“…Photosynthetic pigments, i.e., photosynthetic primary donors, antenna Chls and carotenoids have been extensively investigated in their triplet states by transient and pulse ENDOR spectroscopy in order to derive the hfcs of magnetic nuclei like 1 H and thus the spin density distribution in the triplet state (Di Valentin et al 1996;Lendzian et al 1998Lendzian et al , 2003Niklas et al 2007;Salvadori et al 2012;Carbonera et al 2014b;Marchanka et al 2014). ENDOR spectra have also been reported for many porphyrins, e.g., Kay et al (1995), Tait et al (2015), Richert et al (2017), Barbon et al (2020) and (bacterio)chlorophyll model systems dissolved in organic solvents or inserted in the protein environment of the Water-Soluble Chlorophyll Protein (WSCP) (Marchanka et al 2009;Agostini et al 2017Agostini et al , 2019aAgostini et al , 2020. In the specific case of 3 P680, the "primary donor" of Photosystem II (PSII), X-band 1 H-ENDOR spectra have been reported (Di Valentin et al 1996;Lendzian et al 2003) while no ENDOR data are available so far for 3 P700, the primary donor of Photosystem I (PSI).…”