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CP: Chemische Physik

CP 11: Einzelteilchenspektroskopie

CP 11.1: Poster

Tuesday, March 10, 1998, 18:00–20:00, P1

Identification and Quantification of Single Molecules in Aqueous Solution — •Joachim Fries, Christian Eggeling, Jörg Schaffer, Leif Brand, and Claus Seidel — MPI für biophysikalische Chemie Göttingen

Recent advances in laser-induced fluorescence detection have made it possible to characterize single fluorescent molecules in solution. Such experiments eliminate ensemble averaging and allow the probing of individual members of an ensemble. Using a confocal microscope together with pulsed excitation, the fluorescence burst of a single molecule diffusing through the microscopic, open measurement volume was detected and analyzed by a real-time spectroscopic technique, denoted BIFL (burst-integrated fluorescence lifetime), and fluorescence correlation spectroscopy (FCS). BIFL enables to generate a fluorescence decay time histogram and to construct a macroscopic time scale for a given number of consecutive detected photons. Thus, a specific fluorescence burst can be selected and the fluorescence lifetime of the single molecule causing this burst can be determined. This feature was used to monitor a mixture of dye molecules with different lifetimes. The single molecule transits could be denoted to a specific dye, which enabled selective counting of the dyes. The results are concurrent with those obtained from FCS.