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oai:figshare.com:article/32805743 2026-10-01T16:13:35Z portal_1172 item_type_8 month_year_10_2026

Identification and functional study of peptides from the skin secretion of Phyllomedusa azurea Zehao Li (3807931) PUREID: 688011572 Antimicrobial peptides peptide modification protease resistance dermaseptin phylloseptin Antimicrobial peptides (AMPs) from Phyllomedusa frog skin secretions represent a rich source of membrane-active anti-infective agents. In this work, three major AMP lineages, dermaseptins (QUB-2480, DRS-01) and phylloseptins (PS-12), were comprehensively-investigated alongside rationally-designed analogue libraries to elucidate the structural determinants governing antimicrobial, cytotoxic, enzymatic, and biophysical properties. All peptides and analogues were chemically-synthesised and structurally-validated by RP-HPLC, ESI-MS, and circular dichroism spectroscopy, confirming amphipathic α-helical conformations under membrane-mimetic conditions.<br><br>QUB-2480, a newly identified dermaseptin from Phyllomedusa azurea, displayed potent broad-spectrum antibacterial activity, with MIC values in the low micromolar range against both Gram-positive and Gram-negative bacteria，particularly against Gram-negative bacteria. Analogues with enhanced cationicity apparently improved potency and therapeutic indices, whereas reduced hydrophobicity or loss of C-terminal amidation attenuated activity. PS-12 displayed moderate antibacterial activity, with MIC values ranging from 2–64 µM across tested strains. Rational modification of cationicity and α-helical propensity generated more potent analogues, with PS-12-1 showing improved activity (MIC = 1–4 µM against S. aureus and E. coli). However, excessive hydrophobicity or structural disruption reduced selectivity. Hydrocarbon stapling (PS-12-5) enhanced resistance to proteolytic degradation but resulted in reduced antimicrobial potency (MIC ≥64 µM), highlighting a trade-off between stability and activity. For the dermaseptin DRS-01, activity was robust across bacterial species but markedly-compromised by trypsin digestion, whereas the N-terminal Nal-modified analogue DRS-N preserved both potency and partial protease resistance. Modifications aimed at sequence shortening or charge redistribution generated apparent loss of activity.<br><br>Across all peptide families, mechanistic assays demonstrated rapid bactericidal effects mediated by membrane perturbation, including outer- and inner-membrane permeabilisation, depolarisation, and time-dependent disruption consistent with a carpet-like mode of action. Several analogues exhibited reduced haemolytic activity and improved antiproliferative effects against cancer cell lines, underscoring the tunability of bioactivity profiles. Resistance-development assays revealed minimal MIC shifts over serial passaging, indicating a low propensity for resistance induction.<br><br>Collectively, these studies have established QUB-2480, PS-12, DRS-01, and their optimised analogues, as promising membrane-active AMPs, and provide detailed structure–activity insights to guide the rational design of next-generation antimicrobial therapeutics with improved stability, potency, and safety.<br><br><i>Thesis is embaragoed until 31 July 2031.</i> 2026-10-01T16:13:35Z Text Thesis 10.17034/32805743.v1 https://figshare.com/articles/thesis/Identification_and_functional_study_of_peptides_from_the_skin_secretion_of_Phyllomedusa_azurea/32805743 All Rights Reserved Open Access after 2031-07-31