In these models, all residues within 4.0 Å from the corresponding inner pair were calcu- This redistribution leads to a better agreement with the experimental ENDOR results predicting 82% of spin being localized at P D1 . Based on these calculations and on experimental measurements reported in Ref. , it can be assumed that the remaining spin-density distribution is probably localized at P D2 rather than at the axial His. In order to verify this assumption, larger molecular models, which explicitly include two histidine molecules coordinated at the inner pair Chls, need to be calculated with FDEdiab. However, the current implementation of the FDE-diab approach does not allow us to calculate couplings between more than two diabatic states and, therefore, prevents us from conducting these calculations. Comparing experimental photo-CIDNP MAS NMR results and theoretical calculations of protein binding pockets in Figs. ) and d), respectively, it can be seen that most of measured signals are successfully reproduced with FDE-diab.