Fig. 6: Global analysis of the photoinduced mid-IR absorption changes of the isolated carbonmonoxy β chains in the region of ground-state bleach at the parallel, perpendicular, and magic angle polarization settings.
From: Direct observation of two-channel photodissociation of carbon monoxide from the hemoglobin subunits
a Global SVD of the spectra associated with the intermediate species evolving in the first 100 picoseconds after the photoexcitation. b, c Global SVD of the spectra associated with the intermediate species evolving over a timescale ranging from nanoseconds to hundreds of microseconds. Global SVD in (a), as in (b), (c), was performed on the global data matrix composed of data obtained at three polarization settings. Description of (a) and (b) is the same as for Fig. 5. In (a), as in (b), the global fitting of the time-dependent amplitudes s1V1 at three polarization settings was performed as described in Supplementary Note 2. In (c), the time-dependent amplitude (V2) of the second basis spectrum, multiplied by the corresponding singular value (s2) is plotted at three polarization settings. The time course of s2V2 at the magic angle polarization setting is determined by (i) an overall decrease in amplitude due to the CO rebinding to the deoxygenated chains and (ii) spectral changes caused by the interconversion between the A0 and A1 conformational substates. In the inset to (c), the second basis spectrum (U2) and its fit with a Gaussian function are shown in black as circles and the solid line, respectively. U2 exhibits a band at 1968 cm–1 near the stretching band of CO bound to the isolated Hb chains in the A0 substate45. In all insets, the ground-state FTIR absorption spectrum normalized to an arbitrary value is shown as the orange solid line for comparison. In the insets of (b) and (c), the ground-state FTIR absorption spectrum is additionally offset for clarity. The positions of the vibrational bands of CO in the A0 and A1 substate45 are shown as the vertical dashed and solid lines, respectively. Note the difference in the range for the horizontal axis in (a) vs. b, c. Source data are provided as a Source Data file.
