The complete denaturation of DNA with high molecular mass (full transition from doublestranded, DS, helical nucleic acids to single-stranded, SS coils or DNA "melting") is a twostage reversible consecutive dissociation reaction. Intermediate partial denaturation (PD) is the first stage. This happens with the formation of forks and/or bubbles inside the DNA helical structure and/or coils created from the initial helix, which continue to be bound to the initial helix. This first partial denaturation stage can be expressed as: