Peptide Bioconjugates 209 209 From: Methods in Molecular Biology, vol. 298: Peptide Synthesis and Applications Edited by: J. Howl © Humana Press Inc., Totowa, NJ 13 Synthesis of Peptide Bioconjugates Ferenc Hudecz Summary Bioconjugates play an important role in several fields of biomolecular and bio- medicinal sciences. Protein/polypeptide-based conjugates with covalently attached epitope peptides are considered as potential synthetic vaccine candidates and/or target antigens in affinity-based bioassays. This chapter describes the synthesis of two- and three-component bioconjugates using water-soluble branched chain poly- meric polypeptides with multiple amino and/or carboxyl groups as macromolecular partners and oligopeptides as epitopes with small molecular mass. The synthetic procedures outline three major strategies for the incorporation of multiple copies of uniformly oriented peptide epitopes. In the first example, chloroacetylated poly- peptide is conjugated with SH-peptide to form a thioether linkage. Second, two independent oligopeptides are introduced into a macromolecule by amide and disul- fide bonds, respectively. In the third example, a new procedure is reported for the formation of disulfide bridges by the use of Npys-modified polypeptide and SH- peptide. Key Words: Peptide–macromolecule conjugate; amide bond; thioether bond; disulfide bridge; antibody epitope; T-cell epitope peptide. 1. Introduction Bioconjugates play an important role in several fields of biomolecular and biomedicinal sciences. Protein/polypeptide-based conjugates with covalently attached epitope peptides are considered as potential synthetic vaccine candi- dates and/or target antigens in affinity-based bioassays (e.g., ELISA, BIACORE) (1,2). Drugs such as daunomycin, methotrexate, and a GnRH analog coupled either to monoclonal antibodies or to synthetic linear or branched polypeptides