Title:	Structure and interactions in the anomalous swelling regime of phospholipid bilayers
Authors:	Pabst, G. Katsaras, J. Raghunathan, V.A. Rappolt, M.
Issue Date:	2003
Publisher:	American Chemical Society
Citation:	Langmuir, 2003, Vol.19, p1716-1722
Abstract:	We have carried out X-ray and neutron diffraction experiments, as a function of temperature, on fully hydrated samples of dimyristoyl phosphatidylcholine bilayers. The data show the following: (a) In the vicinity of the L to P' transition, we find an anomalous expansion of the water layer of ~1.7 Å. (b) The lipid bilayer thickness increases quasi-linearly and is similar to the increase in the lamellar repeat spacing d found in dimyristoyl ethanolamine bilayers in the temperature range of TM to TM + 13 C. (c) In contrast to an earlier study, we find no significant changes to the steric size of the phosphatidylcholine head group. The anomalous increase in d is thus dominated by an expansion of the water layer. This expansion is caused by a distinct increase in bilayer fluctuations as revealed by an analysis of the Caillé parameter. Additional osmotic pressure experiments not only support this notion but have allowed us to further estimate the temperature dependence of both the bilayer bending rigidity, Kc, and the interbilayer compressional parameter, B. Both Kc and B experience an abrupt decrease on approaching TM from above, indicative of a "softening" of the bilayers.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/2858
ISSN:	0743-7463 1520-5827 (Online)
Alternative Location:	http://dx.doi.org/10.1021/la026052e
Copyright:	2003 American Chemical Society
Appears in Collections:	Research Papers (SCM)

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