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Femtosecond stimulated raman spectroscopy of flavin after optical excitation

  • In blue-light photoreceptors using flavin (BLUF), the signaling state is formed already within several 100 ps after illumination, with only small changes of the absorption spectrum. The accompanying structural evolution can, in principle, be monitored by femtosecond stimulated Raman spectroscopy (FSRS). The method is used here to characterize the excited-state properties of riboflavin and flavin adenine dinucleotide in polar solvents. Raman modes are observed in the range 90-1800 cm(-1) for the electronic ground state S-0 and upon excitation to the S-1 state, and modes >1000 cm(-1) of both states are assigned with the help of quantum-chemical calculations. Line shapes are shown to depend sensitively on resonance conditions. They are affected by wavepacket motion in any of the participating electronic states, resulting in complex amplitude modulation of the stimulated Raman spectra. Wavepackets in S-1 can be marked, and thus isolated, by stimulated-emission pumping with the picosecond Raman pulses. Excited-state absorption spectra areIn blue-light photoreceptors using flavin (BLUF), the signaling state is formed already within several 100 ps after illumination, with only small changes of the absorption spectrum. The accompanying structural evolution can, in principle, be monitored by femtosecond stimulated Raman spectroscopy (FSRS). The method is used here to characterize the excited-state properties of riboflavin and flavin adenine dinucleotide in polar solvents. Raman modes are observed in the range 90-1800 cm(-1) for the electronic ground state S-0 and upon excitation to the S-1 state, and modes >1000 cm(-1) of both states are assigned with the help of quantum-chemical calculations. Line shapes are shown to depend sensitively on resonance conditions. They are affected by wavepacket motion in any of the participating electronic states, resulting in complex amplitude modulation of the stimulated Raman spectra. Wavepackets in S-1 can be marked, and thus isolated, by stimulated-emission pumping with the picosecond Raman pulses. Excited-state absorption spectra are obtained from a quantitative comparison of broadband transient fluorescence and absorption. In this way, the resonance conditions for FSRS are determined. Early differences of the emission spectrum depend on excess vibrational energy, and solvation is seen as dynamic Stokes shift of the emission band. The ne state is evidenced only through changes of emission oscillator strength during solvation. S-1 quenching by adenine is seen with all methods in terms of dynamics, not by spectral intermediates.show moreshow less

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Metadaten
Author:A. Weigel, A. Dobryakov, Bastian Klaumünzer, M. Sajadi, Peter SaalfrankORCiDGND, N. P. Ernsting
DOI:https://doi.org/10.1021/jp1117129
ISSN:1520-6106 (print)
Parent Title (English):The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
Publisher:American Chemical Society
Place of publication:Washington
Document Type:Article
Language:English
Year of first Publication:2011
Year of Completion:2011
Release Date:2017/03/26
Volume:115
Issue:13
Pagenumber:25
First Page:3656
Last Page:3680
Funder:Deutsche Forschungsgemeinschaft [304]; Fonds der Chemischen Industrie
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer Review:Referiert