Figure 1: Molecular music.
From: Diagnosis on disc
A conventional compact-disc pick-up reader works by focusing laser light onto the surface of the CD. As the CD rotates above the reader, information encoded as pits along a spiral track on its metal-coated surface can be read by means of light reflected back through a lens onto a photodiode. Lange and colleagues' immunoassay system1 works in exactly the same way, but with a substrate covered with a regularly spaced array of capture antibodies taking the place of the CD. When an antigen binds to an antibody, its presence is signalled by a second, gold-containing detector antibody that catalyses the deposition of reflective silver particles onto the substrate.
