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. 2005 Nov 18;90(4):1175–1190. doi: 10.1529/biophysj.105.070904

FIGURE 6.

FIGURE 6

The length-dependence of the electrostatic part of the free energy. Inline graphic and Inline graphic are the electrostatic free energies per base stack. N − 1 is the number of base stacks for a N-bp helix. (a,b) The electrostatic free energy Inline graphic (per base stack) for dsDNA (solid lines) and the respective ssDNA (dashed lines) as functions of sequence length N in NaCl (a) and MgCl2 (b) solutions. (a) [NaCl] = 3 mM, 10 mM, 30 mM, 100 mM, 300 mM, and 1 M (from the top to bottom); (b) [MgCl2] = 0.1, 0.3, 1, 3, 10, and 30 mM (from the top to bottom). (c,d) The length N-dependence of electrostatic contribution Inline graphic (per base stack) to folding free energy for dsDNA helix formation in NaCl (c) and MgCl2 (d) solutions. (Dotted lines) Poisson-Boltzmann theory; (solid lines) the TBI theory. [NaCl] = 3 mM, 10 mM, 30 mM, 100 mM, 300 mM, and 1 M (from the top to bottom); [MgCl2] = 0.1, 0.3, 1, 3, 10, and 30 mM (from the top to bottom).