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Ion selectivity and membrane potential effects of two scorpion pore-forming peptides / D. Elgar

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dc.contributor.author Elgar, Dale
dc.date.accessioned 2009-02-19T12:46:10Z
dc.date.available 2009-02-19T12:46:10Z
dc.date.issued 2005
dc.identifier.uri http://hdl.handle.net/10394/991
dc.description Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2006.
dc.description.abstract Parabutoporin (PP) and opistoporin 1 (OP1) are cation, a-helical antimicrobial peptides isolated from the southern African scorpion species, Parabuthus schlechteri and Opistophthalmus carinatus, respectively. Along with their antimicrobial action against bacteria and fungi, these peptides show pore-forming properties in the membranes of mammalian cells. Pore-formation and ion selectivity in cardiac myocytes were investigated by measuring the whole cell leak current by means of the patch clamp technique. Pore-formation was observed as the induction of leak currents. Ion selectivity of the pores was indicated by the shift of the reversal potential (E,,,) upon substitution of intra (K' with CS' and CI- with aspartate) and extracellular (Na' with NMDG') ions. Results were compared with the effect of gramicidin A used as a positive control for monovalent cation selective pores. PP and OP I induced a fluctuating leak current and indicate non-selectivity of PP and OP1-induced pores. An osmotic protection assay to determine estimated pore size was performed on the cardiac myocytes. PP and OP1-induced pores had an estimate pore size of 1.38-1.78 nm in diameter. The effect of PP and OP1 on the membrane potential (MP) of a neuroblastoma cell line and cardiac myocytes was investigated. TMRM was used to mark the MP fluorescently and a confocal microscope used to record the data digitally. The resting membrane potential (RMP) of the neuroblastoma cells was calculated at -38.3 f 1.9 mV. PP (0.5 uM) and OP1 (0.5-1 uM) depolarized the entire cell uniformly to a MP of -1 1.9 k 3.9 mV and -9.4 k 1.9 mV, respectively. This occurred after 20-30 min of peptide exposure. In the case of the cardiac myocytes depolarization was induced to -39.7 f 8.4 mV and -32.6 f 5.2 mV by 0.5-1 uM PP and 1.5-2.5 uM OPl, respectively.
dc.publisher North-West University
dc.subject Scorpion toxins en
dc.subject Antimicrobial peptides en
dc.subject Pore-formation en
dc.subject Ion selectivity en
dc.subject Pore size en
dc.subject Membrane potential en
dc.title Ion selectivity and membrane potential effects of two scorpion pore-forming peptides / D. Elgar en
dc.type Thesis en
dc.description.thesistype Masters


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