Effect of the vitamin D photosynthesis products on thermodynamic parameters of model lipid membranes

Aim. To compare effects of vitamin D (VitD), provitamin D (ProD) and its photo- and thermoisomerization products on thermodynamical parameters of hydrated dipalmitoylphoshpatidylcholine (DPPC) multilayers. Methods. Differential scanning calorimetry, UV spectroscopy. Results. A regular decrease was established in the melting temperature accompanied with the pronounced broadening of the appropriate peaks for DPPC multilayers doped with the sterols in the order ProD3 < < ProD3 + UV < ProD3 + UV + dark storage < VitD3. Conclusions. The destabilizing effect of VitD3 on the membrane appeared to be stronger than that of ProD3 and its photoisomerization products. This can facilitate VitD3 withdrawal from the membrane into intercellular space under its biosinthesis in vivo. A possible molecular mechanism of the phenomena observed is related to the higher conformational flexibility and anisometry of VitD3 as compared to ProD3.