Spectral variability in phycocyanin cryptophyte antenna complexes is controlled by changes in the α polypeptide chains
M. Corbella, L. Cupellini, F. Lipparini, G. D. Scholes, C. Curutchet. ChemPhotoChem, 3 (2019) 945.
Multiscale simulations indicate that differences in the light harvesting properties of the PC577, PC612, PC630 and PC645 cryptophyte antenna complexes arise from changes in the α polypeptide chains in the structure.
Quantitative models of light harvesting in photosynthetic antenna complexes depend sensitively on the challenging determination of the relative site energies of the pigments. This study analyzed the basis of the light harvesting properties of four antennae from cryptophyte algae (PC577, PC612, PC630 and PC645), which have attracted much attention due to the recent observation of coherence effects in their light-harvesting mechanisms. By using multiscale polarizable quantum/molecular mechanics (QM/MMPol) calculations, it demonstrates that these four proteins share a common energetic ordering PCB82 < PCB158 < DBV51/61 for pigments located in the highly-conserved β chains, whereas bilins in the more divergent α chains cause their spectral differences. Moreover, the study provides a solid excitonic Hamiltonian of these proteins that paves the way for a detailed analysis of the basis supporting the coherence effects observed in their energy transport processes.