Date of Graduation

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Servoss, Shannon L.

Committee Member

Beitle, Robert R. Jr.

Second Committee Member

Havens, Jerry A.

Third Committee Member

Hestekin, Christa N.

Fourth Committee Member

Koeppe, Roger E. II

Keywords

Membrane science; Bicelles; Peptoids

Abstract

Membrane-affiliated interactions are significant in understanding cell function, detecting biomarkers to diagnose disease, and in testing the efficiency of new therapeutic targets. Model membrane systems have been developed to study membrane proteins, allowing for stable protein structure and maintaining native activity. Bicelles, disc-shaped lipid bilayers created by combining long- and short-chain phospholipids, are the model membrane system of focus in this study. Bicelles are accessible from both sides and have a wide size range, which make them attractive for studying membrane proteins without affecting function. In this work, bicelles were functionalized with two peptoids to alter the edge and face chemistry. Peptoids are suitable for this application because of the large diversity of available side chain chemistries that can be easily incorporated in a sequence-specific manner. The peptoids sequence consist of three functional regions to promote insertion into the edge of bicelles. The insertion sequence at the C-terminus contains two alkyl chains and two hydrophobic, chiral aromatic groups that anchor into the bicelle edge or face. The facially amphipathic helix contains chiral aromatic groups on one side that interact with the lipid tails and positively charged groups on the other side, which interact with the lipid head groups. Thiol groups are included at the N-terminus to allow for determination of peptoid location in the bicelle. Bicelle morphology and size were assessed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Peptoid location in the bicelle was determined by attachment of gold nanoparticles, which confirm preferential incorporation of the peptoid into the bicelle edge or face. Results from this study show that peptoid-functionalized bicelles are a promising model membrane system. Specifically, the designed peptoids sequence were found to incorporate preferentially into the edges and faces of bicelles with 82% and 92% specificity, respectively. Additionally, the peptoid-functionalized bicelles are of similar size and morphology to non-functionalized bicelles. Potential applications would include customization to anchor in biosensors or facilitate interactions with specific membrane proteins or complexes.

Download

Share

COinS