Photophysics of the Trp-Gly dipeptide: Role of electron and proton transfer processes for efficient excited-state deactivation

Dorit Shemesha,*, Christof Hättigb, Wolfgang Domckea
a Department of Chemistry, Technische Universität München, 85747 Garching, Germany
b Department of Chemistry, Ruhr-Universität Bochum, 44801 Bochum, Germany

Chem. Phys. Lett., 482, 38-43 (2009).
Received 5 August 2009; accepted 25 September 2009. Available online 30 September 2009.

The excited-state potential-energy surfaces of the lowest-energy conformer of the tryptophan-glycine dipeptide have been investigated with ab initio electronic-structure methods. The calculations reveal a potentially very efficient excited-state deactivation mechanism via conical intersections of the excited states of the indole chromophore with locally-excited and charge-transfer states of the peptide backbone. These findings suggest that the excited-state lifetime of the lowest-energy conformer of the Trp-Gly dipeptide may be too short to allow the detection of a resonant two-photon ionization signal. It is proposed that the efficient excited-state deactivation enhances the photostability of the dipeptide. (C) 2009 Elsevier B. V. All rights reserved.

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