sAPPβ is the extracellular protein that is released from the transmembrane amyloid precursor protein (APP) upon cleavage with β-secretase. The remaining fragment of APP, C99, is cleaved by γ-secretase to release Aβ peptides. This kit provides basic components for the quantitative determination of both natural and recombinant human soluble amyloid precursor protein beta (sAPPβ). Base kits generally include only MSD plates coated with the capture antibody, SULFO-TAG-labeled antibody, and MSD proprietary read buffer. (See product insert for a list of kit components). Base kits are most commonly used for high-throughput screening and assay development.