Protein Interaction Analysis by Surface Plasmon Resonance

Surface plasmon resonance (SPR) is an optical technique that is utilized for detecting molecular interactions that occur in direct protein-protein interactions. Binding of a mobile molecule (analyte) to a molecule immobilized on a thin metal film (ligand) changes the refractive index of the film. The angle of extinction of light that is completely reflected, after polarized light impinges upon the surface, is altered and monitored as a change in detector position for a dip in reflected intensity (the surface plasmon resonance phenomenon). Because the method strictly detects mass, there is no need to label the interacting components, thus eliminating possible changes of their molecular properties. One of the advantages in SPR is its high sensitivity, compatible with the need for purification of small amounts of protein for analysis. This chapter concentrates on practical methodologies for performing surface plasmon resonance analysis.