The proposal concerns the assembly of high density antibody binding surfaces to increase the sensitivity of medical diagnostics. Previously we showed that antibody binding proteins can be assembled on gold surfaces and the complex layers resolved using magnetic contrast neutron reflectivity. The first protein design was analysed and showed that the bound antibodies formed the expected layer. However the antigen only decreased the water content of this layer and did not increase its thickness; indicating that the antibodies were poorly oriented. We have a new set of proteins with improved antibody binding properties and we wish to define their surface arrangement by NR. We used a small amount of deuterated antibody binding protein previously and we now know how to make this protein more efficiently. We hope to dissect out the layers with more precision and see where the antigen binds.