Infrared study of phospholipid hydration. New thermodynamic data about the main phase transition of saturated phosphatidylcholine water multidispersions.
Infrared spectra measurements are performed with fully hydrated phospholipid multilamellar dispersions. The temperature profiles of the delta (OH) bending vibration at 1645 cm-1, corresponding to the water molecules, show three marked transitions in such temperature ranges that they can be respectively associated with the fusion of free water molecules, with pretransition phenomena and with the main phase transition. From absorbance variations and calorimetric data, main phase transition enthalpies and entropies were calculated for both the acyl chains and the polar head-water regions. Negative contributions of the polar head-water region are consistent with previous results, indicating a more ordered water layer in the fluid phase. On the other hand, a decrease of the amount of bound water molecules with increasing chain length is pointed out.
Laboratoire d'Optique Moléculaire, Poitiers, France.
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D008081:Liposomes; D008962:Models, Theoretical; D008968:Molecular Conformation; D010713:Phosphatidylcholines; D013055:Spectrophotometry, Infrared / Q000379:methods; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014867:Water
D008081:Liposomes; D010713:Phosphatidylcholines; D014867:Water