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.

Facile aqueous synthesis and stabilization of nearly monodispersed gold nanospheres by poly(L‐proline)

“…MilliQ water was obtained from a MilliQ Plus 185 instrument featuring a UV lamp for sterilization. The synthesis of PLP homopolypeptides has been reported elsewhere 30. Briefly, the L ‐proline‐ N ‐carboxy anhydride (LP‐NCA) was dissolved in acetonitrile, followed by the addition of the appropriate amount of initiator (solution of dimethylamine in acetonitrile), under vigorous stirring.…”

“…Herein, we present the “dual” role of well‐defined water‐soluble PLP30 as an efficient reductant of Au(III) and simultaneously as a stabilizing agent of Au‐NPs. The influence of temperature, molecular weight of PLP, initial Au(III) concentration, and Au(III)/PLP molar ratio on the size and dispersity of Au‐NPs is examined.…”

Hybrid Block Copolymers Constituted by Peptides and Synthetic Polymers: An Overview of Synthetic Approaches, Supramolecular Behavior and Potential Applications

“…One of these studies is related to synthesis of water soluble poly(L-proline) (PLP) to be employed to get AB or ABA block copolymers [78]. From circular dichroism (CD), infrared spectroscopy (IR) and X-ray diffraction (XRD) measurements, the two characteristic forms of poly(L-proline) were detected (i.e., form I with a low crystallinity and form II with a well-organized macromolecular structure).…”

Ring-Opening Polymerization of N-Carboxyanhydrides for Preparation of Polypeptides and Polypeptide-Based Hybrid Materials with Various Molecular Architectures

“…The livingness of the polypeptides under high-vacuum conditions can be preserved indefinitely, thus making possible the use of linking chemistry for the synthesis of a wide variety of macromolecular architectures. The high-vacuum technique for purification of NCAs and subsequent polymerization was shown to be very effective for preparation of highly reactive NCAs, e.g., L-prolin and well-defined poly(L-prolin) homopolypeptides as well as diblock and triblock hybrids with PEO, where poly (L-prolin) forms a hydrophilic helix independent of pH and temperature within the physiological range [12].…”