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For the first time, rupture event scanning (REVS) procedure based on quartz crystal microbalance (QCM) and involving only mechanical action was used to determine the height of the energy barrier for dsDNA unwinding. Melting point was determined with the help of this procedure. To determine the thermodynamic parameters including enthalpy, DNA denaturation was represented as a unimolecular process. This allowed us to recover the energy profiles from the experimental data obtained by force measurements at different scanning times (reaction times) for different temperatures. The thus obtained results were compared with the data obtained with the help of another mechanical method, namely, atomic force microscopy. The mechanism of DNA unwinding in QCM-based experiments through the unzipping mode, as proposed by us in previous works, was confirmed. Thus, we demonstrated that REVS procedure may be used to assess the thermodynamic parameters of dsDNA unwinding.

Measurement of the forces of unwinding of DNA double helix was conducted. Silicon wafers were chosen as substrates. It is demonstrated that the use of gold for surface modification causes the bimodal probability distribution of rupture forces because of the surface roughness. Surface modification with the help of Langmuir–Blodgett procedure is proposed as an alternative. The use of this method gives unimodal distribution of rupture forces. The forces of double helix unwinding are reported for oligonucleotides containing 20 base pairs depending on salt concentration. Furthermore, forces for the shear mode and unzipping mode are measured.