Supramolecular structures of peptide assemblies in membranes by neutron off-plane scattering: Method of analysis

Lin Yang, Thomas M. Weiss, Thad A. Harroun, William T. Heller, Huey W. Huang

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Abstract

In a previous paper (Yang et al., Biophys. J. 75:641-645, 1996), we showed a simple, efficient method of recording the diffraction patterns of supramolecular peptide assemblies in membranes where the samples were prepared in the form of oriented multilayers. Here we develop a method of analysis based on the diffraction theory of two-dimensional liquids. Gramicidin was used as a prototype model because its pore structure in membrane in known. At full hydration, the diffraction patterns of alamethicin and magainin are similar to gramicidin except in the scale of q (the momentum 'transfer of scattering), clearly indicating that both alamethicin and magainin form pores in membranes but of different sizes. When the hydration of the multilayer samples was decreased while the bilayers were still fluid, the in-plane positions of the membrane pores became correlated from one bilayer to the next. We believe that this is a new manifestation of the hydration force. The effect is most prominent in magainin patterns, which are used to demonstrate the method of analysis. When magainin samples were further dehydrated or cooled, the liquid-like diffraction turned into crystal-like patterns. This discovery points to the possibility of investigating the supramolecular structures with high-order diffraction.

Original languageEnglish
Pages (from-to)2648-2656
Number of pages9
JournalBiophysical Journal
Volume77
Issue number5
DOIs
StatePublished - Nov 1999
Externally publishedYes

Funding

This work was supported by NIH grant GM55203 and NIH training grant GM08280, and by the Robert A. Welch Foundation. We acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the neutron research facilities used in this work, which was also supported by the National Science Foundation under agreement No. DMR-942310.

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