A single DSC experiment can provide a large amount of thermodynamic information, much of which
cannot be obtained by any other technique. The area under the experimental heat capacity curve can be
used to determine the calorimetric transition enthalpy (Hcal):
(11.7)This calorimetrically determined enthalpy is model-independent and is thus unrelated to the nature of
the transition. The temperature at which excess heat capacity is at a maximum defines the transition tem-
perature(Tm). Differences in the initial and final baselines provide a measure of the heat capacity change
that accompanies the transition. The experimental data can be converted into Cp,xs/T versus Tcurves and,
since (Equation (11.8)),
SCTT∫(/)pxs, d (11.8)
HCTcal ∫ p⋅d
Physical and Structural Techniques Applied to Nucleic Acids 445
Figure 11.14 (a) Primary ITC data for ligand binding to DNA. Initially the baseline equilibrates at a preset
value. After about 2 min an initial 3mL preinjection is made and 5 min later the first experimental
injection of 15mL is made. The magnitude of the peaks is directly proportional to the power that is
supplied to return cell feedback to the equilibrium value. (b) Integration of the peaks in Panel A
with respect to time and correction to a per mole basis gives the binding isotherm