ProteinChip array-based amyloid beta assays.
Amyloid-beta (A beta) fragments are found in plaques of patients with Alzheimers. Three secretases cleave the amyloid precursor protein, producing multiple A beta fragments that accumulate in the brain and fluids of patients with Alzheimers. A beta peptides are difficult to detect using standard methods because of their small size and multiple isoforms. However, multiple peptide fragments can be detected using a single ProteinChip Array-Based assay. Specific antibodies recognizing various amyloid epitopes are immobilized on a ProteinChip Array. Crude samples, such as tissue lysates, serum, cerebral spinal fluid (CSF), or cell culture media, are applied to the antibody-coated arrays. A beta peptides are specifically retained by the antibody, whereas other sample components are removed by washing. The multiple peptide fragments are detected by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), which can easily resolve the different fragments because of the corresponding changes in peptide mass.