# Determining the pharmacophore of a group of isosteres

1. Jul 27, 2012

### mycotheology

Heres the question:
http://img442.imageshack.us/img442/484/sarr.png [Broken]
Firstly does anyone know what Ki is? Ionisation constant? I'm guessing its proportional to the drugs potency. I could take a good guess by observing the differences between each isostere but I'm guessing theres some kind of method I should be able to use here.

Last edited by a moderator: May 6, 2017
2. Jul 27, 2012

### Ygggdrasil

In biochemistry, KI is the binding constant for an inhibitor. Put more precisely, in the binding interaction between an inhibitor I and enzyme E, which form enzyme-inhibitor complex EI:

E + I <--> EI

KI is the equilibrium dissociation constant for the binding reaction:

$$K_I = \frac{[E]}{[EI]}$$

Therefore, more potent inhibitor have lower KI values.