Fig 3. Extension of partially covered polymers as function of the pulling force.

(Panel A) Extension of a polymer in the presence of a ligand as a function of the applied force for different coverages c, occluded monomers per ligand m, and a/m ratios, for a ligand with a single binding mode. The dotted vertical line marks the force value K_B T/L_p, which separates the low and the high-force regime. In the high-force limit ($F\gg \frac{K_{B}T}{L_p}$), the extension x(F) depends only on both a/m and c. Changes in the Kuhn length per occluded monomer a/m shift the curves, but do not alter the slopes. However, changes in coverage c do alter these slopes. (Panel B): In the intermediate-force regime ($F\sim \frac{K_{B}T}{L_p}$), the three parameters (c, a/m, and m) have subtle effects on the extension of the polymer. In the low-force limit ($F\ll \frac{K_{B}T}{L_p}$) the extension x(F) is proportional to the force F and the proportionality constant is given in Eq (11). For both panels, d₀ = 0.57 nm. K₀ = 700 pN, L_p = 0.715 nm (which are of the order of the values for ssDNA [24]), and K_BT = 4.11 pN nm, the value at 25°C.