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. Author manuscript; available in PMC: 2012 Dec 1.
Published in final edited form as: Curr Opin Colloid Interface Sci. 2011 Dec;16(6):551–556. doi: 10.1016/j.cocis.2011.04.010

Figure 2.

Figure 2

The dependence of DNA-DNA forces on NaBr concentration is shown. The diameter of DNA is ~ 20 Å. Forces converge at high pressures for all salt concentrations. For ionic strengths less than ~ 0.8 M, an electrostatic interaction dominates at low pressures. The decay length of the apparent exponential in this regime is consistent with the Debye-Huckel shielding length. At higher ionic strengths, the forces at low pressures converge. The apparent exponential decay length is ~ 4.2 Å. The decay length of the high pressure force obtained after subtracting the low pressure forces is ~ 2 Å and has an amplitude independent of salt concentration.