Specific features of plastoquinone conformation in different redox states and diuron action mechanism in photosynthesis

By semi-empirical methods of quantum chemistry, the most probable configurations of molecules of plastoquinones in different states and herbicides that inhibit electron transport at plastoquinone binding sites are determined. It is shown that plastoquinone in a once-reduced state has a turned end group. The structure of a diuron molecule is similar to that of a once-reduced plastoquinone which may be the factor responsible for strong binding of a diuron molecule with the binding site of quinone $Q_B$ at the reactive center ofphotosystem II.