Design and synthesis of diyne constrained peptides for targeting protein-protein interactions

McDougall, Laura (2020) Design and synthesis of diyne constrained peptides for targeting protein-protein interactions. PhD thesis, University of Glasgow.

Abstract

In recent years, peptides have emerged as potential therapeutic tools for the disruption of protein-protein interactions (PPIs). These interactions are twice as likely to contain a key α-helical interface as any other secondary structure. Incorporation of chemical constraints to pre-organise peptides into their α-helical bioactive conformation can increase binding affinity to protein targets, enhance stability to protease enzymes and allow cellular uptake. This thesis focusses on the design, synthesis and characterisation of peptides containing a novel diyne constraint as an improvement on the current state-of-the-art all-hydrocarbon linkage.

Chapter 2 focusses on the synthesis of a series of truncated Omomyc peptides, constrained through the ring closing metathesis (RCM) of two unnatural terminal alkene amino acids. A staple scan was utilised to compare sequences for targeting the Myc/Max protein-protein interaction. Helicity and thermal melt analysis using circular dichroism (CD) upon incubating the peptides with the Myc protein allowed for determination of the optimal stapling position in the Omomyc sequence. An increase in protease resistance was observed for this stapled peptide, however no uptake into the cell line of interest was achieved.

Chapter 3 describes the development of a new stapling strategy in which a diyne is formed through a Glaser coupling of two terminal alkynes. Alkyne containing amino acids were synthesised through a diastereoselective alkylation using a Ni(II) Schiff base complex. A model conotoxin peptide was synthesised and the Glaser reaction was optimised on this system, so it could be carried out on-resin to allow excess reagents to be washed away. The stability of the constrained mimetics was assessed in rat serum and the inhibition of the target voltage gated sodium channels (Nav1.4 and 1.6) was also studied. The peptides exhibited comparable binding to that of an all-hydrocarbon mimetic control.

Chapter 4 details the production of alkyne stapled peptides to study the inhibition of Sam68 dimerisation. The Sam68 dimer is key in the process of alternative splicing which can lead to the generation of cancerous proteins. Initially, an alkene stapled control was synthesised and binding to Sam68 confirmed using FP. An in vitro splicing assay was developed to determine the effect of the alkene stapled mimetic on splicing function of Sam68, however no effect was observed using these conditions. A series of alkyne containing amino acids were synthesised to identify the optimal stereochemistry and chain length of the alkyne bridge required for the Glaser reaction. Peptides containing varying diyne bridges were synthesised with an S₇S₇ bridge shown to be the optimal configuration through both Glaser conversion and conferred helicity.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: peptides, stapled peptides, α-helix, protein-protein interaction.
• Subjects: Q Science > Q Science (General); Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Jamieson, Dr. Andrew
• Date of Award: 2020
• Embargo Date: 11 December 2023
• Depositing User: Miss Laura McDougall
• Unique ID: glathesis:2020-81861
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Dec 2020 07:54
• Last Modified: 08 Apr 2022 17:04
• Thesis DOI: 10.5525/gla.thesis.81861
• URI: https://theses.gla.ac.uk/id/eprint/81861

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