Date of Award

Spring 5-20-2023

Degree Type

Dissertation

Degree Name

PhD. Chemistry

Department

Chemistry and Biochemistry

Advisor

Gregory Wiedman Ph.D.

Committee Member

Wyatt Murphy Ph.D.

Committee Member

Cosimo Antonacci Ph.D.

Committee Member

Gary E. Martin Ph.D.

Keywords

membrane active peptides, melittin, maculatin 1.1, buforin II, azobenzene, photoswitch

Abstract

Membrane active peptides (MAPs) bind and partition into the cell membrane thus causing permeabilization. Many α-helical membrane active peptides contain central proline residues that distinguish the hydrophobic and hydrophilic faces of the helix. The proline induces a bend that produces a helix-hinge-helix motif. Mutation of these proline residues has a significant effect on the activity of the MAP. Azobenzene is a photoisomerizable molecule that switches from its trans to cis isomer upon excitation with ultraviolet (UV) light and from its cis to trans isomer upon excitation with visible light (VL). In this work it is hypothesized that the hinge function of proline can be preserved by replacing it with an azobenzene amino acid that also allows for control over the isomeric states of the peptide. This has enabled the activity of the peptides to be manipulated with light. A 1.5-fold increase in activity was seen for UV-treated photomelittin compared to the VL-treated peptide in synthetic vesicle leakage assays. Conversely a 1.3-fold increase in activity was seen for visible light treated photomaculatin 1.1 compared to the UV-treated peptide. All of the photoswitchable peptides retained their activity and the amino acid substitution did not change their mechanism of action. Novel peptide photobuforin II is fluorescent with an emission peak at 390 nm. This work provides useful insights about the structure-function relationship of the helix-hinge-helix motif as well as a foundation for future studies optimizing azo-containing MAPs for uses in photopharmacology.

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