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BP: Fachverband Biologische Physik

BP 26: Posters II

BP 26.29: Poster

Donnerstag, 28. Februar 2008, 17:00–19:30, Poster A

Scanning FCS applied to precise measurement of diffusion coefficients — •Susan Derenko, Zdeněk Petrášek, and Petra Schwille — Biophysics Group, Biotechnologisches Zentrum, TU Dresden, Germany

Although fluorescence correlation spectroscopy (FCS) is a useful technique to obtain diffusion coefficients of fluorescent molecules in solution, the precision of the measurement is limited due to difficulties in the determination of the fixed volume size in standard FCS. In order to avoid the reference to the inaccurate volume size, the beam is scanned in a circle with either two galvanometer scanners or a 2-axis piezo scanner. The diffusion coefficent is then related to the scan radius R and the scanning freqency using the spatial cross-correlated signal. The radius needs to be calibrated carefully and is therefore the most important value for the calculation of the diffusion coefficient D.

To test the applicability of the new approach, several dyes were tested under two-photon excitation, and the important parameters, mainly radius and frequency, were optimized. The method is being extended to one-photon excitation, where triplet-effects of the fluorescent molecules have to be considered. Further, operation under non-ideal conditions and in biological samples will be investigated.