Artifacts from photobleaching and dye-dissociation in fluorescence correlation spectroscopy

Fluorescence correlation spectroscopy (FCS) is an optical technique in which the fluctuations in fluorescence intensity are quantified. The time correlation function gives insight into the dynamics of the molecule in its environment: typically the diffusion coefficient in a dilute solution is measured, but the technique has been expanded to uses in more complex environments, including living cells. In these environments photobleaching and dye-dissociation can substantially introduce artifacts in the FCS data. We present a technique to correct for the artifacts introduced by photobleaching and study dye dissociation in DNA solutions.