Differences between DNA base pair stacking energies are conserved over a wide range of ionic conditions

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Base pair stacking is crucial for DNA stability and function.
• Understanding stacking energies in different ionic conditions is essential for predicting DNA behavior.

Purpose of the Study:

• To determine DNA base pair stacking free energy parameters in a low ionic strength solvent.
• To compare these parameters with those determined in higher salt concentrations.

Main Methods:

• Temperature gradient gel electrophoresis (TGGE) was used to analyze DNA fragments.
• Transition midpoint temperatures (Tu) were measured for DNA sequences with single base pair substitutions.
• Singular value decomposition (SVD) was employed to derive nearest-neighbor free energy parameters.

Main Results:

• Ten nearest-neighbor free energy parameters were determined.
• The stability order of base pair stacks was established (e.g., TA < AT < AA).
• Experimental free energy differences closely matched predictions from parameters derived in various salt concentrations.

Conclusions:

• Differences in DNA base pair stacking energies are conserved across a wide range of ionic conditions.
• These energy differences are consistent in both DNA oligomers and polymers.
• The derived parameters accurately predict free energy differences in different salt environments.