AlphaScreen

AlphaScreen is a bead-based luminescent proximity assay. Donor beads convert ambient oxygen to singlet oxygen on laser illumination; if an acceptor bead is brought within ~200 nm by a molecular interaction, the singlet oxygen triggers a chemiluminescent cascade and light is emitted. No proximity means no signal. The assay is homogeneous (no wash steps), extremely sensitive, and miniaturizes well — making it a workhorse for high-throughput interaction screening and biomarker quantitation (AlphaLISA).

Instrument

TECAN SPARK 10M

Sample Requirements

• Sample types: Purified proteins, peptides, tagged constructs, cell-culture supernatants, lysates.
• Protein–protein interaction (PPI) assay: Two interacting partners each linked to donor or acceptor beads (directly or via tags such as His, biotin, GST, FLAG). Proteins typically at low nM; bead reagents at manufacturer-recommended concentrations; total well volumes of a few to tens of microliters.
• AlphaLISA biomarker quantitation: Analyte-specific antibody pairs on donor and acceptor beads; works in complex matrices (serum, supernatant).
• Buffer/handling constraints: Light-sensitive (assay performed under subdued/green light); sensitive to biotin, certain metals, and strong reducing agents; some compounds quench singlet oxygen.