Biomimetic polypeptides with reversible pH-dependent thermal responsive property

- A series of copoly(L-glutamate)s with both the oligo(ethylene glycol) (OEG) moiety and glutamic acid residues are synthesized.
- An entirely reversible pH-dependent thermal-responsive behavior with tunable phase transition temperatures is demonstrated.
- The reduced CD signal upon heating above the clouding point (CP) is entirely due to the aggregation of the polymer chains.
- The solution behavior of block copolypeptide is less dependent on pH.

Smart protein-mimetic materials have received increasing interest for many applications. Here, we reported a facile and efficient approach to prepare a class of dual-responsive copoly(l-glutamate)s by ring-opening polymerization (ROP) and post-modification strategy. Both the oligo(ethylene glycol) (OEG) and glutamic acid residues were incorporated to offer thermal- and pH-responsive property simultaneously. We present a systematic study of the influence of both temperature and pH on the solution properties of the copolypeptides. The copolypeptides show entirely reversible pH-dependent thermal-responsive behaviors with tunable phase transition temperatures. It is demonstrated that the sequence of the polymer units can also influence the solution behavior. The α-helix conformation appears to be the dominant secondary conformation, which shows the pH dependence, but generally irrespective of the temperature. We further verify that the reduced circular dichroism (CD) signal upon heating above the clouding point (CP) is entirely due to the aggregation of the polymer chains. All these features make the obtained polypeptides potential candidates for next generation of smart protein-mimetic materials.

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