Figure 6.
Schematic representation of the selective oxidation of PPD in a suspension of HRP-encapsulating POPC LUV200 and externally added H2O2 and PPD or ABTS2−. The cross-section of one spherical and unilamellar vesicle is shown. Since the POPC bilayer is permeable for H2O2 and PPD, but not for ABTS2−, vesicle-trapped HRP can oxidize PPD (λmax = 300 nm) to yield Bandrowski’s base (λiso = 500 nm), while ABTS2− (λmax = 340 nm) is only oxidized to ABTS•− (λmax = 414 nm) by HRP which is present in the bulk solution. The average size of one POPC vesicle is about 180 nm with a bilayer thickness of about 3.7 nm.