Sequence-Defined Peptidocopolymers: The Effect of Small Molecular Linkers

In this paper, the contribution of nonpeptido small molecular linkers to the properties of sequence-defined peptidocopolymers was investigated. We synthesized four novel bioinspired peptidocopolymers (P1-P4) based on elastin motif pentapeptide (Gly-Pro-Gly-Gly-Ala) by step growth polymerization. Small molecular linkers, including tetraethylene glycol (M1), adipic acid (M2), isophthalic acid (M3), and terephthalic acid (M4) with different length and flexibility are employed to tune the conformation, physical, and mechanical properties of the corresponding peptidocopolymers P1-P4 respectively. Raman spectroscopy, solid state NMR, and circular dichroism spectroscopy were used to characterize the conformation of the four peptidocopolymers. The experimental results were further confirmed by molecular dynamics simulation of typical P2 and P4 with different repeating units. High ratio of β-turn conformation was observed in P2 due to flexible linker M2; while affected by the hydrophobic and rigid M4 linker, P4 retained less β-turn conformation and showed drastic difference on macroscopic properties. These simple step growth synthesis techniques provide an efficient approach toward a broad range of bioinspired peptidocopolymers, which takes a further insight into the significant effect of nonpeptido linkages toward chemical-synthesized peptidocopolymers.