Measuring Energies of a Specific Biomolecular Interaction Using DSC

We describe here a method using differential scanning calorimetry (DSC) to determine the energy of biomolecular halogen bonds (X-bonds) in a DNA system. This system is unique because we are able to isolate the energetics of a specific molecular interaction from the thermodynamic properties of an entire system. To achieve this goal, we engineered DNA Holliday junctions that are stabilized by either an X-bond or a hydrogen bond (H-bond); the thermodynamic stability of these Holliday junctions are measured through DSC melting studies. Stabilizing energies of the competing Xand H-bonds were determined outside of all of the other interactions by subtracting the energies of these junctions. Overall, the X-bond was shown to have a greater stabilizing potential than the H-bond in this DNA junction system.