Skip to main content
Biology LibreTexts

A. Introduction to Reversible Binding

Skills to Develop

  • write equations for the dissociation constant (KD), mass balance of total macromolecule (M0), total ligand (L0), and [ML]  as a function of L or Lo ([ML] = [M0][L]/(KD+ [L])  (when Lo >> Mo or when free [L] is known) and Y = fractional saturation =  Y = ([ML]/[M0] = [L]/(KD+ [L])
  • decide which of two given equations for [ML] should be used under conditions when the above conditions for L0 and L are given
  • based on the equation ([ML] = [M0][L]/(KD+ [L]) draw qualitative graphs for different given L0, L, and Kd values
  • determine fraction saturation given relatives values of Kd and L, assuming L0 >> M0
  • compare relative % bound for covalent binding of protons to an acid and noncovalent binding of a ligand to a macromolecule given pka/pH and Kd/L values
  • describe differences in binding curves for binding of a ligand to a macromolecule and the dimerization of a macromolecule
  • derive an equation which shows the relationships between the rate constant for binding (kon), dissociation (koff) and the thermodynamic dissociation (Kd) or equilibrium constant (Keq).
  • describe the structural and mathematic differences between specific and nonspecific binding
  • given a Kd, estimate t1/2 values for the lifetime of the ML complex.
  • describe techniques used to determine ML for given L or L0 values, including those that do and do not require separation of ML from M , so that Kd values for a M and L interaction can be determined
  • List advantages of isothermal titration calorimetry and surface plasmon resonance in determination of binding interaction parameters