Scatchard analysis of [3H]PIB binding to aggregated, synthetic Aβ1-40 and 1-42 fibrils and PS1/APP and AD brain homogenates
| Kd (nm) (High Aff) | Bmaxa (High Aff) | BPb (High Aff) | Kd (nm) (Low Aff) | Bmaxa (Low Aff) | BPb (Low Aff) | BPb (total) | % High Aff 1 nm PIBd | |
|---|---|---|---|---|---|---|---|---|
| Aβ1-40 | 1.02 | 0.61 | c | 50.1 | 8.1 | c | c | 79 |
| Aβ1-42 | 0.91 | 0.45 | c | 51.5 | 9.6 | c | c | 73 |
| PS1/APP | 0.10 | 0.21 | 78 | 32.5 | 119 | 134 | 212 | 37 |
| AD | 2.5 | 565 | 563 | 264e | 3888e | 50 | 613 | 92 |
High Aff, High affinity; Low Aff, low affinity.
↵ a Picomoles of [3H]PIB bound per nanomole of Aβ.
↵ b BP = Bmax/Kd after conversion of Bmax values to nanomolar units.
↵ c BP data are not meaningful for synthetic Aβ because the concentration of the Aβ is arbitrarily set and not based on in vivo concentrations.
↵ d Expected percentage of PIB bound to the high-affinity binding site in the presence of 1 nm PIB. This was determined from the BP values because binding at tracer concentrations is proportional to BP.
↵ e The low-affinity component is detectable in less than half of AD brain samples.