a) CD spectra of α-syn as a function of lipid addition in the form of SUVs. From top to bottom: 10 μM α-syn no lipids, 10 μM α-syn:1mM lipids, 10 μM α-syn:2mM lipids, 10 μM α-syn:3mM lipids, 10 μM α-syn:4mM lipids. CD signal intensity reaches a maximum at a lipid:α-syn molar ratio of 300:1. b) Cu2+ titration of 10 μM α-syn:3mM lipid complex. Cu2+ concentrations of 0, 10 and 100 μM give overlapping α-syn CD spectra.