<p>(A) Presumed secondary structure of the top strand generating a cruciform in the presence of 60 mM of MgCl<sub>2</sub>, as predicted using the M-fold program <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031533#pone.0031533-Zuker1" target="_blank">[20]</a>. (B) Absolute value of the Gibbs' free energy change during DNA folding and generation of a cruciform by the top strand. Arrows represent the marginal points in which the lengths are threshold values of the free energy change. (C) Number of integrations into nucleotide 1130 in the top strand cruciform. Arrows represent the marginal points in which the lengths are the threshold value. Arrows correspond well to the positions of those in (B) (n = 6; mean ± s.d.). The square of the correlation coefficient for the absolute energy value shown in (B) and the number of integrations shown in (C) was 0.838.</p
