Mitteilung - Preisträger für das Sommersemester 2021

Für das vergangene Sommersemester 2021 wird mit dem Promotionspreis der Berliner-Ungewitter-Stiftung die Dissertation von Herrn Dr. Arindam Ghosh zu Single Molecule Fluorescence Spectroscopy and Imaging: Advanced Methods and Applications in Life Sciences ausgezeichnet, welche er in der Arbeitsgruppe von Prof. Dr. Jörg Enderlein (III.Physikalisches Institut) anfertigte.

Zum Inhalt der Arbeit:
This dissertation involves development of advanced methodologies in fluorescence microscopy and spectroscopy for looking into structural details and fast dynamics of biomolecules at spatiotemporal resolution down to nanometer (nm) and nanosecond (ns) regime. Emergence of various fluorescence imaging tools popularly classified under superresolution fluorescence microscopy has enabled us to visualize biological structures with a resolution of a few nanometers (nm) along the lateral dimension (xy). However, the spatial resolution along the third dimension (z) remains three to five times worse impeding the possibility of three-dimensional imaging with isotropic nanometer resolution. In this thesis, I developed a novel technique, graphene-induced energy transfer (GIET) which enhances the spatial resolution along z dimension down to subnanometer regime. GIET relies on near-field energy transfer between a fluorescent molecule and a monolayer of graphene up to ~30 nm from the graphene surface. Consequentially, a fluorescent molecule experiences distance-dependent loss of fluorescence signal and shortening of excited-state lifetime near the graphene surface. In GIET, one measures fluorescence lifetimes of a fluorophore and converts them to axial distance values using a mathematical model. I have demonstrated the potential of GIET by measuring overall thickness (~5 nm) of two bilayer membranes differing only by ~1 nm in thickness. Next, I focus on single molecule fluorescence spectroscopy (SMFS) for resolving fast temporal dynamics of fluorescent molecules under observation. To this end, I used fluorescence lifetime correlation spectroscopy (FLCS) to disentangle two emission states and their microsecond (μs) switching kinetics in an autofluorescent protein. In complex fluorescent emitters like an autofluorescent protein, existence of two or more emission states with highly overlapping spectra at room temperature is very common. FLCS can be a method of choice in these cases for detailed investigation of photophysics of these states separately at room temperature, which is otherwise not possible with existing techniques.