Time-resolved Raman spectroscopy is a very powerful method to study the dynamics of simple and complex molecules, and it has been extensively utilized for clarifying the mechanism of their photochemical processes. Utilizing the stimulated Raman process in the time- or frequency-domain, we are now able to track femtosecond dynamics of the molecules with time-resolved Raman spectroscopy. A big advantage of femtosecond Raman spectroscopy over femtosecond IR spectroscopy is that we can selectively observe the ultrafast dynamics of a specific chromophore with the resonance Raman effect, by tuning the Raman probing wavelength to the electronic transition of the chromophore. In this presentation, we report on our recent femtosecond Raman studies on the primary processes of photo-responsive proteins. We clarified the ultrafast proton transfer and photoisomerization of the chromophores in green fluorescence protein (GFP) [1] and photoactive yellow protein (PYP) [2], respectively, using time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS) carried out with sub-7 fs pulses in the visible region [3]. We also performed UV resonance femtosecond stimulated Raman spectroscopy (UV-FSRS) [4] to study the ultrafast response of the protein backbone of retinal proteins by measuring the femtosecond temporal change of the Raman signals due to aromatic residues.                  [1] T. Fujisawa, H. Kuramochi, H. Hosoi, S. Takeuchi and T. Tahara, J. Am. Chem. Soc. 138, 3942-3945 (2016). [2] H. Kuramochi, S. Takeuchi, K. Yonezawa, H. Kamikubo, M. Kataoka and T. Tahara, T. Nat. Chem. 9, 660−666 (2017). [3] H. Kuramochi, S. Takeuchi and T. Tahara, Rev. Sci. Instru. 87, 043107/1−10 (2016). [4] H. Kuramochi, S. Takeuchi and T. Tahara, J. Phys. Chem. Lett., 3, 2025-2029 (2012).

Ultrafast primary process of photo-responsive proteins revealed by femtosecond Raman spectroscopy

255th National Meeting (2018)

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