FCS is a spectroscopic technique for the study of molecular interactions in solution. FCS monitors the random motion of fluorescently labelled molecules inside a defined volume element irradiated by a focused laser beam. These fluctuations provide information on the rate of diffusion (diffusion time) of a particle and this, in turn, is directly dependent on the particle's mass. As a consequence, any increase in the mass of biomolecules, e.g. as a result of an interaction with a second molecule, is readily detected as an increase in the particle's diffusion time.

Because FCS measurement is made through diffraction limited volume, FCS can be used to study molecule-molecule interactions in living cell. The system can be used to study:

1. Receptor-ligand interactions

2. Transcription factor-DNA interactions

3. Lipid-protein interactions, etc.

The FCS system at the Facility is integrated part of the Multi-photon and the LSM710/Zeiss LSM NLO systems with all the laser lines for common fluorophores and 2 detectors which enable cross correlation analysis.

Reference: http://www.graduate-studies-in-cancer-research.org/CIF/CIFequip6.htm