Title
Highly ordered polypeptide with UCST phase-separation behavior
Author
Sotaro Kuroyanagi, Naohiko Shimada, Shota Fujii, Tadaomi Furuta, Atsushi Harada, Kazuo Sakurai, Atsushi Maruyama
Year
2018
Journal
JACS
Abstract
Manipulating phase separation structures of thermo-responsive polymers will enhance the usefulness of structure-controllable materials in the fields such as drug delivery and tissue engineering. However, behaviors of upper critical solution temperature (UCST) have been less investigated so far, despite of the importance of UCST. Here, we examined two citrulline-based polypeptides, poly(D-ornithine-co-D-citrulline) (PDOC) and poly(DL-ornithine-co-DL-citrulline) (PDLOC), to investigate how stereoregularity of the polypeptides influences UCST behavior, in addition with poly(L-ornithine-co-L-citrulline) (PLOC) previously studied. Homochiral PLOC and PDOC showed phase separation temperatures (Tps) higher than that of racemic PDLOC. Moreover, PDLOC underwent liquid to coacervate phase separation at Tp, whereas PLOC and PDOC underwent liquid to solid-like aggregation transitions. From the structural point of view, circular dichroism and small-angle X-ray scattering measurements revealed that homochiral PLOC and PDOC polypeptides formed α-helical structures, and assembled into a regular hexagonal lattice upon phase separation. Interactions between the pendent ureido groups of homochiral POCs appear to play pivotal roles in helical folding and assembly into the hexagonal structure. In addition, Tp change in response to biodegradation was confirmed for both PLOC and PDLOC. The biodegradability was considerably influenced by phase-separated structures. These findings of UCST-type POCs in this study would provide important insights into structure-controllable and thermo-responsive biomaterials.
Full Article
Instrument
J-820
Keywords
Circular dichroism, Secondary structure, Thermal stability, Polymers, Materials