Theory of the Intermediate Rippled Phase of Phospholipid Bilayers

A mathematical model of the periodic, rippled P_β' phase of phosphatidylcholine is described. In this model the P_β' phase shows a periodic variation in membrane properties corresponding to a lateral periodic variation between fluid-like and crystal-like states. The model is based on a curvature-dependent Landau-de Gennes free-energy functional. Our proposed form of the curvature-dependent free energy remedies a subtle mathematical flaw in an earlier model having similar physical content [Falkovitz, M. F., Seul, M., Frisch, H. L. & McConnell, H. M. (1982) Proc. Natl. Acad. Sci. USA 79, 3918-3921].