For these models, inclusion of the nearby protein environment did not considerably affect the spin distributions. In the hinge model from PSII, deprotonation of the His molecule at the π-N position drastically decreased the electronic levels separation and led to couplings of the quasi-diabatic states at acute angles θ with a subsequent shifts of the spin density towards His. This effect of spin-density re-distribution was previosly predicted on the basis of experimental results in Ref. . Our calculations, therefore, partially support the proposed explanation and show that the tilt of the angle θ can, indeed, cause a change in the spin density of the complex. Calculations for the truncated hinge model from PSII showed a wrong spin-density localization with 60% being localized at His in the ground state at ∆θ = -15 degrees. This was explained by an inverted ordering of the nearly degenerate ground and excited electronic states of the complex. The non-truncated model demonstrated a correct spin-density localization at Chl a (86%) and agreed well with ENDOR measurements predicting 82% of spin density at Chl a. Contrary to the results reported in Ref. , we did not observe a considerable shift of the spin density within Chl a under the angle tilt. Therefore, the reported strong asymmetry in the spin-density pattern of Chl a was not observed in calculated FDE-diab spin densities.