Lipid Bilayers Influenced by Taurin and Betain

Abstract

We studied the influence of natural osmolytes Taurin and Betain on the stability and fluidity of lipid model membranes. They components of daily products aim at our well-being, such as energy drinks or baby creams. We used a combination of simultaneous SAXS/WAXS/DSC measurements, being able to identify the structures, their dimensions and the phase transition temperatures. Thermal scans show morphologies similar to aqueous solution of the pure lipids, although with different dimensions and transition temperatures. In POPE, we observe structures with high curvature, and upon temperature cycling, the induction of possible cubic phases. Fully hydrated POPE hydrated with solutions of such osmolytes surprisingly lacks anomalous diffraction patterns over a wide temperature range on cooling from the hexagonal phase. The diffraction peaks in the last patterns are much less intense than at the beginning of the scan. The DSC shows a higher phase transition temperature on heating than for pure aqueous POPE, while during cooling this is not seen. DSC of POPE in on these samples shows a transition at a different temperature than purely hydrated POPE. The SAXS scan indicates a less organized stack of bilayers and the hexagonal phase, normally following the lamellar upon heating, could not be clearly seen up to 85oC. Moreover, no well-organized structure was formed during cooling. On combining SAXS/WAXS and DSC results obtained from dispersions of POPE in either aqueous solution of Taurin and Betain, one can see their effect from a structural perspective, that is, their influence on the macro organization of the self-assembled mesogenic units. Both osmolytes seem to require high temperatures (weaker interactions between headgroups of neighbouring lipids) to effectively interact with the POPE (headgroups) and influence the dispersion.