Hybrid polymers bearing oligo-l-lysine(carboxybenzyl)s: synthesis and investigations of secondary structure

• Published in: RSC advances Vol. 10; no. 3; pp. 1287 - 1295
• Main Authors: Canalp, Merve Basak, Binder, Wolfgang H
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 07.01.2020; The Royal Society of Chemistry
• Subjects: Chemical synthesis; Chemistry; Folding; Infrared spectroscopy; Lysine; Molecular conformation; Molecular weight; NMR; Nuclear magnetic resonance; Organic chemistry; Peptides; Polydispersity; Polymerization; Polymers; Ring opening polymerization; Spectrum analysis
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c9ra09189k

Hybrid polymers of peptides resembling (partially) folded protein structures are promising materials in biomedicine, especially in view of folding-interactions between different segments. In this study polymers bearing repetitive peptidic folding elements, composed of N-terminus functionalized bis-ω-ene-functional oligo-l-lysine(carboxybenzyl(Z))s (Lys ) with repeating units ( ) of 3, 6, 12, 24 and 30 were successfully synthesized to study their secondary structure introduced by conformational interactions between their chains. The pre-polymers of ADMET, narrowly dispersed Lys s, were obtained by ring opening polymerization (ROP) of -carboxyanhydride (NCA) initiated with 11-amino-undecene, following N-terminus functionalization with 10-undecenoyl chloride. The resulting Lys s were subsequently polymerized ADMET polymerization by using Grubbs' first generation (G1) catalyst in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) generating the ADMET polymers (A-[Lys ] ) ( = 2-12) with molecular weights ranging from 3 to 28 kDa, displaying polydispersity ( ) values in the range of 1.5-3.2. After chemical analyses of Lys s and A-[Lys ] s by H-NMR, GPC and MALDI-ToF MS, secondary structural investigations were probed by CD spectroscopy and IR spectroscopy in 2,2,2-trifluoroethanol (TFE). In order to study A-[Lys ] s with defined molecular weights and low polydispersity values ( = 1.03-1.48), the ADMET polymers A-[Lys ] and A-[Lys ] were fractionated by preparative GPC, and subsequently analysed by H-NMR, analytical GPC, MALDI-ToF MS and CD spectroscopy. We can demonstrate the influence of chain length of the generated polymers on the formation of secondary structures by comparing Lys s with varying values to the ADMET-polymers with the help of spectroscopic techniques such as CD and FTIR-spectroscopy in a helicogenic solvent.