Example: Feeling about scales

Suppose the assoc. const. of a DNA-protein interaction is 10⁹M^-1 and the assoc. rate const. is 10⁶M^-1s^-1. (1) What is the dissoc. const. of this interation? (2) What is the half-life of the DNA-protein complex?

Ans:

1. For a simple DNA-protein interaction (stoichiometry = 1: 1), the assoc. const. can be expressed by the rate constants:

2. The DNA-protein complex dissoc. is a first order reaction, which is simililar to isotope decay. Thus, half-life can be expressed as a function of dissoc. rate const.