two sites ligand-receptor interaction

[Ian A. Paul, Ph.D.]

Dear Dr. Bologna,

There are several iterative curve fitting programs which can 
provide a two site model (saturation or displacement) and, 
usually, can compare the goodness-of-fit between 1-, 2- or more 
site models.  These include GraphPad/Prism, Lundon, and 
Ligand/EBDA.  I believe Sigma-Plot also now handles 
radioligand-type curve fitting but, I'm not familiar with the 
algorithm that it employs.

As far as statistical analysis goes, most of these programs can 
handle goodness-of-fit comparisons as mentioned.  Some, such as 
Prism, will perform comparisons between curves using a 
two-factor ANOVA (i.e. treatment x ligand concentration).  
However, this method makes the assumption that each factor 
level is an independent variable.  While this is usually valid 
for treatment, ligand concentration is usually more accurately 
viewed as a repeated measure.  This is because the results 
(dependent variables such as fmol/mg bound) at each 
concentration are related inasmuch as the samples are drawn 
from the same tissue pool.  For that level of analysis, you 
would need a serious statistical package (e.g. BMDP, SPSS, 
Systat, SAS and the like).

Hope this helps.

Ian.

-- 
======================================================
Ian A. Paul, Ph.D.
Laboratory of Neurobehavioral Pharmacology and Immunology
Department of Psychiatry and Human Behavior
Division of Neurobiology and Behavior Research
Box 127
University of Mississippi Medical Center
2500 North State Street
Jackson, MS  39216-4505
Tel.:  (601) 984-5883/5898
Fax.:  (601) 984-5884/5899
URL:  http://fiona.umsmed.edu/~iapaul/lnpi.html

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