FCCS - The Method

FCCS (Fluorescence Cross-Correlation Spectroscopy) can be measured using the Leica TCS SMD FCS system. Similar to FCS, it analyzes fluorescence intensity fluctuations derived from a small observation volume.

In FCCS potential binding partners are marked with spectrally different fluorophores. Their emitted photons are detected in two separate channels.

Quantitative parameters derived from cross-correlation curve

The diffusion of double-marked dimers creates synchronized (i.e., correlated) signal fluctuations, while single marked monomers cause independent fluctuations. An increasing amplitude of the cross-correlation curve reflects an enlargement of the bound fraction. Additionally, like in FCS, information about particle concentration, particle mass, viscosity, and bound fraction can be achieved.