DIELECTRIC CONSTANT 



249 



4 A, and 5.0 X 10^ volts/cm at 5 A. Using curve (1) of Fig. 6-12 it is seen 

 that beyond 5 A distance no significant effect on D would be expected but 

 at shorter distances from the dipole, D would be reduced. It is likely that 

 in most enzyme dipole-dipole interactions of importance, the dipoles are 



10 A 



Fig. 6-13. Energy-distance curves for the interaction of two uni- 

 valent ions. Curve B represents the interaction in a vacuum and 

 curve A in water. The repulsion constant (Eq. 6-50) was assumed 

 to be J. = 5 X 10' kcal/A"^^. 9? is in kcal/mole. 



quite close together and uninfluenced by water molecules; in such cases it 

 is probably legitimate to use a value of D = 1. If two dipoles are immersed 

 in water and are several A apart, the potential energy is negligible. Amis 

 (1953) has presented experimental evidence that the dielectric constant 

 influences the rate of dipole-dipole interactions. 



