Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 12: Single Molecules

BP 12.7: Talk

Wednesday, March 25, 2009, 11:45–12:00, HÜL 186

Determining the hydrodynamic size and shape of biomolecules by probing single-molecule Brownian motion — •Sandeep Pallikkuth and Andreas Volkmer — 3rd Institute of Physics, University of Stuttgart, Germany

Information regarding the hydrodynamic volume of a fluorescent biomolecule is obtained by monitoring its Brownian motion in solution. While the translational diffusion of a fluorescent biomolecule, occurring on the micro- to millisecond time scale, is conveniently obtained from a conventional fluorescence correlation spectroscopy experiment, the more size-sensitive Brownian rotational dynamics of the molecule, occurring on the pico- and nanosecond time scale, is generally obtained from the measurement of its time-resolved fluorescence anisotropy upon pulsed excitation. The application of the latter technique, however, is limited by its fluorescence lifetime, preventing the accurate measurement of rotational diffusion time when in the order of tens of nanoseconds. Based on recent experimental advances allowing the calculation of second-order correlation function from distinct photon arrival times with picosecond time resolution and applying an exact theoretical model, we demonstrate probing of Brownian rotational diffusion of a biomolecule in free solution at time scales between a picosecond and hundreds of nanoseconds without the need for pulsed excitation. Moreover, the simultaneous measurement of both the translational and rotational diffusion of a biological macromolecule with this technique allows the determination of the hydrodynamic size and shape of the biomolecule.