AlphaScreen®

AlphaScreen® relies on hydrogel-coated donor and acceptor beads providing functional groups for conjugation to biomolecules. The beads come in proximity when the biomolecules interact by molecular binding, e.g. antibody-antigen or receptor-ligand. Laser excitation at 680 nm of a photosensitizer present on the donor bead results in the production of singlet oxygen. The singlet oxygen migrates to react with a chemiluminescent coating on the acceptor bead. The chemiluminescent coating then activates fluorophores emitting light at 520 - 620 nm. This reaction cascade results in a huge amplification of the signal. The short lifetime of singlet oxygen in aqueous solution (~4 μs) allows diffusion over a distance up to ~200 nm. This means that if donor and acceptor beads are not in proximity no signal is produced.