posted on 2024-03-01, 15:35authored byCasey
A. Morrison, Ethan P. Chan, Thatcher Lee, Timothy J. Deming
Our group recently developed a family of side-chain amino
acid-functionalized
poly(S-alkyl-l-homocysteines), Xaa-CH (Xaa = generic amino acid), which possess the ability
to form environmentally responsive coacervates in water. In an effort
to further study how the molecular structure affects polypeptide coacervate
formation, we prepared side-chain amino acid-functionalized poly(S-alkyl-rac-cysteines), Xaa-rac-C, via post-polymerization modification of
poly(dehydroalanine), ADH. The
use of the ADH platform allowed
straightforward synthesis of a diverse range of side-chain amino acid-functionalized
polypeptides via direct reaction of unprotected l-amino acid
2-mercaptoethylamides with ADH. Despite their differences in the main-chain structure, we found
that Xaa-rac-C can form coacervates with properties similar to those seen with Xaa-CH. These results suggest that
the incorporation of side-chain amino acids onto polypeptides may
be a way to generally favor coacervation. The incorporation of l-methionine in Met-rac-C allowed the preparation of coacervates with improved
stability against high ionic strength media. Further, the presence
of additional thioether groups in Met-rac-C resulted in an increased solubility change
upon oxidation allowing facile reversible redox switching of coacervate
formation in aqueous media.