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. Author manuscript; available in PMC: 2010 Jan 1.
Published in final edited form as: Angew Chem Int Ed Engl. 2009;48(37):6790–6810. doi: 10.1002/anie.200900231

Figure 8.

Figure 8

Schematic illustration of the bead-based immunoassay for bacteriophage MS2. Biotinylated rabbit anti-MS2 IgG (biotin-1° Ab) is attached to the streptavidin-coated microbead. Bacteriophage MS2 is sandwiched between the biotin-1° Ab and rabbit anti-MS2 IgG labeled with β-galactosidase (conjugate). The enzyme label converts p-amino-phenyl-β-D-galactopyranoside (PAPG) into p-aminophenol (PAP). PAP is oxidized through a two-electron reaction to p-quinone imine (PQI) at an electrode with an applied potential of + 290 mV versus Ag/AgCl and PQI can be reduced to PAP at −300 mV.[132]