Molecular Modelling of the Interactions between Optically Active Triazine Herbicides and Photosystem II

The Q b binding site o f photosystem II in green plants displays stereoselectivity for the (S') stereoisomer o f the a-methylbenzyl derivative o f atrazine but not for derivatives with smaller substituents such as sec-butyl. We have shown that interactive models reflect the experimental data by determining the intermolecular energies between the D 1 protein binding region (resi­ dues Leu 210 to Val 280) and the triazine analogs. The intermolecular energy was calculated by van der Waals and electrostatic interactions after energy minimization o f the combined structures to reduce inter and intramolecular strain. On the basis o f these assumptions the role of stereoselectivity for optically active triazines was site responsible such stereoselectivity was identified.