November 20, 2023 Käss, H., P. Fromme, H.T. Witt, and W. Lubitz, (2001) Orientation and electronic structure of the primary donor radical cation in photosystem I: A single crystals EPR and ENDOR study. The Journal of Physical Chemistry B, 105(6): 1225-1239. Home » Käss, H., P. Fromme, H.T. Witt, and W. Lubitz, (2001) Orientation and electronic structure of the primary donor radical cation in photosystem I: A single crystals EPR and ENDOR study. The Journal of Physical Chemistry B, 105(6): 1225-1239.