INFLUENCE OF ETHER LINKAGES ON THE STRUCTURE OF DOUBLE-CHAIN PHOSPHOLIPID MONOLAYERS

The structure of phosphatidylcholine monolayers has been studied by Synchrotron X-ray diffraction at the air/water interface varying the ester and ether linkages of the aliphatic tails at the glycerol backbone. All systems investigated exhibit an oblique lattice structure with extremely large tilt angles of the chains from vertical, even at high lateral pressures. Although no large difference is seen in the isotherms, the replacement of ester by ether linkages causes a reduction of the tilt angle and of the area per molecule. These changes also depend on the position of the ether group with respect to the glycerol backbone and can be understood within a model where the carbonyl group of the ester at the C2 position pulls the attached chain towards the water subphase.