Ions modify the strength of interaction of diquat and paraquat with some proteins and cellulose.

The interaction of the bipyridylium herbicides diquat and paraquat with the proteins gliadin and human serum albumin (HSA) as well as with cellulose and the effect of various ions on the strength of interaction were studied by charge-transfer chromatography. Both compound showed very similar behaviour. The ions decreased in each case the strength of interaction, the effect depended nonlinearly on the ion concentration and was of saturation character. Gliadin showed the weakest interaction. HSA binds the bipyridylium compounds in an ion-dependent manner, the strength of interaction is higher than that of cellulose at higher ion concentration. This finding indicates an ion-mediated interaction of unknown character between the bipyridylium herbicides and HSA.