Nanoanalytical measurement of protein orientation on conductive sensor surfaces

The control of protein immobilisation and orientation at surfaces is of increasing relevance in biotechnological devices. These devices include reproducible biosensors, biofuel cells, and protein arrays, all of which require the immobilisation of protein/enzymatic sensing elements with retention of their activity. The control of protein orientation upon immobilisation is of importance in (1) facilitating equal access of analyte molecules to the protein that acts as a sensing element and (2) creating favourable interactions to stabilise the protein on the surface for long-term storage and usage of bio-devices. This review presents a comparison of a number of surface analysis techniques that have been widely used in the chemical analysis of surfaces that offer the potential to discriminate different orientations of the same protein on a conductive surface.