CALORIMETRIC DETERMINATION OF PHOSPHOLIPID-MELITTIN INTERACTIONS

Linus N. Okoro

Abstract


The effect of melittin incorporated into the phospholipid bilayer DPPC at mole fractions up to 3.75 mol% have been investigated. The study reveals a considerable influence of melittin on the phase transition profile and volumetric properties of the DPPC bilayer. The temperature dependence of the coefficient of expansion, a, and the volume fluctuations of DPPC – melittin bilayer membranes in their different transition phases were determined by using pressure perturbation calorimetry (PPC), a relatively new and efficient technique, and differential scanning calorimetry (DSC). The experiments were carried out in the temperature range from 10 to 85 °C. Incorporating melittin up to 1.25 mol% into the lipid bilayer abolishes the pretransition. Remarkably, there is no shift in the transition temperature up to 2.5 mol% melittin, while more than one shoulder is observed at the low-temperature side of the DSC peak for 3.75 mol%, and a slight shift in melting temperature,Tm to 32oC. This could be linked to the lytic property of melittin at these high peptide concentrations.

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DOI: http://dx.doi.org/10.17628/ecb.2013.2.107-111

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