Controlling self-assembly of co-polypeptide by block ratio and block sequence

Abstract

Block ratio and block sequence of polypeptide influenced the self-assembly of copolymer significantly. Tuning self-assembly to form various nanostructures with different properties through molecular design was a rather feasible strategy. Triblock copolymers based on poly( l -alanine) (PA), poly( l -valine) (PV) and poly (ethylene glycol) (PEG) with various block ratio and block sequence were synthesized. The number of amino acid residues was kept at 10. The sol-gel transition behavior, self-assemble nanostructure, secondary structure of the copolymers in aqueous solution were investigated to reveal that PA block between PEG and PV segment interfered the β-sheet structure, resulting in the reduced or increased sol-gel transition temperature or precipitation depended on the block ratio of PA and PV. Shorter PA or PV block displayed more significant influence on sol-gel transition. Interestingly, PV block between PEG and PA segment induced the formation of more stable β-sheet stacking structures, leading to sol-gel transition at higher temperature. PEG dehydration and the enhancement of ordered structure with temperature rising caused the sol-gel transition of these copolymers. We concluded herein that disordered structure in co-polypeptide can enhance thermo-sensitivity. • Conformation of synthesized non-natural polypeptides based on side-chain design. • Block sequence of non-natural polypeptides affected sol-gel transition. • Shorter peptide block influenced more significantly on sol-gel transition. • Less hydrophobic and weaker steric hindrance block at the tail enhanced the stability of nanostructures. • Disordered structure in co-polypeptide enhanced thermo-sensitivity.