242 



6. INTERACTIONS OF INHIBITORS WITH ENZYMES 



more complex situations have not been treated, it is obvious that repulsion 

 forces will play a large role in the orientation of two interacting molecules 

 in the position of maximal stability. 



Table 6-14 

 Effect of Orientation on Interaction Energy in H, " 



" Data from Mason and Hirschfelder (1957). The values of d^ and (p^ were calculated 

 from energy-distance curves. The treatment was based on the consideration of inter- 

 acting and overlapping orbitals and the evaluation of the various exchange integrals 

 was involved. It is an elegant, but laborious, method that at present cannot be ap- 

 plied to more complex interactions. 



RELATIVE CONTRIBUTIONS OF DIFFERENT INTERACTION 



FORCES 



Interactions between groups or molecules usually involve more than a 

 single attractive force and occasionally more than one repulsive force. It 

 is now necessary to consider in general terms contributions made by differ- 

 ent attractive forces to the total equilibrium potential energy. In calcu- 

 lating either interaction energies or equilibrium distances from experi- 

 mentally determined energies, it is necessary to take into account all the 

 forms of attraction that contribute significantly. The contributions will 

 depend on the distance between the interacting groups or molecules because 

 the respective potential energies vary with different powers of the distance. 

 This is illustrated in Table 6-15 where the relative contributions are cal- 

 culated for two distances of separation. There is no change for the dipole- 

 dipole interaction because all energy terms involved contain lld^; however, 

 for the other three examples it may be observed that one energy term is 

 more likely to be dominant at greater distances. Dispersion energies par- 



