Mode of action of novel 2-(benzylamino)-4-methyl-6-(trifluoromethyl)-1,3,5-triazine herbicides: Inhibition of photosynthetic electron transport and binding studies

Novel 2-(benzylamino)-4-methyl-6-(trifluoromethyl)-1,3,5-triazines have the same 1,3,5-triazine skeleton as atrazine, although some of them, for examp le, 2-(3 -chlorobenzylamino)-4-methyl-6-(trifluoromethyl)-1,3,5-triazine [p I(50)(spinach) = 7.21], show a >3 times stronger photosynthetic electron tr ansport inhibitory activity than atrazine [pI(50)(spinach) = 6.72]. The new triazines have only one amino group at the triazine ring, and their molecu lar shapes are different from atrazine. The replacement of the bound [C-14] atrazine by 1,3,5-triazines was tested to determine whether the novel 1,3,5 -triazine analogues exhibit the same binding pattern at the D1-protein as a trazine. It was found that [C-14]atrazine bound to the D1-protein was repla ced by the triazine tested by a clearly competitive interaction. Obviously, the novel 1,3,5-triazines are attached to the same binding niche as atrazi ne.