A mutant low-density lipoprotein receptor related protein-1 binds to Alzheimer amyloid-beta (Aβ) peptide with greater affinity compared to its wild- type homolog. This binding may be used to detect Aβ or to separate Aβ from the rest of a subject's body. In Alzheimer disease, it may be used to provide diagnostic results by detecting Aβ, treatment by removing Aβ, or both.