302 



6. INTERACTIONS OF INHIBITORS WITH ENZYMES 



stance could be expressed in an exact and quantitative manner. Let us 

 take as a measure for this the change in interaction energy occurring when 

 the separation distance is altered by a small amount; thus the greater the 

 energy change upon displacement, the greater is the requirement for pro- 

 per fit. The value of dq'Idd can be evaluated if the dependence of energy 

 on distance is known. In the general case where (p = Ajd'^ — Bfd^ (Eq. 6-50), 

 differentiation leads to: 



d. aA bB ^g_^^g^ 



dd 



d"*' 



^"+1 



Fig. 6-19. Energy-distance curve for the interaction of a methyl 

 group within a protein cavity. The equation used is: 



1.86 X 10' 



9.73 X 10^ 



Displacement of two water molecules is assumed. <Pe =^ — 1-26 

 kcal/mole and d. = 3.95 A. 



