Diagram demonstrating the structural features of the device with the OmpF and lipids adsorbed to the gold electrode surface. The neutron beam passes through the magnetic reference layer (green) prior to and after reflecting from the device interface.
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Studying protein/lipid nanostructures
The development of sensors utilising both chemical and structural interactions between proteins and antibodies, bacteria, etc., requires the production of oriented protein arrays. In the present study, a membrane protein, OmpF, has been engineered to produce oriented arrays on gold. These arrays are multi-component devices with a number of assembly steps. Neutron Reflectometry (NR) offers in-situ characterisation throughout the assembly process. The characterisation of these complex structures requires contrast matching (the use of deuterated water / H2O mixtures with the same contrast as part of the sample to highlight particular sample areas) and simultaneous data refinement. This particular problem does not lend itself to the use of deuterium labelling. Instead, we have used a different approach by inserting a magnetic reference layer between the gold electrode surface and the silicon substrate. NR is then performed with both up and down polarised neutrons after each assembly step. We are therefore certain that our contrast variation is performed on exactly the same system.
SA Holt (ISIS), JH Lakey, A LeBrun (University of Newcastle) and CF Majkrzak (NIST Centre for Neutron Research, USA)
Research date: December 2006
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