Doctor of Philosophy (PhD)
Polypeptoids are an emerging class of peptidomimetic polymers featuring N-substituted polyglycine backbones. Polypeptoids are cyto-compatible and backbone degradable, making them appealing to many biological applications. When the highly polar polyamide backbone is coupled with non-polar aliphatic side chains, polypeptoids can be considered as facial amphiphiles. Without extensive hydrogen bonding along the backbone, the conformation of polypeptoid is largely controlled by the N-substituent structures. The hydrophobicity-lipophilicity balance of polypeptoids can be readily tuned with the N-substituent structures as well as the molar ratio between the hydrophilic and hydrophobic segments in their copolymers. In view of these combined attributes, amphiphilic polypeptoids represent an attractive polymer platform to systematically investigate the effect of polymer composition and N-substituent structures on their performance as facial amphiphiles. This dissertation includes four chapters introducing the use of facially amphiphilic polypeptoids towards environmental and biological applications.
Chapter 1 gives a general introduction to the recent development on the materials and methods used in the isolation and stabilization of membrane proteins in aqueous solutions.
Chapter 2 presents the investigation of fragmentation of synthetic liposomes using hydrophobically modified polypeptoids (HMP) towards membrane protein extraction. The effects of molecular characteristics of polypeptoids on the relative rate and extent of liposome fragmentation were elucidated by using a combination of SLS, DLS and cryo-TEM methods.
Chapter 3 reports the design and synthesis of amphiphilic polypeptoids-functionalized Halloysites nanotubes (HNTs), a class of naturally occurring clay nanotubes, as Pickering emulsions stabilizers towards oil-spill remediation application. The effects of polypeptoid grafting and the molecular characteristics of grafted polypeptoids on HNTs on emulsion performances and the cell proliferation of hydrocarbon degrading bacteria were also investigated.
Chapter 4 presents a work on the synthesis, characterization and investigation of structural change of ABC thermo-responsive triblock copolypeptoids during the reversible sol-gel transition in water. The temperature-dependent structural evolution and the effect of polymer hydrophobic fraction on the polymer self-assembly were investigated by SANS and cryo-TEM method.
Yu, Tianyi, "Synthesis and Investigation of Amphiphilic Polypeptoids for Environmental and Biological Applications" (2020). LSU Doctoral Dissertations. 5391.