Institute of Neurophysiology and Cellular Biophysics

Director: Prof. Dr. Dr. D. Schild i.R.

Methods used in the lab

Fluorescence correlation spectroscopy (FCS)

Fluorescence correlation spectroscopy is an optical method that allows the determination of diffusion coefficients, hydrodynamic radii, average concentrations, kinetic chemical reaction rates and singlet-triplet dynamics. The generation of an FCS-spectrum requires the focussing of laser light into a diffraction-limited spot. The intensity fluctuations of fluorophores moving through the focal volume are detected and auto-correlated. The auto-correlation-function is than mathematically modelled to extract the parameters of interest. Therefore, it is necessary to have an exact description of the geometrical and physiological conditions in the focal volume (Gennerich and Schild, 2000; Gennerich and Schild, 2002).

We designed and built a confocal laser scanning FCS-system that allows confocal microscopy and fluorescence correlation spectroscopy at the same time, thereby enabling the almost simultaneous investigation of e.g. different cytosolic compartments. Photon detection is accomplished by an avalanche photo diode with significantly higher detection efficiency than common photomultiplier tubes used in cLSM achieve.