Membrane proteins require a lipid environment for their folding, assembly, and activity. The structure of the lipid bilayer is an important determinant of the structure, and hence the function, of the embedded membrane proteins, and thus many studies have been aimed at structural characterization of fluid bilayers. Furthermore, the bilayer plays an active role during the processes of folding, insertion, and translocation of proteins, and therefore studies have also focused on the effect of the embedded proteins on bilayer structure. Structural studies of fluid bilayers, however, are challenging due to the very high thermal disorder that is intrinsic to the native membrane state. This thermal disorder challenges the traditional views of structure and requires novel approaches for structure determination.

The Hristova group has used a new approach to monitor changes in the hydrocarbon core using neutron diffraction and deuterated lipids that are commercially available. The lipid they used is 1-Palmitoyl (D31)-2-Oleoyl-sn-Glycero-3-Phosphocholine, a POPC derivative with the palmitoyl chain deuterated. The comparison of scattering profiles of POPC bilayers with different concentrations of the deuterated POPC analog allows a straightforward determination of the HC distribution via contrast variation, and an easy calculation of the hydrocarbon core thickness.

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