ARS | Publication request: Lipid immiscibility and biophysical properties: Molecular order within and among unit cell volumes

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 25, 2011
Publication Date: November 4, 2011
Citation: Schmidt, W.F., Mookherji, S., Mitchell, A.D., Crawford, M. 2011. Lipid immiscibility and biophysical properties: Molecular order within and among unit cell volumes. Meeting Proceedings.

Technical Abstract: Saturated and unsaturated fatty acids clearly have a discrete chemical structure in the solid state. In a saturated solution, the solid state and solution state are in chemical equilibrium. The lipid stearic acid packs in unit cell volumes in the liquid state as well as in the solid state. Normally, crystals in the solid state grow from adding individual molecules to a nucleation site. In lipids, the solid state forms from order between and among adjacent unit cell volumes: stearic acid molecules are already aggregated in unit cells. The precise (and limited) solubility of stearic acid in oleic acid confirms unsaturated fats also pack in a liquid state in unit cell volumes. Interestingly, adding stearic acid at levels higher than its solubility in oleic acid results in a slow-forming lipid phase immiscible in the initial phase: the immiscible phase is simply a more efficiently packed mixture of precisely the same lipids present initially. Mixtures of lipids can pack more efficiently than pure single component lipids. Unit cell volumes of lipids of a similar size often will gradually self associate into forming films.