Inhibition Curves: one more trouble

Dmitry Yuryev yur77 at
Mon Sep 2 09:05:01 EST 1996

   Note my paper which proves that upgrades of traditional
Cheng-Prusoff procedure (ncluding computer approaches) can not
be used for analysis of inhibition experiment beyond "Cheng-Prusoff
   The summary is appended below. Full text (MS Word 6.0 f.W. format)
is available from:



   Dmitriy K. Yuryev   
   yur77 at

   A generalisation of the Cheng-Prusoff formula relating affinity
constant and the concentration of inhibitor giving 50% inhibition has
been derived for the case when concentrations of ligands are not in
a great excess. It shows that methods ensuring precise solving of
binding equations (including computer approaches and equations derived
in the present work) can not be used if these "Cheng-Prusoff
conditions" of ligands' excess are not observed. 
   The trouble is that beyond these conditions analysis becomes 
unreliable: the error contained in estimations of necessary parameters
appears abruptly multiplied in the calculated affinity constant

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