Guanine-rich DNA oligonucleotides can adopt G-quadruplex (G4) structures in the presence of specific cations. Folding and unfolding of G4 can be characterized thermodynamically, providing the information on the stability of various G4 conformations. We show how the relevant thermodynamic and sometimes kinetic parameters are obtained by employing differential scanning calorimetry (DSC) and global fitting of an appropriate model to the DSC data. We demonstrate that best-fit values of the thermodynamic parameters can be interpreted in terms of the driving forces accompanying the G4 folding/interconversion and how they are translated into the phase diagrams, which provide an elegant description of the G4 phase space over a wide range of solution conditions.
Keywords: DNA; DSC; Folding; G-quadruplex; Kinetics; Phase diagram; Stability; Thermodynamics.