We compared the thermotropic properties (transition temperatures and associated enthalpies) of phosphatidylcholine (PC) bilayers of varying chain length containing either cholesterol or vitamin D-3. The two sterols are structurally similar but behave in rather different ways. Both transition temperature and associated enthalpy decrease on raising the amount of sterol dissolved in the lipid matrix; the decrease, however, depends on the PC's chain length and is markedly different for cholesterol and vitamin D-3. These differences have been rationalized on the basis of a simple theoretical model by employing a mean field statistical thermodynamics approach. The model has been developed in a perturbation scheme by considering cholesterol as reference molecule and vitamin D-3 as a slightly modified cholesterol. Taking together experimental and theoretical results, we infer that the different thermotropic behavior of the two sterols is mainly due to (a) weaker PC-vitamin D-3 pair interactions as compared with PC-cholesterol and (b) greater ability of cholesterol to reduce the co-operative melting of PC lipid chains.
|Titolo:||Calorimetric analysis of lipid-sterol systems: a comparison between structurally similar cholesterol and vitamin D3 interacting with phospholipid bilayers of different thickness|
|Autori interni:||CASTELLI, Francesco|
SARPIETRO, MARIA GRAZIA
|Data di pubblicazione:||1994|
|Rivista:||CHEMISTRY AND PHYSICS OF LIPIDS|
|Appare nelle tipologie:||1.1 Articolo in rivista|