Halide Exchange in Multi-Site Systems

When several sites, B, C, D etc. (- we reserve site A for the free ions -) on a macromolecule M are available for halide ion (X ) binding as indicated in Fig. 8.2 below, the equations for the observed x relaxation parameters presented above must be modified. Direct halide 

It may be pointed out that Wallach s result in the limit of rapid internal rotation means that the quadrupole.interaction in a specific bond is effectively reduced by the factor (3 cos 0j - 1) while the correlation time remains unchanged i,e. in the absence of chemical exchange still equals Tr for isotropic rotational diffusion). Since there appears to be some uncertainty concerning this point it is reiterated here. 

AVobs actually observed line width and Av is the line width of 

When extreme narrowing conditions can be assumed for the halide 

---