Fig. 5

a Force-extension curves for dsDNA stretch (solid lines) and return (dashed lines) with no protein and in the presence of 30 nM SIV NC or HIV-1 NC. b, c Dependence of the measured transition slope (b) and hysteresis area ratio (c) on protein concentration (see Additional file 4) for HIV-1 NC and SIV NC. The lines in (b) are fits to a simple binding isotherm (Additional file 4: Eq. 6), revealing equilibrium dissociation constants K _d = 5.5 ± 0.4 nM for SIV NC and K _d = 4.2 ± 0.4 nM for HIV-1 NC. Error bars are standard errors for three or more measurements