Structure of the ripple phase of phospholipid multibilayers

Kheya Sengupta, V. A. Raghunathan, and John Katsaras
Phys. Rev. E 68, 031710 – Published 29 September 2003
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Abstract

We present electron density maps (EDMs) of the ripple phase formed by phosphorylcholine lipids such as dimyristoyl phosphatidylcholine (DMPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dihexadecyl phosphatidylcholine, and dilauroyl phosphatidylcholine (DLPC). With the exception of DLPC, the rippled bilayers have a sawtooth shape in all the systems, with one arm being almost twice as long as the other. For DMPC and POPC bilayers, EDMs have been obtained at different temperatures at a fixed relative humidity, and the overall shape of the ripples and the ratio of the lengths of the two arms are found to be insensitive to temperature. EDMs of all the systems with saturated hydrocarbon chains suggest the existence of a mean chain tilt along the ripple wave vector. In the literature it is generally assumed that the asymmetry of the rippled bilayers (absence of a mirror plane normal to the ripple wave vector) arises from a sawtoothlike height profile. However, in the case of DLPC, the height profile is found to be almost symmetric and the asymmetry results mainly from different bilayer thicknesses in the two arms of the ripple. We also present EDMs of the metastable ripple phase of dipalmitoyl phosphatidylcholine, formed on cooling from the Lα phase.

  • Received 10 May 2003

DOI:https://doi.org/10.1103/PhysRevE.68.031710

©2003 American Physical Society

Authors & Affiliations

Kheya Sengupta1,*, V. A. Raghunathan1,†, and John Katsaras2,‡

  • 1Raman Research Institute, Bangalore 560 080, India
  • 2National Research Council, Steacie Institute for Molecular Sciences, Building 459, Station 18, Chalk River, Ontario, Canada K0J 1J0

  • *Present address: Physik Department E22, TU Muenchen, 85747 Garching, Germany. Electronic address: ksengupt@physik.tu-muenchen.de
  • Electronic address: varaghu@rri.res.in
  • Electronic address: john.katsaras@nrc.ca

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Issue

Vol. 68, Iss. 3 — September 2003

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