Heidelberg 2015 – scientific programme

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MO: Fachverband Molekülphysik

MO 22: Femtosecond Spectroscopy 3

MO 22.8: Talk

Friday, March 27, 2015, 12:45–13:00, PH/HS1

Real-time tracking of structural rearrangements in wt-GFP after photoexcitation — •Christoph Schnedermann, Torsten Wende, Giovanni Bassolino, Matz Liebel, and Philipp Kukura — Physical & Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ

A vast number of biological and chemical processes rely on the efficient conversion of photon energy into atomic motion. In order to understand the factors determining the energy flow after photoexcitation, it is necessary to track the atomic motion in real-time directly after the absorption of a photon has occurred. Here, we present a time-domain approach capable of resolving the temporal evolution of excited state nuclear degrees of freedom with broadband impulsive vibrational spectroscopy. An actinic pump pulse (15 fs) excites the system followed, after a variable time-delay, by an impulsive Raman pulse (10 fs), which generates vibrational coherences in all excited molecules. These coherences are subsequently recorded by a probe pulse for varying actinic-impulsive pump delay. We use this approach to investigate the excited state proton transfer in wild-type green fluorescent protein and reveal signatures of vibrational coupling between FC and excited state nuclear degrees of freedom akin to multi-dimensional infrared spectroscopy. The observed cross-peaks throughout the fingerprint regime reveal the atomic motions occurring during proton-transfer after photoexcitation.