Nataša Poklar1, Jure Fritz1, Peter Maèek2
and Gorazd Vesnaver1
1Department of Chemistry, Aškerèeva 5,
2Department of Biology, Veèna pot 111, University of Ljubljana, 1000 Ljubljana, Slovenia
The nature of the interaction of Equinatoxin II (EqTxII) with small zwitterionic unilamellar phospholipid vesicles at pH 3.0 in 100 mM glycine/100 mM NaCl buffer was investigated by differential scanning calorimetry (DSC), CD-spectropolarimetry and intrinsic fluorescence emission spectroscopy. EqTxII binding to the zwitterionic DPPC vesicles at pH 3.0 does not influence significantly the cooperativity, the enthalpy and the temperature of the gel/liquid-crystaline phase transition of the lipids. Similarly, the zwitterionic DPPC lipids at the same conditions do not influence significantly the EqTxII structural transitions since in the presence or absence of DPPC EqTxII exhibits the same properties. Our results suggest that there is no strong interactions between EqTxII and zwitterionic small unilamellar vesicles in glycine/NaCl buffer at pH 3.0.