Dynamic molecular movements and aggregation structures of lipids in a liquid state

This paper discusses the molecular conformations and the liquid structures of triacylglycerols (TGs) and fatty acids in their melts. Three models for liquid state ordering have been proposed for TG melts to date: the smectic liquid crystal model, the nematic liquid crystal model, and the discotic model. To completely resolve the liquid structure of TGs, further research is required. However, some information on the molecular level has been obtained for fatty acids that are relatively simple compounds. The combination of various spectroscopic and thermodynamic measurements revealed that the hydrogen-bonded dimers of fatty acids are units of intermolecular and intramolecular movements in the liquids and in non-polar solvents. The dimers that construct the clusters resemble the smectic liquid crystal and determine the physicochemical properties of the liquid of the fatty acid. Cholesterol stabilizes the clusters, while ethanol destroys them. Self-diffusion and neutron diffraction measurements revealed that two kinds of fatty acids exist in their binary liquid mixture exist as the homodimers composed of same species.

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► Three models for liquid state ordering have been proposed for triacylglycerols.
► Stable dimers of fatty acid make clusters, which determine the liquid properties.
► Cholesterol added in oleic-acid liquid makes a complex, which stabilizes the cluster structure in the liquid.
► Is the dimer in the binary fatty acid mixture in the liquid state a homo- or heterodimer?