The Binding Reaction in Equilibrium

The binding reaction is in equilibrium when the concentrations of the binding variables such as binding protein/ligand complex, free ligand, and so on are not time dependent an3rmore (after about 3 to 4 Ti see Section 2.3.2). The basis of the analysis of equilibrium binding data is the law of mass action and the retention equations. 

The number of binding sites n is calculated quickly if n = Bm,/R . Bm, is measured, Ro must be known (e.g., by using pure binding protein). 

In the simplest case, a ligand L binds to a binding protein R according to binding mechanism I. The corresponding binding parameters Kp and B x are determined via the Scatchard plot  

Scatchard plots are often not linear but curved. This holds, for example, when there are often two or more binding sites with different affinity for the ligand. The high-affinity site and the low-affinity site. Suddenly there are three players (one ligand and two binding sites), and the story becomes correspondingly complicated (see equations for binding mechanisms II and III). In these cases, the constants Rio, R20, Km, and Kd2 are determined numerically. 

No thanks to a knight-errant for going mad when he has cause the thing is to turn crazy without any provocation. 

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