Bindingsterkte

Bindingsterkte, or binding strength, describes how tightly two molecules interact with each other. It is most often discussed in the context of a ligand binding to a target such as a receptor, enzyme, antibody, or nucleic acid. The strength of the interaction is commonly referred to as affinity and is frequently quantified by the dissociation constant, Kd. A smaller Kd indicates stronger binding. Equally, the association constant Ka = 1/Kd or the standard binding free energy ΔG° = RT ln(Kd) can be used to describe the interaction in thermodynamic terms.

Binding strength is determined by both thermodynamics and kinetics. The equilibrium affinity reflects how favorable the bound state is, while the kinetics describe how quickly the complex forms and dissociates, characterized by kon and koff. The overall affinity is related to these rates by Ka = kon/koff and Kd = koff/kon. Temperature, pH, ionic strength, and molecular conformation influence binding, as do enthalpic interactions (such as hydrogen bonds and electrostatics) and entropic factors (including solvent effects and conformational freedom).

Measurement methods include isothermal titration calorimetry (ITC), which provides ΔH, ΔS, and Kd; surface plasmon resonance (SPR) and biolayer interferometry (BLI), which give kon and koff; and various ligand-binding assays (radioligand, fluorescence polarization). The term binding strength is essential in fields such as drug discovery, where high-affinity interactions are often desirable, and in immunology, where antibody-antigen binding is critical. It is important to distinguish binding strength from functional outcomes; a high-affinity interaction does not necessarily produce a strong biological effect, and vice versa.