Interactions of Mono- and Di-Saccharides with Three Lipid Phases

Abstract

Sugars play important biological roles in lipid membranes; however, a quantitative picture of their interactions is still being developed. In particular, we have studied the effects of fructose, glucose, sucrose and trehalose. We present phase diagrams showing the effects of these mono- and di-saccharides on the gel-lamellar, fluid-lamellar and inverted hexagonal phases of the lipid SOPE. Our results suggest that all the sugars we have tested are all excluded from a thin layer immediately in front of the lipid head groups. Consequently, they are entirely excluded in the gel-lamellar phase and only partially included in the gaps between head groups in the fluid lamellar phase. The amount of inclusion in the fluid lamellar phase is similar among the monosaccharides and among the disaccharides, with the monosaccharides showing a higher degree of inclusion. In the inverted hexagonal phase, for all of the sugars, there appears to be the aforementioned exclusion zone which surrounds a core of sugar and water which matches the bulk concentration.