Ice-Regulating Properties of Side-Modified Poly(ethylene glycol)-Poly(l-methionine)

Controlling ice nucleation and growth plays an important role in the cryopreservation of biological samples. Increasing efforts have been made to develop ice-regulating materials focused on functional polypeptides that are mimetic to naturally occurring antifreeze (glyco)proteins. Herein, poly(ethylene glycol)-poly(l-methionine) was synthesized by ring-opening polymerization and subsequently transformed into a series of postmodified derivatives, including two trehalose-modified glycopolypeptides with different linkers, a carboxylated polypeptide with zwitterions, and two polypeptides with varying hydroxyl ester residues for comparison. The glycopolypeptide with a long linker in a 10 mg/mL aqueous solution exhibited a higher ice nucleation temperature at -15.9 °C than that of water at -21.2 °C. Results of differential scanning calorimetry (200 mg/mL) and low-field nuclear magnetic resonance (100 mg/mL) suggested that the polyhydroxy side-structure might influence the interaction between the polypeptides and water molecules that had an impact on regulating ice generation and recrystallization. This study provides an accessible strategy for the synthesis of polypeptides with ice-regulating activities.