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Impact of different cations on thermal properties of DPPS and DPPC lipid bilayers

Phospholipid molecules present an essential part of biomembranes. Phosphatidylserine (PS) is the major anionic phospholipid present in eukaryotic membranes located on the cytosolic leaflet. One of its primary functions seems to be to impart a negative charge to the inner surface of the membrane lipid bilayer [1] which is required for the binding and activation of various peripheral membrane proteins [2]. The most abundant phospholipid in eukaryotic membranes, zwitterionic phosphatidylcholine (PC), can be distributed in both, inner and outer, membrane leaflets [3]. Lipid-constituted membranes undergo phase transitions, which in addition to temperature, pressure, and pH also depend on the chemical potentials of ions [4]. In this work we are focused on monitoring thermal properties of lipid bilayers constituted from 1, 2dipalmitoyl-sn- glycero-3-phosphatidylserine (DPPS) and 1, 2- dipalmitoyl-sn-glycero-3phosphatidylcholine (DPPC) in the presence of guanidinium (Gdm+) and ammonium (NH4+) cations which is manifested in a change in melting temperature (Tm). Using FT-IR spectroscopy, UV-Vis spectrophotometry, and differential scanning calorimetry (DSC) our goal is to understand how these cations affects thermal properties of DPPS and DPPC lipid membranes. All experimental results are supported by the computational study.

biomembranes ; phosphatidylcholine ; phosphatidylserine ; spectroscopy ; calorimetry

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