Intermolecular Forces and Energies Between Ligands and Receptors

TLDR

The study investigates the recognition mechanisms and dissociation pathways of the avidin‑biotin complex and actin monomers, and proposes a model linking binding forces, intermolecular potential, and molecular function. They propose a model correlating binding forces, intermolecular potential, and molecular function. Unbinding forces of avidin/streptavidin–biotin analogs scale with enthalpy change but not free energy, implying adiabatic unbinding with post‑unbinding entropy changes, and the measured forces yield an effective rupture length of ~9.5 Å for biotin‑avidin pairs and 1–3 Å for actin monomer interactions.

Abstract

The recognition mechanisms and dissociation pathways of the avidin-biotin complex and of actin monomers in actin filaments were investigated. The unbinding forces of discrete complexes of avidin or streptavidin with biotin analogs are proportional to the enthalpy change of the complex formation but independent of changes in the free energy. This result indicates that the unbinding process is adiabatic and that entropic changes occur after unbinding. On the basis of the measured forces and binding energies, an effective rupture length of 9.5 ± 1 angstroms was calculated for all biotin-avidin pairs and approximately 1 to 3 angstroms for the actin monomer-monomer interaction. A model for the correlation among binding forces, intermolecular potential, and molecular function is proposed.