QSAR of 1,4‐Naphthoquinones as Inhibitors of Photosystem II Electron Transport

Abstract 42 1,4‐naphthoquinones with substituents in the 2‐ and 3‐position were examined for their inhibitory activity on photosynthetic electron transport through photosystem II. The best ones were active in concentrations in the μM range or less. A QSAR was established, using the sum of the σ‐Hammett parameters and Taft's steric E parameter for the substituents in the 2‐ and 3‐position. The QSAR could be improved, if instead of the E , the STERIMOL parameters L (for the 2‐position) and B 3 and B 4 (for the 3‐position) were applied. QSAR for different types of photosystem I1 inhibitors (urea, phenolic, quinoid) were compared. The differences in between them do support the idea of nonidentical though possibly overlapping binding sites at the reaction center complex of photosystem II.