Mechanics, thermodynamics, and kinetics of ligand binding to biopolymers
(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 KB T/Lp, which separates the low and the high-force regime. In the high-force limit (), 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 (), the three parameters (c, a/m, and m) have subtle effects on the extension of the polymer. In the low-force limit () 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, Lp = 0.715 nm (which are of the order of the values for ssDNA ), and KBT = 4.11 pN nm, the value at 25°C.