230 



6. INTERACTIONS OF INHIBITORS WITH ENZYMES 



However, the variation in results between the different methods and the 

 variation between substances in a particular method make it impossible 

 to assign a reliable value to a in a specified case. For groups and molecules 

 of the type here of interest, we shall arbitrarily assume a = 12; this value 

 is indicated by data from compressibility and heat of vaporization but it 

 should be considered only as a reasonable approximation. 



The importance of the repulsion constants for our purpose is in the 

 determination of the equilibrium distances and energies of interacting 

 molecules. The interaction energy of the greatest significance is that at 

 the separation distance corresponding to the stable configuration, i.e., 

 where attractive and repulsive forces are equal. This is illustrated on 

 the energy-distance curve in Fig. 6-6: the equilibrium energy (p^ is the 



Fig. 6-6. Energy curve for a generalized interaction involving 

 attraction and short-range repulsion. The dotted curve repre- 

 sents the energy from the attraction alone, (p^ is the energy of 

 interaction at the equilibrium distance d^. 



