Thermodynamics of carbohydrate-lipid interactions.

Thermodynamic analyses of carbohydrate-lipid interactions were performed by investigating the effects of a series of carbohydrates, including monosaccharides, disaccharides, and trisaccharides, on the phase-transition properties of aqueous dispersions of 1,2-dipalmitoyl phosphatidylcholine (DPPC). The temperature of the lipid's main phase transition from the gel to liquid-crystalline phase is essentially unchanged in the presence of carbohydrate. The change in the free energy (delta G) of the transition is zero when a carbohydrate is added to aqueous dispersions of DPPC, while the enthalpy (delta H) and the entropy of the melting of DPPC are decreased. The thermodynamic information was used to examine carbohydrate-lipid interactions. Such interactions were elucidated according to our knowledge of the specific properties of carbohydrates in aqueous solutions and the previously proposed hydrophobic interaction involving hydrocarbon tails of the lipid in aqueous dispersions.