The images on AFM-tested mica slides show DNA denaturation regions. Quantitative analysis of the distinctly denatured areas on the slides was performed by imaging software, and using the worm-like-chain model allowed authors to reveal the dependence of DNA persistence length on the concentration of DMSO. Analysis of this data led authors to conclude that the persistent length of DNA decreases with the addition of DMSO. A substantial decrease in persistent length (from 50 to 12 nm) occurs at the addition of only 3% DMSO to the solution, which is significantly below the DMSO concentration corresponding to the melting point. The addition of 1% DMSO leads to 11% denaturation of 5000bp DNA.