Theoretical studies are especially important for investigating the spin-density asymmetry as they provide a direct access to electronic structures of photosynthetic pigments and can be applied to obtain spin densities and hyperfine coupling constants of many shortlived open-shell intermediates produced in electron-transfer reactions. However, reliable calculations of inner pair spin-density distributions may require the consideration of the surrounding protein environment. This considerably increases the size of molecular models to be computed and restricts the choice of the electronic structure method to Kohn-Sham Density Function Theory (KS-DFT). The latter is affected by the self-interaction error (SIE) and often produces overly delocalized spin-density distributions . This effect can be especially strong for non-covalently bonded molecular systems (for examples, see Refs. ) and, therefore, is expected to be crucial for pigments in RC models. Moreover, the degree of spin delocalization may strongly depend on the exchangecorrelation (XC) functional applied . Although many different approaches were proposed in the literature to overcome this problem , the ultimate solution is not yet found and the issue remains relevant.