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QUB-1942: a bioactive peptide from Phyllomedusa hypochodrialis skin secretion Jin Han (9149) PUREID: 365374941 Antimicrobial peptides phyllomedusa hypochondrialis phylloseptin antibacterial anticancer Antimicrobial peptides, separated and identified from frog and toad skin secretions, have been studied for years. In this thesis, QUB-1942, a peptide belonging to the phylloseptin family, was derived from the skin secretion of the orange-legged leaf frog, Phyllomedusa hypochondrialis. The peptide sequence was obtained through ‘shotgun’ cloning by constructing a cDNA library using frog skin secretion isolated mRNA. The peptide was then synthesised by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and structural-confirmed by matrix-assisted, laser desorption, ionisation, time-of-flight mass spectrometry. In bioassays, QUB-1942 showed inhibitory effects on the Gram-positive bacterium, Staphylococcus aureus (S. aureus ATCC CRM6538)at a concentration from 2 μM, the Gram-negative bacterium, Escherichia coli (E. coli ATCC CRM8739) at a concentration from 8 μM, and the yeast, Candida albicans (C. albicans ATCC CRM10231) at a concentration 64 μM. The minimum inhibitory concentration (MIC) value of the three microbes are 4 μM , 8 μM, 64 μM, respectively. In terms of MTT anticancer cell proliferation assay, QUB-1942 was proven to have anti-proliferative activity against a human lung cancer cell line (H838) in a range of concentrations from 10-6 M to 10-4 M. The trypan blue exclusion assay confirmed the killing effect of the peptide on H838 cells. However, QUB-1942 had a haemolytic effect higher than 20% on horse red blood cells when the concentration was higher than 64 μM. In conclusion, QUB-1942 has potential to become a safe antimicrobial and anticancer drug in the future after its haemolytic toxicity at high concentrations can be substantially decreased through structural modification.<br><br><i>Thesis embargoed until 31 December 2027</i> 2026-10-01T17:04:01Z Text Thesis 10.17034/32633352.v1 https://figshare.com/articles/thesis/QUB-1942_a_bioactive_peptide_from_Phyllomedusa_hypochodrialis_skin_secretion/32633352 All Rights Reserved Open Access after 2027-12-31