Figure 7. Simplified scheme of the intermediary binding reactions in the harmonic oscillator model. The circles marked S1 and S2 symbolize the two insulin receptor binding sites, in a symmetrical antiparallel disposition. The insulin molecule is symbolized by a black dot. a1 and a2: association rate constants for sites 1 and 2 respectively. d1 and d2: dissociation rate constants for sites 1 and 2 respectively. kcr: crosslinking constant. see text for explanations. From reference 64, used with permission.