The secondary structure of a 16 amino acid containing helical peptide has been compared to that on gold nanoparticles having increasing core diameter. The degree of surface curvature has a profound effect on the structure of the peptide, and a 3D SAM on nanoparticles does not always resemble the conventional 2D SAM. The peptide changes primarily to the beta-sheet conformation on 5 nm GNPs and gradually transforms into the native helical structure as the surface curvature is reduced by increasing the core size.