[en] The reaction dynamics of Cry1Ab toxin from Bacillus thuringiensis with sodium, calcium and lead ions was studied by fluorescence quenching technique. Gradual quenching was observed by titration of Cry1Ab toxin with metal ions (Na+, Ca/sup 2+/ or Pb/sup 2+/). The quenched strength of these ions in the descending order was: lead ion > calcium ion > sodium ion. The quenching equilibrium of Cry1Ab toxin by metal ions reached within 60 min, and the quenching dynamics of Cry1Ab toxin could be expressed by the Elovich model. The toxin concentration, pH and temperature had influence on the quenching dynamics. The interaction between Cry1Ab toxin and metal ions is based on static quenching mechanism. (author)