Identification, isolation and bioactivity assessment of a novel peptide from the skin secretion of the Tiger-striped Leaf Frog (Phyllomedusa tomopterna)

  • Ziqi Chen

Student thesis: Masters ThesisMaster of Philosophy

Abstract

In the early twentieth century, the first antimicrobial peptide was found. Nearly forty years later, antimicrobial peptides from frogs were discovered, after which, frogs and their skin secretions were treated as a great source of peptides with bioactive functions. Results from decades of research have shown that many peptides have been found with pharmacological functions such as antimicrobial activity and anticancer activity, which have great potential uses in clinical applications against the resistance generated to conventional antibiotics.

In this thesis, a peptide named QUB-2982 with antimicrobial and anticancer activities was identified first by ‘shotgun’ cloning of the lyophilized frog skin secretion of Phyllomedusa tomopterna. After this, a crude peptide was synthesised and purified. The purified peptide was used in a series of bioactivity tests. QUB-2982 displayed antimicrobial activities towards E. coli, S.aureus, and C.albicans. The MICs were 8 μM, 4 μM, and 32 μM. QUB-2982 also inhibited the growth of three kinds of human cancer cells: U251MG, PC-3, and H157. At the concentration of 10-4 μM, the cancer cell viabilities were 0.33 %, 1.33 %, and 3.33 %, respectively. The outcome of haemolysis assays showed a moderate 10.65 % haemolysis at a concentration of 128 μM.

According to previous experiments, the novel peptide QUB-2982 from the dermaseptin family displayed potent bacteriostatic and bactericidal activities against Gram-positive and Gramnegative bacteria. Moreover, it exerted its antiproliferative influence on multiple cancer cells, without killing effects towards normal mammalian cell membranes. This peptide thus shows promise as a potential medical substitute.
Date of AwardDec 2019
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorTianbao Chen (Supervisor), Mei Zhou (Supervisor), Lei Wang (Supervisor) & Chengbang Ma (Supervisor)

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