Cardiolipin in phospholipid bilayers : a calorimetric study

Abstract: The purpose of this study was to understand cardiolipins behavior in different pH: 5.5, 7 and 9. Cardiolipins miscibility in other bilayers as 1,2-dimyrilstoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were also studied. The instrument used in this study was a differential scanning calorimetry. The conclusions that could be drawn from the scans were that cardiolipin has different phase behavior in different pH because of the charge and that the phase behavior get more complex with higher charge. With the mixed systems with cardiolipin and DMPC it was shown that cardiolipin was miscible in DMPC bilayers with a low concentration cardiolipin and that the miscibility decreased with increased concentration of cardiolipin. But with higher pH values cardiolipin was miscible in even higher concentrations of cardiolipin. This indicates that with higher charge on the cardiolipins headgroup it is easier for cardiolipin to dissolve in a bilayer. It was also show that cardiolipin was easier dissolved in bilayers in liquid crystalline phase as DOPC, than bilayers in a solid phase as DMPC.