Various methods are available for attaching proteins to solid surfaces. Most rely on either (1) non-specific adsorption, or (2) the reaction of chemical groups within proteins (e.g., amino and carboxylic acid groups) with surfaces containing complementary reactive groups. In both cases the protein is attached to the surface in random orientations. The use of recombinant affinity tags addresses the orientation issue, but the interactions of the tags are often reversible. Therefore, the recombinant affinity tags require large mediator proteins in order to remain stable over the course of subsequent assays.
Methods for the chemoselective attachment of proteins to surfaces have been developed. (See J. A. Camarero, “Chemoselective Ligation Methods for the Ordered Attachment of Proteins to Surfaces”, in Solid-fluid Interfaces to Nanostructural Engineering, J. J. de Yoreo, Editor. 2004, Plenum/Kluwer Academic Publisher New York and C. L. Cheung et al., Fabrication of Assembled Virus Nanostructures on Templates of Chemoselective Linkers Formed by Scanning Probe Nanolithography, J. Am. Chem. Soc. 125, p. 6848, 2003.) These methods rely on the introduction of two unique and mutually reactive groups on the protein and the support surface. The reaction between these two groups usually gives rise to the selective attachment of the protein to the surface with total control over the orientation. However, these methods, although highly selective, rely on uncatalyzed pseudo-bimolecular reactions with little or no entropic activation at all. This lack of entropic activation means that the efficiency of these bimolecular-like reactions will depend strongly on the concentration of the reagents (i.e., the protein to be attached).