Title:	Structure of the ripple phase of phospholipid multibilayers
Authors:	Sengupta, Kheya Raghunathan, V.A. Katsaras, J.
Issue Date:	29-Sep-2003
Publisher:	The American Physical Society
Citation:	Physical Review E, 2003, Vol.68, 031710
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 Lalpha phase.
URI:	http://hdl.handle.net/2289/1251
ISSN:	ISSN 1550-2376 (online) 1539-3755
Alternative Location:	http://link.aps.org/abstract/PRE/v68/e031710
Copyright:	(2003) by the American Physical Society
Appears in Collections:	Research Papers (SCM)

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