Fig. 4.

Overstretching force as a function of intercalator concentration for YO-PRO (blue circles, error bars, s.d., $⟨n⟩$ = 6.3) and ethidium bromide (red triangles) fitted with a linear relation. The concentrations are scaled on the concentration required to shift the overstretching force to 75 pN (542 nM for YO-PRO, 6.8 nM for EtBr). The obtained slopes are (1.7 ± 0.1) × 10⁻² pN nM⁻¹ for YO-PRO and (1.4 ± 0.1) pN nM⁻¹ for EtBr. The data on EtBr is extracted from results previously published in ref. ¹⁸