MOLECULAR MODELING OF THE INTERACTIONS BETWEEN OPTICALLY-ACTIVE TRIAZINE HERBICIDES AND PHOTOSYSTEM-II

The Q(B) binding site of photosystem II in green plants displays stere oselectivity for the (S) stereoisomer of the alpha-methylbenzyl deriva tive of atrazine but not for derivatives with smaller substituents suc h as sec-butyl. We have shown that interactive models reflect the expe rimental data by determining the intermolecular energies between the D 1 protein binding region (residues Leu 210 to Val 280) and the triazin e analogs. The intermolecular energy was calculated by van der Waals a nd electrostatic interactions after energy minimization of the combine d structures to reduce inter and intramolecular strain. On the basis o f these assumptions the role of stereoselectivity for optically active triazines was calculated and the region of the binding site responsib le such stereoselectivity was identified.