Functional protein arrays can exploit the specificity of protein-protein interactions for medical diagnosis. To this end engineered arrays which present a surface composed of fully functional folded proteins for interaction with molecules in solution have been developed. To ‘sense’ the interaction, engineered membrane proteins are anchored to gold surfaces for electronic, optical and acoustic detection purposes.  Proteins, for example IgG, are then reversibly bound to this scaffold layer,  to define the surface selectivity.  Characterisation of the scaffold array before and after the binding of three further proteins has been carried out using the newly implemented technique of magnetic contrast reflectivity on the Surf reflectometer.  Enhanced resolution has been achieved by the deuteration of the scaffold protein and constrained fitting of datasets with variable mixtures of D₂O and H₂O.λ This has provided a uniquely definitive structural characterisation of the molecular structure. Optimisation of molecular orientation is critical to device miniaturisation and allows more clinical tests per square millimetre, reducing costs and increasing efficiency.

AP Le Brun, JH Lakey (University of Newcastle), DS Shah (Orla Protein Technologies Ltd), SA Holt (ISIS)

Research date: December 2008