Figure 1. Schematic diagram of some of the important components of an SPR detector system. The blue area on the backside of the thin gold mirror is the active area where changes in the dielectric constant change the angle of the dark band in the reflected light. The light source (monochromatic) is directed through a prism to a detector (here represented by an eye) where changes in the dielectric constant are recorded. For example, when proteins bind to ligands attached (through a linker) to the gold surface, a change in dielectric constant occurs which is correlated with SPR change.

Figure 2. A binding signal (here ETS-1 DBD (part of an oncogene) and a peptide RV (a domain of the associated protein)) shows initial binding followed by a stochastic steady state (loosely, an equilibrium) from a Biacore instrument. When the flow of peptide/analyte (RV) is replaced with a flow of buffer, this reversible binding reaction relaxes towards a zero-bound complex concentration, as shown by reduction in the SPR signal. The signal is measured in response units (RU). Each RU represents about 1/3000th of a degree.