Research ArticleCHEMICAL PHYSICS

Fifth-order time-domain Raman spectroscopy of photoactive yellow protein for visualizing vibrational coupling in its excited state

See allHide authors and affiliations

Science Advances  07 Jun 2019:
Vol. 5, no. 6, eaau4490
DOI: 10.1126/sciadv.aau4490
  • Fig. 1 Structure of the chromophore pocket in PYP.

    Structure of trans-pCA chromophore of PYP. Blue dotted lines denote hydrogen bonds with the surrounding amino acid residues. Vibrational couplings between low-frequency modes involving intermolecular motions through the hydrogen bonds (blue shaded) and fingerprint vibrations reflecting the pCA skeleton (green shaded) are of particular interest in the present study.

  • Fig. 2 Principle of the fifth-order time-domain Raman spectroscopy of PYP.

    (A) Schematic illustration of the optical process involved in the present fifth-order time-domain Raman measurement. (B) Pump-probe signals of PYP in a tris-HCl buffer solution (pH 7), which were measured with (blue) and without (red) the P2 pulse at ΔT = 0.5 ps. The raw TR-ISRS signal was obtained as a difference between these signals (i.e., P2 on − P2 off). P1-induced (red) and P2-induced (blue) oscillatory signals were obtained after subtraction of the slowly varying population component from the raw signals, and they are shown with magnification (×4 and ×20, respectively). (C) Fourier transform (FT) power spectra of the P1- and P2-induced oscillatory signals.

  • Fig. 3 Fifth-order time-domain Raman data of PYP.

    (A) 2D representation of the P2-induced oscillatory signals obtained at various ΔT delay times. (B) Fourier transform power spectra of the oscillatory signals obtained at various ΔT delay times. (C) 2D representation of the time-resolved Fourier amplitude spectra.

  • Fig. 4 Temporal change of the Raman band intensities of excited-state PYP.

    Temporal profiles of the Fourier amplitude for selected bands. Dashed lines denote the best fit to the data, which takes account of the oscillatory component with slowly varying population component.

  • Fig. 5 2D representation of the fifth-order time-domain Raman data.

    2D frequency-frequency correlation map obtained by the fifth-order time-domain Raman spectroscopy of PYP. Top half of the 2D map (gray-shaded area) was not directly obtained because of the undersampling in the ΔT axis but is folded to the lower half. Diagonal peaks on the red broken line correspond to the depletion of P1-induced vibrational coherence. Off-diagonal peaks on the blue broken line correspond to the folded diagonal peaks that appear as a result of the undersampling. Spectra on the top and right represent the Fourier transform power spectrum of the oscillatory component of the TR-ISRS signal, averaged over all the measured ΔT delays, and that of the pump-probe signal, respectively, the latter of which is the same as Fig. 2C.

  • Fig. 6 Low-frequency oscillatory dynamics of the high-frequency fingerprint vibrational mode.

    (A) Pump-probe signal of PYP in the early time window, measured with 75-fs pump and 6.5-fs probe pulses. (B) Fourier transform power spectrum of the oscillatory component of the pump-probe signal in (A). (C) Temporal profile of the Fourier amplitude of the 751-cm−1 band of excited-state PYP obtained by TR-ISRS using the 75-fs P1 pulse. Red and blue lines represent the data measured with the different ΔT step sizes. The data taken with the different ΔT steps confirm that the oscillatory feature of the 751-cm−1 band is not undersampled. (D) Fourier transform power spectra of the amplitude oscillation of the 751-cm−1 band in (C). (E) Steady-state preresonance stimulated Raman spectrum of the ground-state PYP, obtained with 490-nm Raman excitation.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/6/eaau4490/DC1

    Experimental condition

    Origin of the diagonal peaks in the 2D frequency-frequency correlation map

    Fifth-order signal versus lower-order cascades

    Fig. S1. Resonance condition for the measurements.

    Fig. S2. Depletion of vibrational coherence in the TR-ISRS experiment.

  • Supplementary Materials

    This PDF file includes:

    • Experimental condition
    • Origin of the diagonal peaks in the 2D frequency-frequency correlation map
    • Fifth-order signal versus lower-order cascades
    • Fig. S1. Resonance condition for the measurements.
    • Fig. S2. Depletion of vibrational coherence in the TR-ISRS experiment.

    Download PDF

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article