Alternative methods of determining phase transition temperatures of phospholipids that constitute liposomes on the example of DPPC and DMPC

• New phase transition for DMPC was found.
• FT-IR method is an important addition to the DSC studies.
• The proposed method for determining the TC give very consistent results.

In this work, alternatives to differential scanning calorimetry (DSC) as a method of determining the main phospholipid phase transition temperature are presented. The bilayer phase transitions from the ripple gel phase (Pβ′Pβ′) to the liquid-crystal phase (Lα) of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were studied by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) methods. In this work, two correlations between the DSC and FT-IR methods, and NMR and EPR methods are shown. The proposed methods allow for determining the TC temperature with a high degree of accuracy. Furthermore, a comparison of results obtained using the DSC and FT-IR methods allowed for an observation of a new DMPC phase transition. The liposomes analyzed in this work were obtained by the modified reverse-phase evaporation method (mREV).