2020 Impact factor 1.890
Soft Matter and Biological Physics
Eur. Phys. J. E 2, 229-245

Electron density modeling and reconstruction of infinite periodic minimal surfaces (IPMS) based phases in lipid-water systems.
II. Reconstruction of D surface based phases

P.E. Harper1 - S.M. Gruner1 - R.N.A.H. Lewis2 - R.N. McElhaney2

1 Department of Physics, Joseph Henry Laboratories, Jadwin Hall, Princeton University, Princeton NJ 08544, USA
2 Department of Biochemistry, The University of Alberta, Edmonton, Alberta, Canada T6G 2H7
smg26@cornell.edu

Received 15 January 1999 and Received in final form 20 October 1999

Abstract
This is the second of two papers dealing with the structure of lipid-water phases based on Infinite Periodic Minimal Surfaces (IPMS). The first paper describes mathematical modeling of such phases. In this paper, a new reconstruction method, called the methyl trough search, is described and used to solve the structures based on powder pattern X-ray diffraction data. Structures are derived for both a single chain lipid-water system (mono-olein) and a diacyl phospholipid-water system (2-2 methyl butyl 16:0 phosphatidylcholine). The methyl trough search uses the low electron density of the lipid methyl tails to determine the correct phasing for the electron density reconstruction. The data are consistent with a structure based on the IPMS D surface. The results are compared to other methods used to solve the mono-olein structure; the structure of the diacyl lipid has never before been solved. We discuss the subtleties involved in reconstruction of D surface based phases and the substantial artifacts that arise in low-resolution reconstructions of hydrocarbon lipids lacking heavy-atom sites.

PACS
61.30.Cz Theory and models of liquid crystal structure - 87.15.By Structure and bonding - 83.70.Jr Liquid crystals: nematic, cholesteric, smectic, discotic, etc

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