose of the Study:

• To investigate the thermodynamic properties of stacking-unstacking transitions in short ssDNA sequences.
• To identify sequence-specific factors influencing ssDNA thermal stability.

Main Methods:

• Differential scanning calorimetry (DSC) was used to study 46 ssDNA sequences (10-12 bases) in sodium phosphate buffer.
• Thermodynamic parameters (transition temperature, enthalpy) were determined across a temperature range of 10-95°C.

Main Results:

• 24 ssDNA sequences exhibited stacking transitions, while 22 did not.
• Transition properties were concentration-independent for sequences with ≤60% self-complementarity.
• Nucleation is unlikely to be determined by specific doublets or triplets, but quadruplets play a role.

Conclusions:

• The thermal stability of stacked ssDNA conformations depends on the presence of specific nucleation quadruplets and sequence length.
• G/C content and purine base count do not significantly affect thermal stability.