Packing of a triacylglucolipid from the membrane of Acholeplasma laidlawii strain A at the air/water interface

Abstract

Pressure-area curves were generated at 22°C and 40°C for three glucolipids isolated from Acholeplasma laidlawii strain A-EF22. The glucolipids are 1,2- diacyl-3-O-(α- D)- glucopyranosyl)-sn- glycerol (MGIcDAG), 1,2- diacyl-3-O-[α- D-glucopyranosyl- (1 → 2)-O-α- D- glucopyranosyl]-sn- glycerol (DGIcDAG), and 1,2- diacyl-3-O-[3-O- acyl-(α- D- glucopyranosyl)]-sn- glycerol (MAMGIcDAG). The curves for MGlcDAG and DGlcDAG are characteristic for monolayers in a liquid phase at both temperatures. MGIcDAG has a smaller molecular area at all surface pressures compared to DGlcDAG. At 22°C MAMGlcDAG shows a phase transition at 13 mN/m. However, at 40°C the pressure-area curve for this lipid is characteristic for a monolayer in a liquid state. Mixed MAMGlcDAG-DGlcDAG and MGIcDAG-DGlcDAG monolayers showed no significant deviation from the additivity rule at 40°C. The area per acyl chain is nearly the same for MAMGIcDAG and MGlcDAG. Our study supports our previous results that aqueous dispersions of these lipids form non-lamellar, reversed aggregates.