DNA thermal melting can also be analyzed by measuring absorbance at 260 nm in a temperature gradient. In this study, we used a short oligonucleotide (oligoDNA) with a palindromic sequence of 5'-CGCGAATTCGCG-3', which forms B-form dsDNA, for two reasons. First, oligoDNA has a lower Tm than ctDNA, which enables measurements in a temperature gradient below the boiling temperature of water. Second, in contrast to long ctDNA strands, short oligoDNA strands can reform the dsDNA structure after heating and cooling to room temperature through a process known as DNA annealing. This ability of short oligoDNA strands to anneal allowed us to assess COSAN effects not only on DNA melting but also on the hybridization of two complementary ssDNA molecules into the dsDNA helix. 2) before and after heating and cooling back to 25 °C. The CD spectra of oligoDNA and oligoDNA with COSAN, measured before heating, are similar and indicate that COSAN does not affect the structure of DNA, in line with CD measurements of ctDNA with COSAN. No differences were found between the CD spectra of free oligoDNA or oligoDNA with COSAN, measured before and after heating. These results demonstrate that oligoDNA can return to the helical, ds B-form after melting despite the presence of COSAN (Figure and).