Cheng-Prusoff Equation: Upgrades Un

Dmitry Yuryev yur77 at
Tue Jun 25 10:44:37 EST 1996

   Note my a paper which proves that analysis of inhibition
curves with formally exact computer programs can be performed only 
if experiment is conducted under "Cheng-Prusoff conditions".
   The summary is appended below. Full text (MS Word 6.0 for Win 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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