First-Principles Determination of Hybrid Bilayer Membrane Structure by Phase-Sensitive Neutron Reflectometry

The application of a new, phase-sensitive neutron reflectometry method to reveal the compositional depth profiles of biomimetic membranes is reported. Determination of the complex reflection amplitude allows the related scattering length density (SLD) profile to be obtained by a first-principles inv...

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Bibliographic Details
Published in:Biophysical journal 2000-12, Vol.79 (6), p.3330-3340
Main Authors: Majkrzak, C.F., Berk, N.F., Krueger, S., Dura, J.A., Tarek, M., Tobias, D., Silin, V., Meuse, C.W., Woodward, J., Plant, A.L.
Format: Article
Language:English
Subjects:
Analysis
Biophysics - instrumentation
Biophysics - methods
Cells
Dimyristoylphosphatidylcholine - chemistry
Equipment Design
Lipid Bilayers - chemistry
Membranes
Metals
Models, Biological
Neutrons
Scattering, Radiation
Sensitivity and Specificity
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Summary:The application of a new, phase-sensitive neutron reflectometry method to reveal the compositional depth profiles of biomimetic membranes is reported. Determination of the complex reflection amplitude allows the related scattering length density (SLD) profile to be obtained by a first-principles inversion without the need for fitting or adjustable parameters. The SLD profile so obtained is unique for most membranes and can therefore be directly compared with the SLD profile corresponding to the chemical compositional profile of the film, as predicted, for example, by a molecular dynamics simulation. Knowledge of the real part of the reflection amplitude, in addition to enabling the inversion, makes it possible to assign a spatial resolution to the profile for a given range of wavevector transfer over which the reflectivity data are collected. Furthermore, the imaginary part of the reflection amplitude can be used as a sensitive diagnostic tool for recognizing the existence of certain in-plane inhomogeneities in the sample. Measurements demonstrating the practical realization of this phase-sensitive technique were performed on a hybrid bilayer membrane (self-assembled monolayer of thiahexa (ethylene oxide) alkane on gold and a phospholipid layer) in intimate contact with an aqueous reservoir. Analysis of the experimental results shows that accurate compositional depth profiles can now be obtained with a spatial resolution in the subnanometer range, primarily limited by the background originating from the reservoir and the roughness of the film's supporting substrate.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(00)76564-7