Figure 3.

Surface plasmon resonance—ATR via the Kretschmann configuration. Light is focused onto a metal film through a glass prism and the subsequent reflection is detected. At a certain incident angle (or resonance angle), the plasmons resonate at the same light frequency, resulting in the absorption of light at that angle. This determines a dark line in the reflected beam. That dark line contains a wealth of information. The resonance angle can be obtained by observing a dip in SPR reflection intensity. A shift in the reflectivity curve represents a molecular binding event taking place on or near the metal film, or a conformational change in the molecules bound to the film. By monitoring, this shift vs. time is possible to study the molecular binding events and binding kinetics.