Structural relaxations of phospholipids and water in planar membranes

• We have used dielectric spectroscopy and temperature modulated differential scanning calorimetryTMDSC to investigate the structural relaxation processes and phase transitions of water and lipidsin multilamellar, planar phospholipids. At low hydration levels we observe the main structuralrelaxation related to the glass transition of the phospholipids. With increasing water content a morepronounced pretransition, attributed to a gel to ripple phase transition, is observed in the TMDSCdata. In the proximity of this pretransition, a distinct change in the temperature dependence oralternatively a bifurcation into two processes is observed in the dielectric data. Around thistemperature a crossover in the long-range ionic conductivity across the membranes is also observed,which is one of the key parameters for biological membranes. Thus, the major dynamical changesdo not occur at the main, i.e., the gel to liquid structural phase transition, but at a pretransition thatoccurs roughly 20 K below the main transition.

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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