To allow for the incorporation of t

To allow for the incorporation of the peptide into the protein, we initially investigated the incorporation of YKYKY into IGF-1 using a conventional recombinant technology approach (Figure S1). The synthesis of the IGF- 1 derivative was confirmed by PAGE (Figure S2) and western blot analysis using an anti-IGF-1 antibody (Figure S3). After tyrosinase treatment, the hydroxylation of all of the tyrosine residues in the IGF-1 derivative was confirmed by mass spectrometry (Figure 3 a). All of tyrosine residues, including the native tyrosine residues and those introduced by the modification process, were hydrogenated by tyrosinase.