Thermodynamics of protein binding

Protein binding can be considered to be an adsorption process obeying the law of mass action. If D represents drug and P the protein we can write 

It is obvious that kf /c, . The rate constant for dissociation, is the rate-limiting step in the exchange of drug between free and bound forms. From equation (10.10) we obtain 

Protein binding results are often quoted as the fraction of drug bound,, 8. This fraction varies generally with the concentration of both drug and protein, as shown in equation (10.17), which relates / with n, K and concentration  

Reproduced from A. Hasseblatt, Proc. Eur. Soc. Study Drug Toxicity, 13, 89 (1972). 

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