Protonation Heterogeneity Modulates the Ultrafast Photocycle Initiation Dynamics of Phytochrome Cph1
A combined effort between the Larsen and Lagarias labs resolved the underlying heterogeneity of the photocycle initiation dynamics of the Cph1 phytochrome photoreceptor that strongly affects kinetics, absorption, fluorescence, and quantum yields (both photochemical and fluorescent) and implicates how structural rearrangements can affects in vivo function. The used a novel dual-excitation-wavelength-interleaved pump-probe (DEWI) approach to demonstrate that both spectral and kinetic heterogeneity in the excited-state dynamics could be described with a self-consistent model comprised of three spectrally distinct populations with different protonation states. This model also successfully simulated reported 2D electronic spectra, demonstrating that existing approaches for interpreting heterogeneity in such spectra can be misleading.
More information at https://pubs.acs.org/doi/10.1021/acs.jpclett.8b01133