Discovery, modifications and functional evaluations of peptides extracted from amphibians for combating drug-resistant microorganisms

In Chapter 4, a Temporin-RN2-based sequential Lys compensation strategy was established, and RN2-4K and RN2-5K are presented as potent broad-spectrum and salt-stable leads. In Chapter 5, a rationally designed analogue, RN2-4Dap-PEG214, is presented which incorporated helical structure optimisation using unnatural amino acids and balanced hydrophilic-hydrophobic property through use of polyethylene glycolylation (PEGylation) and structural PEGylation strategies.

RN2-4Dap-PEG214 exhibited potent broad-spectrum antimicrobial activity, excellent membrane selectivity and stability. Mechanistic studies suggested membrane disruption and depolarisation. In Chapter 6, several novel Bowman Birk inhibitor (BBI) peptide-based rational designs were presented to treat Candida albicans (C. albicans) by enabling translocation, adjusting the steric hindrance at the P1 residue, enhancing substrate interactions through hydrogen-bond formation, employing a dual-targeting approach, and incorporating synergy-based strategies.

Through antimicrobial screening against 3 strains of C. albicans, TAT-HECI-NAL and TAT-FF-HECI demonstrated enhanced antifungal activity against amphotericin B-resistant C. albicans NCYC 1467. Moreover, TAT-FF-HECI exhibited synergistic effects when used in combination with the mitochondria-targeting peptide, KChaA. Also both peptides displayed negligible cytotoxicity at their antifungal effective concentrations.

Despite the need for further in vivo confirmation, this research offers an adaptable BBI peptide-based platform for tackling antifungal-resistant C. albicans NCYC 1467.<br><br><i>Thesis is embargoed until 31 July 2031.</i>