title: Well-defined homopolypeptides, copolypeptides, and hybrids of poly(l-proline).
abstract: l-Proline is the only, out of 20 essential, amino acid that contains a cyclized substituted α-amino group (is formally an imino acid), which restricts its conformational shape. The synthesis of well-defined homo- and copolymers of l-proline has been plagued either by the low purity of the monomer or the inability of most initiating species to polymerize the corresponding N-carboxy anhydride (NCA) because they require a hydrogen on the 3-N position of the five-member ring of the NCA, which is missing. Herein, highly pure l-proline NCA was synthesized by using the Boc-protected, rather than the free amino acid. The protection of the amine group as well as the efficient purification method utilized resulted in the synthesis of highly pure l-proline NCA. The high purity of the monomer and the use of an amino initiator, which does not require the presence of the 3-N hydrogen, led for the first time to well-defined poly(l-proline) (PLP) homopolymers, poly(ethylene oxide)-b-poly(l-proline), and poly(l-proline)-b-poly(ethylene oxide)-b-poly(l-proline) hybrids, along with poly(γ-benzyl-l-glutamate)-b-poly(l-proline) and poly(Boc-l-lysine)-b-poly(l-proline) copolypeptides. The combined characterization (NMR, FTIR, and MS) that results for the l-proline NCA revealed its high purity. In addition, all synthesized polymers exhibit high molecular and compositional homogeneity.
authors.affiliation: University of Athens, Chemistry Department, Panepistimiopolis, Zografou, Athens, Greece.
authors.forename: Manos
authors.initials: M
authors.lastname: Gkikas
authors.forename: Hermis
authors.initials: H
authors.lastname: Iatrou
authors.forename: Nikolaos S
authors.initials: NS
authors.lastname: Thomaidis
authors.forename: Paschalis
authors.initials: P
authors.lastname: Alexandridis
authors.forename: Nikos
authors.initials: N
authors.lastname: Hadjichristidis
mesh_terms: D000812:Anhydrides / Q000737:chemistry*; D001672:Biocompatible Materials / Q000138:chemical synthesis*; D002942:Circular Dichroism; D004337:Drug Carriers / Q000138:chemical synthesis*; D008239:Lysine / Q000031:analogs & derivatives / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008968:Molecular Conformation; D010455:Peptides / Q000138:chemical synthesis*; D011092:Polyethylene Glycols / Q000737:chemistry; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D000812:Anhydrides; D001672:Biocompatible Materials; D004337:Drug Carriers; D010455:Peptides; C517076:proline N-carboxyanhydride; C040741:epsilon-tert-butyloxycarbonyl-lysine; C011083:polyproline; D011092:Polyethylene Glycols; D011392:Proline; D008239:Lysine