Fig. 7: Species-associated-difference spectra (SADS) in the mid-IR spectral range.
From: Confinement in crystal lattice alters entire photocycle pathway of the Photoactive Yellow Protein
The SADS have been resolved from fitting the target model shown in Fig. 4 to the experimental data, and display the bleached ground state as negative feature and product state absorption as positive feature. a SADS of PYPS, b SADS of PYPC. c An accumulated PYP light-minus-dark difference FTIR spectrum and the SADS of the pB state of PYP in solution (also shown in a). Absorption changes in the 1740–1760 cm−1 region report on the hydrogen bond interaction between Glu46 and the phenol ring of pCa: higher frequency indicates weakened bond, lower frequency a stronger bond; Absorption changes in the 1690–1630 cm−1 region report on carbonyl stretches with a similar effect of a hydrogen bond on its frequency. The 1555 cm−1 band has been assigned to pCa C = C stretch and phenol ring modes50,51,53, see also Supplementary Table 1.
