Review of lipid bilayer structure.

The structure of well-hydrated, single-component, lipid bilayers is reviewed. Definitions are provided for the parameters that describe structure at various levels of refinement. Comparisons in the structure are made for lipids with different head groups and hydrocarbon chains. Experimental methods include x-ray scattering, neutron scattering, NMR, and densimetry. Interpretation of the scattering experiments is reviewed in some detail and critically examined. Comparison is made to structural parameters obtained from simulations. Chain disordered fluid phase structure is compared to chain ordered gel phase structure, and other chain ordered structures are also briefly reviewed. Even for these simple lipid bilayers, some structural aspects remain unresolved and await further research.