Graphic determination of IC50:by graphing% inhibition vs. log concentr.

3 posts / 0 new
alex.stopar
Graphic determination of IC50:by graphing% inhibition vs. log concentr.

i have to determinate the IC50: how equation is better to use?

Guy Sovak
alex.stopar wrote:i have to

alex.stopar wrote:

i have to determinate the IC50: how equation is better to use?

Hi There
http://www.ncgc.nih.gov/guidance/section3.html
Some examples and explanation about IC50 and EC50
Guy

fcs
Hi,

Hi,

I am a representative from the MiraiBio Group of Hitachi Software Engineering and I help a lot of our customers analyze their ELISA data and determine the IC50/EC50 values.

There are 2 common methods used to calculate the IC50/EC50 value:

1. The 4 Parameter Logistic (4PL) nonlinear regression model can be used for the curve fitting of your data points (dose and absorbance/OD/fluorescence intensity).  The C parameter from the 4PL function represents the IC50/EC50 value because it is the inflection point (or midway point) of the curve which is symmetrical.  This is easier of the 2 methods.
2. The 5 Parameter Logistic (5PL) nonlinear regression model can be used as well.  The IC50/EC50 in this case will be a function of several parameters from the 5PL: x = (C(2^(1/E) – 1))^(1/B)

Here is a blog that I wrote with more details on the 5PL nonlinear regression model.  It discusses all the parameters that are involved and what they represent.

Here is another blog of mine that goes into IC50/EC50 determination with our software, MasterPlex ReaderFit.

Allen Liu
The MiraiBio Group of Hitachi Software Engineering