Bayreuth 1998 – scientific programme

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CP: Chemische Physik

CP 18: Sondersymposium: Einzelmolekülspektroskopie

CP 18.1: Talk

Thursday, March 12, 1998, 11:30–11:50, H18

Monitoring Conformational Dynamics of a Single Molecule by Selective Fluorescence — •Claus Seidel, Leif Brand, Christian Eggeling, Joachim Fries, and Jörg Schaffer — MPI f. biophys. Chemie, Göttingen

A new, real-time spectroscopic technique, burst-integrated fluorescence lifetime (BIFL), is shown to be well-suited for monitoring the individual molecular conformational dynamics of a single molecule. The two-dimensional BIFL data allow a complementary analysis of the time-dependent fluctuations in fluorescence lifetime and intensity. Using a highly diluted aqueous solution of 20-mer oligonucleotide strand of DNA duplex labelled with the environment-sensitive fluorescent dye tetra- methyl-rhodamine (TMR), bursts in fluorescence intensity indicating traces of individual molecules diffusing through the microscopic, open measurement volume of a confocal set-up are registered and further subjected to selective burst analysis. To check the consistency the dynamics is analyzed in three different ways by direct determination of the relaxation time of the conformational states in fluorescence lifetime traces as well as by autocorrelation analysis of fluorescence lifetime and intensity traces, respectively. The consistent results strongly support the hypothesized three-state model of the conformational dynamics of the TMR-DNA duplex.