An analysis of Ca2+ influence on the thermotropic behaviour of different phosphatidylcholine-vitamin D3 mixtures was carried out by differential scanning calorimetry technique (DSC). A competitive effect between Ca2+ and vitamin D3 on the membrane fluidity was detected. The observed shifts of the gel-liquid crystal transition temperature were correlated with the mole fraction of vitamin D3 dissolved within the lipid bilayer as well as with the Ca2+ concentration in the surrounding medium. These shifts were rationalized on the ground of a simple microscopic model through the calculation of the internal pressure exerted by the adsorbed Ca2+ on the lipid matrix by the Clapeyron equation. The experimental results and the obtained equations accord with each other and support the idea of micro-domain formation richer in one lipid component. The extent of such lateral phase separation of the lipid components seems to be favoured by the adsorption of Ca2+ at the membrane-water interface.
CALCIUM-ION INFLUENCE ON THERMOTROPIC BEHAVIOR OF DIPALMITOYLPHOSPHATIDYLCHOLINE-VITAMIN-D3 SYSTEMS
CASTELLI, Francesco;RAUDINO, Antonio;
1990-01-01
Abstract
An analysis of Ca2+ influence on the thermotropic behaviour of different phosphatidylcholine-vitamin D3 mixtures was carried out by differential scanning calorimetry technique (DSC). A competitive effect between Ca2+ and vitamin D3 on the membrane fluidity was detected. The observed shifts of the gel-liquid crystal transition temperature were correlated with the mole fraction of vitamin D3 dissolved within the lipid bilayer as well as with the Ca2+ concentration in the surrounding medium. These shifts were rationalized on the ground of a simple microscopic model through the calculation of the internal pressure exerted by the adsorbed Ca2+ on the lipid matrix by the Clapeyron equation. The experimental results and the obtained equations accord with each other and support the idea of micro-domain formation richer in one lipid component. The extent of such lateral phase separation of the lipid components seems to be favoured by the adsorption of Ca2+ at the membrane-water interface.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
