Amyloid β-protein (1-40) that is N-terminally modified with the fluorescent dye (7-diethylaminocoumarin-3-yl)carbonyl (DAC or DEAC). This derivative can be utilized to assess the binding properties of amyloid β-protein (1-40) for various membranes since it behaves very similar to the native peptide. In aqueous environments the fluorophore is almost non-fluorescent whereas binding to membranes results in an increase in fluorescence intensity (λex = 430 nm, λem = 470 nm). Increases in the GM1 ganglioside and cholesterol content in the lipid bilayers facilitated the binding of this peptide. For phosphatidylcholine and phosphatidylserine no affinity was observed.