I am reading the paper "Activity of the bcr-abl kinase inhibitor PD180970" but I don't understand how IC50 works on table 1. Can you tell with simple words and give me an easy example?
The IC50 is the concentration of an inhibitor at which you observe the half maximal inhibition. See the figure from the Wikipedia:
The IC50 can be seen as a way to measure the effectiveness of an inhibitor on a biological function as an enzyme. In the case of PD180970 you have an inhibitor which inhibits the p210 Bcr-Abl tyrosine kinase. The IC50 is the concentration at which 50% of the kinase is inhibited.
In table 1 different mutations of the tyrosine kinase are tested against the inhibitor to see, if the mutations have an influence on the IC50. This is important as PD180970 is considered as an anti-cancer drug and possible mutations would make it less effective here.
The IC50 is the concentration of inhibitor required to reduce the activity of a molecule/protein by one-half. It is the inverse of EC50. Usually inhibition curves looks sigmoidal so the IC50 is the middle point of the S curve. Here an example. (Note that the Y-axis can be pretty much anything, like enzyme activity and the X-axis is the concentration in a logarithmic scale).