Figure 6.

Proteinase K treatment of free and apoE-bound soluble Aβ in AD subjects. The total brain homogenate from AD subjects was treated with increasing concentrations of proteinase K (PK) for 1 hr at 37°C. The soluble fraction was then analyzed in SDS/PAGE. The unbound pool of Aβ (gray bars) and the apoE-bound Aβ (white bars), detected and quantified with the monoclonal antibody 6E10, show different sensitivities to proteinase K. The Aβ present in the complex with apoE is completely digested after treatment with proteinase K at 50 μg/ml, whereas the unbound soluble Aβ is resistant to proteinase K at concentrations up to 300 μg/ml.