Binding of prefibrillar IAPP to POPC/POPS LUVs. (A) Changes in molar ellipticity at 222 nm arising from a coil-to-helix conformational change upon membrane binding as a function of lipid concentration. Freshly dissolved IAPP (10 μM) was titrated with the indicated concentrations of 7:3 POPC/POPS LUVs containing 0 mol % (black), 20% (red), 30% (green), 40% (gray), or 50% (blue) cholesterol. Experiments were performed at 25°C in 10 mM phosphate buffer with 100 mM NaF, pH 7.4. Results are the average of three experiments. (B and C) CD spectra of IAPP in the presence of 200 μM LUVs of 7:3 POPC/POPS (B) and 1:2 DOPC/DPPC (C) containing varying amounts of cholesterol. To see this figure in color, go online.