Abstract: A metal nanoparticle-phosphopeptide complex comprising a metal nanoparticle and a phosphopeptide is provided. The phosphopeptide comprises two or more contiguous peptide motifs and two or more phosphorus-containing groups capable of interacting with the surface of the metal nanoparticle. The amino acids at the equivalent position in each peptide motif have similar structural and/or electronic properties. Each phosphorus-containing group is bound to an amino acid in the two or more contiguous peptide motifs. Methods for preparing the metal nanoparticle-phosphopeptide complex are also provided.