L. Chen, Y.Wang, and G. Yang 53 studied partially denatured DNA compaction related to the change in conformation of DNA in the presence of DMSO and magnesium chloride using AFM, Dynamic Light Scattering, and electrophoretic mobility methods. The authors show that adding DMSO and a divalent cation (magnesium ) to the DNA-containing system leads to the compaction of DNA even at its partial (low) denaturation. Authors show that the compaction of DNA increases at low concentrations of magnesium chloride and decreases at its higher concentrations (with the same concentration of DMSO). The electrophoretic mobility of DNA particles shows nonlinear dependence with rising concentrations of magnesium chloride (curve with maximum). The authors explained some of these effects by the influence of ionic strength on the electrostatic repulsion of the segments of DNA with negatively charged phosphate groups. The change in the degree of denaturation accompanying these effects was not measured. C Tongu, T Kenmotsu, Y Yoshikawa 54 studied shrinking of T4 DNA (166 kbp) samples by adding divalent and trivalent cations. DNA samples were again placed on a mica slide surface, incubated, and dried at room temperature. Then, the DNA on the mica slides was analyzed using AFM imaging with scanning probe microscopy at a constant temperature.