Thesis
Guanidinium mimetics, synthesis and application as next-generation analogues in cell penetrating peptides
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2020
- Thesis identifier
- T15846
- Person Identifier (Local)
- 201688177
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Cell penetrating peptides (CPPs) are short peptide sequences, usually between five and thirty amino acids long, that are able to traverse cell membranes. Since they were first discovered in 1989, CPPs have been widely used to deliver various molecular cargoes into cells, from small molecule therapeutics through to larger biologics such as oligonucleotides and proteins. A molecular hallmark of most CPPs is the incorporation of multiple arginine residues in their primary sequence (e.g. 1.1 and 1.2) [Figures in thesis text]. Although there has been extensive research and optimisation of arginine-rich CPPs, there remain multiple drawbacks in their utility as drug delivery agents. The most significant and limiting is their the toxicity in vivo, associated with the high basicity gained from multiple arginine residues within the primary sequence of these peptides. Therefore, the development of guanidine functional group analogues to mimic the arginine side-chain, while both maintaining the hydrogen bond profile and mitigating the associated toxicity could provide a new generation of delivery vehicles for valuable molecular payloads. This thesis describes the development of robust synthetic routes towards the preparation and validation of amidines as bio-isosteres of the guanidinium functional group present in arginine. Chapter one introduces the importance of the guanidinium group in the structure and function of commonly used CPPs. It will also address how they interact with the cell membrane architecture so as to be internalised into the cell. Chapter two describes the design rationale and synthesis of CPPs containing minimal arginine residues and compares their cellular permeability with common arginine-rich CPPs. The mechanism of cell uptake, viability, compartmentalisation and important regions of these peptides is also evaluated. Analysis of cell uptake of a suite of CPPs demonstrated that certain low arginine-containing peptides are more cell permeable than arginine-rich CPPs. Chapter three describes the development of mild Chan-Evans-Lam methodology to directly arylate amidines. The reaction mechanism was investigated and new off-cycle Cu-amidine species were identified. Mono N-arylation of amidines was demonstrated under mild conditions on wide variety of substrates including the synthesis of novel analogues of the clinically approved therapeutic pentamidine. Chapter four describes the synthesis of amidine containing amino acids building blocks for solid phase synthesis and the incorporation of arginine mimetics into CPPs. The toxicity profile, cell uptake and subcellular localisation reveal replacing arginine with amidines enhances uptake of peptide within cells without any adverse toxic effects or perturbation of subcellular localisation. Finally, Chapter five summarises the work of this thesis and suggests future directions for the development of less toxic and less basic CPPs.
- Advisor / supervisor
- Burley, Glenn A.
- Jones, Katherine L.
- Resource Type
- Note
- This thesis was previously held under moratorium from 12th April 2021 until 12th April 2024.
- DOI
- Date Created
- 2020
- Former identifier
- 9912982093402996
- Embargo Note
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