Conjugation of epitope peptides with SH group to branched chain polymeric polypeptides via Cys(Npys)

Since bioconjugates may play an important role as therapeutics in the futur e, the development of new and effective conjugation strategies is necessary . For the attachment of peptide-like molecules to carriers, there are two m ain coupling methods involving amide or disulfide bonds. Conjugation throug h an amide bond can be achieved in several well-defined ways known from pep tide chemistry. However, the formation of disulfide bridges between cystein e-containing peptides and earlier molecules still has some problems. In thi s paper, we describe a novel api,roach in which the carrier polypeptide is modified by 3-nitro-2-pyridinesulfenyl (Npys)-protected cysteine and this d erivative has been applied for conjugation of Cys-containing epitope peptid es with poly(L-lysine)-based branched polypeptides. Considering the stabili ty of Npys group in the presence of pentafluorophenol, Boc-Cys(Npys)-OPfp d ervivative was selected for introduction to the N-terminal of branches of p olypeptides backbone. The branches of the polymers were built up from oligo (DL-alanine) (poly[Lys(DL-Ala(m))], AK) and elongated by an optically activ e amino acid [poly[Lys(X-i-DL-Ala(m))], XAK]. We found that the nature of X (Glu, Ser, Thr) has great influence on the incorporation of the protected cysteine residue. Herpes simplex virus and adenovirus epitope peptides were conjugated to Boc-Cys(Npys)-modified polypeptides. Results indicate that t he incorporation of epitope peptides depends on the number of Npys group on the polymers as well as on the presence/absence of Boc-protecting group on the Cys residue. This new class of Cys(Npys)-derivatized branched polypept ides is stable for a couple of months and suitable for effective preparatio n of epitope peptide conjugates possessing increased water solubility.