Figure 7:

A simplified representation of the binding kinetics between the unbound receptor (R), unbound ligand (L) and the bound receptor-ligand complex (RL). (a) The binding kinetics of a system with only one transient state (TS) along the binding reaction coordinate. The figure shows a binding scenario where both receptor and ligand undergo conformational changes in the binding process. The kinetic residence time (i.e., the inverse of the RNA-ligand dissociation constant k_off) depends on the free energy difference (ΔG_off) between the bound state and transient state, while the thermodynamic binding energy (ΔG_bind) is determined by the free energy difference between the unbound state (R+L) and bound state (RL). (b) In practice, often the binding kinetic profile of a system contains multiple transient states (TS) and intermediate states (IS) with a much more complicated kinetic mechanism.