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