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

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 beta-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 beta-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.

Automated summary

The block ratio and block sequence of a polypeptide significantly influence the self-assembly of copolymers. By tuning the self-assembly through molecular design, it is possible to form various nanostructures with different properties. In the studied triblock copolymers, the PA block between the PEG and PV segments interfered with the beta-sheet structure, affecting the sol-gel transition behavior. The length of the PA or PV block had a more significant influence on the sol-gel transition. Interestingly, the PV block between the PEG and PA segments induced the formation of more stable beta-sheet stacking structures, resulting in a higher sol-gel transition temperature.