Figure 6.

Dependence of the molecular extension of ssDNA on temperature and force. (a) Unzipping/rezipping traces for the same molecule at 5°C and 29°C. By measuring the change in distance between different peaks along an FDC (horizontal black arrows), we determine the molecular extension of the hairpin as a function of the temperature and force. (b) Extension/basepair versus temperature. Each dot represents the average over four molecules in either 1-M NaCl or 100-mM NaCl buffer solution. The force was not held constant; rather, the extensions were taken at the equilibrium zipping force, which varied with temperature, as shown in (a). Although the distance between basepairs does change with T, it does not appreciably change when the salt concentration is varied. (c) Extension/base versus unzipping force. Results were averaged over four molecules in either 1-M NaCl or 100-mM NaCl buffer solution. The distance between bases changes with force in both conditions. To see this figure in color, go online.